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8 @settitle GNAT User's Guide for Native Platforms
13 @dircategory GNU Ada Tools
15 * gnat_ugn: (gnat_ugn.info). gnat_ugn
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24 GNAT User's Guide for Native Platforms , Nov 09, 2018
28 Copyright @copyright{} 2008-2018, Free Software Foundation
34 @title GNAT User's Guide for Native Platforms
39 @c %** start of user preamble
41 @c %** end of user preamble
45 @top GNAT User's Guide for Native Platforms
50 @anchor{gnat_ugn doc}@anchor{0}
51 @emph{GNAT, The GNU Ada Development Environment}
54 @include gcc-common.texi
55 GCC version @value{version-GCC}@*
58 Permission is granted to copy, distribute and/or modify this document
59 under the terms of the GNU Free Documentation License, Version 1.3 or
60 any later version published by the Free Software Foundation; with no
61 Invariant Sections, with the Front-Cover Texts being
62 "GNAT User's Guide for Native Platforms",
63 and with no Back-Cover Texts. A copy of the license is
64 included in the section entitled @ref{1,,GNU Free Documentation License}.
68 * Getting Started with GNAT::
69 * The GNAT Compilation Model::
70 * Building Executable Programs with GNAT::
71 * GNAT Utility Programs::
72 * GNAT and Program Execution::
73 * Platform-Specific Information::
74 * Example of Binder Output File::
75 * Elaboration Order Handling in GNAT::
77 * GNU Free Documentation License::
81 --- The Detailed Node Listing ---
85 * What This Guide Contains::
86 * What You Should Know before Reading This Guide::
87 * Related Information::
88 * A Note to Readers of Previous Versions of the Manual::
91 Getting Started with GNAT
94 * Running a Simple Ada Program::
95 * Running a Program with Multiple Units::
96 * Using the gnatmake Utility::
98 The GNAT Compilation Model
100 * Source Representation::
101 * Foreign Language Representation::
102 * File Naming Topics and Utilities::
103 * Configuration Pragmas::
104 * Generating Object Files::
105 * Source Dependencies::
106 * The Ada Library Information Files::
107 * Binding an Ada Program::
108 * GNAT and Libraries::
109 * Conditional Compilation::
110 * Mixed Language Programming::
111 * GNAT and Other Compilation Models::
112 * Using GNAT Files with External Tools::
114 Foreign Language Representation
117 * Other 8-Bit Codes::
118 * Wide_Character Encodings::
119 * Wide_Wide_Character Encodings::
121 File Naming Topics and Utilities
123 * File Naming Rules::
124 * Using Other File Names::
125 * Alternative File Naming Schemes::
126 * Handling Arbitrary File Naming Conventions with gnatname::
127 * File Name Krunching with gnatkr::
128 * Renaming Files with gnatchop::
130 Handling Arbitrary File Naming Conventions with gnatname
132 * Arbitrary File Naming Conventions::
134 * Switches for gnatname::
135 * Examples of gnatname Usage::
137 File Name Krunching with gnatkr
142 * Examples of gnatkr Usage::
144 Renaming Files with gnatchop
146 * Handling Files with Multiple Units::
147 * Operating gnatchop in Compilation Mode::
148 * Command Line for gnatchop::
149 * Switches for gnatchop::
150 * Examples of gnatchop Usage::
152 Configuration Pragmas
154 * Handling of Configuration Pragmas::
155 * The Configuration Pragmas Files::
159 * Introduction to Libraries in GNAT::
160 * General Ada Libraries::
161 * Stand-alone Ada Libraries::
162 * Rebuilding the GNAT Run-Time Library::
164 General Ada Libraries
166 * Building a library::
167 * Installing a library::
170 Stand-alone Ada Libraries
172 * Introduction to Stand-alone Libraries::
173 * Building a Stand-alone Library::
174 * Creating a Stand-alone Library to be used in a non-Ada context::
175 * Restrictions in Stand-alone Libraries::
177 Conditional Compilation
179 * Modeling Conditional Compilation in Ada::
180 * Preprocessing with gnatprep::
181 * Integrated Preprocessing::
183 Modeling Conditional Compilation in Ada
185 * Use of Boolean Constants::
186 * Debugging - A Special Case::
187 * Conditionalizing Declarations::
188 * Use of Alternative Implementations::
191 Preprocessing with gnatprep
193 * Preprocessing Symbols::
195 * Switches for gnatprep::
196 * Form of Definitions File::
197 * Form of Input Text for gnatprep::
199 Mixed Language Programming
202 * Calling Conventions::
203 * Building Mixed Ada and C++ Programs::
204 * Generating Ada Bindings for C and C++ headers::
205 * Generating C Headers for Ada Specifications::
207 Building Mixed Ada and C++ Programs
209 * Interfacing to C++::
210 * Linking a Mixed C++ & Ada Program::
212 * Interfacing with C++ constructors::
213 * Interfacing with C++ at the Class Level::
215 Generating Ada Bindings for C and C++ headers
217 * Running the Binding Generator::
218 * Generating Bindings for C++ Headers::
221 Generating C Headers for Ada Specifications
223 * Running the C Header Generator::
225 GNAT and Other Compilation Models
227 * Comparison between GNAT and C/C++ Compilation Models::
228 * Comparison between GNAT and Conventional Ada Library Models::
230 Using GNAT Files with External Tools
232 * Using Other Utility Programs with GNAT::
233 * The External Symbol Naming Scheme of GNAT::
235 Building Executable Programs with GNAT
237 * Building with gnatmake::
238 * Compiling with gcc::
239 * Compiler Switches::
241 * Binding with gnatbind::
242 * Linking with gnatlink::
243 * Using the GNU make Utility::
245 Building with gnatmake
248 * Switches for gnatmake::
249 * Mode Switches for gnatmake::
250 * Notes on the Command Line::
251 * How gnatmake Works::
252 * Examples of gnatmake Usage::
256 * Compiling Programs::
257 * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
258 * Order of Compilation Issues::
263 * Alphabetical List of All Switches::
264 * Output and Error Message Control::
265 * Warning Message Control::
266 * Debugging and Assertion Control::
267 * Validity Checking::
270 * Using gcc for Syntax Checking::
271 * Using gcc for Semantic Checking::
272 * Compiling Different Versions of Ada::
273 * Character Set Control::
274 * File Naming Control::
275 * Subprogram Inlining Control::
276 * Auxiliary Output Control::
277 * Debugging Control::
278 * Exception Handling Control::
279 * Units to Sources Mapping Files::
280 * Code Generation Control::
282 Binding with gnatbind
285 * Switches for gnatbind::
286 * Command-Line Access::
287 * Search Paths for gnatbind::
288 * Examples of gnatbind Usage::
290 Switches for gnatbind
292 * Consistency-Checking Modes::
293 * Binder Error Message Control::
294 * Elaboration Control::
296 * Dynamic Allocation Control::
297 * Binding with Non-Ada Main Programs::
298 * Binding Programs with No Main Subprogram::
300 Linking with gnatlink
303 * Switches for gnatlink::
305 Using the GNU make Utility
307 * Using gnatmake in a Makefile::
308 * Automatically Creating a List of Directories::
309 * Generating the Command Line Switches::
310 * Overcoming Command Line Length Limits::
312 GNAT Utility Programs
314 * The File Cleanup Utility gnatclean::
315 * The GNAT Library Browser gnatls::
316 * The Cross-Referencing Tools gnatxref and gnatfind::
317 * The Ada to HTML Converter gnathtml::
319 The File Cleanup Utility gnatclean
321 * Running gnatclean::
322 * Switches for gnatclean::
324 The GNAT Library Browser gnatls
327 * Switches for gnatls::
328 * Example of gnatls Usage::
330 The Cross-Referencing Tools gnatxref and gnatfind
332 * gnatxref Switches::
333 * gnatfind Switches::
334 * Configuration Files for gnatxref and gnatfind::
335 * Regular Expressions in gnatfind and gnatxref::
336 * Examples of gnatxref Usage::
337 * Examples of gnatfind Usage::
339 Examples of gnatxref Usage
342 * Using gnatxref with vi::
344 The Ada to HTML Converter gnathtml
346 * Invoking gnathtml::
347 * Installing gnathtml::
349 GNAT and Program Execution
351 * Running and Debugging Ada Programs::
353 * Improving Performance::
354 * Overflow Check Handling in GNAT::
355 * Performing Dimensionality Analysis in GNAT::
356 * Stack Related Facilities::
357 * Memory Management Issues::
359 Running and Debugging Ada Programs
361 * The GNAT Debugger GDB::
363 * Introduction to GDB Commands::
364 * Using Ada Expressions::
365 * Calling User-Defined Subprograms::
366 * Using the next Command in a Function::
367 * Stopping When Ada Exceptions Are Raised::
369 * Debugging Generic Units::
370 * Remote Debugging with gdbserver::
371 * GNAT Abnormal Termination or Failure to Terminate::
372 * Naming Conventions for GNAT Source Files::
373 * Getting Internal Debugging Information::
375 * Pretty-Printers for the GNAT runtime::
379 * Non-Symbolic Traceback::
380 * Symbolic Traceback::
384 * Profiling an Ada Program with gprof::
386 Profiling an Ada Program with gprof
388 * Compilation for profiling::
389 * Program execution::
391 * Interpretation of profiling results::
393 Improving Performance
395 * Performance Considerations::
396 * Text_IO Suggestions::
397 * Reducing Size of Executables with Unused Subprogram/Data Elimination::
399 Performance Considerations
401 * Controlling Run-Time Checks::
402 * Use of Restrictions::
403 * Optimization Levels::
404 * Debugging Optimized Code::
405 * Inlining of Subprograms::
406 * Floating_Point_Operations::
407 * Vectorization of loops::
408 * Other Optimization Switches::
409 * Optimization and Strict Aliasing::
410 * Aliased Variables and Optimization::
411 * Atomic Variables and Optimization::
412 * Passive Task Optimization::
414 Reducing Size of Executables with Unused Subprogram/Data Elimination
416 * About unused subprogram/data elimination::
417 * Compilation options::
418 * Example of unused subprogram/data elimination::
420 Overflow Check Handling in GNAT
423 * Management of Overflows in GNAT::
424 * Specifying the Desired Mode::
426 * Implementation Notes::
428 Stack Related Facilities
430 * Stack Overflow Checking::
431 * Static Stack Usage Analysis::
432 * Dynamic Stack Usage Analysis::
434 Memory Management Issues
436 * Some Useful Memory Pools::
437 * The GNAT Debug Pool Facility::
439 Platform-Specific Information
441 * Run-Time Libraries::
442 * Specifying a Run-Time Library::
444 * Microsoft Windows Topics::
449 * Summary of Run-Time Configurations::
451 Specifying a Run-Time Library
453 * Choosing the Scheduling Policy::
457 * Required Packages on GNU/Linux::
459 Microsoft Windows Topics
461 * Using GNAT on Windows::
462 * Using a network installation of GNAT::
463 * CONSOLE and WINDOWS subsystems::
465 * Disabling Command Line Argument Expansion::
466 * Mixed-Language Programming on Windows::
467 * Windows Specific Add-Ons::
469 Mixed-Language Programming on Windows
471 * Windows Calling Conventions::
472 * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
473 * Using DLLs with GNAT::
474 * Building DLLs with GNAT Project files::
475 * Building DLLs with GNAT::
476 * Building DLLs with gnatdll::
477 * Ada DLLs and Finalization::
478 * Creating a Spec for Ada DLLs::
479 * GNAT and Windows Resources::
480 * Using GNAT DLLs from Microsoft Visual Studio Applications::
482 * Setting Stack Size from gnatlink::
483 * Setting Heap Size from gnatlink::
485 Windows Calling Conventions
487 * C Calling Convention::
488 * Stdcall Calling Convention::
489 * Win32 Calling Convention::
490 * DLL Calling Convention::
494 * Creating an Ada Spec for the DLL Services::
495 * Creating an Import Library::
497 Building DLLs with gnatdll
499 * Limitations When Using Ada DLLs from Ada::
500 * Exporting Ada Entities::
501 * Ada DLLs and Elaboration::
503 Creating a Spec for Ada DLLs
505 * Creating the Definition File::
508 GNAT and Windows Resources
510 * Building Resources::
511 * Compiling Resources::
516 * Program and DLL Both Built with GCC/GNAT::
517 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
519 Windows Specific Add-Ons
526 * Codesigning the Debugger::
528 Elaboration Order Handling in GNAT
531 * Elaboration Order::
532 * Checking the Elaboration Order::
533 * Controlling the Elaboration Order in Ada::
534 * Controlling the Elaboration Order in GNAT::
535 * Common Elaboration-model Traits::
536 * Dynamic Elaboration Model in GNAT::
537 * Static Elaboration Model in GNAT::
538 * SPARK Elaboration Model in GNAT::
539 * Legacy Elaboration Model in GNAT::
540 * Mixing Elaboration Models::
541 * Elaboration Circularities::
542 * Resolving Elaboration Circularities::
543 * Resolving Task Issues::
544 * Elaboration-related Compiler Switches::
545 * Summary of Procedures for Elaboration Control::
546 * Inspecting the Chosen Elaboration Order::
550 * Basic Assembler Syntax::
551 * A Simple Example of Inline Assembler::
552 * Output Variables in Inline Assembler::
553 * Input Variables in Inline Assembler::
554 * Inlining Inline Assembler Code::
555 * Other Asm Functionality::
557 Other Asm Functionality
559 * The Clobber Parameter::
560 * The Volatile Parameter::
565 @node About This Guide,Getting Started with GNAT,Top,Top
566 @anchor{gnat_ugn/about_this_guide about-this-guide}@anchor{2}@anchor{gnat_ugn/about_this_guide doc}@anchor{3}@anchor{gnat_ugn/about_this_guide gnat-user-s-guide-for-native-platforms}@anchor{4}@anchor{gnat_ugn/about_this_guide id1}@anchor{5}
567 @chapter About This Guide
571 This guide describes the use of GNAT,
572 a compiler and software development
573 toolset for the full Ada programming language.
574 It documents the features of the compiler and tools, and explains
575 how to use them to build Ada applications.
577 GNAT implements Ada 95, Ada 2005 and Ada 2012, and it may also be
578 invoked in Ada 83 compatibility mode.
579 By default, GNAT assumes Ada 2012, but you can override with a
580 compiler switch (@ref{6,,Compiling Different Versions of Ada})
581 to explicitly specify the language version.
582 Throughout this manual, references to 'Ada' without a year suffix
583 apply to all Ada 95/2005/2012 versions of the language.
586 * What This Guide Contains::
587 * What You Should Know before Reading This Guide::
588 * Related Information::
589 * A Note to Readers of Previous Versions of the Manual::
594 @node What This Guide Contains,What You Should Know before Reading This Guide,,About This Guide
595 @anchor{gnat_ugn/about_this_guide what-this-guide-contains}@anchor{7}
596 @section What This Guide Contains
599 This guide contains the following chapters:
605 @ref{8,,Getting Started with GNAT} describes how to get started compiling
606 and running Ada programs with the GNAT Ada programming environment.
609 @ref{9,,The GNAT Compilation Model} describes the compilation model used
613 @ref{a,,Building Executable Programs with GNAT} describes how to use the
614 main GNAT tools to build executable programs, and it also gives examples of
615 using the GNU make utility with GNAT.
618 @ref{b,,GNAT Utility Programs} explains the various utility programs that
619 are included in the GNAT environment
622 @ref{c,,GNAT and Program Execution} covers a number of topics related to
623 running, debugging, and tuning the performace of programs developed
627 Appendices cover several additional topics:
633 @ref{d,,Platform-Specific Information} describes the different run-time
634 library implementations and also presents information on how to use
635 GNAT on several specific platforms
638 @ref{e,,Example of Binder Output File} shows the source code for the binder
639 output file for a sample program.
642 @ref{f,,Elaboration Order Handling in GNAT} describes how GNAT helps
643 you deal with elaboration order issues.
646 @ref{10,,Inline Assembler} shows how to use the inline assembly facility
650 @node What You Should Know before Reading This Guide,Related Information,What This Guide Contains,About This Guide
651 @anchor{gnat_ugn/about_this_guide what-you-should-know-before-reading-this-guide}@anchor{11}
652 @section What You Should Know before Reading This Guide
655 @geindex Ada 95 Language Reference Manual
657 @geindex Ada 2005 Language Reference Manual
659 This guide assumes a basic familiarity with the Ada 95 language, as
660 described in the International Standard ANSI/ISO/IEC-8652:1995, January
662 It does not require knowledge of the features introduced by Ada 2005
664 Reference manuals for Ada 95, Ada 2005, and Ada 2012 are included in
665 the GNAT documentation package.
667 @node Related Information,A Note to Readers of Previous Versions of the Manual,What You Should Know before Reading This Guide,About This Guide
668 @anchor{gnat_ugn/about_this_guide related-information}@anchor{12}
669 @section Related Information
672 For further information about Ada and related tools, please refer to the
679 @cite{Ada 95 Reference Manual}, @cite{Ada 2005 Reference Manual}, and
680 @cite{Ada 2012 Reference Manual}, which contain reference
681 material for the several revisions of the Ada language standard.
684 @cite{GNAT Reference_Manual}, which contains all reference material for the GNAT
685 implementation of Ada.
688 @cite{Using the GNAT Programming Studio}, which describes the GPS
689 Integrated Development Environment.
692 @cite{GNAT Programming Studio Tutorial}, which introduces the
693 main GPS features through examples.
696 @cite{Debugging with GDB},
697 for all details on the use of the GNU source-level debugger.
700 @cite{GNU Emacs Manual},
701 for full information on the extensible editor and programming
705 @node A Note to Readers of Previous Versions of the Manual,Conventions,Related Information,About This Guide
706 @anchor{gnat_ugn/about_this_guide a-note-to-readers-of-previous-versions-of-the-manual}@anchor{13}
707 @section A Note to Readers of Previous Versions of the Manual
710 In early 2015 the GNAT manuals were transitioned to the
711 reStructuredText (rst) / Sphinx documentation generator technology.
712 During that process the @cite{GNAT User's Guide} was reorganized
713 so that related topics would be described together in the same chapter
714 or appendix. Here's a summary of the major changes realized in
715 the new document structure.
721 @ref{9,,The GNAT Compilation Model} has been extended so that it now covers
722 the following material:
728 The @code{gnatname}, @code{gnatkr}, and @code{gnatchop} tools
731 @ref{14,,Configuration Pragmas}
734 @ref{15,,GNAT and Libraries}
737 @ref{16,,Conditional Compilation} including @ref{17,,Preprocessing with gnatprep}
738 and @ref{18,,Integrated Preprocessing}
741 @ref{19,,Generating Ada Bindings for C and C++ headers}
744 @ref{1a,,Using GNAT Files with External Tools}
748 @ref{a,,Building Executable Programs with GNAT} is a new chapter consolidating
749 the following content:
755 @ref{1b,,Building with gnatmake}
758 @ref{1c,,Compiling with gcc}
761 @ref{1d,,Binding with gnatbind}
764 @ref{1e,,Linking with gnatlink}
767 @ref{1f,,Using the GNU make Utility}
771 @ref{b,,GNAT Utility Programs} is a new chapter consolidating the information about several
779 @ref{20,,The File Cleanup Utility gnatclean}
782 @ref{21,,The GNAT Library Browser gnatls}
785 @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind}
788 @ref{23,,The Ada to HTML Converter gnathtml}
792 @ref{c,,GNAT and Program Execution} is a new chapter consolidating the following:
798 @ref{24,,Running and Debugging Ada Programs}
804 @ref{26,,Improving Performance}
807 @ref{27,,Overflow Check Handling in GNAT}
810 @ref{28,,Performing Dimensionality Analysis in GNAT}
813 @ref{29,,Stack Related Facilities}
816 @ref{2a,,Memory Management Issues}
820 @ref{d,,Platform-Specific Information} is a new appendix consolidating the following:
826 @ref{2b,,Run-Time Libraries}
829 @ref{2c,,Microsoft Windows Topics}
832 @ref{2d,,Mac OS Topics}
836 The @emph{Compatibility and Porting Guide} appendix has been moved to the
837 @cite{GNAT Reference Manual}. It now includes a section
838 @emph{Writing Portable Fixed-Point Declarations} which was previously
839 a separate chapter in the @cite{GNAT User's Guide}.
842 @node Conventions,,A Note to Readers of Previous Versions of the Manual,About This Guide
843 @anchor{gnat_ugn/about_this_guide conventions}@anchor{2e}
848 @geindex typographical
850 @geindex Typographical conventions
852 Following are examples of the typographical and graphic conventions used
859 @code{Functions}, @code{utility program names}, @code{standard names},
875 [optional information or parameters]
878 Examples are described by text
881 and then shown this way.
885 Commands that are entered by the user are shown as preceded by a prompt string
886 comprising the @code{$} character followed by a space.
889 Full file names are shown with the '/' character
890 as the directory separator; e.g., @code{parent-dir/subdir/myfile.adb}.
891 If you are using GNAT on a Windows platform, please note that
892 the '\' character should be used instead.
895 @node Getting Started with GNAT,The GNAT Compilation Model,About This Guide,Top
896 @anchor{gnat_ugn/getting_started_with_gnat getting-started-with-gnat}@anchor{8}@anchor{gnat_ugn/getting_started_with_gnat doc}@anchor{2f}@anchor{gnat_ugn/getting_started_with_gnat id1}@anchor{30}
897 @chapter Getting Started with GNAT
900 This chapter describes how to use GNAT's command line interface to build
901 executable Ada programs.
902 On most platforms a visually oriented Integrated Development Environment
903 is also available, the GNAT Programming Studio (GPS).
904 GPS offers a graphical "look and feel", support for development in
905 other programming languages, comprehensive browsing features, and
906 many other capabilities.
907 For information on GPS please refer to
908 @cite{Using the GNAT Programming Studio}.
912 * Running a Simple Ada Program::
913 * Running a Program with Multiple Units::
914 * Using the gnatmake Utility::
918 @node Running GNAT,Running a Simple Ada Program,,Getting Started with GNAT
919 @anchor{gnat_ugn/getting_started_with_gnat running-gnat}@anchor{31}@anchor{gnat_ugn/getting_started_with_gnat id2}@anchor{32}
920 @section Running GNAT
923 Three steps are needed to create an executable file from an Ada source
930 The source file(s) must be compiled.
933 The file(s) must be bound using the GNAT binder.
936 All appropriate object files must be linked to produce an executable.
939 All three steps are most commonly handled by using the @code{gnatmake}
940 utility program that, given the name of the main program, automatically
941 performs the necessary compilation, binding and linking steps.
943 @node Running a Simple Ada Program,Running a Program with Multiple Units,Running GNAT,Getting Started with GNAT
944 @anchor{gnat_ugn/getting_started_with_gnat running-a-simple-ada-program}@anchor{33}@anchor{gnat_ugn/getting_started_with_gnat id3}@anchor{34}
945 @section Running a Simple Ada Program
948 Any text editor may be used to prepare an Ada program.
949 (If Emacs is used, the optional Ada mode may be helpful in laying out the
951 The program text is a normal text file. We will assume in our initial
952 example that you have used your editor to prepare the following
953 standard format text file:
956 with Ada.Text_IO; use Ada.Text_IO;
959 Put_Line ("Hello WORLD!");
963 This file should be named @code{hello.adb}.
964 With the normal default file naming conventions, GNAT requires
966 contain a single compilation unit whose file name is the
968 with periods replaced by hyphens; the
969 extension is @code{ads} for a
970 spec and @code{adb} for a body.
971 You can override this default file naming convention by use of the
972 special pragma @code{Source_File_Name} (for further information please
973 see @ref{35,,Using Other File Names}).
974 Alternatively, if you want to rename your files according to this default
975 convention, which is probably more convenient if you will be using GNAT
976 for all your compilations, then the @code{gnatchop} utility
977 can be used to generate correctly-named source files
978 (see @ref{36,,Renaming Files with gnatchop}).
980 You can compile the program using the following command (@code{$} is used
981 as the command prompt in the examples in this document):
987 @code{gcc} is the command used to run the compiler. This compiler is
988 capable of compiling programs in several languages, including Ada and
989 C. It assumes that you have given it an Ada program if the file extension is
990 either @code{.ads} or @code{.adb}, and it will then call
991 the GNAT compiler to compile the specified file.
993 The @code{-c} switch is required. It tells @code{gcc} to only do a
994 compilation. (For C programs, @code{gcc} can also do linking, but this
995 capability is not used directly for Ada programs, so the @code{-c}
996 switch must always be present.)
998 This compile command generates a file
999 @code{hello.o}, which is the object
1000 file corresponding to your Ada program. It also generates
1001 an 'Ada Library Information' file @code{hello.ali},
1002 which contains additional information used to check
1003 that an Ada program is consistent.
1004 To build an executable file,
1005 use @code{gnatbind} to bind the program
1006 and @code{gnatlink} to link it. The
1007 argument to both @code{gnatbind} and @code{gnatlink} is the name of the
1008 @code{ALI} file, but the default extension of @code{.ali} can
1009 be omitted. This means that in the most common case, the argument
1010 is simply the name of the main program:
1017 A simpler method of carrying out these steps is to use @code{gnatmake},
1018 a master program that invokes all the required
1019 compilation, binding and linking tools in the correct order. In particular,
1020 @code{gnatmake} automatically recompiles any sources that have been
1021 modified since they were last compiled, or sources that depend
1022 on such modified sources, so that 'version skew' is avoided.
1024 @geindex Version skew (avoided by `@w{`}gnatmake`@w{`})
1027 $ gnatmake hello.adb
1030 The result is an executable program called @code{hello}, which can be
1037 assuming that the current directory is on the search path
1038 for executable programs.
1040 and, if all has gone well, you will see:
1046 appear in response to this command.
1048 @node Running a Program with Multiple Units,Using the gnatmake Utility,Running a Simple Ada Program,Getting Started with GNAT
1049 @anchor{gnat_ugn/getting_started_with_gnat id4}@anchor{37}@anchor{gnat_ugn/getting_started_with_gnat running-a-program-with-multiple-units}@anchor{38}
1050 @section Running a Program with Multiple Units
1053 Consider a slightly more complicated example that has three files: a
1054 main program, and the spec and body of a package:
1057 package Greetings is
1062 with Ada.Text_IO; use Ada.Text_IO;
1063 package body Greetings is
1066 Put_Line ("Hello WORLD!");
1069 procedure Goodbye is
1071 Put_Line ("Goodbye WORLD!");
1083 Following the one-unit-per-file rule, place this program in the
1084 following three separate files:
1089 @item @emph{greetings.ads}
1091 spec of package @code{Greetings}
1093 @item @emph{greetings.adb}
1095 body of package @code{Greetings}
1097 @item @emph{gmain.adb}
1099 body of main program
1102 To build an executable version of
1103 this program, we could use four separate steps to compile, bind, and link
1104 the program, as follows:
1108 $ gcc -c greetings.adb
1113 Note that there is no required order of compilation when using GNAT.
1114 In particular it is perfectly fine to compile the main program first.
1115 Also, it is not necessary to compile package specs in the case where
1116 there is an accompanying body; you only need to compile the body. If you want
1117 to submit these files to the compiler for semantic checking and not code
1118 generation, then use the @code{-gnatc} switch:
1121 $ gcc -c greetings.ads -gnatc
1124 Although the compilation can be done in separate steps as in the
1125 above example, in practice it is almost always more convenient
1126 to use the @code{gnatmake} tool. All you need to know in this case
1127 is the name of the main program's source file. The effect of the above four
1128 commands can be achieved with a single one:
1131 $ gnatmake gmain.adb
1134 In the next section we discuss the advantages of using @code{gnatmake} in
1137 @node Using the gnatmake Utility,,Running a Program with Multiple Units,Getting Started with GNAT
1138 @anchor{gnat_ugn/getting_started_with_gnat using-the-gnatmake-utility}@anchor{39}@anchor{gnat_ugn/getting_started_with_gnat id5}@anchor{3a}
1139 @section Using the @code{gnatmake} Utility
1142 If you work on a program by compiling single components at a time using
1143 @code{gcc}, you typically keep track of the units you modify. In order to
1144 build a consistent system, you compile not only these units, but also any
1145 units that depend on the units you have modified.
1146 For example, in the preceding case,
1147 if you edit @code{gmain.adb}, you only need to recompile that file. But if
1148 you edit @code{greetings.ads}, you must recompile both
1149 @code{greetings.adb} and @code{gmain.adb}, because both files contain
1150 units that depend on @code{greetings.ads}.
1152 @code{gnatbind} will warn you if you forget one of these compilation
1153 steps, so that it is impossible to generate an inconsistent program as a
1154 result of forgetting to do a compilation. Nevertheless it is tedious and
1155 error-prone to keep track of dependencies among units.
1156 One approach to handle the dependency-bookkeeping is to use a
1157 makefile. However, makefiles present maintenance problems of their own:
1158 if the dependencies change as you change the program, you must make
1159 sure that the makefile is kept up-to-date manually, which is also an
1160 error-prone process.
1162 The @code{gnatmake} utility takes care of these details automatically.
1163 Invoke it using either one of the following forms:
1166 $ gnatmake gmain.adb
1170 The argument is the name of the file containing the main program;
1171 you may omit the extension. @code{gnatmake}
1172 examines the environment, automatically recompiles any files that need
1173 recompiling, and binds and links the resulting set of object files,
1174 generating the executable file, @code{gmain}.
1175 In a large program, it
1176 can be extremely helpful to use @code{gnatmake}, because working out by hand
1177 what needs to be recompiled can be difficult.
1179 Note that @code{gnatmake} takes into account all the Ada rules that
1180 establish dependencies among units. These include dependencies that result
1181 from inlining subprogram bodies, and from
1182 generic instantiation. Unlike some other
1183 Ada make tools, @code{gnatmake} does not rely on the dependencies that were
1184 found by the compiler on a previous compilation, which may possibly
1185 be wrong when sources change. @code{gnatmake} determines the exact set of
1186 dependencies from scratch each time it is run.
1188 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
1190 @node The GNAT Compilation Model,Building Executable Programs with GNAT,Getting Started with GNAT,Top
1191 @anchor{gnat_ugn/the_gnat_compilation_model doc}@anchor{3b}@anchor{gnat_ugn/the_gnat_compilation_model the-gnat-compilation-model}@anchor{9}@anchor{gnat_ugn/the_gnat_compilation_model id1}@anchor{3c}
1192 @chapter The GNAT Compilation Model
1195 @geindex GNAT compilation model
1197 @geindex Compilation model
1199 This chapter describes the compilation model used by GNAT. Although
1200 similar to that used by other languages such as C and C++, this model
1201 is substantially different from the traditional Ada compilation models,
1202 which are based on a centralized program library. The chapter covers
1203 the following material:
1209 Topics related to source file makeup and naming
1215 @ref{3d,,Source Representation}
1218 @ref{3e,,Foreign Language Representation}
1221 @ref{3f,,File Naming Topics and Utilities}
1225 @ref{14,,Configuration Pragmas}
1228 @ref{40,,Generating Object Files}
1231 @ref{41,,Source Dependencies}
1234 @ref{42,,The Ada Library Information Files}
1237 @ref{43,,Binding an Ada Program}
1240 @ref{15,,GNAT and Libraries}
1243 @ref{16,,Conditional Compilation}
1246 @ref{44,,Mixed Language Programming}
1249 @ref{45,,GNAT and Other Compilation Models}
1252 @ref{1a,,Using GNAT Files with External Tools}
1256 * Source Representation::
1257 * Foreign Language Representation::
1258 * File Naming Topics and Utilities::
1259 * Configuration Pragmas::
1260 * Generating Object Files::
1261 * Source Dependencies::
1262 * The Ada Library Information Files::
1263 * Binding an Ada Program::
1264 * GNAT and Libraries::
1265 * Conditional Compilation::
1266 * Mixed Language Programming::
1267 * GNAT and Other Compilation Models::
1268 * Using GNAT Files with External Tools::
1272 @node Source Representation,Foreign Language Representation,,The GNAT Compilation Model
1273 @anchor{gnat_ugn/the_gnat_compilation_model source-representation}@anchor{3d}@anchor{gnat_ugn/the_gnat_compilation_model id2}@anchor{46}
1274 @section Source Representation
1285 Ada source programs are represented in standard text files, using
1286 Latin-1 coding. Latin-1 is an 8-bit code that includes the familiar
1287 7-bit ASCII set, plus additional characters used for
1288 representing foreign languages (see @ref{3e,,Foreign Language Representation}
1289 for support of non-USA character sets). The format effector characters
1290 are represented using their standard ASCII encodings, as follows:
1295 @multitable {xxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxx}
1372 Source files are in standard text file format. In addition, GNAT will
1373 recognize a wide variety of stream formats, in which the end of
1374 physical lines is marked by any of the following sequences:
1375 @code{LF}, @code{CR}, @code{CR-LF}, or @code{LF-CR}. This is useful
1376 in accommodating files that are imported from other operating systems.
1378 @geindex End of source file; Source file@comma{} end
1380 @geindex SUB (control character)
1382 The end of a source file is normally represented by the physical end of
1383 file. However, the control character @code{16#1A#} (@code{SUB}) is also
1384 recognized as signalling the end of the source file. Again, this is
1385 provided for compatibility with other operating systems where this
1386 code is used to represent the end of file.
1388 @geindex spec (definition)
1389 @geindex compilation (definition)
1391 Each file contains a single Ada compilation unit, including any pragmas
1392 associated with the unit. For example, this means you must place a
1393 package declaration (a package @emph{spec}) and the corresponding body in
1394 separate files. An Ada @emph{compilation} (which is a sequence of
1395 compilation units) is represented using a sequence of files. Similarly,
1396 you will place each subunit or child unit in a separate file.
1398 @node Foreign Language Representation,File Naming Topics and Utilities,Source Representation,The GNAT Compilation Model
1399 @anchor{gnat_ugn/the_gnat_compilation_model foreign-language-representation}@anchor{3e}@anchor{gnat_ugn/the_gnat_compilation_model id3}@anchor{47}
1400 @section Foreign Language Representation
1403 GNAT supports the standard character sets defined in Ada as well as
1404 several other non-standard character sets for use in localized versions
1405 of the compiler (@ref{48,,Character Set Control}).
1409 * Other 8-Bit Codes::
1410 * Wide_Character Encodings::
1411 * Wide_Wide_Character Encodings::
1415 @node Latin-1,Other 8-Bit Codes,,Foreign Language Representation
1416 @anchor{gnat_ugn/the_gnat_compilation_model id4}@anchor{49}@anchor{gnat_ugn/the_gnat_compilation_model latin-1}@anchor{4a}
1422 The basic character set is Latin-1. This character set is defined by ISO
1423 standard 8859, part 1. The lower half (character codes @code{16#00#}
1424 ... @code{16#7F#)} is identical to standard ASCII coding, but the upper
1425 half is used to represent additional characters. These include extended letters
1426 used by European languages, such as French accents, the vowels with umlauts
1427 used in German, and the extra letter A-ring used in Swedish.
1429 @geindex Ada.Characters.Latin_1
1431 For a complete list of Latin-1 codes and their encodings, see the source
1432 file of library unit @code{Ada.Characters.Latin_1} in file
1433 @code{a-chlat1.ads}.
1434 You may use any of these extended characters freely in character or
1435 string literals. In addition, the extended characters that represent
1436 letters can be used in identifiers.
1438 @node Other 8-Bit Codes,Wide_Character Encodings,Latin-1,Foreign Language Representation
1439 @anchor{gnat_ugn/the_gnat_compilation_model other-8-bit-codes}@anchor{4b}@anchor{gnat_ugn/the_gnat_compilation_model id5}@anchor{4c}
1440 @subsection Other 8-Bit Codes
1443 GNAT also supports several other 8-bit coding schemes:
1452 @item @emph{ISO 8859-2 (Latin-2)}
1454 Latin-2 letters allowed in identifiers, with uppercase and lowercase
1465 @item @emph{ISO 8859-3 (Latin-3)}
1467 Latin-3 letters allowed in identifiers, with uppercase and lowercase
1478 @item @emph{ISO 8859-4 (Latin-4)}
1480 Latin-4 letters allowed in identifiers, with uppercase and lowercase
1491 @item @emph{ISO 8859-5 (Cyrillic)}
1493 ISO 8859-5 letters (Cyrillic) allowed in identifiers, with uppercase and
1494 lowercase equivalence.
1497 @geindex ISO 8859-15
1504 @item @emph{ISO 8859-15 (Latin-9)}
1506 ISO 8859-15 (Latin-9) letters allowed in identifiers, with uppercase and
1507 lowercase equivalence
1510 @geindex code page 437 (IBM PC)
1515 @item @emph{IBM PC (code page 437)}
1517 This code page is the normal default for PCs in the U.S. It corresponds
1518 to the original IBM PC character set. This set has some, but not all, of
1519 the extended Latin-1 letters, but these letters do not have the same
1520 encoding as Latin-1. In this mode, these letters are allowed in
1521 identifiers with uppercase and lowercase equivalence.
1524 @geindex code page 850 (IBM PC)
1529 @item @emph{IBM PC (code page 850)}
1531 This code page is a modification of 437 extended to include all the
1532 Latin-1 letters, but still not with the usual Latin-1 encoding. In this
1533 mode, all these letters are allowed in identifiers with uppercase and
1534 lowercase equivalence.
1536 @item @emph{Full Upper 8-bit}
1538 Any character in the range 80-FF allowed in identifiers, and all are
1539 considered distinct. In other words, there are no uppercase and lowercase
1540 equivalences in this range. This is useful in conjunction with
1541 certain encoding schemes used for some foreign character sets (e.g.,
1542 the typical method of representing Chinese characters on the PC).
1544 @item @emph{No Upper-Half}
1546 No upper-half characters in the range 80-FF are allowed in identifiers.
1547 This gives Ada 83 compatibility for identifier names.
1550 For precise data on the encodings permitted, and the uppercase and lowercase
1551 equivalences that are recognized, see the file @code{csets.adb} in
1552 the GNAT compiler sources. You will need to obtain a full source release
1553 of GNAT to obtain this file.
1555 @node Wide_Character Encodings,Wide_Wide_Character Encodings,Other 8-Bit Codes,Foreign Language Representation
1556 @anchor{gnat_ugn/the_gnat_compilation_model id6}@anchor{4d}@anchor{gnat_ugn/the_gnat_compilation_model wide-character-encodings}@anchor{4e}
1557 @subsection Wide_Character Encodings
1560 GNAT allows wide character codes to appear in character and string
1561 literals, and also optionally in identifiers, by means of the following
1562 possible encoding schemes:
1567 @item @emph{Hex Coding}
1569 In this encoding, a wide character is represented by the following five
1576 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1577 characters (using uppercase letters) of the wide character code. For
1578 example, ESC A345 is used to represent the wide character with code
1580 This scheme is compatible with use of the full Wide_Character set.
1582 @item @emph{Upper-Half Coding}
1584 @geindex Upper-Half Coding
1586 The wide character with encoding @code{16#abcd#} where the upper bit is on
1587 (in other words, 'a' is in the range 8-F) is represented as two bytes,
1588 @code{16#ab#} and @code{16#cd#}. The second byte cannot be a format control
1589 character, but is not required to be in the upper half. This method can
1590 be also used for shift-JIS or EUC, where the internal coding matches the
1593 @item @emph{Shift JIS Coding}
1595 @geindex Shift JIS Coding
1597 A wide character is represented by a two-character sequence,
1599 @code{16#cd#}, with the restrictions described for upper-half encoding as
1600 described above. The internal character code is the corresponding JIS
1601 character according to the standard algorithm for Shift-JIS
1602 conversion. Only characters defined in the JIS code set table can be
1603 used with this encoding method.
1605 @item @emph{EUC Coding}
1609 A wide character is represented by a two-character sequence
1611 @code{16#cd#}, with both characters being in the upper half. The internal
1612 character code is the corresponding JIS character according to the EUC
1613 encoding algorithm. Only characters defined in the JIS code set table
1614 can be used with this encoding method.
1616 @item @emph{UTF-8 Coding}
1618 A wide character is represented using
1619 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1620 10646-1/Am.2. Depending on the character value, the representation
1621 is a one, two, or three byte sequence:
1624 16#0000#-16#007f#: 2#0xxxxxxx#
1625 16#0080#-16#07ff#: 2#110xxxxx# 2#10xxxxxx#
1626 16#0800#-16#ffff#: 2#1110xxxx# 2#10xxxxxx# 2#10xxxxxx#
1629 where the @code{xxx} bits correspond to the left-padded bits of the
1630 16-bit character value. Note that all lower half ASCII characters
1631 are represented as ASCII bytes and all upper half characters and
1632 other wide characters are represented as sequences of upper-half
1633 (The full UTF-8 scheme allows for encoding 31-bit characters as
1634 6-byte sequences, and in the following section on wide wide
1635 characters, the use of these sequences is documented).
1637 @item @emph{Brackets Coding}
1639 In this encoding, a wide character is represented by the following eight
1646 where @code{a}, @code{b}, @code{c}, @code{d} are the four hexadecimal
1647 characters (using uppercase letters) of the wide character code. For
1648 example, ['A345'] is used to represent the wide character with code
1649 @code{16#A345#}. It is also possible (though not required) to use the
1650 Brackets coding for upper half characters. For example, the code
1651 @code{16#A3#} can be represented as @code{['A3']}.
1653 This scheme is compatible with use of the full Wide_Character set,
1654 and is also the method used for wide character encoding in some standard
1655 ACATS (Ada Conformity Assessment Test Suite) test suite distributions.
1660 Some of these coding schemes do not permit the full use of the
1661 Ada character set. For example, neither Shift JIS nor EUC allow the
1662 use of the upper half of the Latin-1 set.
1666 @node Wide_Wide_Character Encodings,,Wide_Character Encodings,Foreign Language Representation
1667 @anchor{gnat_ugn/the_gnat_compilation_model id7}@anchor{4f}@anchor{gnat_ugn/the_gnat_compilation_model wide-wide-character-encodings}@anchor{50}
1668 @subsection Wide_Wide_Character Encodings
1671 GNAT allows wide wide character codes to appear in character and string
1672 literals, and also optionally in identifiers, by means of the following
1673 possible encoding schemes:
1678 @item @emph{UTF-8 Coding}
1680 A wide character is represented using
1681 UCS Transformation Format 8 (UTF-8) as defined in Annex R of ISO
1682 10646-1/Am.2. Depending on the character value, the representation
1683 of character codes with values greater than 16#FFFF# is a
1684 is a four, five, or six byte sequence:
1687 16#01_0000#-16#10_FFFF#: 11110xxx 10xxxxxx 10xxxxxx
1689 16#0020_0000#-16#03FF_FFFF#: 111110xx 10xxxxxx 10xxxxxx
1691 16#0400_0000#-16#7FFF_FFFF#: 1111110x 10xxxxxx 10xxxxxx
1692 10xxxxxx 10xxxxxx 10xxxxxx
1695 where the @code{xxx} bits correspond to the left-padded bits of the
1696 32-bit character value.
1698 @item @emph{Brackets Coding}
1700 In this encoding, a wide wide character is represented by the following ten or
1701 twelve byte character sequence:
1705 [ " a b c d e f g h " ]
1708 where @code{a-h} are the six or eight hexadecimal
1709 characters (using uppercase letters) of the wide wide character code. For
1710 example, ["1F4567"] is used to represent the wide wide character with code
1711 @code{16#001F_4567#}.
1713 This scheme is compatible with use of the full Wide_Wide_Character set,
1714 and is also the method used for wide wide character encoding in some standard
1715 ACATS (Ada Conformity Assessment Test Suite) test suite distributions.
1718 @node File Naming Topics and Utilities,Configuration Pragmas,Foreign Language Representation,The GNAT Compilation Model
1719 @anchor{gnat_ugn/the_gnat_compilation_model id8}@anchor{51}@anchor{gnat_ugn/the_gnat_compilation_model file-naming-topics-and-utilities}@anchor{3f}
1720 @section File Naming Topics and Utilities
1723 GNAT has a default file naming scheme and also provides the user with
1724 a high degree of control over how the names and extensions of the
1725 source files correspond to the Ada compilation units that they contain.
1728 * File Naming Rules::
1729 * Using Other File Names::
1730 * Alternative File Naming Schemes::
1731 * Handling Arbitrary File Naming Conventions with gnatname::
1732 * File Name Krunching with gnatkr::
1733 * Renaming Files with gnatchop::
1737 @node File Naming Rules,Using Other File Names,,File Naming Topics and Utilities
1738 @anchor{gnat_ugn/the_gnat_compilation_model file-naming-rules}@anchor{52}@anchor{gnat_ugn/the_gnat_compilation_model id9}@anchor{53}
1739 @subsection File Naming Rules
1742 The default file name is determined by the name of the unit that the
1743 file contains. The name is formed by taking the full expanded name of
1744 the unit and replacing the separating dots with hyphens and using
1745 lowercase for all letters.
1747 An exception arises if the file name generated by the above rules starts
1748 with one of the characters
1749 @code{a}, @code{g}, @code{i}, or @code{s}, and the second character is a
1750 minus. In this case, the character tilde is used in place
1751 of the minus. The reason for this special rule is to avoid clashes with
1752 the standard names for child units of the packages System, Ada,
1753 Interfaces, and GNAT, which use the prefixes
1754 @code{s-}, @code{a-}, @code{i-}, and @code{g-},
1757 The file extension is @code{.ads} for a spec and
1758 @code{.adb} for a body. The following table shows some
1759 examples of these rules.
1764 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
1771 Ada Compilation Unit
1791 @code{arith_functions.ads}
1795 Arith_Functions (package spec)
1799 @code{arith_functions.adb}
1803 Arith_Functions (package body)
1807 @code{func-spec.ads}
1811 Func.Spec (child package spec)
1815 @code{func-spec.adb}
1819 Func.Spec (child package body)
1827 Sub (subunit of Main)
1835 A.Bad (child package body)
1841 Following these rules can result in excessively long
1842 file names if corresponding
1843 unit names are long (for example, if child units or subunits are
1844 heavily nested). An option is available to shorten such long file names
1845 (called file name 'krunching'). This may be particularly useful when
1846 programs being developed with GNAT are to be used on operating systems
1847 with limited file name lengths. @ref{54,,Using gnatkr}.
1849 Of course, no file shortening algorithm can guarantee uniqueness over
1850 all possible unit names; if file name krunching is used, it is your
1851 responsibility to ensure no name clashes occur. Alternatively you
1852 can specify the exact file names that you want used, as described
1853 in the next section. Finally, if your Ada programs are migrating from a
1854 compiler with a different naming convention, you can use the gnatchop
1855 utility to produce source files that follow the GNAT naming conventions.
1856 (For details see @ref{36,,Renaming Files with gnatchop}.)
1858 Note: in the case of Windows or Mac OS operating systems, case is not
1859 significant. So for example on Windows if the canonical name is
1860 @code{main-sub.adb}, you can use the file name @code{Main-Sub.adb} instead.
1861 However, case is significant for other operating systems, so for example,
1862 if you want to use other than canonically cased file names on a Unix system,
1863 you need to follow the procedures described in the next section.
1865 @node Using Other File Names,Alternative File Naming Schemes,File Naming Rules,File Naming Topics and Utilities
1866 @anchor{gnat_ugn/the_gnat_compilation_model id10}@anchor{55}@anchor{gnat_ugn/the_gnat_compilation_model using-other-file-names}@anchor{35}
1867 @subsection Using Other File Names
1872 In the previous section, we have described the default rules used by
1873 GNAT to determine the file name in which a given unit resides. It is
1874 often convenient to follow these default rules, and if you follow them,
1875 the compiler knows without being explicitly told where to find all
1878 @geindex Source_File_Name pragma
1880 However, in some cases, particularly when a program is imported from
1881 another Ada compiler environment, it may be more convenient for the
1882 programmer to specify which file names contain which units. GNAT allows
1883 arbitrary file names to be used by means of the Source_File_Name pragma.
1884 The form of this pragma is as shown in the following examples:
1887 pragma Source_File_Name (My_Utilities.Stacks,
1888 Spec_File_Name => "myutilst_a.ada");
1889 pragma Source_File_name (My_Utilities.Stacks,
1890 Body_File_Name => "myutilst.ada");
1893 As shown in this example, the first argument for the pragma is the unit
1894 name (in this example a child unit). The second argument has the form
1895 of a named association. The identifier
1896 indicates whether the file name is for a spec or a body;
1897 the file name itself is given by a string literal.
1899 The source file name pragma is a configuration pragma, which means that
1900 normally it will be placed in the @code{gnat.adc}
1901 file used to hold configuration
1902 pragmas that apply to a complete compilation environment.
1903 For more details on how the @code{gnat.adc} file is created and used
1904 see @ref{56,,Handling of Configuration Pragmas}.
1908 GNAT allows completely arbitrary file names to be specified using the
1909 source file name pragma. However, if the file name specified has an
1910 extension other than @code{.ads} or @code{.adb} it is necessary to use
1911 a special syntax when compiling the file. The name in this case must be
1912 preceded by the special sequence @code{-x} followed by a space and the name
1913 of the language, here @code{ada}, as in:
1916 $ gcc -c -x ada peculiar_file_name.sim
1919 @code{gnatmake} handles non-standard file names in the usual manner (the
1920 non-standard file name for the main program is simply used as the
1921 argument to gnatmake). Note that if the extension is also non-standard,
1922 then it must be included in the @code{gnatmake} command, it may not
1925 @node Alternative File Naming Schemes,Handling Arbitrary File Naming Conventions with gnatname,Using Other File Names,File Naming Topics and Utilities
1926 @anchor{gnat_ugn/the_gnat_compilation_model id11}@anchor{57}@anchor{gnat_ugn/the_gnat_compilation_model alternative-file-naming-schemes}@anchor{58}
1927 @subsection Alternative File Naming Schemes
1930 @geindex File naming schemes
1931 @geindex alternative
1935 The previous section described the use of the @code{Source_File_Name}
1936 pragma to allow arbitrary names to be assigned to individual source files.
1937 However, this approach requires one pragma for each file, and especially in
1938 large systems can result in very long @code{gnat.adc} files, and also create
1939 a maintenance problem.
1941 @geindex Source_File_Name pragma
1943 GNAT also provides a facility for specifying systematic file naming schemes
1944 other than the standard default naming scheme previously described. An
1945 alternative scheme for naming is specified by the use of
1946 @code{Source_File_Name} pragmas having the following format:
1949 pragma Source_File_Name (
1950 Spec_File_Name => FILE_NAME_PATTERN
1951 [ , Casing => CASING_SPEC]
1952 [ , Dot_Replacement => STRING_LITERAL ] );
1954 pragma Source_File_Name (
1955 Body_File_Name => FILE_NAME_PATTERN
1956 [ , Casing => CASING_SPEC ]
1957 [ , Dot_Replacement => STRING_LITERAL ] ) ;
1959 pragma Source_File_Name (
1960 Subunit_File_Name => FILE_NAME_PATTERN
1961 [ , Casing => CASING_SPEC ]
1962 [ , Dot_Replacement => STRING_LITERAL ] ) ;
1964 FILE_NAME_PATTERN ::= STRING_LITERAL
1965 CASING_SPEC ::= Lowercase | Uppercase | Mixedcase
1968 The @code{FILE_NAME_PATTERN} string shows how the file name is constructed.
1969 It contains a single asterisk character, and the unit name is substituted
1970 systematically for this asterisk. The optional parameter
1971 @code{Casing} indicates
1972 whether the unit name is to be all upper-case letters, all lower-case letters,
1973 or mixed-case. If no
1974 @code{Casing} parameter is used, then the default is all
1977 The optional @code{Dot_Replacement} string is used to replace any periods
1978 that occur in subunit or child unit names. If no @code{Dot_Replacement}
1979 argument is used then separating dots appear unchanged in the resulting
1981 Although the above syntax indicates that the
1982 @code{Casing} argument must appear
1983 before the @code{Dot_Replacement} argument, but it
1984 is also permissible to write these arguments in the opposite order.
1986 As indicated, it is possible to specify different naming schemes for
1987 bodies, specs, and subunits. Quite often the rule for subunits is the
1988 same as the rule for bodies, in which case, there is no need to give
1989 a separate @code{Subunit_File_Name} rule, and in this case the
1990 @code{Body_File_name} rule is used for subunits as well.
1992 The separate rule for subunits can also be used to implement the rather
1993 unusual case of a compilation environment (e.g., a single directory) which
1994 contains a subunit and a child unit with the same unit name. Although
1995 both units cannot appear in the same partition, the Ada Reference Manual
1996 allows (but does not require) the possibility of the two units coexisting
1997 in the same environment.
1999 The file name translation works in the following steps:
2005 If there is a specific @code{Source_File_Name} pragma for the given unit,
2006 then this is always used, and any general pattern rules are ignored.
2009 If there is a pattern type @code{Source_File_Name} pragma that applies to
2010 the unit, then the resulting file name will be used if the file exists. If
2011 more than one pattern matches, the latest one will be tried first, and the
2012 first attempt resulting in a reference to a file that exists will be used.
2015 If no pattern type @code{Source_File_Name} pragma that applies to the unit
2016 for which the corresponding file exists, then the standard GNAT default
2017 naming rules are used.
2020 As an example of the use of this mechanism, consider a commonly used scheme
2021 in which file names are all lower case, with separating periods copied
2022 unchanged to the resulting file name, and specs end with @code{.1.ada}, and
2023 bodies end with @code{.2.ada}. GNAT will follow this scheme if the following
2027 pragma Source_File_Name
2028 (Spec_File_Name => ".1.ada");
2029 pragma Source_File_Name
2030 (Body_File_Name => ".2.ada");
2033 The default GNAT scheme is actually implemented by providing the following
2034 default pragmas internally:
2037 pragma Source_File_Name
2038 (Spec_File_Name => ".ads", Dot_Replacement => "-");
2039 pragma Source_File_Name
2040 (Body_File_Name => ".adb", Dot_Replacement => "-");
2043 Our final example implements a scheme typically used with one of the
2044 Ada 83 compilers, where the separator character for subunits was '__'
2045 (two underscores), specs were identified by adding @code{_.ADA}, bodies
2046 by adding @code{.ADA}, and subunits by
2047 adding @code{.SEP}. All file names were
2048 upper case. Child units were not present of course since this was an
2049 Ada 83 compiler, but it seems reasonable to extend this scheme to use
2050 the same double underscore separator for child units.
2053 pragma Source_File_Name
2054 (Spec_File_Name => "_.ADA",
2055 Dot_Replacement => "__",
2056 Casing = Uppercase);
2057 pragma Source_File_Name
2058 (Body_File_Name => ".ADA",
2059 Dot_Replacement => "__",
2060 Casing = Uppercase);
2061 pragma Source_File_Name
2062 (Subunit_File_Name => ".SEP",
2063 Dot_Replacement => "__",
2064 Casing = Uppercase);
2069 @node Handling Arbitrary File Naming Conventions with gnatname,File Name Krunching with gnatkr,Alternative File Naming Schemes,File Naming Topics and Utilities
2070 @anchor{gnat_ugn/the_gnat_compilation_model handling-arbitrary-file-naming-conventions-with-gnatname}@anchor{59}@anchor{gnat_ugn/the_gnat_compilation_model id12}@anchor{5a}
2071 @subsection Handling Arbitrary File Naming Conventions with @code{gnatname}
2074 @geindex File Naming Conventions
2077 * Arbitrary File Naming Conventions::
2078 * Running gnatname::
2079 * Switches for gnatname::
2080 * Examples of gnatname Usage::
2084 @node Arbitrary File Naming Conventions,Running gnatname,,Handling Arbitrary File Naming Conventions with gnatname
2085 @anchor{gnat_ugn/the_gnat_compilation_model arbitrary-file-naming-conventions}@anchor{5b}@anchor{gnat_ugn/the_gnat_compilation_model id13}@anchor{5c}
2086 @subsubsection Arbitrary File Naming Conventions
2089 The GNAT compiler must be able to know the source file name of a compilation
2090 unit. When using the standard GNAT default file naming conventions
2091 (@code{.ads} for specs, @code{.adb} for bodies), the GNAT compiler
2092 does not need additional information.
2094 When the source file names do not follow the standard GNAT default file naming
2095 conventions, the GNAT compiler must be given additional information through
2096 a configuration pragmas file (@ref{14,,Configuration Pragmas})
2098 When the non-standard file naming conventions are well-defined,
2099 a small number of pragmas @code{Source_File_Name} specifying a naming pattern
2100 (@ref{58,,Alternative File Naming Schemes}) may be sufficient. However,
2101 if the file naming conventions are irregular or arbitrary, a number
2102 of pragma @code{Source_File_Name} for individual compilation units
2104 To help maintain the correspondence between compilation unit names and
2105 source file names within the compiler,
2106 GNAT provides a tool @code{gnatname} to generate the required pragmas for a
2109 @node Running gnatname,Switches for gnatname,Arbitrary File Naming Conventions,Handling Arbitrary File Naming Conventions with gnatname
2110 @anchor{gnat_ugn/the_gnat_compilation_model running-gnatname}@anchor{5d}@anchor{gnat_ugn/the_gnat_compilation_model id14}@anchor{5e}
2111 @subsubsection Running @code{gnatname}
2114 The usual form of the @code{gnatname} command is:
2117 $ gnatname [ switches ] naming_pattern [ naming_patterns ]
2118 [--and [ switches ] naming_pattern [ naming_patterns ]]
2121 All of the arguments are optional. If invoked without any argument,
2122 @code{gnatname} will display its usage.
2124 When used with at least one naming pattern, @code{gnatname} will attempt to
2125 find all the compilation units in files that follow at least one of the
2126 naming patterns. To find these compilation units,
2127 @code{gnatname} will use the GNAT compiler in syntax-check-only mode on all
2130 One or several Naming Patterns may be given as arguments to @code{gnatname}.
2131 Each Naming Pattern is enclosed between double quotes (or single
2133 A Naming Pattern is a regular expression similar to the wildcard patterns
2134 used in file names by the Unix shells or the DOS prompt.
2136 @code{gnatname} may be called with several sections of directories/patterns.
2137 Sections are separated by the switch @code{--and}. In each section, there must be
2138 at least one pattern. If no directory is specified in a section, the current
2139 directory (or the project directory if @code{-P} is used) is implied.
2140 The options other that the directory switches and the patterns apply globally
2141 even if they are in different sections.
2143 Examples of Naming Patterns are:
2151 For a more complete description of the syntax of Naming Patterns,
2152 see the second kind of regular expressions described in @code{g-regexp.ads}
2153 (the 'Glob' regular expressions).
2155 When invoked without the switch @code{-P}, @code{gnatname} will create a
2156 configuration pragmas file @code{gnat.adc} in the current working directory,
2157 with pragmas @code{Source_File_Name} for each file that contains a valid Ada
2160 @node Switches for gnatname,Examples of gnatname Usage,Running gnatname,Handling Arbitrary File Naming Conventions with gnatname
2161 @anchor{gnat_ugn/the_gnat_compilation_model id15}@anchor{5f}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatname}@anchor{60}
2162 @subsubsection Switches for @code{gnatname}
2165 Switches for @code{gnatname} must precede any specified Naming Pattern.
2167 You may specify any of the following switches to @code{gnatname}:
2169 @geindex --version (gnatname)
2174 @item @code{--version}
2176 Display Copyright and version, then exit disregarding all other options.
2179 @geindex --help (gnatname)
2186 If @code{--version} was not used, display usage, then exit disregarding
2189 @item @code{--subdirs=@emph{dir}}
2191 Real object, library or exec directories are subdirectories <dir> of the
2194 @item @code{--no-backup}
2196 Do not create a backup copy of an existing project file.
2200 Start another section of directories/patterns.
2203 @geindex -c (gnatname)
2208 @item @code{-c@emph{filename}}
2210 Create a configuration pragmas file @code{filename} (instead of the default
2212 There may be zero, one or more space between @code{-c} and
2214 @code{filename} may include directory information. @code{filename} must be
2215 writable. There may be only one switch @code{-c}.
2216 When a switch @code{-c} is
2217 specified, no switch @code{-P} may be specified (see below).
2220 @geindex -d (gnatname)
2225 @item @code{-d@emph{dir}}
2227 Look for source files in directory @code{dir}. There may be zero, one or more
2228 spaces between @code{-d} and @code{dir}.
2229 @code{dir} may end with @code{/**}, that is it may be of the form
2230 @code{root_dir/**}. In this case, the directory @code{root_dir} and all of its
2231 subdirectories, recursively, have to be searched for sources.
2232 When a switch @code{-d}
2233 is specified, the current working directory will not be searched for source
2234 files, unless it is explicitly specified with a @code{-d}
2235 or @code{-D} switch.
2236 Several switches @code{-d} may be specified.
2237 If @code{dir} is a relative path, it is relative to the directory of
2238 the configuration pragmas file specified with switch
2240 or to the directory of the project file specified with switch
2242 if neither switch @code{-c}
2243 nor switch @code{-P} are specified, it is relative to the
2244 current working directory. The directory
2245 specified with switch @code{-d} must exist and be readable.
2248 @geindex -D (gnatname)
2253 @item @code{-D@emph{filename}}
2255 Look for source files in all directories listed in text file @code{filename}.
2256 There may be zero, one or more spaces between @code{-D}
2257 and @code{filename}.
2258 @code{filename} must be an existing, readable text file.
2259 Each nonempty line in @code{filename} must be a directory.
2260 Specifying switch @code{-D} is equivalent to specifying as many
2261 switches @code{-d} as there are nonempty lines in
2266 Follow symbolic links when processing project files.
2268 @geindex -f (gnatname)
2270 @item @code{-f@emph{pattern}}
2272 Foreign patterns. Using this switch, it is possible to add sources of languages
2273 other than Ada to the list of sources of a project file.
2274 It is only useful if a -P switch is used.
2278 gnatname -Pprj -f"*.c" "*.ada"
2281 will look for Ada units in all files with the @code{.ada} extension,
2282 and will add to the list of file for project @code{prj.gpr} the C files
2283 with extension @code{.c}.
2285 @geindex -h (gnatname)
2289 Output usage (help) information. The output is written to @code{stdout}.
2291 @geindex -P (gnatname)
2293 @item @code{-P@emph{proj}}
2295 Create or update project file @code{proj}. There may be zero, one or more space
2296 between @code{-P} and @code{proj}. @code{proj} may include directory
2297 information. @code{proj} must be writable.
2298 There may be only one switch @code{-P}.
2299 When a switch @code{-P} is specified,
2300 no switch @code{-c} may be specified.
2301 On all platforms, except on VMS, when @code{gnatname} is invoked for an
2302 existing project file <proj>.gpr, a backup copy of the project file is created
2303 in the project directory with file name <proj>.gpr.saved_x. 'x' is the first
2304 non negative number that makes this backup copy a new file.
2306 @geindex -v (gnatname)
2310 Verbose mode. Output detailed explanation of behavior to @code{stdout}.
2311 This includes name of the file written, the name of the directories to search
2312 and, for each file in those directories whose name matches at least one of
2313 the Naming Patterns, an indication of whether the file contains a unit,
2314 and if so the name of the unit.
2317 @geindex -v -v (gnatname)
2324 Very Verbose mode. In addition to the output produced in verbose mode,
2325 for each file in the searched directories whose name matches none of
2326 the Naming Patterns, an indication is given that there is no match.
2328 @geindex -x (gnatname)
2330 @item @code{-x@emph{pattern}}
2332 Excluded patterns. Using this switch, it is possible to exclude some files
2333 that would match the name patterns. For example,
2336 gnatname -x "*_nt.ada" "*.ada"
2339 will look for Ada units in all files with the @code{.ada} extension,
2340 except those whose names end with @code{_nt.ada}.
2343 @node Examples of gnatname Usage,,Switches for gnatname,Handling Arbitrary File Naming Conventions with gnatname
2344 @anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatname-usage}@anchor{61}@anchor{gnat_ugn/the_gnat_compilation_model id16}@anchor{62}
2345 @subsubsection Examples of @code{gnatname} Usage
2349 $ gnatname -c /home/me/names.adc -d sources "[a-z]*.ada*"
2352 In this example, the directory @code{/home/me} must already exist
2353 and be writable. In addition, the directory
2354 @code{/home/me/sources} (specified by
2355 @code{-d sources}) must exist and be readable.
2357 Note the optional spaces after @code{-c} and @code{-d}.
2360 $ gnatname -P/home/me/proj -x "*_nt_body.ada"
2361 -dsources -dsources/plus -Dcommon_dirs.txt "body_*" "spec_*"
2364 Note that several switches @code{-d} may be used,
2365 even in conjunction with one or several switches
2366 @code{-D}. Several Naming Patterns and one excluded pattern
2367 are used in this example.
2369 @node File Name Krunching with gnatkr,Renaming Files with gnatchop,Handling Arbitrary File Naming Conventions with gnatname,File Naming Topics and Utilities
2370 @anchor{gnat_ugn/the_gnat_compilation_model file-name-krunching-with-gnatkr}@anchor{63}@anchor{gnat_ugn/the_gnat_compilation_model id17}@anchor{64}
2371 @subsection File Name Krunching with @code{gnatkr}
2376 This section discusses the method used by the compiler to shorten
2377 the default file names chosen for Ada units so that they do not
2378 exceed the maximum length permitted. It also describes the
2379 @code{gnatkr} utility that can be used to determine the result of
2380 applying this shortening.
2385 * Krunching Method::
2386 * Examples of gnatkr Usage::
2390 @node About gnatkr,Using gnatkr,,File Name Krunching with gnatkr
2391 @anchor{gnat_ugn/the_gnat_compilation_model id18}@anchor{65}@anchor{gnat_ugn/the_gnat_compilation_model about-gnatkr}@anchor{66}
2392 @subsubsection About @code{gnatkr}
2395 The default file naming rule in GNAT
2396 is that the file name must be derived from
2397 the unit name. The exact default rule is as follows:
2403 Take the unit name and replace all dots by hyphens.
2406 If such a replacement occurs in the
2407 second character position of a name, and the first character is
2408 @code{a}, @code{g}, @code{s}, or @code{i},
2409 then replace the dot by the character
2413 The reason for this exception is to avoid clashes
2414 with the standard names for children of System, Ada, Interfaces,
2415 and GNAT, which use the prefixes
2416 @code{s-}, @code{a-}, @code{i-}, and @code{g-},
2420 The @code{-gnatk@emph{nn}}
2421 switch of the compiler activates a 'krunching'
2422 circuit that limits file names to nn characters (where nn is a decimal
2425 The @code{gnatkr} utility can be used to determine the krunched name for
2426 a given file, when krunched to a specified maximum length.
2428 @node Using gnatkr,Krunching Method,About gnatkr,File Name Krunching with gnatkr
2429 @anchor{gnat_ugn/the_gnat_compilation_model id19}@anchor{67}@anchor{gnat_ugn/the_gnat_compilation_model using-gnatkr}@anchor{54}
2430 @subsubsection Using @code{gnatkr}
2433 The @code{gnatkr} command has the form:
2436 $ gnatkr name [ length ]
2439 @code{name} is the uncrunched file name, derived from the name of the unit
2440 in the standard manner described in the previous section (i.e., in particular
2441 all dots are replaced by hyphens). The file name may or may not have an
2442 extension (defined as a suffix of the form period followed by arbitrary
2443 characters other than period). If an extension is present then it will
2444 be preserved in the output. For example, when krunching @code{hellofile.ads}
2445 to eight characters, the result will be hellofil.ads.
2447 Note: for compatibility with previous versions of @code{gnatkr} dots may
2448 appear in the name instead of hyphens, but the last dot will always be
2449 taken as the start of an extension. So if @code{gnatkr} is given an argument
2450 such as @code{Hello.World.adb} it will be treated exactly as if the first
2451 period had been a hyphen, and for example krunching to eight characters
2452 gives the result @code{hellworl.adb}.
2454 Note that the result is always all lower case.
2455 Characters of the other case are folded as required.
2457 @code{length} represents the length of the krunched name. The default
2458 when no argument is given is 8 characters. A length of zero stands for
2459 unlimited, in other words do not chop except for system files where the
2460 implied crunching length is always eight characters.
2462 The output is the krunched name. The output has an extension only if the
2463 original argument was a file name with an extension.
2465 @node Krunching Method,Examples of gnatkr Usage,Using gnatkr,File Name Krunching with gnatkr
2466 @anchor{gnat_ugn/the_gnat_compilation_model id20}@anchor{68}@anchor{gnat_ugn/the_gnat_compilation_model krunching-method}@anchor{69}
2467 @subsubsection Krunching Method
2470 The initial file name is determined by the name of the unit that the file
2471 contains. The name is formed by taking the full expanded name of the
2472 unit and replacing the separating dots with hyphens and
2474 for all letters, except that a hyphen in the second character position is
2475 replaced by a tilde if the first character is
2476 @code{a}, @code{i}, @code{g}, or @code{s}.
2477 The extension is @code{.ads} for a
2478 spec and @code{.adb} for a body.
2479 Krunching does not affect the extension, but the file name is shortened to
2480 the specified length by following these rules:
2486 The name is divided into segments separated by hyphens, tildes or
2487 underscores and all hyphens, tildes, and underscores are
2488 eliminated. If this leaves the name short enough, we are done.
2491 If the name is too long, the longest segment is located (left-most
2492 if there are two of equal length), and shortened by dropping
2493 its last character. This is repeated until the name is short enough.
2495 As an example, consider the krunching of @code{our-strings-wide_fixed.adb}
2496 to fit the name into 8 characters as required by some operating systems:
2499 our-strings-wide_fixed 22
2500 our strings wide fixed 19
2501 our string wide fixed 18
2502 our strin wide fixed 17
2503 our stri wide fixed 16
2504 our stri wide fixe 15
2505 our str wide fixe 14
2512 Final file name: oustwifi.adb
2516 The file names for all predefined units are always krunched to eight
2517 characters. The krunching of these predefined units uses the following
2518 special prefix replacements:
2521 @multitable {xxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx}
2565 These system files have a hyphen in the second character position. That
2566 is why normal user files replace such a character with a
2567 tilde, to avoid confusion with system file names.
2569 As an example of this special rule, consider
2570 @code{ada-strings-wide_fixed.adb}, which gets krunched as follows:
2573 ada-strings-wide_fixed 22
2574 a- strings wide fixed 18
2575 a- string wide fixed 17
2576 a- strin wide fixed 16
2577 a- stri wide fixed 15
2578 a- stri wide fixe 14
2585 Final file name: a-stwifi.adb
2589 Of course no file shortening algorithm can guarantee uniqueness over all
2590 possible unit names, and if file name krunching is used then it is your
2591 responsibility to ensure that no name clashes occur. The utility
2592 program @code{gnatkr} is supplied for conveniently determining the
2593 krunched name of a file.
2595 @node Examples of gnatkr Usage,,Krunching Method,File Name Krunching with gnatkr
2596 @anchor{gnat_ugn/the_gnat_compilation_model id21}@anchor{6a}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatkr-usage}@anchor{6b}
2597 @subsubsection Examples of @code{gnatkr} Usage
2601 $ gnatkr very_long_unit_name.ads --> velounna.ads
2602 $ gnatkr grandparent-parent-child.ads --> grparchi.ads
2603 $ gnatkr Grandparent.Parent.Child.ads --> grparchi.ads
2604 $ gnatkr grandparent-parent-child --> grparchi
2605 $ gnatkr very_long_unit_name.ads/count=6 --> vlunna.ads
2606 $ gnatkr very_long_unit_name.ads/count=0 --> very_long_unit_name.ads
2609 @node Renaming Files with gnatchop,,File Name Krunching with gnatkr,File Naming Topics and Utilities
2610 @anchor{gnat_ugn/the_gnat_compilation_model id22}@anchor{6c}@anchor{gnat_ugn/the_gnat_compilation_model renaming-files-with-gnatchop}@anchor{36}
2611 @subsection Renaming Files with @code{gnatchop}
2616 This section discusses how to handle files with multiple units by using
2617 the @code{gnatchop} utility. This utility is also useful in renaming
2618 files to meet the standard GNAT default file naming conventions.
2621 * Handling Files with Multiple Units::
2622 * Operating gnatchop in Compilation Mode::
2623 * Command Line for gnatchop::
2624 * Switches for gnatchop::
2625 * Examples of gnatchop Usage::
2629 @node Handling Files with Multiple Units,Operating gnatchop in Compilation Mode,,Renaming Files with gnatchop
2630 @anchor{gnat_ugn/the_gnat_compilation_model id23}@anchor{6d}@anchor{gnat_ugn/the_gnat_compilation_model handling-files-with-multiple-units}@anchor{6e}
2631 @subsubsection Handling Files with Multiple Units
2634 The basic compilation model of GNAT requires that a file submitted to the
2635 compiler have only one unit and there be a strict correspondence
2636 between the file name and the unit name.
2638 The @code{gnatchop} utility allows both of these rules to be relaxed,
2639 allowing GNAT to process files which contain multiple compilation units
2640 and files with arbitrary file names. @code{gnatchop}
2641 reads the specified file and generates one or more output files,
2642 containing one unit per file. The unit and the file name correspond,
2643 as required by GNAT.
2645 If you want to permanently restructure a set of 'foreign' files so that
2646 they match the GNAT rules, and do the remaining development using the
2647 GNAT structure, you can simply use @code{gnatchop} once, generate the
2648 new set of files and work with them from that point on.
2650 Alternatively, if you want to keep your files in the 'foreign' format,
2651 perhaps to maintain compatibility with some other Ada compilation
2652 system, you can set up a procedure where you use @code{gnatchop} each
2653 time you compile, regarding the source files that it writes as temporary
2654 files that you throw away.
2656 Note that if your file containing multiple units starts with a byte order
2657 mark (BOM) specifying UTF-8 encoding, then the files generated by gnatchop
2658 will each start with a copy of this BOM, meaning that they can be compiled
2659 automatically in UTF-8 mode without needing to specify an explicit encoding.
2661 @node Operating gnatchop in Compilation Mode,Command Line for gnatchop,Handling Files with Multiple Units,Renaming Files with gnatchop
2662 @anchor{gnat_ugn/the_gnat_compilation_model operating-gnatchop-in-compilation-mode}@anchor{6f}@anchor{gnat_ugn/the_gnat_compilation_model id24}@anchor{70}
2663 @subsubsection Operating gnatchop in Compilation Mode
2666 The basic function of @code{gnatchop} is to take a file with multiple units
2667 and split it into separate files. The boundary between files is reasonably
2668 clear, except for the issue of comments and pragmas. In default mode, the
2669 rule is that any pragmas between units belong to the previous unit, except
2670 that configuration pragmas always belong to the following unit. Any comments
2671 belong to the following unit. These rules
2672 almost always result in the right choice of
2673 the split point without needing to mark it explicitly and most users will
2674 find this default to be what they want. In this default mode it is incorrect to
2675 submit a file containing only configuration pragmas, or one that ends in
2676 configuration pragmas, to @code{gnatchop}.
2678 However, using a special option to activate 'compilation mode',
2680 can perform another function, which is to provide exactly the semantics
2681 required by the RM for handling of configuration pragmas in a compilation.
2682 In the absence of configuration pragmas (at the main file level), this
2683 option has no effect, but it causes such configuration pragmas to be handled
2684 in a quite different manner.
2686 First, in compilation mode, if @code{gnatchop} is given a file that consists of
2687 only configuration pragmas, then this file is appended to the
2688 @code{gnat.adc} file in the current directory. This behavior provides
2689 the required behavior described in the RM for the actions to be taken
2690 on submitting such a file to the compiler, namely that these pragmas
2691 should apply to all subsequent compilations in the same compilation
2692 environment. Using GNAT, the current directory, possibly containing a
2693 @code{gnat.adc} file is the representation
2694 of a compilation environment. For more information on the
2695 @code{gnat.adc} file, see @ref{56,,Handling of Configuration Pragmas}.
2697 Second, in compilation mode, if @code{gnatchop}
2698 is given a file that starts with
2699 configuration pragmas, and contains one or more units, then these
2700 configuration pragmas are prepended to each of the chopped files. This
2701 behavior provides the required behavior described in the RM for the
2702 actions to be taken on compiling such a file, namely that the pragmas
2703 apply to all units in the compilation, but not to subsequently compiled
2706 Finally, if configuration pragmas appear between units, they are appended
2707 to the previous unit. This results in the previous unit being illegal,
2708 since the compiler does not accept configuration pragmas that follow
2709 a unit. This provides the required RM behavior that forbids configuration
2710 pragmas other than those preceding the first compilation unit of a
2713 For most purposes, @code{gnatchop} will be used in default mode. The
2714 compilation mode described above is used only if you need exactly
2715 accurate behavior with respect to compilations, and you have files
2716 that contain multiple units and configuration pragmas. In this
2717 circumstance the use of @code{gnatchop} with the compilation mode
2718 switch provides the required behavior, and is for example the mode
2719 in which GNAT processes the ACVC tests.
2721 @node Command Line for gnatchop,Switches for gnatchop,Operating gnatchop in Compilation Mode,Renaming Files with gnatchop
2722 @anchor{gnat_ugn/the_gnat_compilation_model id25}@anchor{71}@anchor{gnat_ugn/the_gnat_compilation_model command-line-for-gnatchop}@anchor{72}
2723 @subsubsection Command Line for @code{gnatchop}
2726 The @code{gnatchop} command has the form:
2729 $ gnatchop switches file_name [file_name ...]
2733 The only required argument is the file name of the file to be chopped.
2734 There are no restrictions on the form of this file name. The file itself
2735 contains one or more Ada units, in normal GNAT format, concatenated
2736 together. As shown, more than one file may be presented to be chopped.
2738 When run in default mode, @code{gnatchop} generates one output file in
2739 the current directory for each unit in each of the files.
2741 @code{directory}, if specified, gives the name of the directory to which
2742 the output files will be written. If it is not specified, all files are
2743 written to the current directory.
2745 For example, given a
2746 file called @code{hellofiles} containing
2751 with Ada.Text_IO; use Ada.Text_IO;
2761 $ gnatchop hellofiles
2764 generates two files in the current directory, one called
2765 @code{hello.ads} containing the single line that is the procedure spec,
2766 and the other called @code{hello.adb} containing the remaining text. The
2767 original file is not affected. The generated files can be compiled in
2770 When gnatchop is invoked on a file that is empty or that contains only empty
2771 lines and/or comments, gnatchop will not fail, but will not produce any
2774 For example, given a
2775 file called @code{toto.txt} containing
2787 will not produce any new file and will result in the following warnings:
2790 toto.txt:1:01: warning: empty file, contains no compilation units
2791 no compilation units found
2792 no source files written
2795 @node Switches for gnatchop,Examples of gnatchop Usage,Command Line for gnatchop,Renaming Files with gnatchop
2796 @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatchop}@anchor{73}@anchor{gnat_ugn/the_gnat_compilation_model id26}@anchor{74}
2797 @subsubsection Switches for @code{gnatchop}
2800 @code{gnatchop} recognizes the following switches:
2802 @geindex --version (gnatchop)
2807 @item @code{--version}
2809 Display Copyright and version, then exit disregarding all other options.
2812 @geindex --help (gnatchop)
2819 If @code{--version} was not used, display usage, then exit disregarding
2823 @geindex -c (gnatchop)
2830 Causes @code{gnatchop} to operate in compilation mode, in which
2831 configuration pragmas are handled according to strict RM rules. See
2832 previous section for a full description of this mode.
2834 @item @code{-gnat@emph{xxx}}
2836 This passes the given @code{-gnat@emph{xxx}} switch to @code{gnat} which is
2837 used to parse the given file. Not all @emph{xxx} options make sense,
2838 but for example, the use of @code{-gnati2} allows @code{gnatchop} to
2839 process a source file that uses Latin-2 coding for identifiers.
2843 Causes @code{gnatchop} to generate a brief help summary to the standard
2844 output file showing usage information.
2847 @geindex -k (gnatchop)
2852 @item @code{-k@emph{mm}}
2854 Limit generated file names to the specified number @code{mm}
2856 This is useful if the
2857 resulting set of files is required to be interoperable with systems
2858 which limit the length of file names.
2859 No space is allowed between the @code{-k} and the numeric value. The numeric
2860 value may be omitted in which case a default of @code{-k8},
2862 with DOS-like file systems, is used. If no @code{-k} switch
2864 there is no limit on the length of file names.
2867 @geindex -p (gnatchop)
2874 Causes the file modification time stamp of the input file to be
2875 preserved and used for the time stamp of the output file(s). This may be
2876 useful for preserving coherency of time stamps in an environment where
2877 @code{gnatchop} is used as part of a standard build process.
2880 @geindex -q (gnatchop)
2887 Causes output of informational messages indicating the set of generated
2888 files to be suppressed. Warnings and error messages are unaffected.
2891 @geindex -r (gnatchop)
2893 @geindex Source_Reference pragmas
2900 Generate @code{Source_Reference} pragmas. Use this switch if the output
2901 files are regarded as temporary and development is to be done in terms
2902 of the original unchopped file. This switch causes
2903 @code{Source_Reference} pragmas to be inserted into each of the
2904 generated files to refers back to the original file name and line number.
2905 The result is that all error messages refer back to the original
2907 In addition, the debugging information placed into the object file (when
2908 the @code{-g} switch of @code{gcc} or @code{gnatmake} is
2910 also refers back to this original file so that tools like profilers and
2911 debuggers will give information in terms of the original unchopped file.
2913 If the original file to be chopped itself contains
2914 a @code{Source_Reference}
2915 pragma referencing a third file, then gnatchop respects
2916 this pragma, and the generated @code{Source_Reference} pragmas
2917 in the chopped file refer to the original file, with appropriate
2918 line numbers. This is particularly useful when @code{gnatchop}
2919 is used in conjunction with @code{gnatprep} to compile files that
2920 contain preprocessing statements and multiple units.
2923 @geindex -v (gnatchop)
2930 Causes @code{gnatchop} to operate in verbose mode. The version
2931 number and copyright notice are output, as well as exact copies of
2932 the gnat1 commands spawned to obtain the chop control information.
2935 @geindex -w (gnatchop)
2942 Overwrite existing file names. Normally @code{gnatchop} regards it as a
2943 fatal error if there is already a file with the same name as a
2944 file it would otherwise output, in other words if the files to be
2945 chopped contain duplicated units. This switch bypasses this
2946 check, and causes all but the last instance of such duplicated
2947 units to be skipped.
2950 @geindex --GCC= (gnatchop)
2955 @item @code{--GCC=@emph{xxxx}}
2957 Specify the path of the GNAT parser to be used. When this switch is used,
2958 no attempt is made to add the prefix to the GNAT parser executable.
2961 @node Examples of gnatchop Usage,,Switches for gnatchop,Renaming Files with gnatchop
2962 @anchor{gnat_ugn/the_gnat_compilation_model id27}@anchor{75}@anchor{gnat_ugn/the_gnat_compilation_model examples-of-gnatchop-usage}@anchor{76}
2963 @subsubsection Examples of @code{gnatchop} Usage
2967 $ gnatchop -w hello_s.ada prerelease/files
2970 Chops the source file @code{hello_s.ada}. The output files will be
2971 placed in the directory @code{prerelease/files},
2973 files with matching names in that directory (no files in the current
2974 directory are modified).
2980 Chops the source file @code{archive}
2981 into the current directory. One
2982 useful application of @code{gnatchop} is in sending sets of sources
2983 around, for example in email messages. The required sources are simply
2984 concatenated (for example, using a Unix @code{cat}
2986 @code{gnatchop} is used at the other end to reconstitute the original
2990 $ gnatchop file1 file2 file3 direc
2993 Chops all units in files @code{file1}, @code{file2}, @code{file3}, placing
2994 the resulting files in the directory @code{direc}. Note that if any units
2995 occur more than once anywhere within this set of files, an error message
2996 is generated, and no files are written. To override this check, use the
2998 in which case the last occurrence in the last file will
2999 be the one that is output, and earlier duplicate occurrences for a given
3000 unit will be skipped.
3002 @node Configuration Pragmas,Generating Object Files,File Naming Topics and Utilities,The GNAT Compilation Model
3003 @anchor{gnat_ugn/the_gnat_compilation_model id28}@anchor{77}@anchor{gnat_ugn/the_gnat_compilation_model configuration-pragmas}@anchor{14}
3004 @section Configuration Pragmas
3007 @geindex Configuration pragmas
3010 @geindex configuration
3012 Configuration pragmas include those pragmas described as
3013 such in the Ada Reference Manual, as well as
3014 implementation-dependent pragmas that are configuration pragmas.
3015 See the @code{Implementation_Defined_Pragmas} chapter in the
3016 @cite{GNAT_Reference_Manual} for details on these
3017 additional GNAT-specific configuration pragmas.
3018 Most notably, the pragma @code{Source_File_Name}, which allows
3019 specifying non-default names for source files, is a configuration
3020 pragma. The following is a complete list of configuration pragmas
3030 Allow_Integer_Address
3033 Assume_No_Invalid_Values
3035 Check_Float_Overflow
3039 Compile_Time_Warning
3041 Compiler_Unit_Warning
3043 Convention_Identifier
3046 Default_Scalar_Storage_Order
3047 Default_Storage_Pool
3048 Disable_Atomic_Synchronization
3052 Enable_Atomic_Synchronization
3055 External_Name_Casing
3064 No_Component_Reordering
3065 No_Heap_Finalization
3071 Overriding_Renamings
3072 Partition_Elaboration_Policy
3075 Prefix_Exception_Messages
3076 Priority_Specific_Dispatching
3079 Propagate_Exceptions
3086 Restrictions_Warnings
3088 Short_Circuit_And_Or
3091 Source_File_Name_Project
3095 Suppress_Exception_Locations
3096 Task_Dispatching_Policy
3097 Unevaluated_Use_Of_Old
3104 Wide_Character_Encoding
3108 * Handling of Configuration Pragmas::
3109 * The Configuration Pragmas Files::
3113 @node Handling of Configuration Pragmas,The Configuration Pragmas Files,,Configuration Pragmas
3114 @anchor{gnat_ugn/the_gnat_compilation_model id29}@anchor{78}@anchor{gnat_ugn/the_gnat_compilation_model handling-of-configuration-pragmas}@anchor{56}
3115 @subsection Handling of Configuration Pragmas
3118 Configuration pragmas may either appear at the start of a compilation
3119 unit, or they can appear in a configuration pragma file to apply to
3120 all compilations performed in a given compilation environment.
3122 GNAT also provides the @code{gnatchop} utility to provide an automatic
3123 way to handle configuration pragmas following the semantics for
3124 compilations (that is, files with multiple units), described in the RM.
3125 See @ref{6f,,Operating gnatchop in Compilation Mode} for details.
3126 However, for most purposes, it will be more convenient to edit the
3127 @code{gnat.adc} file that contains configuration pragmas directly,
3128 as described in the following section.
3130 In the case of @code{Restrictions} pragmas appearing as configuration
3131 pragmas in individual compilation units, the exact handling depends on
3132 the type of restriction.
3134 Restrictions that require partition-wide consistency (like
3135 @code{No_Tasking}) are
3136 recognized wherever they appear
3137 and can be freely inherited, e.g. from a @emph{with}ed unit to the @emph{with}ing
3138 unit. This makes sense since the binder will in any case insist on seeing
3139 consistent use, so any unit not conforming to any restrictions that are
3140 anywhere in the partition will be rejected, and you might as well find
3141 that out at compile time rather than at bind time.
3143 For restrictions that do not require partition-wide consistency, e.g.
3144 SPARK or No_Implementation_Attributes, in general the restriction applies
3145 only to the unit in which the pragma appears, and not to any other units.
3147 The exception is No_Elaboration_Code which always applies to the entire
3148 object file from a compilation, i.e. to the body, spec, and all subunits.
3149 This restriction can be specified in a configuration pragma file, or it
3150 can be on the body and/or the spec (in eithe case it applies to all the
3151 relevant units). It can appear on a subunit only if it has previously
3152 appeared in the body of spec.
3154 @node The Configuration Pragmas Files,,Handling of Configuration Pragmas,Configuration Pragmas
3155 @anchor{gnat_ugn/the_gnat_compilation_model the-configuration-pragmas-files}@anchor{79}@anchor{gnat_ugn/the_gnat_compilation_model id30}@anchor{7a}
3156 @subsection The Configuration Pragmas Files
3161 In GNAT a compilation environment is defined by the current
3162 directory at the time that a compile command is given. This current
3163 directory is searched for a file whose name is @code{gnat.adc}. If
3164 this file is present, it is expected to contain one or more
3165 configuration pragmas that will be applied to the current compilation.
3166 However, if the switch @code{-gnatA} is used, @code{gnat.adc} is not
3167 considered. When taken into account, @code{gnat.adc} is added to the
3168 dependencies, so that if @code{gnat.adc} is modified later, an invocation of
3169 @code{gnatmake} will recompile the source.
3171 Configuration pragmas may be entered into the @code{gnat.adc} file
3172 either by running @code{gnatchop} on a source file that consists only of
3173 configuration pragmas, or more conveniently by direct editing of the
3174 @code{gnat.adc} file, which is a standard format source file.
3176 Besides @code{gnat.adc}, additional files containing configuration
3177 pragmas may be applied to the current compilation using the switch
3178 @code{-gnatec=@emph{path}} where @code{path} must designate an existing file that
3179 contains only configuration pragmas. These configuration pragmas are
3180 in addition to those found in @code{gnat.adc} (provided @code{gnat.adc}
3181 is present and switch @code{-gnatA} is not used).
3183 It is allowable to specify several switches @code{-gnatec=}, all of which
3184 will be taken into account.
3186 Files containing configuration pragmas specified with switches
3187 @code{-gnatec=} are added to the dependencies, unless they are
3188 temporary files. A file is considered temporary if its name ends in
3189 @code{.tmp} or @code{.TMP}. Certain tools follow this naming
3190 convention because they pass information to @code{gcc} via
3191 temporary files that are immediately deleted; it doesn't make sense to
3192 depend on a file that no longer exists. Such tools include
3193 @code{gprbuild}, @code{gnatmake}, and @code{gnatcheck}.
3195 If you are using project file, a separate mechanism is provided using
3199 @c See :ref:`Specifying_Configuration_Pragmas` for more details.
3201 @node Generating Object Files,Source Dependencies,Configuration Pragmas,The GNAT Compilation Model
3202 @anchor{gnat_ugn/the_gnat_compilation_model generating-object-files}@anchor{40}@anchor{gnat_ugn/the_gnat_compilation_model id31}@anchor{7b}
3203 @section Generating Object Files
3206 An Ada program consists of a set of source files, and the first step in
3207 compiling the program is to generate the corresponding object files.
3208 These are generated by compiling a subset of these source files.
3209 The files you need to compile are the following:
3215 If a package spec has no body, compile the package spec to produce the
3216 object file for the package.
3219 If a package has both a spec and a body, compile the body to produce the
3220 object file for the package. The source file for the package spec need
3221 not be compiled in this case because there is only one object file, which
3222 contains the code for both the spec and body of the package.
3225 For a subprogram, compile the subprogram body to produce the object file
3226 for the subprogram. The spec, if one is present, is as usual in a
3227 separate file, and need not be compiled.
3236 In the case of subunits, only compile the parent unit. A single object
3237 file is generated for the entire subunit tree, which includes all the
3241 Compile child units independently of their parent units
3242 (though, of course, the spec of all the ancestor unit must be present in order
3243 to compile a child unit).
3248 Compile generic units in the same manner as any other units. The object
3249 files in this case are small dummy files that contain at most the
3250 flag used for elaboration checking. This is because GNAT always handles generic
3251 instantiation by means of macro expansion. However, it is still necessary to
3252 compile generic units, for dependency checking and elaboration purposes.
3255 The preceding rules describe the set of files that must be compiled to
3256 generate the object files for a program. Each object file has the same
3257 name as the corresponding source file, except that the extension is
3260 You may wish to compile other files for the purpose of checking their
3261 syntactic and semantic correctness. For example, in the case where a
3262 package has a separate spec and body, you would not normally compile the
3263 spec. However, it is convenient in practice to compile the spec to make
3264 sure it is error-free before compiling clients of this spec, because such
3265 compilations will fail if there is an error in the spec.
3267 GNAT provides an option for compiling such files purely for the
3268 purposes of checking correctness; such compilations are not required as
3269 part of the process of building a program. To compile a file in this
3270 checking mode, use the @code{-gnatc} switch.
3272 @node Source Dependencies,The Ada Library Information Files,Generating Object Files,The GNAT Compilation Model
3273 @anchor{gnat_ugn/the_gnat_compilation_model id32}@anchor{7c}@anchor{gnat_ugn/the_gnat_compilation_model source-dependencies}@anchor{41}
3274 @section Source Dependencies
3277 A given object file clearly depends on the source file which is compiled
3278 to produce it. Here we are using "depends" in the sense of a typical
3279 @code{make} utility; in other words, an object file depends on a source
3280 file if changes to the source file require the object file to be
3282 In addition to this basic dependency, a given object may depend on
3283 additional source files as follows:
3289 If a file being compiled @emph{with}s a unit @code{X}, the object file
3290 depends on the file containing the spec of unit @code{X}. This includes
3291 files that are @emph{with}ed implicitly either because they are parents
3292 of @emph{with}ed child units or they are run-time units required by the
3293 language constructs used in a particular unit.
3296 If a file being compiled instantiates a library level generic unit, the
3297 object file depends on both the spec and body files for this generic
3301 If a file being compiled instantiates a generic unit defined within a
3302 package, the object file depends on the body file for the package as
3303 well as the spec file.
3308 @geindex -gnatn switch
3314 If a file being compiled contains a call to a subprogram for which
3315 pragma @code{Inline} applies and inlining is activated with the
3316 @code{-gnatn} switch, the object file depends on the file containing the
3317 body of this subprogram as well as on the file containing the spec. Note
3318 that for inlining to actually occur as a result of the use of this switch,
3319 it is necessary to compile in optimizing mode.
3321 @geindex -gnatN switch
3323 The use of @code{-gnatN} activates inlining optimization
3324 that is performed by the front end of the compiler. This inlining does
3325 not require that the code generation be optimized. Like @code{-gnatn},
3326 the use of this switch generates additional dependencies.
3328 When using a gcc-based back end (in practice this means using any version
3329 of GNAT other than for the JVM, .NET or GNAAMP platforms), then the use of
3330 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
3331 Historically front end inlining was more extensive than the gcc back end
3332 inlining, but that is no longer the case.
3335 If an object file @code{O} depends on the proper body of a subunit through
3336 inlining or instantiation, it depends on the parent unit of the subunit.
3337 This means that any modification of the parent unit or one of its subunits
3338 affects the compilation of @code{O}.
3341 The object file for a parent unit depends on all its subunit body files.
3344 The previous two rules meant that for purposes of computing dependencies and
3345 recompilation, a body and all its subunits are treated as an indivisible whole.
3347 These rules are applied transitively: if unit @code{A} @emph{with}s
3348 unit @code{B}, whose elaboration calls an inlined procedure in package
3349 @code{C}, the object file for unit @code{A} will depend on the body of
3350 @code{C}, in file @code{c.adb}.
3352 The set of dependent files described by these rules includes all the
3353 files on which the unit is semantically dependent, as dictated by the
3354 Ada language standard. However, it is a superset of what the
3355 standard describes, because it includes generic, inline, and subunit
3358 An object file must be recreated by recompiling the corresponding source
3359 file if any of the source files on which it depends are modified. For
3360 example, if the @code{make} utility is used to control compilation,
3361 the rule for an Ada object file must mention all the source files on
3362 which the object file depends, according to the above definition.
3363 The determination of the necessary
3364 recompilations is done automatically when one uses @code{gnatmake}.
3367 @node The Ada Library Information Files,Binding an Ada Program,Source Dependencies,The GNAT Compilation Model
3368 @anchor{gnat_ugn/the_gnat_compilation_model id33}@anchor{7d}@anchor{gnat_ugn/the_gnat_compilation_model the-ada-library-information-files}@anchor{42}
3369 @section The Ada Library Information Files
3372 @geindex Ada Library Information files
3376 Each compilation actually generates two output files. The first of these
3377 is the normal object file that has a @code{.o} extension. The second is a
3378 text file containing full dependency information. It has the same
3379 name as the source file, but an @code{.ali} extension.
3380 This file is known as the Ada Library Information (@code{ALI}) file.
3381 The following information is contained in the @code{ALI} file.
3387 Version information (indicates which version of GNAT was used to compile
3388 the unit(s) in question)
3391 Main program information (including priority and time slice settings,
3392 as well as the wide character encoding used during compilation).
3395 List of arguments used in the @code{gcc} command for the compilation
3398 Attributes of the unit, including configuration pragmas used, an indication
3399 of whether the compilation was successful, exception model used etc.
3402 A list of relevant restrictions applying to the unit (used for consistency)
3406 Categorization information (e.g., use of pragma @code{Pure}).
3409 Information on all @emph{with}ed units, including presence of
3410 @code{Elaborate} or @code{Elaborate_All} pragmas.
3413 Information from any @code{Linker_Options} pragmas used in the unit
3416 Information on the use of @code{Body_Version} or @code{Version}
3417 attributes in the unit.
3420 Dependency information. This is a list of files, together with
3421 time stamp and checksum information. These are files on which
3422 the unit depends in the sense that recompilation is required
3423 if any of these units are modified.
3426 Cross-reference data. Contains information on all entities referenced
3427 in the unit. Used by tools like @code{gnatxref} and @code{gnatfind} to
3428 provide cross-reference information.
3431 For a full detailed description of the format of the @code{ALI} file,
3432 see the source of the body of unit @code{Lib.Writ}, contained in file
3433 @code{lib-writ.adb} in the GNAT compiler sources.
3435 @node Binding an Ada Program,GNAT and Libraries,The Ada Library Information Files,The GNAT Compilation Model
3436 @anchor{gnat_ugn/the_gnat_compilation_model id34}@anchor{7e}@anchor{gnat_ugn/the_gnat_compilation_model binding-an-ada-program}@anchor{43}
3437 @section Binding an Ada Program
3440 When using languages such as C and C++, once the source files have been
3441 compiled the only remaining step in building an executable program
3442 is linking the object modules together. This means that it is possible to
3443 link an inconsistent version of a program, in which two units have
3444 included different versions of the same header.
3446 The rules of Ada do not permit such an inconsistent program to be built.
3447 For example, if two clients have different versions of the same package,
3448 it is illegal to build a program containing these two clients.
3449 These rules are enforced by the GNAT binder, which also determines an
3450 elaboration order consistent with the Ada rules.
3452 The GNAT binder is run after all the object files for a program have
3453 been created. It is given the name of the main program unit, and from
3454 this it determines the set of units required by the program, by reading the
3455 corresponding ALI files. It generates error messages if the program is
3456 inconsistent or if no valid order of elaboration exists.
3458 If no errors are detected, the binder produces a main program, in Ada by
3459 default, that contains calls to the elaboration procedures of those
3460 compilation unit that require them, followed by
3461 a call to the main program. This Ada program is compiled to generate the
3462 object file for the main program. The name of
3463 the Ada file is @code{b~xxx}.adb` (with the corresponding spec
3464 @code{b~xxx}.ads`) where @code{xxx} is the name of the
3467 Finally, the linker is used to build the resulting executable program,
3468 using the object from the main program from the bind step as well as the
3469 object files for the Ada units of the program.
3471 @node GNAT and Libraries,Conditional Compilation,Binding an Ada Program,The GNAT Compilation Model
3472 @anchor{gnat_ugn/the_gnat_compilation_model gnat-and-libraries}@anchor{15}@anchor{gnat_ugn/the_gnat_compilation_model id35}@anchor{7f}
3473 @section GNAT and Libraries
3476 @geindex Library building and using
3478 This section describes how to build and use libraries with GNAT, and also shows
3479 how to recompile the GNAT run-time library. You should be familiar with the
3480 Project Manager facility (see the @emph{GNAT_Project_Manager} chapter of the
3481 @emph{GPRbuild User's Guide}) before reading this chapter.
3484 * Introduction to Libraries in GNAT::
3485 * General Ada Libraries::
3486 * Stand-alone Ada Libraries::
3487 * Rebuilding the GNAT Run-Time Library::
3491 @node Introduction to Libraries in GNAT,General Ada Libraries,,GNAT and Libraries
3492 @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-libraries-in-gnat}@anchor{80}@anchor{gnat_ugn/the_gnat_compilation_model id36}@anchor{81}
3493 @subsection Introduction to Libraries in GNAT
3496 A library is, conceptually, a collection of objects which does not have its
3497 own main thread of execution, but rather provides certain services to the
3498 applications that use it. A library can be either statically linked with the
3499 application, in which case its code is directly included in the application,
3500 or, on platforms that support it, be dynamically linked, in which case
3501 its code is shared by all applications making use of this library.
3503 GNAT supports both types of libraries.
3504 In the static case, the compiled code can be provided in different ways. The
3505 simplest approach is to provide directly the set of objects resulting from
3506 compilation of the library source files. Alternatively, you can group the
3507 objects into an archive using whatever commands are provided by the operating
3508 system. For the latter case, the objects are grouped into a shared library.
3510 In the GNAT environment, a library has three types of components:
3519 @code{ALI} files (see @ref{42,,The Ada Library Information Files}), and
3522 Object files, an archive or a shared library.
3525 A GNAT library may expose all its source files, which is useful for
3526 documentation purposes. Alternatively, it may expose only the units needed by
3527 an external user to make use of the library. That is to say, the specs
3528 reflecting the library services along with all the units needed to compile
3529 those specs, which can include generic bodies or any body implementing an
3530 inlined routine. In the case of @emph{stand-alone libraries} those exposed
3531 units are called @emph{interface units} (@ref{82,,Stand-alone Ada Libraries}).
3533 All compilation units comprising an application, including those in a library,
3534 need to be elaborated in an order partially defined by Ada's semantics. GNAT
3535 computes the elaboration order from the @code{ALI} files and this is why they
3536 constitute a mandatory part of GNAT libraries.
3537 @emph{Stand-alone libraries} are the exception to this rule because a specific
3538 library elaboration routine is produced independently of the application(s)
3541 @node General Ada Libraries,Stand-alone Ada Libraries,Introduction to Libraries in GNAT,GNAT and Libraries
3542 @anchor{gnat_ugn/the_gnat_compilation_model general-ada-libraries}@anchor{83}@anchor{gnat_ugn/the_gnat_compilation_model id37}@anchor{84}
3543 @subsection General Ada Libraries
3547 * Building a library::
3548 * Installing a library::
3553 @node Building a library,Installing a library,,General Ada Libraries
3554 @anchor{gnat_ugn/the_gnat_compilation_model building-a-library}@anchor{85}@anchor{gnat_ugn/the_gnat_compilation_model id38}@anchor{86}
3555 @subsubsection Building a library
3558 The easiest way to build a library is to use the Project Manager,
3559 which supports a special type of project called a @emph{Library Project}
3560 (see the @emph{Library Projects} section in the @emph{GNAT Project Manager}
3561 chapter of the @emph{GPRbuild User's Guide}).
3563 A project is considered a library project, when two project-level attributes
3564 are defined in it: @code{Library_Name} and @code{Library_Dir}. In order to
3565 control different aspects of library configuration, additional optional
3566 project-level attributes can be specified:
3575 @item @code{Library_Kind}
3577 This attribute controls whether the library is to be static or dynamic
3584 @item @code{Library_Version}
3586 This attribute specifies the library version; this value is used
3587 during dynamic linking of shared libraries to determine if the currently
3588 installed versions of the binaries are compatible.
3592 @code{Library_Options}
3598 @item @code{Library_GCC}
3600 These attributes specify additional low-level options to be used during
3601 library generation, and redefine the actual application used to generate
3606 The GNAT Project Manager takes full care of the library maintenance task,
3607 including recompilation of the source files for which objects do not exist
3608 or are not up to date, assembly of the library archive, and installation of
3609 the library (i.e., copying associated source, object and @code{ALI} files
3610 to the specified location).
3612 Here is a simple library project file:
3616 for Source_Dirs use ("src1", "src2");
3617 for Object_Dir use "obj";
3618 for Library_Name use "mylib";
3619 for Library_Dir use "lib";
3620 for Library_Kind use "dynamic";
3624 and the compilation command to build and install the library:
3630 It is not entirely trivial to perform manually all the steps required to
3631 produce a library. We recommend that you use the GNAT Project Manager
3632 for this task. In special cases where this is not desired, the necessary
3633 steps are discussed below.
3635 There are various possibilities for compiling the units that make up the
3636 library: for example with a Makefile (@ref{1f,,Using the GNU make Utility}) or
3637 with a conventional script. For simple libraries, it is also possible to create
3638 a dummy main program which depends upon all the packages that comprise the
3639 interface of the library. This dummy main program can then be given to
3640 @code{gnatmake}, which will ensure that all necessary objects are built.
3642 After this task is accomplished, you should follow the standard procedure
3643 of the underlying operating system to produce the static or shared library.
3645 Here is an example of such a dummy program:
3648 with My_Lib.Service1;
3649 with My_Lib.Service2;
3650 with My_Lib.Service3;
3651 procedure My_Lib_Dummy is
3657 Here are the generic commands that will build an archive or a shared library.
3660 # compiling the library
3661 $ gnatmake -c my_lib_dummy.adb
3663 # we don't need the dummy object itself
3664 $ rm my_lib_dummy.o my_lib_dummy.ali
3666 # create an archive with the remaining objects
3667 $ ar rc libmy_lib.a *.o
3668 # some systems may require "ranlib" to be run as well
3670 # or create a shared library
3671 $ gcc -shared -o libmy_lib.so *.o
3672 # some systems may require the code to have been compiled with -fPIC
3674 # remove the object files that are now in the library
3677 # Make the ALI files read-only so that gnatmake will not try to
3678 # regenerate the objects that are in the library
3682 Please note that the library must have a name of the form @code{lib@emph{xxx}.a}
3683 or @code{lib@emph{xxx}.so} (or @code{lib@emph{xxx}.dll} on Windows) in order to
3684 be accessed by the directive @code{-l@emph{xxx}} at link time.
3686 @node Installing a library,Using a library,Building a library,General Ada Libraries
3687 @anchor{gnat_ugn/the_gnat_compilation_model installing-a-library}@anchor{87}@anchor{gnat_ugn/the_gnat_compilation_model id39}@anchor{88}
3688 @subsubsection Installing a library
3691 @geindex ADA_PROJECT_PATH
3693 @geindex GPR_PROJECT_PATH
3695 If you use project files, library installation is part of the library build
3696 process (see the @emph{Installing a Library with Project Files} section of the
3697 @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}).
3699 When project files are not an option, it is also possible, but not recommended,
3700 to install the library so that the sources needed to use the library are on the
3701 Ada source path and the ALI files & libraries be on the Ada Object path (see
3702 @ref{89,,Search Paths and the Run-Time Library (RTL)}. Alternatively, the system
3703 administrator can place general-purpose libraries in the default compiler
3704 paths, by specifying the libraries' location in the configuration files
3705 @code{ada_source_path} and @code{ada_object_path}. These configuration files
3706 must be located in the GNAT installation tree at the same place as the gcc spec
3707 file. The location of the gcc spec file can be determined as follows:
3713 The configuration files mentioned above have a simple format: each line
3714 must contain one unique directory name.
3715 Those names are added to the corresponding path
3716 in their order of appearance in the file. The names can be either absolute
3717 or relative; in the latter case, they are relative to where theses files
3720 The files @code{ada_source_path} and @code{ada_object_path} might not be
3722 GNAT installation, in which case, GNAT will look for its run-time library in
3723 the directories @code{adainclude} (for the sources) and @code{adalib} (for the
3724 objects and @code{ALI} files). When the files exist, the compiler does not
3725 look in @code{adainclude} and @code{adalib}, and thus the
3726 @code{ada_source_path} file
3727 must contain the location for the GNAT run-time sources (which can simply
3728 be @code{adainclude}). In the same way, the @code{ada_object_path} file must
3729 contain the location for the GNAT run-time objects (which can simply
3732 You can also specify a new default path to the run-time library at compilation
3733 time with the switch @code{--RTS=rts-path}. You can thus choose / change
3734 the run-time library you want your program to be compiled with. This switch is
3735 recognized by @code{gcc}, @code{gnatmake}, @code{gnatbind},
3736 @code{gnatls}, @code{gnatfind} and @code{gnatxref}.
3738 It is possible to install a library before or after the standard GNAT
3739 library, by reordering the lines in the configuration files. In general, a
3740 library must be installed before the GNAT library if it redefines
3743 @node Using a library,,Installing a library,General Ada Libraries
3744 @anchor{gnat_ugn/the_gnat_compilation_model using-a-library}@anchor{8a}@anchor{gnat_ugn/the_gnat_compilation_model id40}@anchor{8b}
3745 @subsubsection Using a library
3748 Once again, the project facility greatly simplifies the use of
3749 libraries. In this context, using a library is just a matter of adding a
3750 @emph{with} clause in the user project. For instance, to make use of the
3751 library @code{My_Lib} shown in examples in earlier sections, you can
3761 Even if you have a third-party, non-Ada library, you can still use GNAT's
3762 Project Manager facility to provide a wrapper for it. For example, the
3763 following project, when @emph{with}ed by your main project, will link with the
3764 third-party library @code{liba.a}:
3768 for Externally_Built use "true";
3769 for Source_Files use ();
3770 for Library_Dir use "lib";
3771 for Library_Name use "a";
3772 for Library_Kind use "static";
3776 This is an alternative to the use of @code{pragma Linker_Options}. It is
3777 especially interesting in the context of systems with several interdependent
3778 static libraries where finding a proper linker order is not easy and best be
3779 left to the tools having visibility over project dependence information.
3781 In order to use an Ada library manually, you need to make sure that this
3782 library is on both your source and object path
3783 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}
3784 and @ref{8c,,Search Paths for gnatbind}). Furthermore, when the objects are grouped
3785 in an archive or a shared library, you need to specify the desired
3786 library at link time.
3788 For example, you can use the library @code{mylib} installed in
3789 @code{/dir/my_lib_src} and @code{/dir/my_lib_obj} with the following commands:
3792 $ gnatmake -aI/dir/my_lib_src -aO/dir/my_lib_obj my_appl \\
3796 This can be expressed more simply:
3802 when the following conditions are met:
3808 @code{/dir/my_lib_src} has been added by the user to the environment
3810 @geindex ADA_INCLUDE_PATH
3811 @geindex environment variable; ADA_INCLUDE_PATH
3812 @code{ADA_INCLUDE_PATH}, or by the administrator to the file
3813 @code{ada_source_path}
3816 @code{/dir/my_lib_obj} has been added by the user to the environment
3818 @geindex ADA_OBJECTS_PATH
3819 @geindex environment variable; ADA_OBJECTS_PATH
3820 @code{ADA_OBJECTS_PATH}, or by the administrator to the file
3821 @code{ada_object_path}
3824 a pragma @code{Linker_Options} has been added to one of the sources.
3828 pragma Linker_Options ("-lmy_lib");
3832 Note that you may also load a library dynamically at
3833 run time given its filename, as illustrated in the GNAT @code{plugins} example
3834 in the directory @code{share/examples/gnat/plugins} within the GNAT
3837 @node Stand-alone Ada Libraries,Rebuilding the GNAT Run-Time Library,General Ada Libraries,GNAT and Libraries
3838 @anchor{gnat_ugn/the_gnat_compilation_model stand-alone-ada-libraries}@anchor{82}@anchor{gnat_ugn/the_gnat_compilation_model id41}@anchor{8d}
3839 @subsection Stand-alone Ada Libraries
3842 @geindex Stand-alone libraries
3845 * Introduction to Stand-alone Libraries::
3846 * Building a Stand-alone Library::
3847 * Creating a Stand-alone Library to be used in a non-Ada context::
3848 * Restrictions in Stand-alone Libraries::
3852 @node Introduction to Stand-alone Libraries,Building a Stand-alone Library,,Stand-alone Ada Libraries
3853 @anchor{gnat_ugn/the_gnat_compilation_model introduction-to-stand-alone-libraries}@anchor{8e}@anchor{gnat_ugn/the_gnat_compilation_model id42}@anchor{8f}
3854 @subsubsection Introduction to Stand-alone Libraries
3857 A Stand-alone Library (abbreviated 'SAL') is a library that contains the
3859 elaborate the Ada units that are included in the library. In contrast with
3860 an ordinary library, which consists of all sources, objects and @code{ALI}
3862 library, a SAL may specify a restricted subset of compilation units
3863 to serve as a library interface. In this case, the fully
3864 self-sufficient set of files will normally consist of an objects
3865 archive, the sources of interface units' specs, and the @code{ALI}
3866 files of interface units.
3867 If an interface spec contains a generic unit or an inlined subprogram,
3869 source must also be provided; if the units that must be provided in the source
3870 form depend on other units, the source and @code{ALI} files of those must
3873 The main purpose of a SAL is to minimize the recompilation overhead of client
3874 applications when a new version of the library is installed. Specifically,
3875 if the interface sources have not changed, client applications do not need to
3876 be recompiled. If, furthermore, a SAL is provided in the shared form and its
3877 version, controlled by @code{Library_Version} attribute, is not changed,
3878 then the clients do not need to be relinked.
3880 SALs also allow the library providers to minimize the amount of library source
3881 text exposed to the clients. Such 'information hiding' might be useful or
3882 necessary for various reasons.
3884 Stand-alone libraries are also well suited to be used in an executable whose
3885 main routine is not written in Ada.
3887 @node Building a Stand-alone Library,Creating a Stand-alone Library to be used in a non-Ada context,Introduction to Stand-alone Libraries,Stand-alone Ada Libraries
3888 @anchor{gnat_ugn/the_gnat_compilation_model id43}@anchor{90}@anchor{gnat_ugn/the_gnat_compilation_model building-a-stand-alone-library}@anchor{91}
3889 @subsubsection Building a Stand-alone Library
3892 GNAT's Project facility provides a simple way of building and installing
3893 stand-alone libraries; see the @emph{Stand-alone Library Projects} section
3894 in the @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}.
3895 To be a Stand-alone Library Project, in addition to the two attributes
3896 that make a project a Library Project (@code{Library_Name} and
3897 @code{Library_Dir}; see the @emph{Library Projects} section in the
3898 @emph{GNAT Project Manager} chapter of the @emph{GPRbuild User's Guide}),
3899 the attribute @code{Library_Interface} must be defined. For example:
3902 for Library_Dir use "lib_dir";
3903 for Library_Name use "dummy";
3904 for Library_Interface use ("int1", "int1.child");
3907 Attribute @code{Library_Interface} has a non-empty string list value,
3908 each string in the list designating a unit contained in an immediate source
3909 of the project file.
3911 When a Stand-alone Library is built, first the binder is invoked to build
3912 a package whose name depends on the library name
3913 (@code{b~dummy.ads/b} in the example above).
3914 This binder-generated package includes initialization and
3915 finalization procedures whose
3916 names depend on the library name (@code{dummyinit} and @code{dummyfinal}
3918 above). The object corresponding to this package is included in the library.
3920 You must ensure timely (e.g., prior to any use of interfaces in the SAL)
3921 calling of these procedures if a static SAL is built, or if a shared SAL
3923 with the project-level attribute @code{Library_Auto_Init} set to
3926 For a Stand-Alone Library, only the @code{ALI} files of the Interface Units
3927 (those that are listed in attribute @code{Library_Interface}) are copied to
3928 the Library Directory. As a consequence, only the Interface Units may be
3929 imported from Ada units outside of the library. If other units are imported,
3930 the binding phase will fail.
3932 It is also possible to build an encapsulated library where not only
3933 the code to elaborate and finalize the library is embedded but also
3934 ensuring that the library is linked only against static
3935 libraries. So an encapsulated library only depends on system
3936 libraries, all other code, including the GNAT runtime, is embedded. To
3937 build an encapsulated library the attribute
3938 @code{Library_Standalone} must be set to @code{encapsulated}:
3941 for Library_Dir use "lib_dir";
3942 for Library_Name use "dummy";
3943 for Library_Kind use "dynamic";
3944 for Library_Interface use ("int1", "int1.child");
3945 for Library_Standalone use "encapsulated";
3948 The default value for this attribute is @code{standard} in which case
3949 a stand-alone library is built.
3951 The attribute @code{Library_Src_Dir} may be specified for a
3952 Stand-Alone Library. @code{Library_Src_Dir} is a simple attribute that has a
3953 single string value. Its value must be the path (absolute or relative to the
3954 project directory) of an existing directory. This directory cannot be the
3955 object directory or one of the source directories, but it can be the same as
3956 the library directory. The sources of the Interface
3957 Units of the library that are needed by an Ada client of the library will be
3958 copied to the designated directory, called the Interface Copy directory.
3959 These sources include the specs of the Interface Units, but they may also
3960 include bodies and subunits, when pragmas @code{Inline} or @code{Inline_Always}
3961 are used, or when there is a generic unit in the spec. Before the sources
3962 are copied to the Interface Copy directory, an attempt is made to delete all
3963 files in the Interface Copy directory.
3965 Building stand-alone libraries by hand is somewhat tedious, but for those
3966 occasions when it is necessary here are the steps that you need to perform:
3972 Compile all library sources.
3975 Invoke the binder with the switch @code{-n} (No Ada main program),
3976 with all the @code{ALI} files of the interfaces, and
3977 with the switch @code{-L} to give specific names to the @code{init}
3978 and @code{final} procedures. For example:
3981 $ gnatbind -n int1.ali int2.ali -Lsal1
3985 Compile the binder generated file:
3992 Link the dynamic library with all the necessary object files,
3993 indicating to the linker the names of the @code{init} (and possibly
3994 @code{final}) procedures for automatic initialization (and finalization).
3995 The built library should be placed in a directory different from
3996 the object directory.
3999 Copy the @code{ALI} files of the interface to the library directory,
4000 add in this copy an indication that it is an interface to a SAL
4001 (i.e., add a word @code{SL} on the line in the @code{ALI} file that starts
4002 with letter 'P') and make the modified copy of the @code{ALI} file
4006 Using SALs is not different from using other libraries
4007 (see @ref{8a,,Using a library}).
4009 @node Creating a Stand-alone Library to be used in a non-Ada context,Restrictions in Stand-alone Libraries,Building a Stand-alone Library,Stand-alone Ada Libraries
4010 @anchor{gnat_ugn/the_gnat_compilation_model creating-a-stand-alone-library-to-be-used-in-a-non-ada-context}@anchor{92}@anchor{gnat_ugn/the_gnat_compilation_model id44}@anchor{93}
4011 @subsubsection Creating a Stand-alone Library to be used in a non-Ada context
4014 It is easy to adapt the SAL build procedure discussed above for use of a SAL in
4017 The only extra step required is to ensure that library interface subprograms
4018 are compatible with the main program, by means of @code{pragma Export}
4019 or @code{pragma Convention}.
4021 Here is an example of simple library interface for use with C main program:
4024 package My_Package is
4026 procedure Do_Something;
4027 pragma Export (C, Do_Something, "do_something");
4029 procedure Do_Something_Else;
4030 pragma Export (C, Do_Something_Else, "do_something_else");
4035 On the foreign language side, you must provide a 'foreign' view of the
4036 library interface; remember that it should contain elaboration routines in
4037 addition to interface subprograms.
4039 The example below shows the content of @code{mylib_interface.h} (note
4040 that there is no rule for the naming of this file, any name can be used)
4043 /* the library elaboration procedure */
4044 extern void mylibinit (void);
4046 /* the library finalization procedure */
4047 extern void mylibfinal (void);
4049 /* the interface exported by the library */
4050 extern void do_something (void);
4051 extern void do_something_else (void);
4054 Libraries built as explained above can be used from any program, provided
4055 that the elaboration procedures (named @code{mylibinit} in the previous
4056 example) are called before the library services are used. Any number of
4057 libraries can be used simultaneously, as long as the elaboration
4058 procedure of each library is called.
4060 Below is an example of a C program that uses the @code{mylib} library.
4063 #include "mylib_interface.h"
4068 /* First, elaborate the library before using it */
4071 /* Main program, using the library exported entities */
4073 do_something_else ();
4075 /* Library finalization at the end of the program */
4081 Note that invoking any library finalization procedure generated by
4082 @code{gnatbind} shuts down the Ada run-time environment.
4084 finalization of all Ada libraries must be performed at the end of the program.
4085 No call to these libraries or to the Ada run-time library should be made
4086 after the finalization phase.
4088 Note also that special care must be taken with multi-tasks
4089 applications. The initialization and finalization routines are not
4090 protected against concurrent access. If such requirement is needed it
4091 must be ensured at the application level using a specific operating
4092 system services like a mutex or a critical-section.
4094 @node Restrictions in Stand-alone Libraries,,Creating a Stand-alone Library to be used in a non-Ada context,Stand-alone Ada Libraries
4095 @anchor{gnat_ugn/the_gnat_compilation_model id45}@anchor{94}@anchor{gnat_ugn/the_gnat_compilation_model restrictions-in-stand-alone-libraries}@anchor{95}
4096 @subsubsection Restrictions in Stand-alone Libraries
4099 The pragmas listed below should be used with caution inside libraries,
4100 as they can create incompatibilities with other Ada libraries:
4106 pragma @code{Locking_Policy}
4109 pragma @code{Partition_Elaboration_Policy}
4112 pragma @code{Queuing_Policy}
4115 pragma @code{Task_Dispatching_Policy}
4118 pragma @code{Unreserve_All_Interrupts}
4121 When using a library that contains such pragmas, the user must make sure
4122 that all libraries use the same pragmas with the same values. Otherwise,
4123 @code{Program_Error} will
4124 be raised during the elaboration of the conflicting
4125 libraries. The usage of these pragmas and its consequences for the user
4126 should therefore be well documented.
4128 Similarly, the traceback in the exception occurrence mechanism should be
4129 enabled or disabled in a consistent manner across all libraries.
4130 Otherwise, Program_Error will be raised during the elaboration of the
4131 conflicting libraries.
4133 If the @code{Version} or @code{Body_Version}
4134 attributes are used inside a library, then you need to
4135 perform a @code{gnatbind} step that specifies all @code{ALI} files in all
4136 libraries, so that version identifiers can be properly computed.
4137 In practice these attributes are rarely used, so this is unlikely
4138 to be a consideration.
4140 @node Rebuilding the GNAT Run-Time Library,,Stand-alone Ada Libraries,GNAT and Libraries
4141 @anchor{gnat_ugn/the_gnat_compilation_model id46}@anchor{96}@anchor{gnat_ugn/the_gnat_compilation_model rebuilding-the-gnat-run-time-library}@anchor{97}
4142 @subsection Rebuilding the GNAT Run-Time Library
4145 @geindex GNAT Run-Time Library
4148 @geindex Building the GNAT Run-Time Library
4150 @geindex Rebuilding the GNAT Run-Time Library
4152 @geindex Run-Time Library
4155 It may be useful to recompile the GNAT library in various contexts, the
4156 most important one being the use of partition-wide configuration pragmas
4157 such as @code{Normalize_Scalars}. A special Makefile called
4158 @code{Makefile.adalib} is provided to that effect and can be found in
4159 the directory containing the GNAT library. The location of this
4160 directory depends on the way the GNAT environment has been installed and can
4161 be determined by means of the command:
4167 The last entry in the object search path usually contains the
4168 gnat library. This Makefile contains its own documentation and in
4169 particular the set of instructions needed to rebuild a new library and
4172 @geindex Conditional compilation
4174 @node Conditional Compilation,Mixed Language Programming,GNAT and Libraries,The GNAT Compilation Model
4175 @anchor{gnat_ugn/the_gnat_compilation_model id47}@anchor{98}@anchor{gnat_ugn/the_gnat_compilation_model conditional-compilation}@anchor{16}
4176 @section Conditional Compilation
4179 This section presents some guidelines for modeling conditional compilation in Ada and describes the
4180 gnatprep preprocessor utility.
4182 @geindex Conditional compilation
4185 * Modeling Conditional Compilation in Ada::
4186 * Preprocessing with gnatprep::
4187 * Integrated Preprocessing::
4191 @node Modeling Conditional Compilation in Ada,Preprocessing with gnatprep,,Conditional Compilation
4192 @anchor{gnat_ugn/the_gnat_compilation_model modeling-conditional-compilation-in-ada}@anchor{99}@anchor{gnat_ugn/the_gnat_compilation_model id48}@anchor{9a}
4193 @subsection Modeling Conditional Compilation in Ada
4196 It is often necessary to arrange for a single source program
4197 to serve multiple purposes, where it is compiled in different
4198 ways to achieve these different goals. Some examples of the
4199 need for this feature are
4205 Adapting a program to a different hardware environment
4208 Adapting a program to a different target architecture
4211 Turning debugging features on and off
4214 Arranging for a program to compile with different compilers
4217 In C, or C++, the typical approach would be to use the preprocessor
4218 that is defined as part of the language. The Ada language does not
4219 contain such a feature. This is not an oversight, but rather a very
4220 deliberate design decision, based on the experience that overuse of
4221 the preprocessing features in C and C++ can result in programs that
4222 are extremely difficult to maintain. For example, if we have ten
4223 switches that can be on or off, this means that there are a thousand
4224 separate programs, any one of which might not even be syntactically
4225 correct, and even if syntactically correct, the resulting program
4226 might not work correctly. Testing all combinations can quickly become
4229 Nevertheless, the need to tailor programs certainly exists, and in
4230 this section we will discuss how this can
4231 be achieved using Ada in general, and GNAT in particular.
4234 * Use of Boolean Constants::
4235 * Debugging - A Special Case::
4236 * Conditionalizing Declarations::
4237 * Use of Alternative Implementations::
4242 @node Use of Boolean Constants,Debugging - A Special Case,,Modeling Conditional Compilation in Ada
4243 @anchor{gnat_ugn/the_gnat_compilation_model id49}@anchor{9b}@anchor{gnat_ugn/the_gnat_compilation_model use-of-boolean-constants}@anchor{9c}
4244 @subsubsection Use of Boolean Constants
4247 In the case where the difference is simply which code
4248 sequence is executed, the cleanest solution is to use Boolean
4249 constants to control which code is executed.
4252 FP_Initialize_Required : constant Boolean := True;
4254 if FP_Initialize_Required then
4259 Not only will the code inside the @code{if} statement not be executed if
4260 the constant Boolean is @code{False}, but it will also be completely
4261 deleted from the program.
4262 However, the code is only deleted after the @code{if} statement
4263 has been checked for syntactic and semantic correctness.
4264 (In contrast, with preprocessors the code is deleted before the
4265 compiler ever gets to see it, so it is not checked until the switch
4268 @geindex Preprocessors (contrasted with conditional compilation)
4270 Typically the Boolean constants will be in a separate package,
4275 FP_Initialize_Required : constant Boolean := True;
4276 Reset_Available : constant Boolean := False;
4281 The @code{Config} package exists in multiple forms for the various targets,
4282 with an appropriate script selecting the version of @code{Config} needed.
4283 Then any other unit requiring conditional compilation can do a @emph{with}
4284 of @code{Config} to make the constants visible.
4286 @node Debugging - A Special Case,Conditionalizing Declarations,Use of Boolean Constants,Modeling Conditional Compilation in Ada
4287 @anchor{gnat_ugn/the_gnat_compilation_model debugging-a-special-case}@anchor{9d}@anchor{gnat_ugn/the_gnat_compilation_model id50}@anchor{9e}
4288 @subsubsection Debugging - A Special Case
4291 A common use of conditional code is to execute statements (for example
4292 dynamic checks, or output of intermediate results) under control of a
4293 debug switch, so that the debugging behavior can be turned on and off.
4294 This can be done using a Boolean constant to control whether the code
4299 Put_Line ("got to the first stage!");
4306 if Debugging and then Temperature > 999.0 then
4307 raise Temperature_Crazy;
4311 @geindex pragma Assert
4313 Since this is a common case, there are special features to deal with
4314 this in a convenient manner. For the case of tests, Ada 2005 has added
4315 a pragma @code{Assert} that can be used for such tests. This pragma is modeled
4316 on the @code{Assert} pragma that has always been available in GNAT, so this
4317 feature may be used with GNAT even if you are not using Ada 2005 features.
4318 The use of pragma @code{Assert} is described in the
4319 @cite{GNAT_Reference_Manual}, but as an
4320 example, the last test could be written:
4323 pragma Assert (Temperature <= 999.0, "Temperature Crazy");
4329 pragma Assert (Temperature <= 999.0);
4332 In both cases, if assertions are active and the temperature is excessive,
4333 the exception @code{Assert_Failure} will be raised, with the given string in
4334 the first case or a string indicating the location of the pragma in the second
4335 case used as the exception message.
4337 @geindex pragma Assertion_Policy
4339 You can turn assertions on and off by using the @code{Assertion_Policy}
4342 @geindex -gnata switch
4344 This is an Ada 2005 pragma which is implemented in all modes by
4345 GNAT. Alternatively, you can use the @code{-gnata} switch
4346 to enable assertions from the command line, which applies to
4347 all versions of Ada.
4349 @geindex pragma Debug
4351 For the example above with the @code{Put_Line}, the GNAT-specific pragma
4352 @code{Debug} can be used:
4355 pragma Debug (Put_Line ("got to the first stage!"));
4358 If debug pragmas are enabled, the argument, which must be of the form of
4359 a procedure call, is executed (in this case, @code{Put_Line} will be called).
4360 Only one call can be present, but of course a special debugging procedure
4361 containing any code you like can be included in the program and then
4362 called in a pragma @code{Debug} argument as needed.
4364 One advantage of pragma @code{Debug} over the @code{if Debugging then}
4365 construct is that pragma @code{Debug} can appear in declarative contexts,
4366 such as at the very beginning of a procedure, before local declarations have
4369 @geindex pragma Debug_Policy
4371 Debug pragmas are enabled using either the @code{-gnata} switch that also
4372 controls assertions, or with a separate Debug_Policy pragma.
4374 The latter pragma is new in the Ada 2005 versions of GNAT (but it can be used
4375 in Ada 95 and Ada 83 programs as well), and is analogous to
4376 pragma @code{Assertion_Policy} to control assertions.
4378 @code{Assertion_Policy} and @code{Debug_Policy} are configuration pragmas,
4379 and thus they can appear in @code{gnat.adc} if you are not using a
4380 project file, or in the file designated to contain configuration pragmas
4382 They then apply to all subsequent compilations. In practice the use of
4383 the @code{-gnata} switch is often the most convenient method of controlling
4384 the status of these pragmas.
4386 Note that a pragma is not a statement, so in contexts where a statement
4387 sequence is required, you can't just write a pragma on its own. You have
4388 to add a @code{null} statement.
4392 ... -- some statements
4394 pragma Assert (Num_Cases < 10);
4399 @node Conditionalizing Declarations,Use of Alternative Implementations,Debugging - A Special Case,Modeling Conditional Compilation in Ada
4400 @anchor{gnat_ugn/the_gnat_compilation_model conditionalizing-declarations}@anchor{9f}@anchor{gnat_ugn/the_gnat_compilation_model id51}@anchor{a0}
4401 @subsubsection Conditionalizing Declarations
4404 In some cases it may be necessary to conditionalize declarations to meet
4405 different requirements. For example we might want a bit string whose length
4406 is set to meet some hardware message requirement.
4408 This may be possible using declare blocks controlled
4409 by conditional constants:
4412 if Small_Machine then
4414 X : Bit_String (1 .. 10);
4420 X : Large_Bit_String (1 .. 1000);
4427 Note that in this approach, both declarations are analyzed by the
4428 compiler so this can only be used where both declarations are legal,
4429 even though one of them will not be used.
4431 Another approach is to define integer constants, e.g., @code{Bits_Per_Word},
4432 or Boolean constants, e.g., @code{Little_Endian}, and then write declarations
4433 that are parameterized by these constants. For example
4437 Field1 at 0 range Boolean'Pos (Little_Endian) * 10 .. Bits_Per_Word;
4441 If @code{Bits_Per_Word} is set to 32, this generates either
4445 Field1 at 0 range 0 .. 32;
4449 for the big endian case, or
4453 Field1 at 0 range 10 .. 32;
4457 for the little endian case. Since a powerful subset of Ada expression
4458 notation is usable for creating static constants, clever use of this
4459 feature can often solve quite difficult problems in conditionalizing
4460 compilation (note incidentally that in Ada 95, the little endian
4461 constant was introduced as @code{System.Default_Bit_Order}, so you do not
4462 need to define this one yourself).
4464 @node Use of Alternative Implementations,Preprocessing,Conditionalizing Declarations,Modeling Conditional Compilation in Ada
4465 @anchor{gnat_ugn/the_gnat_compilation_model use-of-alternative-implementations}@anchor{a1}@anchor{gnat_ugn/the_gnat_compilation_model id52}@anchor{a2}
4466 @subsubsection Use of Alternative Implementations
4469 In some cases, none of the approaches described above are adequate. This
4470 can occur for example if the set of declarations required is radically
4471 different for two different configurations.
4473 In this situation, the official Ada way of dealing with conditionalizing
4474 such code is to write separate units for the different cases. As long as
4475 this does not result in excessive duplication of code, this can be done
4476 without creating maintenance problems. The approach is to share common
4477 code as far as possible, and then isolate the code and declarations
4478 that are different. Subunits are often a convenient method for breaking
4479 out a piece of a unit that is to be conditionalized, with separate files
4480 for different versions of the subunit for different targets, where the
4481 build script selects the right one to give to the compiler.
4483 @geindex Subunits (and conditional compilation)
4485 As an example, consider a situation where a new feature in Ada 2005
4486 allows something to be done in a really nice way. But your code must be able
4487 to compile with an Ada 95 compiler. Conceptually you want to say:
4491 ... neat Ada 2005 code
4493 ... not quite as neat Ada 95 code
4497 where @code{Ada_2005} is a Boolean constant.
4499 But this won't work when @code{Ada_2005} is set to @code{False},
4500 since the @code{then} clause will be illegal for an Ada 95 compiler.
4501 (Recall that although such unreachable code would eventually be deleted
4502 by the compiler, it still needs to be legal. If it uses features
4503 introduced in Ada 2005, it will be illegal in Ada 95.)
4508 procedure Insert is separate;
4511 Then we have two files for the subunit @code{Insert}, with the two sets of
4513 If the package containing this is called @code{File_Queries}, then we might
4520 @code{file_queries-insert-2005.adb}
4523 @code{file_queries-insert-95.adb}
4526 and the build script renames the appropriate file to @code{file_queries-insert.adb} and then carries out the compilation.
4528 This can also be done with project files' naming schemes. For example:
4531 for body ("File_Queries.Insert") use "file_queries-insert-2005.ada";
4534 Note also that with project files it is desirable to use a different extension
4535 than @code{ads} / @code{adb} for alternative versions. Otherwise a naming
4536 conflict may arise through another commonly used feature: to declare as part
4537 of the project a set of directories containing all the sources obeying the
4538 default naming scheme.
4540 The use of alternative units is certainly feasible in all situations,
4541 and for example the Ada part of the GNAT run-time is conditionalized
4542 based on the target architecture using this approach. As a specific example,
4543 consider the implementation of the AST feature in VMS. There is one
4544 spec: @code{s-asthan.ads} which is the same for all architectures, and three
4554 @item @code{s-asthan.adb}
4556 used for all non-VMS operating systems
4563 @item @code{s-asthan-vms-alpha.adb}
4565 used for VMS on the Alpha
4572 @item @code{s-asthan-vms-ia64.adb}
4574 used for VMS on the ia64
4578 The dummy version @code{s-asthan.adb} simply raises exceptions noting that
4579 this operating system feature is not available, and the two remaining
4580 versions interface with the corresponding versions of VMS to provide
4581 VMS-compatible AST handling. The GNAT build script knows the architecture
4582 and operating system, and automatically selects the right version,
4583 renaming it if necessary to @code{s-asthan.adb} before the run-time build.
4585 Another style for arranging alternative implementations is through Ada's
4586 access-to-subprogram facility.
4587 In case some functionality is to be conditionally included,
4588 you can declare an access-to-procedure variable @code{Ref} that is initialized
4589 to designate a 'do nothing' procedure, and then invoke @code{Ref.all}
4591 In some library package, set @code{Ref} to @code{Proc'Access} for some
4592 procedure @code{Proc} that performs the relevant processing.
4593 The initialization only occurs if the library package is included in the
4595 The same idea can also be implemented using tagged types and dispatching
4598 @node Preprocessing,,Use of Alternative Implementations,Modeling Conditional Compilation in Ada
4599 @anchor{gnat_ugn/the_gnat_compilation_model preprocessing}@anchor{a3}@anchor{gnat_ugn/the_gnat_compilation_model id53}@anchor{a4}
4600 @subsubsection Preprocessing
4603 @geindex Preprocessing
4605 Although it is quite possible to conditionalize code without the use of
4606 C-style preprocessing, as described earlier in this section, it is
4607 nevertheless convenient in some cases to use the C approach. Moreover,
4608 older Ada compilers have often provided some preprocessing capability,
4609 so legacy code may depend on this approach, even though it is not
4612 To accommodate such use, GNAT provides a preprocessor (modeled to a large
4613 extent on the various preprocessors that have been used
4614 with legacy code on other compilers, to enable easier transition).
4618 The preprocessor may be used in two separate modes. It can be used quite
4619 separately from the compiler, to generate a separate output source file
4620 that is then fed to the compiler as a separate step. This is the
4621 @code{gnatprep} utility, whose use is fully described in
4622 @ref{17,,Preprocessing with gnatprep}.
4624 The preprocessing language allows such constructs as
4627 #if DEBUG or else (PRIORITY > 4) then
4628 sequence of declarations
4630 completely different sequence of declarations
4634 The values of the symbols @code{DEBUG} and @code{PRIORITY} can be
4635 defined either on the command line or in a separate file.
4637 The other way of running the preprocessor is even closer to the C style and
4638 often more convenient. In this approach the preprocessing is integrated into
4639 the compilation process. The compiler is given the preprocessor input which
4640 includes @code{#if} lines etc, and then the compiler carries out the
4641 preprocessing internally and processes the resulting output.
4642 For more details on this approach, see @ref{18,,Integrated Preprocessing}.
4644 @node Preprocessing with gnatprep,Integrated Preprocessing,Modeling Conditional Compilation in Ada,Conditional Compilation
4645 @anchor{gnat_ugn/the_gnat_compilation_model id54}@anchor{a5}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-with-gnatprep}@anchor{17}
4646 @subsection Preprocessing with @code{gnatprep}
4651 @geindex Preprocessing (gnatprep)
4653 This section discusses how to use GNAT's @code{gnatprep} utility for simple
4655 Although designed for use with GNAT, @code{gnatprep} does not depend on any
4656 special GNAT features.
4657 For further discussion of conditional compilation in general, see
4658 @ref{16,,Conditional Compilation}.
4661 * Preprocessing Symbols::
4663 * Switches for gnatprep::
4664 * Form of Definitions File::
4665 * Form of Input Text for gnatprep::
4669 @node Preprocessing Symbols,Using gnatprep,,Preprocessing with gnatprep
4670 @anchor{gnat_ugn/the_gnat_compilation_model id55}@anchor{a6}@anchor{gnat_ugn/the_gnat_compilation_model preprocessing-symbols}@anchor{a7}
4671 @subsubsection Preprocessing Symbols
4674 Preprocessing symbols are defined in @emph{definition files} and referenced in the
4675 sources to be preprocessed. A preprocessing symbol is an identifier, following
4676 normal Ada (case-insensitive) rules for its syntax, with the restriction that
4677 all characters need to be in the ASCII set (no accented letters).
4679 @node Using gnatprep,Switches for gnatprep,Preprocessing Symbols,Preprocessing with gnatprep
4680 @anchor{gnat_ugn/the_gnat_compilation_model using-gnatprep}@anchor{a8}@anchor{gnat_ugn/the_gnat_compilation_model id56}@anchor{a9}
4681 @subsubsection Using @code{gnatprep}
4684 To call @code{gnatprep} use:
4687 $ gnatprep [ switches ] infile outfile [ deffile ]
4699 @item @emph{switches}
4701 is an optional sequence of switches as described in the next section.
4710 is the full name of the input file, which is an Ada source
4711 file containing preprocessor directives.
4718 @item @emph{outfile}
4720 is the full name of the output file, which is an Ada source
4721 in standard Ada form. When used with GNAT, this file name will
4722 normally have an @code{ads} or @code{adb} suffix.
4729 @item @code{deffile}
4731 is the full name of a text file containing definitions of
4732 preprocessing symbols to be referenced by the preprocessor. This argument is
4733 optional, and can be replaced by the use of the @code{-D} switch.
4737 @node Switches for gnatprep,Form of Definitions File,Using gnatprep,Preprocessing with gnatprep
4738 @anchor{gnat_ugn/the_gnat_compilation_model switches-for-gnatprep}@anchor{aa}@anchor{gnat_ugn/the_gnat_compilation_model id57}@anchor{ab}
4739 @subsubsection Switches for @code{gnatprep}
4742 @geindex --version (gnatprep)
4747 @item @code{--version}
4749 Display Copyright and version, then exit disregarding all other options.
4752 @geindex --help (gnatprep)
4759 If @code{--version} was not used, display usage and then exit disregarding
4763 @geindex -b (gnatprep)
4770 Causes both preprocessor lines and the lines deleted by
4771 preprocessing to be replaced by blank lines in the output source file,
4772 preserving line numbers in the output file.
4775 @geindex -c (gnatprep)
4782 Causes both preprocessor lines and the lines deleted
4783 by preprocessing to be retained in the output source as comments marked
4784 with the special string @code{"--! "}. This option will result in line numbers
4785 being preserved in the output file.
4788 @geindex -C (gnatprep)
4795 Causes comments to be scanned. Normally comments are ignored by gnatprep.
4796 If this option is specified, then comments are scanned and any $symbol
4797 substitutions performed as in program text. This is particularly useful
4798 when structured comments are used (e.g., for programs written in a
4799 pre-2014 version of the SPARK Ada subset). Note that this switch is not
4800 available when doing integrated preprocessing (it would be useless in
4801 this context since comments are ignored by the compiler in any case).
4804 @geindex -D (gnatprep)
4809 @item @code{-D@emph{symbol}[=@emph{value}]}
4811 Defines a new preprocessing symbol with the specified value. If no value is given
4812 on the command line, then symbol is considered to be @code{True}. This switch
4813 can be used in place of a definition file.
4816 @geindex -r (gnatprep)
4823 Causes a @code{Source_Reference} pragma to be generated that
4824 references the original input file, so that error messages will use
4825 the file name of this original file. The use of this switch implies
4826 that preprocessor lines are not to be removed from the file, so its
4827 use will force @code{-b} mode if @code{-c}
4828 has not been specified explicitly.
4830 Note that if the file to be preprocessed contains multiple units, then
4831 it will be necessary to @code{gnatchop} the output file from
4832 @code{gnatprep}. If a @code{Source_Reference} pragma is present
4833 in the preprocessed file, it will be respected by
4835 so that the final chopped files will correctly refer to the original
4836 input source file for @code{gnatprep}.
4839 @geindex -s (gnatprep)
4846 Causes a sorted list of symbol names and values to be
4847 listed on the standard output file.
4850 @geindex -T (gnatprep)
4857 Use LF as line terminators when writing files. By default the line terminator
4858 of the host (LF under unix, CR/LF under Windows) is used.
4861 @geindex -u (gnatprep)
4868 Causes undefined symbols to be treated as having the value FALSE in the context
4869 of a preprocessor test. In the absence of this option, an undefined symbol in
4870 a @code{#if} or @code{#elsif} test will be treated as an error.
4873 @geindex -v (gnatprep)
4880 Verbose mode: generates more output about work done.
4883 Note: if neither @code{-b} nor @code{-c} is present,
4884 then preprocessor lines and
4885 deleted lines are completely removed from the output, unless -r is
4886 specified, in which case -b is assumed.
4888 @node Form of Definitions File,Form of Input Text for gnatprep,Switches for gnatprep,Preprocessing with gnatprep
4889 @anchor{gnat_ugn/the_gnat_compilation_model form-of-definitions-file}@anchor{ac}@anchor{gnat_ugn/the_gnat_compilation_model id58}@anchor{ad}
4890 @subsubsection Form of Definitions File
4893 The definitions file contains lines of the form:
4899 where @code{symbol} is a preprocessing symbol, and @code{value} is one of the following:
4905 Empty, corresponding to a null substitution,
4908 A string literal using normal Ada syntax, or
4911 Any sequence of characters from the set @{letters, digits, period, underline@}.
4914 Comment lines may also appear in the definitions file, starting with
4915 the usual @code{--},
4916 and comments may be added to the definitions lines.
4918 @node Form of Input Text for gnatprep,,Form of Definitions File,Preprocessing with gnatprep
4919 @anchor{gnat_ugn/the_gnat_compilation_model id59}@anchor{ae}@anchor{gnat_ugn/the_gnat_compilation_model form-of-input-text-for-gnatprep}@anchor{af}
4920 @subsubsection Form of Input Text for @code{gnatprep}
4923 The input text may contain preprocessor conditional inclusion lines,
4924 as well as general symbol substitution sequences.
4926 The preprocessor conditional inclusion commands have the form:
4929 #if <expression> [then]
4931 #elsif <expression> [then]
4933 #elsif <expression> [then]
4941 In this example, <expression> is defined by the following grammar:
4944 <expression> ::= <symbol>
4945 <expression> ::= <symbol> = "<value>"
4946 <expression> ::= <symbol> = <symbol>
4947 <expression> ::= <symbol> = <integer>
4948 <expression> ::= <symbol> > <integer>
4949 <expression> ::= <symbol> >= <integer>
4950 <expression> ::= <symbol> < <integer>
4951 <expression> ::= <symbol> <= <integer>
4952 <expression> ::= <symbol> 'Defined
4953 <expression> ::= not <expression>
4954 <expression> ::= <expression> and <expression>
4955 <expression> ::= <expression> or <expression>
4956 <expression> ::= <expression> and then <expression>
4957 <expression> ::= <expression> or else <expression>
4958 <expression> ::= ( <expression> )
4961 Note the following restriction: it is not allowed to have "and" or "or"
4962 following "not" in the same expression without parentheses. For example, this
4969 This can be expressed instead as one of the following forms:
4976 For the first test (<expression> ::= <symbol>) the symbol must have
4977 either the value true or false, that is to say the right-hand of the
4978 symbol definition must be one of the (case-insensitive) literals
4979 @code{True} or @code{False}. If the value is true, then the
4980 corresponding lines are included, and if the value is false, they are
4983 When comparing a symbol to an integer, the integer is any non negative
4984 literal integer as defined in the Ada Reference Manual, such as 3, 16#FF# or
4985 2#11#. The symbol value must also be a non negative integer. Integer values
4986 in the range 0 .. 2**31-1 are supported.
4988 The test (<expression> ::= <symbol>'Defined) is true only if
4989 the symbol has been defined in the definition file or by a @code{-D}
4990 switch on the command line. Otherwise, the test is false.
4992 The equality tests are case insensitive, as are all the preprocessor lines.
4994 If the symbol referenced is not defined in the symbol definitions file,
4995 then the effect depends on whether or not switch @code{-u}
4996 is specified. If so, then the symbol is treated as if it had the value
4997 false and the test fails. If this switch is not specified, then
4998 it is an error to reference an undefined symbol. It is also an error to
4999 reference a symbol that is defined with a value other than @code{True}
5002 The use of the @code{not} operator inverts the sense of this logical test.
5003 The @code{not} operator cannot be combined with the @code{or} or @code{and}
5004 operators, without parentheses. For example, "if not X or Y then" is not
5005 allowed, but "if (not X) or Y then" and "if not (X or Y) then" are.
5007 The @code{then} keyword is optional as shown
5009 The @code{#} must be the first non-blank character on a line, but
5010 otherwise the format is free form. Spaces or tabs may appear between
5011 the @code{#} and the keyword. The keywords and the symbols are case
5012 insensitive as in normal Ada code. Comments may be used on a
5013 preprocessor line, but other than that, no other tokens may appear on a
5014 preprocessor line. Any number of @code{elsif} clauses can be present,
5015 including none at all. The @code{else} is optional, as in Ada.
5017 The @code{#} marking the start of a preprocessor line must be the first
5018 non-blank character on the line, i.e., it must be preceded only by
5019 spaces or horizontal tabs.
5021 Symbol substitution outside of preprocessor lines is obtained by using
5028 anywhere within a source line, except in a comment or within a
5029 string literal. The identifier
5030 following the @code{$} must match one of the symbols defined in the symbol
5031 definition file, and the result is to substitute the value of the
5032 symbol in place of @code{$symbol} in the output file.
5034 Note that although the substitution of strings within a string literal
5035 is not possible, it is possible to have a symbol whose defined value is
5036 a string literal. So instead of setting XYZ to @code{hello} and writing:
5039 Header : String := "$XYZ";
5042 you should set XYZ to @code{"hello"} and write:
5045 Header : String := $XYZ;
5048 and then the substitution will occur as desired.
5050 @node Integrated Preprocessing,,Preprocessing with gnatprep,Conditional Compilation
5051 @anchor{gnat_ugn/the_gnat_compilation_model id60}@anchor{b0}@anchor{gnat_ugn/the_gnat_compilation_model integrated-preprocessing}@anchor{18}
5052 @subsection Integrated Preprocessing
5055 As noted above, a file to be preprocessed consists of Ada source code
5056 in which preprocessing lines have been inserted. However,
5057 instead of using @code{gnatprep} to explicitly preprocess a file as a separate
5058 step before compilation, you can carry out the preprocessing implicitly
5059 as part of compilation. Such @emph{integrated preprocessing}, which is the common
5060 style with C, is performed when either or both of the following switches
5061 are passed to the compiler:
5069 @code{-gnatep}, which specifies the @emph{preprocessor data file}.
5070 This file dictates how the source files will be preprocessed (e.g., which
5071 symbol definition files apply to which sources).
5074 @code{-gnateD}, which defines values for preprocessing symbols.
5078 Integrated preprocessing applies only to Ada source files, it is
5079 not available for configuration pragma files.
5081 With integrated preprocessing, the output from the preprocessor is not,
5082 by default, written to any external file. Instead it is passed
5083 internally to the compiler. To preserve the result of
5084 preprocessing in a file, either run @code{gnatprep}
5085 in standalone mode or else supply the @code{-gnateG} switch
5086 (described below) to the compiler.
5088 When using project files:
5096 the builder switch @code{-x} should be used if any Ada source is
5097 compiled with @code{gnatep=}, so that the compiler finds the
5098 @emph{preprocessor data file}.
5101 the preprocessing data file and the symbol definition files should be
5102 located in the source directories of the project.
5106 Note that the @code{gnatmake} switch @code{-m} will almost
5107 always trigger recompilation for sources that are preprocessed,
5108 because @code{gnatmake} cannot compute the checksum of the source after
5111 The actual preprocessing function is described in detail in
5112 @ref{17,,Preprocessing with gnatprep}. This section explains the switches
5113 that relate to integrated preprocessing.
5115 @geindex -gnatep (gcc)
5120 @item @code{-gnatep=@emph{preprocessor_data_file}}
5122 This switch specifies the file name (without directory
5123 information) of the preprocessor data file. Either place this file
5124 in one of the source directories, or, when using project
5125 files, reference the project file's directory via the
5126 @code{project_name'Project_Dir} project attribute; e.g:
5133 for Switches ("Ada") use
5134 ("-gnatep=" & Prj'Project_Dir & "prep.def");
5140 A preprocessor data file is a text file that contains @emph{preprocessor
5141 control lines}. A preprocessor control line directs the preprocessing of
5142 either a particular source file, or, analogous to @code{others} in Ada,
5143 all sources not specified elsewhere in the preprocessor data file.
5144 A preprocessor control line
5145 can optionally identify a @emph{definition file} that assigns values to
5146 preprocessor symbols, as well as a list of switches that relate to
5148 Empty lines and comments (using Ada syntax) are also permitted, with no
5151 Here's an example of a preprocessor data file:
5156 "toto.adb" "prep.def" -u
5157 -- Preprocess toto.adb, using definition file prep.def
5158 -- Undefined symbols are treated as False
5161 -- Preprocess all other sources without using a definition file
5162 -- Suppressed lined are commented
5163 -- Symbol VERSION has the value V101
5165 "tata.adb" "prep2.def" -s
5166 -- Preprocess tata.adb, using definition file prep2.def
5167 -- List all symbols with their values
5171 A preprocessor control line has the following syntax:
5176 <preprocessor_control_line> ::=
5177 <preprocessor_input> [ <definition_file_name> ] @{ <switch> @}
5179 <preprocessor_input> ::= <source_file_name> | '*'
5181 <definition_file_name> ::= <string_literal>
5183 <source_file_name> := <string_literal>
5185 <switch> := (See below for list)
5189 Thus each preprocessor control line starts with either a literal string or
5196 A literal string is the file name (without directory information) of the source
5197 file that will be input to the preprocessor.
5200 The character '*' is a wild-card indicator; the additional parameters on the line
5201 indicate the preprocessing for all the sources
5202 that are not specified explicitly on other lines (the order of the lines is not
5206 It is an error to have two lines with the same file name or two
5207 lines starting with the character '*'.
5209 After the file name or '*', an optional literal string specifies the name of
5210 the definition file to be used for preprocessing
5211 (@ref{ac,,Form of Definitions File}). The definition files are found by the
5212 compiler in one of the source directories. In some cases, when compiling
5213 a source in a directory other than the current directory, if the definition
5214 file is in the current directory, it may be necessary to add the current
5215 directory as a source directory through the @code{-I} switch; otherwise
5216 the compiler would not find the definition file.
5218 Finally, switches similar to those of @code{gnatprep} may optionally appear:
5225 Causes both preprocessor lines and the lines deleted by
5226 preprocessing to be replaced by blank lines, preserving the line number.
5227 This switch is always implied; however, if specified after @code{-c}
5228 it cancels the effect of @code{-c}.
5232 Causes both preprocessor lines and the lines deleted
5233 by preprocessing to be retained as comments marked
5234 with the special string '@cite{--!}'.
5236 @item @code{-D@emph{symbol}=@emph{new_value}}
5238 Define or redefine @code{symbol} to have @code{new_value} as its value.
5239 The permitted form for @code{symbol} is either an Ada identifier, or any Ada reserved word
5240 aside from @code{if},
5241 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
5242 The permitted form for @code{new_value} is a literal string, an Ada identifier or any Ada reserved
5243 word. A symbol declared with this switch replaces a symbol with the
5244 same name defined in a definition file.
5248 Causes a sorted list of symbol names and values to be
5249 listed on the standard output file.
5253 Causes undefined symbols to be treated as having the value @code{FALSE}
5255 of a preprocessor test. In the absence of this option, an undefined symbol in
5256 a @code{#if} or @code{#elsif} test will be treated as an error.
5260 @geindex -gnateD (gcc)
5265 @item @code{-gnateD@emph{symbol}[=@emph{new_value}]}
5267 Define or redefine @code{symbol} to have @code{new_value} as its value. If no value
5268 is supplied, then the value of @code{symbol} is @code{True}.
5269 The form of @code{symbol} is an identifier, following normal Ada (case-insensitive)
5270 rules for its syntax, and @code{new_value} is either an arbitrary string between double
5271 quotes or any sequence (including an empty sequence) of characters from the
5272 set (letters, digits, period, underline).
5273 Ada reserved words may be used as symbols, with the exceptions of @code{if},
5274 @code{else}, @code{elsif}, @code{end}, @code{and}, @code{or} and @code{then}.
5283 -gnateDFoo=\"Foo-Bar\"
5287 A symbol declared with this switch on the command line replaces a
5288 symbol with the same name either in a definition file or specified with a
5289 switch @code{-D} in the preprocessor data file.
5291 This switch is similar to switch @code{-D} of @code{gnatprep}.
5293 @item @code{-gnateG}
5295 When integrated preprocessing is performed on source file @code{filename.extension},
5296 create or overwrite @code{filename.extension.prep} to contain
5297 the result of the preprocessing.
5298 For example if the source file is @code{foo.adb} then
5299 the output file will be @code{foo.adb.prep}.
5302 @node Mixed Language Programming,GNAT and Other Compilation Models,Conditional Compilation,The GNAT Compilation Model
5303 @anchor{gnat_ugn/the_gnat_compilation_model mixed-language-programming}@anchor{44}@anchor{gnat_ugn/the_gnat_compilation_model id61}@anchor{b1}
5304 @section Mixed Language Programming
5307 @geindex Mixed Language Programming
5309 This section describes how to develop a mixed-language program,
5310 with a focus on combining Ada with C or C++.
5313 * Interfacing to C::
5314 * Calling Conventions::
5315 * Building Mixed Ada and C++ Programs::
5316 * Generating Ada Bindings for C and C++ headers::
5317 * Generating C Headers for Ada Specifications::
5321 @node Interfacing to C,Calling Conventions,,Mixed Language Programming
5322 @anchor{gnat_ugn/the_gnat_compilation_model interfacing-to-c}@anchor{b2}@anchor{gnat_ugn/the_gnat_compilation_model id62}@anchor{b3}
5323 @subsection Interfacing to C
5326 Interfacing Ada with a foreign language such as C involves using
5327 compiler directives to import and/or export entity definitions in each
5328 language -- using @code{extern} statements in C, for instance, and the
5329 @code{Import}, @code{Export}, and @code{Convention} pragmas in Ada.
5330 A full treatment of these topics is provided in Appendix B, section 1
5331 of the Ada Reference Manual.
5333 There are two ways to build a program using GNAT that contains some Ada
5334 sources and some foreign language sources, depending on whether or not
5335 the main subprogram is written in Ada. Here is a source example with
5336 the main subprogram in Ada:
5342 void print_num (int num)
5344 printf ("num is %d.\\n", num);
5352 /* num_from_Ada is declared in my_main.adb */
5353 extern int num_from_Ada;
5357 return num_from_Ada;
5363 procedure My_Main is
5365 -- Declare then export an Integer entity called num_from_Ada
5366 My_Num : Integer := 10;
5367 pragma Export (C, My_Num, "num_from_Ada");
5369 -- Declare an Ada function spec for Get_Num, then use
5370 -- C function get_num for the implementation.
5371 function Get_Num return Integer;
5372 pragma Import (C, Get_Num, "get_num");
5374 -- Declare an Ada procedure spec for Print_Num, then use
5375 -- C function print_num for the implementation.
5376 procedure Print_Num (Num : Integer);
5377 pragma Import (C, Print_Num, "print_num");
5380 Print_Num (Get_Num);
5384 To build this example:
5390 First compile the foreign language files to
5391 generate object files:
5399 Then, compile the Ada units to produce a set of object files and ALI
5403 $ gnatmake -c my_main.adb
5407 Run the Ada binder on the Ada main program:
5410 $ gnatbind my_main.ali
5414 Link the Ada main program, the Ada objects and the other language
5418 $ gnatlink my_main.ali file1.o file2.o
5422 The last three steps can be grouped in a single command:
5425 $ gnatmake my_main.adb -largs file1.o file2.o
5428 @geindex Binder output file
5430 If the main program is in a language other than Ada, then you may have
5431 more than one entry point into the Ada subsystem. You must use a special
5432 binder option to generate callable routines that initialize and
5433 finalize the Ada units (@ref{b4,,Binding with Non-Ada Main Programs}).
5434 Calls to the initialization and finalization routines must be inserted
5435 in the main program, or some other appropriate point in the code. The
5436 call to initialize the Ada units must occur before the first Ada
5437 subprogram is called, and the call to finalize the Ada units must occur
5438 after the last Ada subprogram returns. The binder will place the
5439 initialization and finalization subprograms into the
5440 @code{b~xxx.adb} file where they can be accessed by your C
5441 sources. To illustrate, we have the following example:
5445 extern void adainit (void);
5446 extern void adafinal (void);
5447 extern int add (int, int);
5448 extern int sub (int, int);
5450 int main (int argc, char *argv[])
5456 /* Should print "21 + 7 = 28" */
5457 printf ("%d + %d = %d\\n", a, b, add (a, b));
5459 /* Should print "21 - 7 = 14" */
5460 printf ("%d - %d = %d\\n", a, b, sub (a, b));
5469 function Add (A, B : Integer) return Integer;
5470 pragma Export (C, Add, "add");
5476 package body Unit1 is
5477 function Add (A, B : Integer) return Integer is
5487 function Sub (A, B : Integer) return Integer;
5488 pragma Export (C, Sub, "sub");
5494 package body Unit2 is
5495 function Sub (A, B : Integer) return Integer is
5502 The build procedure for this application is similar to the last
5509 First, compile the foreign language files to generate object files:
5516 Next, compile the Ada units to produce a set of object files and ALI
5520 $ gnatmake -c unit1.adb
5521 $ gnatmake -c unit2.adb
5525 Run the Ada binder on every generated ALI file. Make sure to use the
5526 @code{-n} option to specify a foreign main program:
5529 $ gnatbind -n unit1.ali unit2.ali
5533 Link the Ada main program, the Ada objects and the foreign language
5534 objects. You need only list the last ALI file here:
5537 $ gnatlink unit2.ali main.o -o exec_file
5540 This procedure yields a binary executable called @code{exec_file}.
5543 Depending on the circumstances (for example when your non-Ada main object
5544 does not provide symbol @code{main}), you may also need to instruct the
5545 GNAT linker not to include the standard startup objects by passing the
5546 @code{-nostartfiles} switch to @code{gnatlink}.
5548 @node Calling Conventions,Building Mixed Ada and C++ Programs,Interfacing to C,Mixed Language Programming
5549 @anchor{gnat_ugn/the_gnat_compilation_model calling-conventions}@anchor{b5}@anchor{gnat_ugn/the_gnat_compilation_model id63}@anchor{b6}
5550 @subsection Calling Conventions
5553 @geindex Foreign Languages
5555 @geindex Calling Conventions
5557 GNAT follows standard calling sequence conventions and will thus interface
5558 to any other language that also follows these conventions. The following
5559 Convention identifiers are recognized by GNAT:
5561 @geindex Interfacing to Ada
5563 @geindex Other Ada compilers
5565 @geindex Convention Ada
5572 This indicates that the standard Ada calling sequence will be
5573 used and all Ada data items may be passed without any limitations in the
5574 case where GNAT is used to generate both the caller and callee. It is also
5575 possible to mix GNAT generated code and code generated by another Ada
5576 compiler. In this case, the data types should be restricted to simple
5577 cases, including primitive types. Whether complex data types can be passed
5578 depends on the situation. Probably it is safe to pass simple arrays, such
5579 as arrays of integers or floats. Records may or may not work, depending
5580 on whether both compilers lay them out identically. Complex structures
5581 involving variant records, access parameters, tasks, or protected types,
5582 are unlikely to be able to be passed.
5584 Note that in the case of GNAT running
5585 on a platform that supports HP Ada 83, a higher degree of compatibility
5586 can be guaranteed, and in particular records are laid out in an identical
5587 manner in the two compilers. Note also that if output from two different
5588 compilers is mixed, the program is responsible for dealing with elaboration
5589 issues. Probably the safest approach is to write the main program in the
5590 version of Ada other than GNAT, so that it takes care of its own elaboration
5591 requirements, and then call the GNAT-generated adainit procedure to ensure
5592 elaboration of the GNAT components. Consult the documentation of the other
5593 Ada compiler for further details on elaboration.
5595 However, it is not possible to mix the tasking run time of GNAT and
5596 HP Ada 83, All the tasking operations must either be entirely within
5597 GNAT compiled sections of the program, or entirely within HP Ada 83
5598 compiled sections of the program.
5601 @geindex Interfacing to Assembly
5603 @geindex Convention Assembler
5608 @item @code{Assembler}
5610 Specifies assembler as the convention. In practice this has the
5611 same effect as convention Ada (but is not equivalent in the sense of being
5612 considered the same convention).
5615 @geindex Convention Asm
5624 Equivalent to Assembler.
5626 @geindex Interfacing to COBOL
5628 @geindex Convention COBOL
5638 Data will be passed according to the conventions described
5639 in section B.4 of the Ada Reference Manual.
5644 @geindex Interfacing to C
5646 @geindex Convention C
5653 Data will be passed according to the conventions described
5654 in section B.3 of the Ada Reference Manual.
5656 A note on interfacing to a C 'varargs' function:
5660 @geindex C varargs function
5662 @geindex Interfacing to C varargs function
5664 @geindex varargs function interfaces
5666 In C, @code{varargs} allows a function to take a variable number of
5667 arguments. There is no direct equivalent in this to Ada. One
5668 approach that can be used is to create a C wrapper for each
5669 different profile and then interface to this C wrapper. For
5670 example, to print an @code{int} value using @code{printf},
5671 create a C function @code{printfi} that takes two arguments, a
5672 pointer to a string and an int, and calls @code{printf}.
5673 Then in the Ada program, use pragma @code{Import} to
5674 interface to @code{printfi}.
5676 It may work on some platforms to directly interface to
5677 a @code{varargs} function by providing a specific Ada profile
5678 for a particular call. However, this does not work on
5679 all platforms, since there is no guarantee that the
5680 calling sequence for a two argument normal C function
5681 is the same as for calling a @code{varargs} C function with
5682 the same two arguments.
5686 @geindex Convention Default
5693 @item @code{Default}
5698 @geindex Convention External
5705 @item @code{External}
5712 @geindex Interfacing to C++
5714 @geindex Convention C++
5719 @item @code{C_Plus_Plus} (or @code{CPP})
5721 This stands for C++. For most purposes this is identical to C.
5722 See the separate description of the specialized GNAT pragmas relating to
5723 C++ interfacing for further details.
5728 @geindex Interfacing to Fortran
5730 @geindex Convention Fortran
5735 @item @code{Fortran}
5737 Data will be passed according to the conventions described
5738 in section B.5 of the Ada Reference Manual.
5740 @item @code{Intrinsic}
5742 This applies to an intrinsic operation, as defined in the Ada
5743 Reference Manual. If a pragma Import (Intrinsic) applies to a subprogram,
5744 this means that the body of the subprogram is provided by the compiler itself,
5745 usually by means of an efficient code sequence, and that the user does not
5746 supply an explicit body for it. In an application program, the pragma may
5747 be applied to the following sets of names:
5753 Rotate_Left, Rotate_Right, Shift_Left, Shift_Right, Shift_Right_Arithmetic.
5754 The corresponding subprogram declaration must have
5755 two formal parameters. The
5756 first one must be a signed integer type or a modular type with a binary
5757 modulus, and the second parameter must be of type Natural.
5758 The return type must be the same as the type of the first argument. The size
5759 of this type can only be 8, 16, 32, or 64.
5762 Binary arithmetic operators: '+', '-', '*', '/'.
5763 The corresponding operator declaration must have parameters and result type
5764 that have the same root numeric type (for example, all three are long_float
5765 types). This simplifies the definition of operations that use type checking
5766 to perform dimensional checks:
5770 type Distance is new Long_Float;
5771 type Time is new Long_Float;
5772 type Velocity is new Long_Float;
5773 function "/" (D : Distance; T : Time)
5775 pragma Import (Intrinsic, "/");
5777 This common idiom is often programmed with a generic definition and an
5778 explicit body. The pragma makes it simpler to introduce such declarations.
5779 It incurs no overhead in compilation time or code size, because it is
5780 implemented as a single machine instruction.
5787 General subprogram entities. This is used to bind an Ada subprogram
5789 a compiler builtin by name with back-ends where such interfaces are
5790 available. A typical example is the set of @code{__builtin} functions
5791 exposed by the GCC back-end, as in the following example:
5794 function builtin_sqrt (F : Float) return Float;
5795 pragma Import (Intrinsic, builtin_sqrt, "__builtin_sqrtf");
5798 Most of the GCC builtins are accessible this way, and as for other
5799 import conventions (e.g. C), it is the user's responsibility to ensure
5800 that the Ada subprogram profile matches the underlying builtin
5807 @geindex Convention Stdcall
5812 @item @code{Stdcall}
5814 This is relevant only to Windows implementations of GNAT,
5815 and specifies that the @code{Stdcall} calling sequence will be used,
5816 as defined by the NT API. Nevertheless, to ease building
5817 cross-platform bindings this convention will be handled as a @code{C} calling
5818 convention on non-Windows platforms.
5823 @geindex Convention DLL
5830 This is equivalent to @code{Stdcall}.
5835 @geindex Convention Win32
5842 This is equivalent to @code{Stdcall}.
5847 @geindex Convention Stubbed
5852 @item @code{Stubbed}
5854 This is a special convention that indicates that the compiler
5855 should provide a stub body that raises @code{Program_Error}.
5858 GNAT additionally provides a useful pragma @code{Convention_Identifier}
5859 that can be used to parameterize conventions and allow additional synonyms
5860 to be specified. For example if you have legacy code in which the convention
5861 identifier Fortran77 was used for Fortran, you can use the configuration
5865 pragma Convention_Identifier (Fortran77, Fortran);
5868 And from now on the identifier Fortran77 may be used as a convention
5869 identifier (for example in an @code{Import} pragma) with the same
5872 @node Building Mixed Ada and C++ Programs,Generating Ada Bindings for C and C++ headers,Calling Conventions,Mixed Language Programming
5873 @anchor{gnat_ugn/the_gnat_compilation_model id64}@anchor{b7}@anchor{gnat_ugn/the_gnat_compilation_model building-mixed-ada-and-c-programs}@anchor{b8}
5874 @subsection Building Mixed Ada and C++ Programs
5877 A programmer inexperienced with mixed-language development may find that
5878 building an application containing both Ada and C++ code can be a
5879 challenge. This section gives a few hints that should make this task easier.
5882 * Interfacing to C++::
5883 * Linking a Mixed C++ & Ada Program::
5884 * A Simple Example::
5885 * Interfacing with C++ constructors::
5886 * Interfacing with C++ at the Class Level::
5890 @node Interfacing to C++,Linking a Mixed C++ & Ada Program,,Building Mixed Ada and C++ Programs
5891 @anchor{gnat_ugn/the_gnat_compilation_model id65}@anchor{b9}@anchor{gnat_ugn/the_gnat_compilation_model id66}@anchor{ba}
5892 @subsubsection Interfacing to C++
5895 GNAT supports interfacing with the G++ compiler (or any C++ compiler
5896 generating code that is compatible with the G++ Application Binary
5897 Interface ---see @indicateurl{http://www.codesourcery.com/archives/cxx-abi}).
5899 Interfacing can be done at 3 levels: simple data, subprograms, and
5900 classes. In the first two cases, GNAT offers a specific @code{Convention C_Plus_Plus}
5901 (or @code{CPP}) that behaves exactly like @code{Convention C}.
5902 Usually, C++ mangles the names of subprograms. To generate proper mangled
5903 names automatically, see @ref{19,,Generating Ada Bindings for C and C++ headers}).
5904 This problem can also be addressed manually in two ways:
5910 by modifying the C++ code in order to force a C convention using
5911 the @code{extern "C"} syntax.
5914 by figuring out the mangled name (using e.g. @code{nm}) and using it as the
5915 Link_Name argument of the pragma import.
5918 Interfacing at the class level can be achieved by using the GNAT specific
5919 pragmas such as @code{CPP_Constructor}. See the @cite{GNAT_Reference_Manual} for additional information.
5921 @node Linking a Mixed C++ & Ada Program,A Simple Example,Interfacing to C++,Building Mixed Ada and C++ Programs
5922 @anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-ada-program}@anchor{bb}@anchor{gnat_ugn/the_gnat_compilation_model linking-a-mixed-c-and-ada-program}@anchor{bc}
5923 @subsubsection Linking a Mixed C++ & Ada Program
5926 Usually the linker of the C++ development system must be used to link
5927 mixed applications because most C++ systems will resolve elaboration
5928 issues (such as calling constructors on global class instances)
5929 transparently during the link phase. GNAT has been adapted to ease the
5930 use of a foreign linker for the last phase. Three cases can be
5937 Using GNAT and G++ (GNU C++ compiler) from the same GCC installation:
5938 The C++ linker can simply be called by using the C++ specific driver
5941 Note that if the C++ code uses inline functions, you will need to
5942 compile your C++ code with the @code{-fkeep-inline-functions} switch in
5943 order to provide an existing function implementation that the Ada code can
5947 $ g++ -c -fkeep-inline-functions file1.C
5948 $ g++ -c -fkeep-inline-functions file2.C
5949 $ gnatmake ada_unit -largs file1.o file2.o --LINK=g++
5953 Using GNAT and G++ from two different GCC installations: If both
5954 compilers are on the :envvar`PATH`, the previous method may be used. It is
5955 important to note that environment variables such as
5956 @geindex C_INCLUDE_PATH
5957 @geindex environment variable; C_INCLUDE_PATH
5958 @code{C_INCLUDE_PATH},
5959 @geindex GCC_EXEC_PREFIX
5960 @geindex environment variable; GCC_EXEC_PREFIX
5961 @code{GCC_EXEC_PREFIX},
5962 @geindex BINUTILS_ROOT
5963 @geindex environment variable; BINUTILS_ROOT
5964 @code{BINUTILS_ROOT}, and
5966 @geindex environment variable; GCC_ROOT
5967 @code{GCC_ROOT} will affect both compilers
5968 at the same time and may make one of the two compilers operate
5969 improperly if set during invocation of the wrong compiler. It is also
5970 very important that the linker uses the proper @code{libgcc.a} GCC
5971 library -- that is, the one from the C++ compiler installation. The
5972 implicit link command as suggested in the @code{gnatmake} command
5973 from the former example can be replaced by an explicit link command with
5974 the full-verbosity option in order to verify which library is used:
5978 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=c++
5981 If there is a problem due to interfering environment variables, it can
5982 be worked around by using an intermediate script. The following example
5983 shows the proper script to use when GNAT has not been installed at its
5984 default location and g++ has been installed at its default location:
5992 $ gnatlink -v -v ada_unit file1.o file2.o --LINK=./my_script
5996 Using a non-GNU C++ compiler: The commands previously described can be
5997 used to insure that the C++ linker is used. Nonetheless, you need to add
5998 a few more parameters to the link command line, depending on the exception
6001 If the @code{setjmp} / @code{longjmp} exception mechanism is used, only the paths
6002 to the @code{libgcc} libraries are required:
6007 CC $* gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a
6008 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
6011 where CC is the name of the non-GNU C++ compiler.
6013 If the "zero cost" exception mechanism is used, and the platform
6014 supports automatic registration of exception tables (e.g., Solaris),
6015 paths to more objects are required:
6020 CC gcc -print-file-name=crtbegin.o $* \\
6021 gcc -print-file-name=libgcc.a gcc -print-file-name=libgcc_eh.a \\
6022 gcc -print-file-name=crtend.o
6023 $ gnatlink ada_unit file1.o file2.o --LINK=./my_script
6026 If the "zero cost exception" mechanism is used, and the platform
6027 doesn't support automatic registration of exception tables (e.g., HP-UX
6028 or AIX), the simple approach described above will not work and
6029 a pre-linking phase using GNAT will be necessary.
6032 Another alternative is to use the @code{gprbuild} multi-language builder
6033 which has a large knowledge base and knows how to link Ada and C++ code
6034 together automatically in most cases.
6036 @node A Simple Example,Interfacing with C++ constructors,Linking a Mixed C++ & Ada Program,Building Mixed Ada and C++ Programs
6037 @anchor{gnat_ugn/the_gnat_compilation_model id67}@anchor{bd}@anchor{gnat_ugn/the_gnat_compilation_model a-simple-example}@anchor{be}
6038 @subsubsection A Simple Example
6041 The following example, provided as part of the GNAT examples, shows how
6042 to achieve procedural interfacing between Ada and C++ in both
6043 directions. The C++ class A has two methods. The first method is exported
6044 to Ada by the means of an extern C wrapper function. The second method
6045 calls an Ada subprogram. On the Ada side, The C++ calls are modelled by
6046 a limited record with a layout comparable to the C++ class. The Ada
6047 subprogram, in turn, calls the C++ method. So, starting from the C++
6048 main program, the process passes back and forth between the two
6051 Here are the compilation commands:
6054 $ gnatmake -c simple_cpp_interface
6057 $ gnatbind -n simple_cpp_interface
6058 $ gnatlink simple_cpp_interface -o cpp_main --LINK=g++ -lstdc++ ex7.o cpp_main.o
6061 Here are the corresponding sources:
6069 void adainit (void);
6070 void adafinal (void);
6071 void method1 (A *t);
6095 class A : public Origin @{
6097 void method1 (void);
6098 void method2 (int v);
6110 extern "C" @{ void ada_method2 (A *t, int v);@}
6112 void A::method1 (void)
6115 printf ("in A::method1, a_value = %d \\n",a_value);
6118 void A::method2 (int v)
6120 ada_method2 (this, v);
6121 printf ("in A::method2, a_value = %d \\n",a_value);
6127 printf ("in A::A, a_value = %d \\n",a_value);
6132 -- simple_cpp_interface.ads
6134 package Simple_Cpp_Interface is
6137 Vptr : System.Address;
6141 pragma Convention (C, A);
6143 procedure Method1 (This : in out A);
6144 pragma Import (C, Method1);
6146 procedure Ada_Method2 (This : in out A; V : Integer);
6147 pragma Export (C, Ada_Method2);
6149 end Simple_Cpp_Interface;
6153 -- simple_cpp_interface.adb
6154 package body Simple_Cpp_Interface is
6156 procedure Ada_Method2 (This : in out A; V : Integer) is
6162 end Simple_Cpp_Interface;
6165 @node Interfacing with C++ constructors,Interfacing with C++ at the Class Level,A Simple Example,Building Mixed Ada and C++ Programs
6166 @anchor{gnat_ugn/the_gnat_compilation_model id68}@anchor{bf}@anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-constructors}@anchor{c0}
6167 @subsubsection Interfacing with C++ constructors
6170 In order to interface with C++ constructors GNAT provides the
6171 @code{pragma CPP_Constructor} (see the @cite{GNAT_Reference_Manual}
6172 for additional information).
6173 In this section we present some common uses of C++ constructors
6174 in mixed-languages programs in GNAT.
6176 Let us assume that we need to interface with the following
6184 virtual int Get_Value ();
6185 Root(); // Default constructor
6186 Root(int v); // 1st non-default constructor
6187 Root(int v, int w); // 2nd non-default constructor
6191 For this purpose we can write the following package spec (further
6192 information on how to build this spec is available in
6193 @ref{c1,,Interfacing with C++ at the Class Level} and
6194 @ref{19,,Generating Ada Bindings for C and C++ headers}).
6197 with Interfaces.C; use Interfaces.C;
6199 type Root is tagged limited record
6203 pragma Import (CPP, Root);
6205 function Get_Value (Obj : Root) return int;
6206 pragma Import (CPP, Get_Value);
6208 function Constructor return Root;
6209 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ev");
6211 function Constructor (v : Integer) return Root;
6212 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Ei");
6214 function Constructor (v, w : Integer) return Root;
6215 pragma Cpp_Constructor (Constructor, "_ZN4RootC1Eii");
6219 On the Ada side the constructor is represented by a function (whose
6220 name is arbitrary) that returns the classwide type corresponding to
6221 the imported C++ class. Although the constructor is described as a
6222 function, it is typically a procedure with an extra implicit argument
6223 (the object being initialized) at the implementation level. GNAT
6224 issues the appropriate call, whatever it is, to get the object
6225 properly initialized.
6227 Constructors can only appear in the following contexts:
6233 On the right side of an initialization of an object of type @code{T}.
6236 On the right side of an initialization of a record component of type @code{T}.
6239 In an Ada 2005 limited aggregate.
6242 In an Ada 2005 nested limited aggregate.
6245 In an Ada 2005 limited aggregate that initializes an object built in
6246 place by an extended return statement.
6249 In a declaration of an object whose type is a class imported from C++,
6250 either the default C++ constructor is implicitly called by GNAT, or
6251 else the required C++ constructor must be explicitly called in the
6252 expression that initializes the object. For example:
6256 Obj2 : Root := Constructor;
6257 Obj3 : Root := Constructor (v => 10);
6258 Obj4 : Root := Constructor (30, 40);
6261 The first two declarations are equivalent: in both cases the default C++
6262 constructor is invoked (in the former case the call to the constructor is
6263 implicit, and in the latter case the call is explicit in the object
6264 declaration). @code{Obj3} is initialized by the C++ non-default constructor
6265 that takes an integer argument, and @code{Obj4} is initialized by the
6266 non-default C++ constructor that takes two integers.
6268 Let us derive the imported C++ class in the Ada side. For example:
6271 type DT is new Root with record
6272 C_Value : Natural := 2009;
6276 In this case the components DT inherited from the C++ side must be
6277 initialized by a C++ constructor, and the additional Ada components
6278 of type DT are initialized by GNAT. The initialization of such an
6279 object is done either by default, or by means of a function returning
6280 an aggregate of type DT, or by means of an extension aggregate.
6284 Obj6 : DT := Function_Returning_DT (50);
6285 Obj7 : DT := (Constructor (30,40) with C_Value => 50);
6288 The declaration of @code{Obj5} invokes the default constructors: the
6289 C++ default constructor of the parent type takes care of the initialization
6290 of the components inherited from Root, and GNAT takes care of the default
6291 initialization of the additional Ada components of type DT (that is,
6292 @code{C_Value} is initialized to value 2009). The order of invocation of
6293 the constructors is consistent with the order of elaboration required by
6294 Ada and C++. That is, the constructor of the parent type is always called
6295 before the constructor of the derived type.
6297 Let us now consider a record that has components whose type is imported
6298 from C++. For example:
6301 type Rec1 is limited record
6302 Data1 : Root := Constructor (10);
6303 Value : Natural := 1000;
6306 type Rec2 (D : Integer := 20) is limited record
6308 Data2 : Root := Constructor (D, 30);
6312 The initialization of an object of type @code{Rec2} will call the
6313 non-default C++ constructors specified for the imported components.
6320 Using Ada 2005 we can use limited aggregates to initialize an object
6321 invoking C++ constructors that differ from those specified in the type
6322 declarations. For example:
6325 Obj9 : Rec2 := (Rec => (Data1 => Constructor (15, 16),
6330 The above declaration uses an Ada 2005 limited aggregate to
6331 initialize @code{Obj9}, and the C++ constructor that has two integer
6332 arguments is invoked to initialize the @code{Data1} component instead
6333 of the constructor specified in the declaration of type @code{Rec1}. In
6334 Ada 2005 the box in the aggregate indicates that unspecified components
6335 are initialized using the expression (if any) available in the component
6336 declaration. That is, in this case discriminant @code{D} is initialized
6337 to value @code{20}, @code{Value} is initialized to value 1000, and the
6338 non-default C++ constructor that handles two integers takes care of
6339 initializing component @code{Data2} with values @code{20,30}.
6341 In Ada 2005 we can use the extended return statement to build the Ada
6342 equivalent to C++ non-default constructors. For example:
6345 function Constructor (V : Integer) return Rec2 is
6347 return Obj : Rec2 := (Rec => (Data1 => Constructor (V, 20),
6350 -- Further actions required for construction of
6351 -- objects of type Rec2
6357 In this example the extended return statement construct is used to
6358 build in place the returned object whose components are initialized
6359 by means of a limited aggregate. Any further action associated with
6360 the constructor can be placed inside the construct.
6362 @node Interfacing with C++ at the Class Level,,Interfacing with C++ constructors,Building Mixed Ada and C++ Programs
6363 @anchor{gnat_ugn/the_gnat_compilation_model interfacing-with-c-at-the-class-level}@anchor{c1}@anchor{gnat_ugn/the_gnat_compilation_model id69}@anchor{c2}
6364 @subsubsection Interfacing with C++ at the Class Level
6367 In this section we demonstrate the GNAT features for interfacing with
6368 C++ by means of an example making use of Ada 2005 abstract interface
6369 types. This example consists of a classification of animals; classes
6370 have been used to model our main classification of animals, and
6371 interfaces provide support for the management of secondary
6372 classifications. We first demonstrate a case in which the types and
6373 constructors are defined on the C++ side and imported from the Ada
6374 side, and latter the reverse case.
6376 The root of our derivation will be the @code{Animal} class, with a
6377 single private attribute (the @code{Age} of the animal), a constructor,
6378 and two public primitives to set and get the value of this attribute.
6383 virtual void Set_Age (int New_Age);
6385 Animal() @{Age_Count = 0;@};
6391 Abstract interface types are defined in C++ by means of classes with pure
6392 virtual functions and no data members. In our example we will use two
6393 interfaces that provide support for the common management of @code{Carnivore}
6394 and @code{Domestic} animals:
6399 virtual int Number_Of_Teeth () = 0;
6404 virtual void Set_Owner (char* Name) = 0;
6408 Using these declarations, we can now say that a @code{Dog} is an animal that is
6409 both Carnivore and Domestic, that is:
6412 class Dog : Animal, Carnivore, Domestic @{
6414 virtual int Number_Of_Teeth ();
6415 virtual void Set_Owner (char* Name);
6417 Dog(); // Constructor
6424 In the following examples we will assume that the previous declarations are
6425 located in a file named @code{animals.h}. The following package demonstrates
6426 how to import these C++ declarations from the Ada side:
6429 with Interfaces.C.Strings; use Interfaces.C.Strings;
6431 type Carnivore is limited interface;
6432 pragma Convention (C_Plus_Plus, Carnivore);
6433 function Number_Of_Teeth (X : Carnivore)
6434 return Natural is abstract;
6436 type Domestic is limited interface;
6437 pragma Convention (C_Plus_Plus, Domestic);
6439 (X : in out Domestic;
6440 Name : Chars_Ptr) is abstract;
6442 type Animal is tagged limited record
6445 pragma Import (C_Plus_Plus, Animal);
6447 procedure Set_Age (X : in out Animal; Age : Integer);
6448 pragma Import (C_Plus_Plus, Set_Age);
6450 function Age (X : Animal) return Integer;
6451 pragma Import (C_Plus_Plus, Age);
6453 function New_Animal return Animal;
6454 pragma CPP_Constructor (New_Animal);
6455 pragma Import (CPP, New_Animal, "_ZN6AnimalC1Ev");
6457 type Dog is new Animal and Carnivore and Domestic with record
6458 Tooth_Count : Natural;
6461 pragma Import (C_Plus_Plus, Dog);
6463 function Number_Of_Teeth (A : Dog) return Natural;
6464 pragma Import (C_Plus_Plus, Number_Of_Teeth);
6466 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
6467 pragma Import (C_Plus_Plus, Set_Owner);
6469 function New_Dog return Dog;
6470 pragma CPP_Constructor (New_Dog);
6471 pragma Import (CPP, New_Dog, "_ZN3DogC2Ev");
6475 Thanks to the compatibility between GNAT run-time structures and the C++ ABI,
6476 interfacing with these C++ classes is easy. The only requirement is that all
6477 the primitives and components must be declared exactly in the same order in
6480 Regarding the abstract interfaces, we must indicate to the GNAT compiler by
6481 means of a @code{pragma Convention (C_Plus_Plus)}, the convention used to pass
6482 the arguments to the called primitives will be the same as for C++. For the
6483 imported classes we use @code{pragma Import} with convention @code{C_Plus_Plus}
6484 to indicate that they have been defined on the C++ side; this is required
6485 because the dispatch table associated with these tagged types will be built
6486 in the C++ side and therefore will not contain the predefined Ada primitives
6487 which Ada would otherwise expect.
6489 As the reader can see there is no need to indicate the C++ mangled names
6490 associated with each subprogram because it is assumed that all the calls to
6491 these primitives will be dispatching calls. The only exception is the
6492 constructor, which must be registered with the compiler by means of
6493 @code{pragma CPP_Constructor} and needs to provide its associated C++
6494 mangled name because the Ada compiler generates direct calls to it.
6496 With the above packages we can now declare objects of type Dog on the Ada side
6497 and dispatch calls to the corresponding subprograms on the C++ side. We can
6498 also extend the tagged type Dog with further fields and primitives, and
6499 override some of its C++ primitives on the Ada side. For example, here we have
6500 a type derivation defined on the Ada side that inherits all the dispatching
6501 primitives of the ancestor from the C++ side.
6504 with Animals; use Animals;
6505 package Vaccinated_Animals is
6506 type Vaccinated_Dog is new Dog with null record;
6507 function Vaccination_Expired (A : Vaccinated_Dog) return Boolean;
6508 end Vaccinated_Animals;
6511 It is important to note that, because of the ABI compatibility, the programmer
6512 does not need to add any further information to indicate either the object
6513 layout or the dispatch table entry associated with each dispatching operation.
6515 Now let us define all the types and constructors on the Ada side and export
6516 them to C++, using the same hierarchy of our previous example:
6519 with Interfaces.C.Strings;
6520 use Interfaces.C.Strings;
6522 type Carnivore is limited interface;
6523 pragma Convention (C_Plus_Plus, Carnivore);
6524 function Number_Of_Teeth (X : Carnivore)
6525 return Natural is abstract;
6527 type Domestic is limited interface;
6528 pragma Convention (C_Plus_Plus, Domestic);
6530 (X : in out Domestic;
6531 Name : Chars_Ptr) is abstract;
6533 type Animal is tagged record
6536 pragma Convention (C_Plus_Plus, Animal);
6538 procedure Set_Age (X : in out Animal; Age : Integer);
6539 pragma Export (C_Plus_Plus, Set_Age);
6541 function Age (X : Animal) return Integer;
6542 pragma Export (C_Plus_Plus, Age);
6544 function New_Animal return Animal'Class;
6545 pragma Export (C_Plus_Plus, New_Animal);
6547 type Dog is new Animal and Carnivore and Domestic with record
6548 Tooth_Count : Natural;
6549 Owner : String (1 .. 30);
6551 pragma Convention (C_Plus_Plus, Dog);
6553 function Number_Of_Teeth (A : Dog) return Natural;
6554 pragma Export (C_Plus_Plus, Number_Of_Teeth);
6556 procedure Set_Owner (A : in out Dog; Name : Chars_Ptr);
6557 pragma Export (C_Plus_Plus, Set_Owner);
6559 function New_Dog return Dog'Class;
6560 pragma Export (C_Plus_Plus, New_Dog);
6564 Compared with our previous example the only differences are the use of
6565 @code{pragma Convention} (instead of @code{pragma Import}), and the use of
6566 @code{pragma Export} to indicate to the GNAT compiler that the primitives will
6567 be available to C++. Thanks to the ABI compatibility, on the C++ side there is
6568 nothing else to be done; as explained above, the only requirement is that all
6569 the primitives and components are declared in exactly the same order.
6571 For completeness, let us see a brief C++ main program that uses the
6572 declarations available in @code{animals.h} (presented in our first example) to
6573 import and use the declarations from the Ada side, properly initializing and
6574 finalizing the Ada run-time system along the way:
6577 #include "animals.h"
6579 using namespace std;
6581 void Check_Carnivore (Carnivore *obj) @{...@}
6582 void Check_Domestic (Domestic *obj) @{...@}
6583 void Check_Animal (Animal *obj) @{...@}
6584 void Check_Dog (Dog *obj) @{...@}
6587 void adainit (void);
6588 void adafinal (void);
6594 Dog *obj = new_dog(); // Ada constructor
6595 Check_Carnivore (obj); // Check secondary DT
6596 Check_Domestic (obj); // Check secondary DT
6597 Check_Animal (obj); // Check primary DT
6598 Check_Dog (obj); // Check primary DT
6603 adainit (); test(); adafinal ();
6608 @node Generating Ada Bindings for C and C++ headers,Generating C Headers for Ada Specifications,Building Mixed Ada and C++ Programs,Mixed Language Programming
6609 @anchor{gnat_ugn/the_gnat_compilation_model id70}@anchor{c3}@anchor{gnat_ugn/the_gnat_compilation_model generating-ada-bindings-for-c-and-c-headers}@anchor{19}
6610 @subsection Generating Ada Bindings for C and C++ headers
6613 @geindex Binding generation (for C and C++ headers)
6615 @geindex C headers (binding generation)
6617 @geindex C++ headers (binding generation)
6619 GNAT includes a binding generator for C and C++ headers which is
6620 intended to do 95% of the tedious work of generating Ada specs from C
6621 or C++ header files.
6623 Note that this capability is not intended to generate 100% correct Ada specs,
6624 and will is some cases require manual adjustments, although it can often
6625 be used out of the box in practice.
6627 Some of the known limitations include:
6633 only very simple character constant macros are translated into Ada
6634 constants. Function macros (macros with arguments) are partially translated
6635 as comments, to be completed manually if needed.
6638 some extensions (e.g. vector types) are not supported
6641 pointers to pointers or complex structures are mapped to System.Address
6644 identifiers with identical name (except casing) will generate compilation
6645 errors (e.g. @code{shm_get} vs @code{SHM_GET}).
6648 The code generated is using the Ada 2005 syntax, which makes it
6649 easier to interface with other languages than previous versions of Ada.
6652 * Running the Binding Generator::
6653 * Generating Bindings for C++ Headers::
6658 @node Running the Binding Generator,Generating Bindings for C++ Headers,,Generating Ada Bindings for C and C++ headers
6659 @anchor{gnat_ugn/the_gnat_compilation_model id71}@anchor{c4}@anchor{gnat_ugn/the_gnat_compilation_model running-the-binding-generator}@anchor{c5}
6660 @subsubsection Running the Binding Generator
6663 The binding generator is part of the @code{gcc} compiler and can be
6664 invoked via the @code{-fdump-ada-spec} switch, which will generate Ada
6665 spec files for the header files specified on the command line, and all
6666 header files needed by these files transitively. For example:
6669 $ g++ -c -fdump-ada-spec -C /usr/include/time.h
6670 $ gcc -c -gnat05 *.ads
6673 will generate, under GNU/Linux, the following files: @code{time_h.ads},
6674 @code{bits_time_h.ads}, @code{stddef_h.ads}, @code{bits_types_h.ads} which
6675 correspond to the files @code{/usr/include/time.h},
6676 @code{/usr/include/bits/time.h}, etc..., and will then compile these Ada specs
6679 The @code{-C} switch tells @code{gcc} to extract comments from headers,
6680 and will attempt to generate corresponding Ada comments.
6682 If you want to generate a single Ada file and not the transitive closure, you
6683 can use instead the @code{-fdump-ada-spec-slim} switch.
6685 You can optionally specify a parent unit, of which all generated units will
6686 be children, using @code{-fada-spec-parent=@emph{unit}}.
6688 Note that we recommend when possible to use the @emph{g++} driver to
6689 generate bindings, even for most C headers, since this will in general
6690 generate better Ada specs. For generating bindings for C++ headers, it is
6691 mandatory to use the @emph{g++} command, or @emph{gcc -x c++} which
6692 is equivalent in this case. If @emph{g++} cannot work on your C headers
6693 because of incompatibilities between C and C++, then you can fallback to
6696 For an example of better bindings generated from the C++ front-end,
6697 the name of the parameters (when available) are actually ignored by the C
6698 front-end. Consider the following C header:
6701 extern void foo (int variable);
6704 with the C front-end, @code{variable} is ignored, and the above is handled as:
6707 extern void foo (int);
6710 generating a generic:
6713 procedure foo (param1 : int);
6716 with the C++ front-end, the name is available, and we generate:
6719 procedure foo (variable : int);
6722 In some cases, the generated bindings will be more complete or more meaningful
6723 when defining some macros, which you can do via the @code{-D} switch. This
6724 is for example the case with @code{Xlib.h} under GNU/Linux:
6727 $ g++ -c -fdump-ada-spec -DXLIB_ILLEGAL_ACCESS -C /usr/include/X11/Xlib.h
6730 The above will generate more complete bindings than a straight call without
6731 the @code{-DXLIB_ILLEGAL_ACCESS} switch.
6733 In other cases, it is not possible to parse a header file in a stand-alone
6734 manner, because other include files need to be included first. In this
6735 case, the solution is to create a small header file including the needed
6736 @code{#include} and possible @code{#define} directives. For example, to
6737 generate Ada bindings for @code{readline/readline.h}, you need to first
6738 include @code{stdio.h}, so you can create a file with the following two
6739 lines in e.g. @code{readline1.h}:
6743 #include <readline/readline.h>
6746 and then generate Ada bindings from this file:
6749 $ g++ -c -fdump-ada-spec readline1.h
6752 @node Generating Bindings for C++ Headers,Switches,Running the Binding Generator,Generating Ada Bindings for C and C++ headers
6753 @anchor{gnat_ugn/the_gnat_compilation_model id72}@anchor{c6}@anchor{gnat_ugn/the_gnat_compilation_model generating-bindings-for-c-headers}@anchor{c7}
6754 @subsubsection Generating Bindings for C++ Headers
6757 Generating bindings for C++ headers is done using the same options, always
6758 with the @emph{g++} compiler. Note that generating Ada spec from C++ headers is a
6759 much more complex job and support for C++ headers is much more limited that
6760 support for C headers. As a result, you will need to modify the resulting
6761 bindings by hand more extensively when using C++ headers.
6763 In this mode, C++ classes will be mapped to Ada tagged types, constructors
6764 will be mapped using the @code{CPP_Constructor} pragma, and when possible,
6765 multiple inheritance of abstract classes will be mapped to Ada interfaces
6766 (see the @emph{Interfacing to C++} section in the @cite{GNAT Reference Manual}
6767 for additional information on interfacing to C++).
6769 For example, given the following C++ header file:
6774 virtual int Number_Of_Teeth () = 0;
6779 virtual void Set_Owner (char* Name) = 0;
6785 virtual void Set_Age (int New_Age);
6788 class Dog : Animal, Carnivore, Domestic @{
6793 virtual int Number_Of_Teeth ();
6794 virtual void Set_Owner (char* Name);
6800 The corresponding Ada code is generated:
6803 package Class_Carnivore is
6804 type Carnivore is limited interface;
6805 pragma Import (CPP, Carnivore);
6807 function Number_Of_Teeth (this : access Carnivore) return int is abstract;
6809 use Class_Carnivore;
6811 package Class_Domestic is
6812 type Domestic is limited interface;
6813 pragma Import (CPP, Domestic);
6816 (this : access Domestic;
6817 Name : Interfaces.C.Strings.chars_ptr) is abstract;
6821 package Class_Animal is
6822 type Animal is tagged limited record
6823 Age_Count : aliased int;
6825 pragma Import (CPP, Animal);
6827 procedure Set_Age (this : access Animal; New_Age : int);
6828 pragma Import (CPP, Set_Age, "_ZN6Animal7Set_AgeEi");
6832 package Class_Dog is
6833 type Dog is new Animal and Carnivore and Domestic with record
6834 Tooth_Count : aliased int;
6835 Owner : Interfaces.C.Strings.chars_ptr;
6837 pragma Import (CPP, Dog);
6839 function Number_Of_Teeth (this : access Dog) return int;
6840 pragma Import (CPP, Number_Of_Teeth, "_ZN3Dog15Number_Of_TeethEv");
6843 (this : access Dog; Name : Interfaces.C.Strings.chars_ptr);
6844 pragma Import (CPP, Set_Owner, "_ZN3Dog9Set_OwnerEPc");
6846 function New_Dog return Dog;
6847 pragma CPP_Constructor (New_Dog);
6848 pragma Import (CPP, New_Dog, "_ZN3DogC1Ev");
6853 @node Switches,,Generating Bindings for C++ Headers,Generating Ada Bindings for C and C++ headers
6854 @anchor{gnat_ugn/the_gnat_compilation_model switches}@anchor{c8}@anchor{gnat_ugn/the_gnat_compilation_model switches-for-ada-binding-generation}@anchor{c9}
6855 @subsubsection Switches
6858 @geindex -fdump-ada-spec (gcc)
6863 @item @code{-fdump-ada-spec}
6865 Generate Ada spec files for the given header files transitively (including
6866 all header files that these headers depend upon).
6869 @geindex -fdump-ada-spec-slim (gcc)
6874 @item @code{-fdump-ada-spec-slim}
6876 Generate Ada spec files for the header files specified on the command line
6880 @geindex -fada-spec-parent (gcc)
6885 @item @code{-fada-spec-parent=@emph{unit}}
6887 Specifies that all files generated by @code{-fdump-ada-spec} are
6888 to be child units of the specified parent unit.
6898 Extract comments from headers and generate Ada comments in the Ada spec files.
6901 @node Generating C Headers for Ada Specifications,,Generating Ada Bindings for C and C++ headers,Mixed Language Programming
6902 @anchor{gnat_ugn/the_gnat_compilation_model generating-c-headers-for-ada-specifications}@anchor{ca}@anchor{gnat_ugn/the_gnat_compilation_model id73}@anchor{cb}
6903 @subsection Generating C Headers for Ada Specifications
6906 @geindex Binding generation (for Ada specs)
6908 @geindex C headers (binding generation)
6910 GNAT includes a C header generator for Ada specifications which supports
6911 Ada types that have a direct mapping to C types. This includes in particular
6927 Composition of the above types
6930 Constant declarations
6936 Subprogram declarations
6940 * Running the C Header Generator::
6944 @node Running the C Header Generator,,,Generating C Headers for Ada Specifications
6945 @anchor{gnat_ugn/the_gnat_compilation_model running-the-c-header-generator}@anchor{cc}
6946 @subsubsection Running the C Header Generator
6949 The C header generator is part of the GNAT compiler and can be invoked via
6950 the @code{-gnatceg} combination of switches, which will generate a @code{.h}
6951 file corresponding to the given input file (Ada spec or body). Note that
6952 only spec files are processed in any case, so giving a spec or a body file
6953 as input is equivalent. For example:
6956 $ gcc -c -gnatceg pack1.ads
6959 will generate a self-contained file called @code{pack1.h} including
6960 common definitions from the Ada Standard package, followed by the
6961 definitions included in @code{pack1.ads}, as well as all the other units
6962 withed by this file.
6964 For instance, given the following Ada files:
6968 type Int is range 1 .. 10;
6977 Field1, Field2 : Pack2.Int;
6980 Global : Rec := (1, 2);
6982 procedure Proc1 (R : Rec);
6983 procedure Proc2 (R : in out Rec);
6987 The above @code{gcc} command will generate the following @code{pack1.h} file:
6990 /* Standard definitions skipped */
6993 typedef short_short_integer pack2__TintB;
6994 typedef pack2__TintB pack2__int;
6995 #endif /* PACK2_ADS */
6999 typedef struct _pack1__rec @{
7003 extern pack1__rec pack1__global;
7004 extern void pack1__proc1(const pack1__rec r);
7005 extern void pack1__proc2(pack1__rec *r);
7006 #endif /* PACK1_ADS */
7009 You can then @code{include} @code{pack1.h} from a C source file and use the types,
7010 call subprograms, reference objects, and constants.
7012 @node GNAT and Other Compilation Models,Using GNAT Files with External Tools,Mixed Language Programming,The GNAT Compilation Model
7013 @anchor{gnat_ugn/the_gnat_compilation_model id74}@anchor{cd}@anchor{gnat_ugn/the_gnat_compilation_model gnat-and-other-compilation-models}@anchor{45}
7014 @section GNAT and Other Compilation Models
7017 This section compares the GNAT model with the approaches taken in
7018 other environents, first the C/C++ model and then the mechanism that
7019 has been used in other Ada systems, in particular those traditionally
7023 * Comparison between GNAT and C/C++ Compilation Models::
7024 * Comparison between GNAT and Conventional Ada Library Models::
7028 @node Comparison between GNAT and C/C++ Compilation Models,Comparison between GNAT and Conventional Ada Library Models,,GNAT and Other Compilation Models
7029 @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-c-c-compilation-models}@anchor{ce}@anchor{gnat_ugn/the_gnat_compilation_model id75}@anchor{cf}
7030 @subsection Comparison between GNAT and C/C++ Compilation Models
7033 The GNAT model of compilation is close to the C and C++ models. You can
7034 think of Ada specs as corresponding to header files in C. As in C, you
7035 don't need to compile specs; they are compiled when they are used. The
7036 Ada @emph{with} is similar in effect to the @code{#include} of a C
7039 One notable difference is that, in Ada, you may compile specs separately
7040 to check them for semantic and syntactic accuracy. This is not always
7041 possible with C headers because they are fragments of programs that have
7042 less specific syntactic or semantic rules.
7044 The other major difference is the requirement for running the binder,
7045 which performs two important functions. First, it checks for
7046 consistency. In C or C++, the only defense against assembling
7047 inconsistent programs lies outside the compiler, in a makefile, for
7048 example. The binder satisfies the Ada requirement that it be impossible
7049 to construct an inconsistent program when the compiler is used in normal
7052 @geindex Elaboration order control
7054 The other important function of the binder is to deal with elaboration
7055 issues. There are also elaboration issues in C++ that are handled
7056 automatically. This automatic handling has the advantage of being
7057 simpler to use, but the C++ programmer has no control over elaboration.
7058 Where @code{gnatbind} might complain there was no valid order of
7059 elaboration, a C++ compiler would simply construct a program that
7060 malfunctioned at run time.
7062 @node Comparison between GNAT and Conventional Ada Library Models,,Comparison between GNAT and C/C++ Compilation Models,GNAT and Other Compilation Models
7063 @anchor{gnat_ugn/the_gnat_compilation_model comparison-between-gnat-and-conventional-ada-library-models}@anchor{d0}@anchor{gnat_ugn/the_gnat_compilation_model id76}@anchor{d1}
7064 @subsection Comparison between GNAT and Conventional Ada Library Models
7067 This section is intended for Ada programmers who have
7068 used an Ada compiler implementing the traditional Ada library
7069 model, as described in the Ada Reference Manual.
7071 @geindex GNAT library
7073 In GNAT, there is no 'library' in the normal sense. Instead, the set of
7074 source files themselves acts as the library. Compiling Ada programs does
7075 not generate any centralized information, but rather an object file and
7076 a ALI file, which are of interest only to the binder and linker.
7077 In a traditional system, the compiler reads information not only from
7078 the source file being compiled, but also from the centralized library.
7079 This means that the effect of a compilation depends on what has been
7080 previously compiled. In particular:
7086 When a unit is @emph{with}ed, the unit seen by the compiler corresponds
7087 to the version of the unit most recently compiled into the library.
7090 Inlining is effective only if the necessary body has already been
7091 compiled into the library.
7094 Compiling a unit may obsolete other units in the library.
7097 In GNAT, compiling one unit never affects the compilation of any other
7098 units because the compiler reads only source files. Only changes to source
7099 files can affect the results of a compilation. In particular:
7105 When a unit is @emph{with}ed, the unit seen by the compiler corresponds
7106 to the source version of the unit that is currently accessible to the
7112 Inlining requires the appropriate source files for the package or
7113 subprogram bodies to be available to the compiler. Inlining is always
7114 effective, independent of the order in which units are compiled.
7117 Compiling a unit never affects any other compilations. The editing of
7118 sources may cause previous compilations to be out of date if they
7119 depended on the source file being modified.
7122 The most important result of these differences is that order of compilation
7123 is never significant in GNAT. There is no situation in which one is
7124 required to do one compilation before another. What shows up as order of
7125 compilation requirements in the traditional Ada library becomes, in
7126 GNAT, simple source dependencies; in other words, there is only a set
7127 of rules saying what source files must be present when a file is
7130 @node Using GNAT Files with External Tools,,GNAT and Other Compilation Models,The GNAT Compilation Model
7131 @anchor{gnat_ugn/the_gnat_compilation_model using-gnat-files-with-external-tools}@anchor{1a}@anchor{gnat_ugn/the_gnat_compilation_model id77}@anchor{d2}
7132 @section Using GNAT Files with External Tools
7135 This section explains how files that are produced by GNAT may be
7136 used with tools designed for other languages.
7139 * Using Other Utility Programs with GNAT::
7140 * The External Symbol Naming Scheme of GNAT::
7144 @node Using Other Utility Programs with GNAT,The External Symbol Naming Scheme of GNAT,,Using GNAT Files with External Tools
7145 @anchor{gnat_ugn/the_gnat_compilation_model using-other-utility-programs-with-gnat}@anchor{d3}@anchor{gnat_ugn/the_gnat_compilation_model id78}@anchor{d4}
7146 @subsection Using Other Utility Programs with GNAT
7149 The object files generated by GNAT are in standard system format and in
7150 particular the debugging information uses this format. This means
7151 programs generated by GNAT can be used with existing utilities that
7152 depend on these formats.
7154 In general, any utility program that works with C will also often work with
7155 Ada programs generated by GNAT. This includes software utilities such as
7156 gprof (a profiling program), gdb (the FSF debugger), and utilities such
7159 @node The External Symbol Naming Scheme of GNAT,,Using Other Utility Programs with GNAT,Using GNAT Files with External Tools
7160 @anchor{gnat_ugn/the_gnat_compilation_model the-external-symbol-naming-scheme-of-gnat}@anchor{d5}@anchor{gnat_ugn/the_gnat_compilation_model id79}@anchor{d6}
7161 @subsection The External Symbol Naming Scheme of GNAT
7164 In order to interpret the output from GNAT, when using tools that are
7165 originally intended for use with other languages, it is useful to
7166 understand the conventions used to generate link names from the Ada
7169 All link names are in all lowercase letters. With the exception of library
7170 procedure names, the mechanism used is simply to use the full expanded
7171 Ada name with dots replaced by double underscores. For example, suppose
7172 we have the following package spec:
7180 @geindex pragma Export
7182 The variable @code{MN} has a full expanded Ada name of @code{QRS.MN}, so
7183 the corresponding link name is @code{qrs__mn}.
7184 Of course if a @code{pragma Export} is used this may be overridden:
7189 pragma Export (Var1, C, External_Name => "var1_name");
7191 pragma Export (Var2, C, Link_Name => "var2_link_name");
7195 In this case, the link name for @code{Var1} is whatever link name the
7196 C compiler would assign for the C function @code{var1_name}. This typically
7197 would be either @code{var1_name} or @code{_var1_name}, depending on operating
7198 system conventions, but other possibilities exist. The link name for
7199 @code{Var2} is @code{var2_link_name}, and this is not operating system
7202 One exception occurs for library level procedures. A potential ambiguity
7203 arises between the required name @code{_main} for the C main program,
7204 and the name we would otherwise assign to an Ada library level procedure
7205 called @code{Main} (which might well not be the main program).
7207 To avoid this ambiguity, we attach the prefix @code{_ada_} to such
7208 names. So if we have a library level procedure such as:
7211 procedure Hello (S : String);
7214 the external name of this procedure will be @code{_ada_hello}.
7216 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
7218 @node Building Executable Programs with GNAT,GNAT Utility Programs,The GNAT Compilation Model,Top
7219 @anchor{gnat_ugn/building_executable_programs_with_gnat building-executable-programs-with-gnat}@anchor{a}@anchor{gnat_ugn/building_executable_programs_with_gnat doc}@anchor{d7}@anchor{gnat_ugn/building_executable_programs_with_gnat id1}@anchor{d8}
7220 @chapter Building Executable Programs with GNAT
7223 This chapter describes first the gnatmake tool
7224 (@ref{1b,,Building with gnatmake}),
7225 which automatically determines the set of sources
7226 needed by an Ada compilation unit and executes the necessary
7227 (re)compilations, binding and linking.
7228 It also explains how to use each tool individually: the
7229 compiler (gcc, see @ref{1c,,Compiling with gcc}),
7230 binder (gnatbind, see @ref{1d,,Binding with gnatbind}),
7231 and linker (gnatlink, see @ref{1e,,Linking with gnatlink})
7232 to build executable programs.
7233 Finally, this chapter provides examples of
7234 how to make use of the general GNU make mechanism
7235 in a GNAT context (see @ref{1f,,Using the GNU make Utility}).
7239 * Building with gnatmake::
7240 * Compiling with gcc::
7241 * Compiler Switches::
7243 * Binding with gnatbind::
7244 * Linking with gnatlink::
7245 * Using the GNU make Utility::
7249 @node Building with gnatmake,Compiling with gcc,,Building Executable Programs with GNAT
7250 @anchor{gnat_ugn/building_executable_programs_with_gnat the-gnat-make-program-gnatmake}@anchor{1b}@anchor{gnat_ugn/building_executable_programs_with_gnat building-with-gnatmake}@anchor{d9}
7251 @section Building with @code{gnatmake}
7256 A typical development cycle when working on an Ada program consists of
7257 the following steps:
7263 Edit some sources to fix bugs;
7269 Compile all sources affected;
7272 Rebind and relink; and
7278 @geindex Dependency rules (compilation)
7280 The third step in particular can be tricky, because not only do the modified
7281 files have to be compiled, but any files depending on these files must also be
7282 recompiled. The dependency rules in Ada can be quite complex, especially
7283 in the presence of overloading, @code{use} clauses, generics and inlined
7286 @code{gnatmake} automatically takes care of the third and fourth steps
7287 of this process. It determines which sources need to be compiled,
7288 compiles them, and binds and links the resulting object files.
7290 Unlike some other Ada make programs, the dependencies are always
7291 accurately recomputed from the new sources. The source based approach of
7292 the GNAT compilation model makes this possible. This means that if
7293 changes to the source program cause corresponding changes in
7294 dependencies, they will always be tracked exactly correctly by
7297 Note that for advanced forms of project structure, we recommend creating
7298 a project file as explained in the @emph{GNAT_Project_Manager} chapter in the
7299 @emph{GPRbuild User's Guide}, and using the
7300 @code{gprbuild} tool which supports building with project files and works similarly
7304 * Running gnatmake::
7305 * Switches for gnatmake::
7306 * Mode Switches for gnatmake::
7307 * Notes on the Command Line::
7308 * How gnatmake Works::
7309 * Examples of gnatmake Usage::
7313 @node Running gnatmake,Switches for gnatmake,,Building with gnatmake
7314 @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatmake}@anchor{da}@anchor{gnat_ugn/building_executable_programs_with_gnat id2}@anchor{db}
7315 @subsection Running @code{gnatmake}
7318 The usual form of the @code{gnatmake} command is
7321 $ gnatmake [<switches>] <file_name> [<file_names>] [<mode_switches>]
7324 The only required argument is one @code{file_name}, which specifies
7325 a compilation unit that is a main program. Several @code{file_names} can be
7326 specified: this will result in several executables being built.
7327 If @code{switches} are present, they can be placed before the first
7328 @code{file_name}, between @code{file_names} or after the last @code{file_name}.
7329 If @code{mode_switches} are present, they must always be placed after
7330 the last @code{file_name} and all @code{switches}.
7332 If you are using standard file extensions (@code{.adb} and
7333 @code{.ads}), then the
7334 extension may be omitted from the @code{file_name} arguments. However, if
7335 you are using non-standard extensions, then it is required that the
7336 extension be given. A relative or absolute directory path can be
7337 specified in a @code{file_name}, in which case, the input source file will
7338 be searched for in the specified directory only. Otherwise, the input
7339 source file will first be searched in the directory where
7340 @code{gnatmake} was invoked and if it is not found, it will be search on
7341 the source path of the compiler as described in
7342 @ref{89,,Search Paths and the Run-Time Library (RTL)}.
7344 All @code{gnatmake} output (except when you specify @code{-M}) is sent to
7345 @code{stderr}. The output produced by the
7346 @code{-M} switch is sent to @code{stdout}.
7348 @node Switches for gnatmake,Mode Switches for gnatmake,Running gnatmake,Building with gnatmake
7349 @anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatmake}@anchor{dc}@anchor{gnat_ugn/building_executable_programs_with_gnat id3}@anchor{dd}
7350 @subsection Switches for @code{gnatmake}
7353 You may specify any of the following switches to @code{gnatmake}:
7355 @geindex --version (gnatmake)
7360 @item @code{--version}
7362 Display Copyright and version, then exit disregarding all other options.
7365 @geindex --help (gnatmake)
7372 If @code{--version} was not used, display usage, then exit disregarding
7376 @geindex --GCC=compiler_name (gnatmake)
7381 @item @code{--GCC=@emph{compiler_name}}
7383 Program used for compiling. The default is @code{gcc}. You need to use
7384 quotes around @code{compiler_name} if @code{compiler_name} contains
7385 spaces or other separator characters.
7386 As an example @code{--GCC="foo -x -y"}
7387 will instruct @code{gnatmake} to use @code{foo -x -y} as your
7388 compiler. A limitation of this syntax is that the name and path name of
7389 the executable itself must not include any embedded spaces. Note that
7390 switch @code{-c} is always inserted after your command name. Thus in the
7391 above example the compiler command that will be used by @code{gnatmake}
7392 will be @code{foo -c -x -y}. If several @code{--GCC=compiler_name} are
7393 used, only the last @code{compiler_name} is taken into account. However,
7394 all the additional switches are also taken into account. Thus,
7395 @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
7396 @code{--GCC="bar -x -y -z -t"}.
7399 @geindex --GNATBIND=binder_name (gnatmake)
7404 @item @code{--GNATBIND=@emph{binder_name}}
7406 Program used for binding. The default is @code{gnatbind}. You need to
7407 use quotes around @code{binder_name} if @code{binder_name} contains spaces
7408 or other separator characters.
7409 As an example @code{--GNATBIND="bar -x -y"}
7410 will instruct @code{gnatmake} to use @code{bar -x -y} as your
7411 binder. Binder switches that are normally appended by @code{gnatmake}
7412 to @code{gnatbind} are now appended to the end of @code{bar -x -y}.
7413 A limitation of this syntax is that the name and path name of the executable
7414 itself must not include any embedded spaces.
7417 @geindex --GNATLINK=linker_name (gnatmake)
7422 @item @code{--GNATLINK=@emph{linker_name}}
7424 Program used for linking. The default is @code{gnatlink}. You need to
7425 use quotes around @code{linker_name} if @code{linker_name} contains spaces
7426 or other separator characters.
7427 As an example @code{--GNATLINK="lan -x -y"}
7428 will instruct @code{gnatmake} to use @code{lan -x -y} as your
7429 linker. Linker switches that are normally appended by @code{gnatmake} to
7430 @code{gnatlink} are now appended to the end of @code{lan -x -y}.
7431 A limitation of this syntax is that the name and path name of the executable
7432 itself must not include any embedded spaces.
7434 @item @code{--create-map-file}
7436 When linking an executable, create a map file. The name of the map file
7437 has the same name as the executable with extension ".map".
7439 @item @code{--create-map-file=@emph{mapfile}}
7441 When linking an executable, create a map file with the specified name.
7444 @geindex --create-missing-dirs (gnatmake)
7449 @item @code{--create-missing-dirs}
7451 When using project files (@code{-P@emph{project}}), automatically create
7452 missing object directories, library directories and exec
7455 @item @code{--single-compile-per-obj-dir}
7457 Disallow simultaneous compilations in the same object directory when
7458 project files are used.
7460 @item @code{--subdirs=@emph{subdir}}
7462 Actual object directory of each project file is the subdirectory subdir of the
7463 object directory specified or defaulted in the project file.
7465 @item @code{--unchecked-shared-lib-imports}
7467 By default, shared library projects are not allowed to import static library
7468 projects. When this switch is used on the command line, this restriction is
7471 @item @code{--source-info=@emph{source info file}}
7473 Specify a source info file. This switch is active only when project files
7474 are used. If the source info file is specified as a relative path, then it is
7475 relative to the object directory of the main project. If the source info file
7476 does not exist, then after the Project Manager has successfully parsed and
7477 processed the project files and found the sources, it creates the source info
7478 file. If the source info file already exists and can be read successfully,
7479 then the Project Manager will get all the needed information about the sources
7480 from the source info file and will not look for them. This reduces the time
7481 to process the project files, especially when looking for sources that take a
7482 long time. If the source info file exists but cannot be parsed successfully,
7483 the Project Manager will attempt to recreate it. If the Project Manager fails
7484 to create the source info file, a message is issued, but gnatmake does not
7485 fail. @code{gnatmake} "trusts" the source info file. This means that
7486 if the source files have changed (addition, deletion, moving to a different
7487 source directory), then the source info file need to be deleted and recreated.
7490 @geindex -a (gnatmake)
7497 Consider all files in the make process, even the GNAT internal system
7498 files (for example, the predefined Ada library files), as well as any
7499 locked files. Locked files are files whose ALI file is write-protected.
7501 @code{gnatmake} does not check these files,
7502 because the assumption is that the GNAT internal files are properly up
7503 to date, and also that any write protected ALI files have been properly
7504 installed. Note that if there is an installation problem, such that one
7505 of these files is not up to date, it will be properly caught by the
7507 You may have to specify this switch if you are working on GNAT
7508 itself. The switch @code{-a} is also useful
7509 in conjunction with @code{-f}
7510 if you need to recompile an entire application,
7511 including run-time files, using special configuration pragmas,
7512 such as a @code{Normalize_Scalars} pragma.
7515 @code{gnatmake -a} compiles all GNAT
7517 @code{gcc -c -gnatpg} rather than @code{gcc -c}.
7520 @geindex -b (gnatmake)
7527 Bind only. Can be combined with @code{-c} to do
7528 compilation and binding, but no link.
7529 Can be combined with @code{-l}
7530 to do binding and linking. When not combined with
7532 all the units in the closure of the main program must have been previously
7533 compiled and must be up to date. The root unit specified by @code{file_name}
7534 may be given without extension, with the source extension or, if no GNAT
7535 Project File is specified, with the ALI file extension.
7538 @geindex -c (gnatmake)
7545 Compile only. Do not perform binding, except when @code{-b}
7546 is also specified. Do not perform linking, except if both
7548 @code{-l} are also specified.
7549 If the root unit specified by @code{file_name} is not a main unit, this is the
7550 default. Otherwise @code{gnatmake} will attempt binding and linking
7551 unless all objects are up to date and the executable is more recent than
7555 @geindex -C (gnatmake)
7562 Use a temporary mapping file. A mapping file is a way to communicate
7563 to the compiler two mappings: from unit names to file names (without
7564 any directory information) and from file names to path names (with
7565 full directory information). A mapping file can make the compiler's
7566 file searches faster, especially if there are many source directories,
7567 or the sources are read over a slow network connection. If
7568 @code{-P} is used, a mapping file is always used, so
7569 @code{-C} is unnecessary; in this case the mapping file
7570 is initially populated based on the project file. If
7571 @code{-C} is used without
7573 the mapping file is initially empty. Each invocation of the compiler
7574 will add any newly accessed sources to the mapping file.
7577 @geindex -C= (gnatmake)
7582 @item @code{-C=@emph{file}}
7584 Use a specific mapping file. The file, specified as a path name (absolute or
7585 relative) by this switch, should already exist, otherwise the switch is
7586 ineffective. The specified mapping file will be communicated to the compiler.
7587 This switch is not compatible with a project file
7588 (-P`file`) or with multiple compiling processes
7589 (-jnnn, when nnn is greater than 1).
7592 @geindex -d (gnatmake)
7599 Display progress for each source, up to date or not, as a single line:
7602 completed x out of y (zz%)
7605 If the file needs to be compiled this is displayed after the invocation of
7606 the compiler. These lines are displayed even in quiet output mode.
7609 @geindex -D (gnatmake)
7614 @item @code{-D @emph{dir}}
7616 Put all object files and ALI file in directory @code{dir}.
7617 If the @code{-D} switch is not used, all object files
7618 and ALI files go in the current working directory.
7620 This switch cannot be used when using a project file.
7623 @geindex -eI (gnatmake)
7628 @item @code{-eI@emph{nnn}}
7630 Indicates that the main source is a multi-unit source and the rank of the unit
7631 in the source file is nnn. nnn needs to be a positive number and a valid
7632 index in the source. This switch cannot be used when @code{gnatmake} is
7633 invoked for several mains.
7636 @geindex -eL (gnatmake)
7638 @geindex symbolic links
7645 Follow all symbolic links when processing project files.
7646 This should be used if your project uses symbolic links for files or
7647 directories, but is not needed in other cases.
7649 @geindex naming scheme
7651 This also assumes that no directory matches the naming scheme for files (for
7652 instance that you do not have a directory called "sources.ads" when using the
7653 default GNAT naming scheme).
7655 When you do not have to use this switch (i.e., by default), gnatmake is able to
7656 save a lot of system calls (several per source file and object file), which
7657 can result in a significant speed up to load and manipulate a project file,
7658 especially when using source files from a remote system.
7661 @geindex -eS (gnatmake)
7668 Output the commands for the compiler, the binder and the linker
7670 instead of standard error.
7673 @geindex -f (gnatmake)
7680 Force recompilations. Recompile all sources, even though some object
7681 files may be up to date, but don't recompile predefined or GNAT internal
7682 files or locked files (files with a write-protected ALI file),
7683 unless the @code{-a} switch is also specified.
7686 @geindex -F (gnatmake)
7693 When using project files, if some errors or warnings are detected during
7694 parsing and verbose mode is not in effect (no use of switch
7695 -v), then error lines start with the full path name of the project
7696 file, rather than its simple file name.
7699 @geindex -g (gnatmake)
7706 Enable debugging. This switch is simply passed to the compiler and to the
7710 @geindex -i (gnatmake)
7717 In normal mode, @code{gnatmake} compiles all object files and ALI files
7718 into the current directory. If the @code{-i} switch is used,
7719 then instead object files and ALI files that already exist are overwritten
7720 in place. This means that once a large project is organized into separate
7721 directories in the desired manner, then @code{gnatmake} will automatically
7722 maintain and update this organization. If no ALI files are found on the
7723 Ada object path (see @ref{89,,Search Paths and the Run-Time Library (RTL)}),
7724 the new object and ALI files are created in the
7725 directory containing the source being compiled. If another organization
7726 is desired, where objects and sources are kept in different directories,
7727 a useful technique is to create dummy ALI files in the desired directories.
7728 When detecting such a dummy file, @code{gnatmake} will be forced to
7729 recompile the corresponding source file, and it will be put the resulting
7730 object and ALI files in the directory where it found the dummy file.
7733 @geindex -j (gnatmake)
7735 @geindex Parallel make
7740 @item @code{-j@emph{n}}
7742 Use @code{n} processes to carry out the (re)compilations. On a multiprocessor
7743 machine compilations will occur in parallel. If @code{n} is 0, then the
7744 maximum number of parallel compilations is the number of core processors
7745 on the platform. In the event of compilation errors, messages from various
7746 compilations might get interspersed (but @code{gnatmake} will give you the
7747 full ordered list of failing compiles at the end). If this is problematic,
7748 rerun the make process with n set to 1 to get a clean list of messages.
7751 @geindex -k (gnatmake)
7758 Keep going. Continue as much as possible after a compilation error. To
7759 ease the programmer's task in case of compilation errors, the list of
7760 sources for which the compile fails is given when @code{gnatmake}
7763 If @code{gnatmake} is invoked with several @code{file_names} and with this
7764 switch, if there are compilation errors when building an executable,
7765 @code{gnatmake} will not attempt to build the following executables.
7768 @geindex -l (gnatmake)
7775 Link only. Can be combined with @code{-b} to binding
7776 and linking. Linking will not be performed if combined with
7778 but not with @code{-b}.
7779 When not combined with @code{-b}
7780 all the units in the closure of the main program must have been previously
7781 compiled and must be up to date, and the main program needs to have been bound.
7782 The root unit specified by @code{file_name}
7783 may be given without extension, with the source extension or, if no GNAT
7784 Project File is specified, with the ALI file extension.
7787 @geindex -m (gnatmake)
7794 Specify that the minimum necessary amount of recompilations
7795 be performed. In this mode @code{gnatmake} ignores time
7796 stamp differences when the only
7797 modifications to a source file consist in adding/removing comments,
7798 empty lines, spaces or tabs. This means that if you have changed the
7799 comments in a source file or have simply reformatted it, using this
7800 switch will tell @code{gnatmake} not to recompile files that depend on it
7801 (provided other sources on which these files depend have undergone no
7802 semantic modifications). Note that the debugging information may be
7803 out of date with respect to the sources if the @code{-m} switch causes
7804 a compilation to be switched, so the use of this switch represents a
7805 trade-off between compilation time and accurate debugging information.
7808 @geindex Dependencies
7809 @geindex producing list
7811 @geindex -M (gnatmake)
7818 Check if all objects are up to date. If they are, output the object
7819 dependences to @code{stdout} in a form that can be directly exploited in
7820 a @code{Makefile}. By default, each source file is prefixed with its
7821 (relative or absolute) directory name. This name is whatever you
7822 specified in the various @code{-aI}
7823 and @code{-I} switches. If you use
7824 @code{gnatmake -M} @code{-q}
7825 (see below), only the source file names,
7826 without relative paths, are output. If you just specify the @code{-M}
7827 switch, dependencies of the GNAT internal system files are omitted. This
7828 is typically what you want. If you also specify
7829 the @code{-a} switch,
7830 dependencies of the GNAT internal files are also listed. Note that
7831 dependencies of the objects in external Ada libraries (see
7832 switch @code{-aL@emph{dir}} in the following list)
7836 @geindex -n (gnatmake)
7843 Don't compile, bind, or link. Checks if all objects are up to date.
7844 If they are not, the full name of the first file that needs to be
7845 recompiled is printed.
7846 Repeated use of this option, followed by compiling the indicated source
7847 file, will eventually result in recompiling all required units.
7850 @geindex -o (gnatmake)
7855 @item @code{-o @emph{exec_name}}
7857 Output executable name. The name of the final executable program will be
7858 @code{exec_name}. If the @code{-o} switch is omitted the default
7859 name for the executable will be the name of the input file in appropriate form
7860 for an executable file on the host system.
7862 This switch cannot be used when invoking @code{gnatmake} with several
7866 @geindex -p (gnatmake)
7873 Same as @code{--create-missing-dirs}
7876 @geindex -P (gnatmake)
7881 @item @code{-P@emph{project}}
7883 Use project file @code{project}. Only one such switch can be used.
7887 @c :ref:`gnatmake_and_Project_Files`.
7889 @geindex -q (gnatmake)
7896 Quiet. When this flag is not set, the commands carried out by
7897 @code{gnatmake} are displayed.
7900 @geindex -s (gnatmake)
7907 Recompile if compiler switches have changed since last compilation.
7908 All compiler switches but -I and -o are taken into account in the
7910 orders between different 'first letter' switches are ignored, but
7911 orders between same switches are taken into account. For example,
7912 @code{-O -O2} is different than @code{-O2 -O}, but @code{-g -O}
7913 is equivalent to @code{-O -g}.
7915 This switch is recommended when Integrated Preprocessing is used.
7918 @geindex -u (gnatmake)
7925 Unique. Recompile at most the main files. It implies -c. Combined with
7926 -f, it is equivalent to calling the compiler directly. Note that using
7927 -u with a project file and no main has a special meaning.
7931 @c (See :ref:`Project_Files_and_Main_Subprograms`.)
7933 @geindex -U (gnatmake)
7940 When used without a project file or with one or several mains on the command
7941 line, is equivalent to -u. When used with a project file and no main
7942 on the command line, all sources of all project files are checked and compiled
7943 if not up to date, and libraries are rebuilt, if necessary.
7946 @geindex -v (gnatmake)
7953 Verbose. Display the reason for all recompilations @code{gnatmake}
7954 decides are necessary, with the highest verbosity level.
7957 @geindex -vl (gnatmake)
7964 Verbosity level Low. Display fewer lines than in verbosity Medium.
7967 @geindex -vm (gnatmake)
7974 Verbosity level Medium. Potentially display fewer lines than in verbosity High.
7977 @geindex -vm (gnatmake)
7984 Verbosity level High. Equivalent to -v.
7986 @item @code{-vP@emph{x}}
7988 Indicate the verbosity of the parsing of GNAT project files.
7989 See @ref{de,,Switches Related to Project Files}.
7992 @geindex -x (gnatmake)
7999 Indicate that sources that are not part of any Project File may be compiled.
8000 Normally, when using Project Files, only sources that are part of a Project
8001 File may be compile. When this switch is used, a source outside of all Project
8002 Files may be compiled. The ALI file and the object file will be put in the
8003 object directory of the main Project. The compilation switches used will only
8004 be those specified on the command line. Even when
8005 @code{-x} is used, mains specified on the
8006 command line need to be sources of a project file.
8008 @item @code{-X@emph{name}=@emph{value}}
8010 Indicate that external variable @code{name} has the value @code{value}.
8011 The Project Manager will use this value for occurrences of
8012 @code{external(name)} when parsing the project file.
8013 @ref{de,,Switches Related to Project Files}.
8016 @geindex -z (gnatmake)
8023 No main subprogram. Bind and link the program even if the unit name
8024 given on the command line is a package name. The resulting executable
8025 will execute the elaboration routines of the package and its closure,
8026 then the finalization routines.
8029 @subsubheading GCC switches
8032 Any uppercase or multi-character switch that is not a @code{gnatmake} switch
8033 is passed to @code{gcc} (e.g., @code{-O}, @code{-gnato,} etc.)
8035 @subsubheading Source and library search path switches
8038 @geindex -aI (gnatmake)
8043 @item @code{-aI@emph{dir}}
8045 When looking for source files also look in directory @code{dir}.
8046 The order in which source files search is undertaken is
8047 described in @ref{89,,Search Paths and the Run-Time Library (RTL)}.
8050 @geindex -aL (gnatmake)
8055 @item @code{-aL@emph{dir}}
8057 Consider @code{dir} as being an externally provided Ada library.
8058 Instructs @code{gnatmake} to skip compilation units whose @code{.ALI}
8059 files have been located in directory @code{dir}. This allows you to have
8060 missing bodies for the units in @code{dir} and to ignore out of date bodies
8061 for the same units. You still need to specify
8062 the location of the specs for these units by using the switches
8063 @code{-aI@emph{dir}} or @code{-I@emph{dir}}.
8064 Note: this switch is provided for compatibility with previous versions
8065 of @code{gnatmake}. The easier method of causing standard libraries
8066 to be excluded from consideration is to write-protect the corresponding
8070 @geindex -aO (gnatmake)
8075 @item @code{-aO@emph{dir}}
8077 When searching for library and object files, look in directory
8078 @code{dir}. The order in which library files are searched is described in
8079 @ref{8c,,Search Paths for gnatbind}.
8082 @geindex Search paths
8083 @geindex for gnatmake
8085 @geindex -A (gnatmake)
8090 @item @code{-A@emph{dir}}
8092 Equivalent to @code{-aL@emph{dir}} @code{-aI@emph{dir}}.
8094 @geindex -I (gnatmake)
8096 @item @code{-I@emph{dir}}
8098 Equivalent to @code{-aO@emph{dir} -aI@emph{dir}}.
8101 @geindex -I- (gnatmake)
8103 @geindex Source files
8104 @geindex suppressing search
8111 Do not look for source files in the directory containing the source
8112 file named in the command line.
8113 Do not look for ALI or object files in the directory
8114 where @code{gnatmake} was invoked.
8117 @geindex -L (gnatmake)
8119 @geindex Linker libraries
8124 @item @code{-L@emph{dir}}
8126 Add directory @code{dir} to the list of directories in which the linker
8127 will search for libraries. This is equivalent to
8128 @code{-largs} @code{-L@emph{dir}}.
8129 Furthermore, under Windows, the sources pointed to by the libraries path
8130 set in the registry are not searched for.
8133 @geindex -nostdinc (gnatmake)
8138 @item @code{-nostdinc}
8140 Do not look for source files in the system default directory.
8143 @geindex -nostdlib (gnatmake)
8148 @item @code{-nostdlib}
8150 Do not look for library files in the system default directory.
8153 @geindex --RTS (gnatmake)
8158 @item @code{--RTS=@emph{rts-path}}
8160 Specifies the default location of the run-time library. GNAT looks for the
8162 in the following directories, and stops as soon as a valid run-time is found
8163 (@code{adainclude} or @code{ada_source_path}, and @code{adalib} or
8164 @code{ada_object_path} present):
8170 @emph{<current directory>/$rts_path}
8173 @emph{<default-search-dir>/$rts_path}
8176 @emph{<default-search-dir>/rts-$rts_path}
8179 The selected path is handled like a normal RTS path.
8183 @node Mode Switches for gnatmake,Notes on the Command Line,Switches for gnatmake,Building with gnatmake
8184 @anchor{gnat_ugn/building_executable_programs_with_gnat id4}@anchor{df}@anchor{gnat_ugn/building_executable_programs_with_gnat mode-switches-for-gnatmake}@anchor{e0}
8185 @subsection Mode Switches for @code{gnatmake}
8188 The mode switches (referred to as @code{mode_switches}) allow the
8189 inclusion of switches that are to be passed to the compiler itself, the
8190 binder or the linker. The effect of a mode switch is to cause all
8191 subsequent switches up to the end of the switch list, or up to the next
8192 mode switch, to be interpreted as switches to be passed on to the
8193 designated component of GNAT.
8195 @geindex -cargs (gnatmake)
8200 @item @code{-cargs @emph{switches}}
8202 Compiler switches. Here @code{switches} is a list of switches
8203 that are valid switches for @code{gcc}. They will be passed on to
8204 all compile steps performed by @code{gnatmake}.
8207 @geindex -bargs (gnatmake)
8212 @item @code{-bargs @emph{switches}}
8214 Binder switches. Here @code{switches} is a list of switches
8215 that are valid switches for @code{gnatbind}. They will be passed on to
8216 all bind steps performed by @code{gnatmake}.
8219 @geindex -largs (gnatmake)
8224 @item @code{-largs @emph{switches}}
8226 Linker switches. Here @code{switches} is a list of switches
8227 that are valid switches for @code{gnatlink}. They will be passed on to
8228 all link steps performed by @code{gnatmake}.
8231 @geindex -margs (gnatmake)
8236 @item @code{-margs @emph{switches}}
8238 Make switches. The switches are directly interpreted by @code{gnatmake},
8239 regardless of any previous occurrence of @code{-cargs}, @code{-bargs}
8243 @node Notes on the Command Line,How gnatmake Works,Mode Switches for gnatmake,Building with gnatmake
8244 @anchor{gnat_ugn/building_executable_programs_with_gnat id5}@anchor{e1}@anchor{gnat_ugn/building_executable_programs_with_gnat notes-on-the-command-line}@anchor{e2}
8245 @subsection Notes on the Command Line
8248 This section contains some additional useful notes on the operation
8249 of the @code{gnatmake} command.
8251 @geindex Recompilation (by gnatmake)
8257 If @code{gnatmake} finds no ALI files, it recompiles the main program
8258 and all other units required by the main program.
8259 This means that @code{gnatmake}
8260 can be used for the initial compile, as well as during subsequent steps of
8261 the development cycle.
8264 If you enter @code{gnatmake foo.adb}, where @code{foo}
8265 is a subunit or body of a generic unit, @code{gnatmake} recompiles
8266 @code{foo.adb} (because it finds no ALI) and stops, issuing a
8270 In @code{gnatmake} the switch @code{-I}
8271 is used to specify both source and
8272 library file paths. Use @code{-aI}
8273 instead if you just want to specify
8274 source paths only and @code{-aO}
8275 if you want to specify library paths
8279 @code{gnatmake} will ignore any files whose ALI file is write-protected.
8280 This may conveniently be used to exclude standard libraries from
8281 consideration and in particular it means that the use of the
8282 @code{-f} switch will not recompile these files
8283 unless @code{-a} is also specified.
8286 @code{gnatmake} has been designed to make the use of Ada libraries
8287 particularly convenient. Assume you have an Ada library organized
8288 as follows: @emph{obj-dir} contains the objects and ALI files for
8289 of your Ada compilation units,
8290 whereas @emph{include-dir} contains the
8291 specs of these units, but no bodies. Then to compile a unit
8292 stored in @code{main.adb}, which uses this Ada library you would just type:
8295 $ gnatmake -aI`include-dir` -aL`obj-dir` main
8299 Using @code{gnatmake} along with the @code{-m (minimal recompilation)}
8300 switch provides a mechanism for avoiding unnecessary recompilations. Using
8302 you can update the comments/format of your
8303 source files without having to recompile everything. Note, however, that
8304 adding or deleting lines in a source files may render its debugging
8305 info obsolete. If the file in question is a spec, the impact is rather
8306 limited, as that debugging info will only be useful during the
8307 elaboration phase of your program. For bodies the impact can be more
8308 significant. In all events, your debugger will warn you if a source file
8309 is more recent than the corresponding object, and alert you to the fact
8310 that the debugging information may be out of date.
8313 @node How gnatmake Works,Examples of gnatmake Usage,Notes on the Command Line,Building with gnatmake
8314 @anchor{gnat_ugn/building_executable_programs_with_gnat id6}@anchor{e3}@anchor{gnat_ugn/building_executable_programs_with_gnat how-gnatmake-works}@anchor{e4}
8315 @subsection How @code{gnatmake} Works
8318 Generally @code{gnatmake} automatically performs all necessary
8319 recompilations and you don't need to worry about how it works. However,
8320 it may be useful to have some basic understanding of the @code{gnatmake}
8321 approach and in particular to understand how it uses the results of
8322 previous compilations without incorrectly depending on them.
8324 First a definition: an object file is considered @emph{up to date} if the
8325 corresponding ALI file exists and if all the source files listed in the
8326 dependency section of this ALI file have time stamps matching those in
8327 the ALI file. This means that neither the source file itself nor any
8328 files that it depends on have been modified, and hence there is no need
8329 to recompile this file.
8331 @code{gnatmake} works by first checking if the specified main unit is up
8332 to date. If so, no compilations are required for the main unit. If not,
8333 @code{gnatmake} compiles the main program to build a new ALI file that
8334 reflects the latest sources. Then the ALI file of the main unit is
8335 examined to find all the source files on which the main program depends,
8336 and @code{gnatmake} recursively applies the above procedure on all these
8339 This process ensures that @code{gnatmake} only trusts the dependencies
8340 in an existing ALI file if they are known to be correct. Otherwise it
8341 always recompiles to determine a new, guaranteed accurate set of
8342 dependencies. As a result the program is compiled 'upside down' from what may
8343 be more familiar as the required order of compilation in some other Ada
8344 systems. In particular, clients are compiled before the units on which
8345 they depend. The ability of GNAT to compile in any order is critical in
8346 allowing an order of compilation to be chosen that guarantees that
8347 @code{gnatmake} will recompute a correct set of new dependencies if
8350 When invoking @code{gnatmake} with several @code{file_names}, if a unit is
8351 imported by several of the executables, it will be recompiled at most once.
8353 Note: when using non-standard naming conventions
8354 (@ref{35,,Using Other File Names}), changing through a configuration pragmas
8355 file the version of a source and invoking @code{gnatmake} to recompile may
8356 have no effect, if the previous version of the source is still accessible
8357 by @code{gnatmake}. It may be necessary to use the switch
8360 @node Examples of gnatmake Usage,,How gnatmake Works,Building with gnatmake
8361 @anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatmake-usage}@anchor{e5}@anchor{gnat_ugn/building_executable_programs_with_gnat id7}@anchor{e6}
8362 @subsection Examples of @code{gnatmake} Usage
8368 @item @emph{gnatmake hello.adb}
8370 Compile all files necessary to bind and link the main program
8371 @code{hello.adb} (containing unit @code{Hello}) and bind and link the
8372 resulting object files to generate an executable file @code{hello}.
8374 @item @emph{gnatmake main1 main2 main3}
8376 Compile all files necessary to bind and link the main programs
8377 @code{main1.adb} (containing unit @code{Main1}), @code{main2.adb}
8378 (containing unit @code{Main2}) and @code{main3.adb}
8379 (containing unit @code{Main3}) and bind and link the resulting object files
8380 to generate three executable files @code{main1},
8381 @code{main2} and @code{main3}.
8383 @item @emph{gnatmake -q Main_Unit -cargs -O2 -bargs -l}
8385 Compile all files necessary to bind and link the main program unit
8386 @code{Main_Unit} (from file @code{main_unit.adb}). All compilations will
8387 be done with optimization level 2 and the order of elaboration will be
8388 listed by the binder. @code{gnatmake} will operate in quiet mode, not
8389 displaying commands it is executing.
8392 @node Compiling with gcc,Compiler Switches,Building with gnatmake,Building Executable Programs with GNAT
8393 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-with-gcc}@anchor{1c}@anchor{gnat_ugn/building_executable_programs_with_gnat id8}@anchor{e7}
8394 @section Compiling with @code{gcc}
8397 This section discusses how to compile Ada programs using the @code{gcc}
8398 command. It also describes the set of switches
8399 that can be used to control the behavior of the compiler.
8402 * Compiling Programs::
8403 * Search Paths and the Run-Time Library (RTL): Search Paths and the Run-Time Library RTL.
8404 * Order of Compilation Issues::
8409 @node Compiling Programs,Search Paths and the Run-Time Library RTL,,Compiling with gcc
8410 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-programs}@anchor{e8}@anchor{gnat_ugn/building_executable_programs_with_gnat id9}@anchor{e9}
8411 @subsection Compiling Programs
8414 The first step in creating an executable program is to compile the units
8415 of the program using the @code{gcc} command. You must compile the
8422 the body file (@code{.adb}) for a library level subprogram or generic
8426 the spec file (@code{.ads}) for a library level package or generic
8427 package that has no body
8430 the body file (@code{.adb}) for a library level package
8431 or generic package that has a body
8434 You need @emph{not} compile the following files
8440 the spec of a library unit which has a body
8446 because they are compiled as part of compiling related units. GNAT
8448 when the corresponding body is compiled, and subunits when the parent is
8451 @geindex cannot generate code
8453 If you attempt to compile any of these files, you will get one of the
8454 following error messages (where @code{fff} is the name of the file you
8460 cannot generate code for file `@w{`}fff`@w{`} (package spec)
8461 to check package spec, use -gnatc
8463 cannot generate code for file `@w{`}fff`@w{`} (missing subunits)
8464 to check parent unit, use -gnatc
8466 cannot generate code for file `@w{`}fff`@w{`} (subprogram spec)
8467 to check subprogram spec, use -gnatc
8469 cannot generate code for file `@w{`}fff`@w{`} (subunit)
8470 to check subunit, use -gnatc
8474 As indicated by the above error messages, if you want to submit
8475 one of these files to the compiler to check for correct semantics
8476 without generating code, then use the @code{-gnatc} switch.
8478 The basic command for compiling a file containing an Ada unit is:
8481 $ gcc -c [switches] <file name>
8484 where @code{file name} is the name of the Ada file (usually
8485 having an extension @code{.ads} for a spec or @code{.adb} for a body).
8487 @code{-c} switch to tell @code{gcc} to compile, but not link, the file.
8488 The result of a successful compilation is an object file, which has the
8489 same name as the source file but an extension of @code{.o} and an Ada
8490 Library Information (ALI) file, which also has the same name as the
8491 source file, but with @code{.ali} as the extension. GNAT creates these
8492 two output files in the current directory, but you may specify a source
8493 file in any directory using an absolute or relative path specification
8494 containing the directory information.
8496 TESTING: the @code{--foobar@emph{NN}} switch
8500 @code{gcc} is actually a driver program that looks at the extensions of
8501 the file arguments and loads the appropriate compiler. For example, the
8502 GNU C compiler is @code{cc1}, and the Ada compiler is @code{gnat1}.
8503 These programs are in directories known to the driver program (in some
8504 configurations via environment variables you set), but need not be in
8505 your path. The @code{gcc} driver also calls the assembler and any other
8506 utilities needed to complete the generation of the required object
8509 It is possible to supply several file names on the same @code{gcc}
8510 command. This causes @code{gcc} to call the appropriate compiler for
8511 each file. For example, the following command lists two separate
8512 files to be compiled:
8515 $ gcc -c x.adb y.adb
8518 calls @code{gnat1} (the Ada compiler) twice to compile @code{x.adb} and
8520 The compiler generates two object files @code{x.o} and @code{y.o}
8521 and the two ALI files @code{x.ali} and @code{y.ali}.
8523 Any switches apply to all the files listed, see @ref{ea,,Compiler Switches} for a
8524 list of available @code{gcc} switches.
8526 @node Search Paths and the Run-Time Library RTL,Order of Compilation Issues,Compiling Programs,Compiling with gcc
8527 @anchor{gnat_ugn/building_executable_programs_with_gnat id10}@anchor{eb}@anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-and-the-run-time-library-rtl}@anchor{89}
8528 @subsection Search Paths and the Run-Time Library (RTL)
8531 With the GNAT source-based library system, the compiler must be able to
8532 find source files for units that are needed by the unit being compiled.
8533 Search paths are used to guide this process.
8535 The compiler compiles one source file whose name must be given
8536 explicitly on the command line. In other words, no searching is done
8537 for this file. To find all other source files that are needed (the most
8538 common being the specs of units), the compiler examines the following
8539 directories, in the following order:
8545 The directory containing the source file of the main unit being compiled
8546 (the file name on the command line).
8549 Each directory named by an @code{-I} switch given on the @code{gcc}
8550 command line, in the order given.
8552 @geindex ADA_PRJ_INCLUDE_FILE
8555 Each of the directories listed in the text file whose name is given
8557 @geindex ADA_PRJ_INCLUDE_FILE
8558 @geindex environment variable; ADA_PRJ_INCLUDE_FILE
8559 @code{ADA_PRJ_INCLUDE_FILE} environment variable.
8560 @geindex ADA_PRJ_INCLUDE_FILE
8561 @geindex environment variable; ADA_PRJ_INCLUDE_FILE
8562 @code{ADA_PRJ_INCLUDE_FILE} is normally set by gnatmake or by the gnat
8563 driver when project files are used. It should not normally be set
8566 @geindex ADA_INCLUDE_PATH
8569 Each of the directories listed in the value of the
8570 @geindex ADA_INCLUDE_PATH
8571 @geindex environment variable; ADA_INCLUDE_PATH
8572 @code{ADA_INCLUDE_PATH} environment variable.
8573 Construct this value
8576 @geindex environment variable; PATH
8577 @code{PATH} environment variable: a list of directory
8578 names separated by colons (semicolons when working with the NT version).
8581 The content of the @code{ada_source_path} file which is part of the GNAT
8582 installation tree and is used to store standard libraries such as the
8583 GNAT Run Time Library (RTL) source files.
8584 @ref{87,,Installing a library}
8587 Specifying the switch @code{-I-}
8588 inhibits the use of the directory
8589 containing the source file named in the command line. You can still
8590 have this directory on your search path, but in this case it must be
8591 explicitly requested with a @code{-I} switch.
8593 Specifying the switch @code{-nostdinc}
8594 inhibits the search of the default location for the GNAT Run Time
8595 Library (RTL) source files.
8597 The compiler outputs its object files and ALI files in the current
8599 Caution: The object file can be redirected with the @code{-o} switch;
8600 however, @code{gcc} and @code{gnat1} have not been coordinated on this
8601 so the @code{ALI} file will not go to the right place. Therefore, you should
8602 avoid using the @code{-o} switch.
8606 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
8607 children make up the GNAT RTL, together with the simple @code{System.IO}
8608 package used in the @code{"Hello World"} example. The sources for these units
8609 are needed by the compiler and are kept together in one directory. Not
8610 all of the bodies are needed, but all of the sources are kept together
8611 anyway. In a normal installation, you need not specify these directory
8612 names when compiling or binding. Either the environment variables or
8613 the built-in defaults cause these files to be found.
8615 In addition to the language-defined hierarchies (@code{System}, @code{Ada} and
8616 @code{Interfaces}), the GNAT distribution provides a fourth hierarchy,
8617 consisting of child units of @code{GNAT}. This is a collection of generally
8618 useful types, subprograms, etc. See the @cite{GNAT_Reference_Manual}
8619 for further details.
8621 Besides simplifying access to the RTL, a major use of search paths is
8622 in compiling sources from multiple directories. This can make
8623 development environments much more flexible.
8625 @node Order of Compilation Issues,Examples,Search Paths and the Run-Time Library RTL,Compiling with gcc
8626 @anchor{gnat_ugn/building_executable_programs_with_gnat id11}@anchor{ec}@anchor{gnat_ugn/building_executable_programs_with_gnat order-of-compilation-issues}@anchor{ed}
8627 @subsection Order of Compilation Issues
8630 If, in our earlier example, there was a spec for the @code{hello}
8631 procedure, it would be contained in the file @code{hello.ads}; yet this
8632 file would not have to be explicitly compiled. This is the result of the
8633 model we chose to implement library management. Some of the consequences
8634 of this model are as follows:
8640 There is no point in compiling specs (except for package
8641 specs with no bodies) because these are compiled as needed by clients. If
8642 you attempt a useless compilation, you will receive an error message.
8643 It is also useless to compile subunits because they are compiled as needed
8647 There are no order of compilation requirements: performing a
8648 compilation never obsoletes anything. The only way you can obsolete
8649 something and require recompilations is to modify one of the
8650 source files on which it depends.
8653 There is no library as such, apart from the ALI files
8654 (@ref{42,,The Ada Library Information Files}, for information on the format
8655 of these files). For now we find it convenient to create separate ALI files,
8656 but eventually the information therein may be incorporated into the object
8660 When you compile a unit, the source files for the specs of all units
8661 that it @emph{with}s, all its subunits, and the bodies of any generics it
8662 instantiates must be available (reachable by the search-paths mechanism
8663 described above), or you will receive a fatal error message.
8666 @node Examples,,Order of Compilation Issues,Compiling with gcc
8667 @anchor{gnat_ugn/building_executable_programs_with_gnat id12}@anchor{ee}@anchor{gnat_ugn/building_executable_programs_with_gnat examples}@anchor{ef}
8668 @subsection Examples
8671 The following are some typical Ada compilation command line examples:
8677 Compile body in file @code{xyz.adb} with all default options.
8680 $ gcc -c -O2 -gnata xyz-def.adb
8683 Compile the child unit package in file @code{xyz-def.adb} with extensive
8684 optimizations, and pragma @code{Assert}/@cite{Debug} statements
8688 $ gcc -c -gnatc abc-def.adb
8691 Compile the subunit in file @code{abc-def.adb} in semantic-checking-only
8694 @node Compiler Switches,Linker Switches,Compiling with gcc,Building Executable Programs with GNAT
8695 @anchor{gnat_ugn/building_executable_programs_with_gnat compiler-switches}@anchor{f0}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gcc}@anchor{ea}
8696 @section Compiler Switches
8699 The @code{gcc} command accepts switches that control the
8700 compilation process. These switches are fully described in this section:
8701 first an alphabetical listing of all switches with a brief description,
8702 and then functionally grouped sets of switches with more detailed
8705 More switches exist for GCC than those documented here, especially
8706 for specific targets. However, their use is not recommended as
8707 they may change code generation in ways that are incompatible with
8708 the Ada run-time library, or can cause inconsistencies between
8712 * Alphabetical List of All Switches::
8713 * Output and Error Message Control::
8714 * Warning Message Control::
8715 * Debugging and Assertion Control::
8716 * Validity Checking::
8719 * Using gcc for Syntax Checking::
8720 * Using gcc for Semantic Checking::
8721 * Compiling Different Versions of Ada::
8722 * Character Set Control::
8723 * File Naming Control::
8724 * Subprogram Inlining Control::
8725 * Auxiliary Output Control::
8726 * Debugging Control::
8727 * Exception Handling Control::
8728 * Units to Sources Mapping Files::
8729 * Code Generation Control::
8733 @node Alphabetical List of All Switches,Output and Error Message Control,,Compiler Switches
8734 @anchor{gnat_ugn/building_executable_programs_with_gnat id13}@anchor{f1}@anchor{gnat_ugn/building_executable_programs_with_gnat alphabetical-list-of-all-switches}@anchor{f2}
8735 @subsection Alphabetical List of All Switches
8743 @item @code{-b @emph{target}}
8745 Compile your program to run on @code{target}, which is the name of a
8746 system configuration. You must have a GNAT cross-compiler built if
8747 @code{target} is not the same as your host system.
8755 @item @code{-B@emph{dir}}
8757 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
8758 from @code{dir} instead of the default location. Only use this switch
8759 when multiple versions of the GNAT compiler are available.
8760 See the "Options for Directory Search" section in the
8761 @cite{Using the GNU Compiler Collection (GCC)} manual for further details.
8762 You would normally use the @code{-b} or @code{-V} switch instead.
8772 Compile. Always use this switch when compiling Ada programs.
8774 Note: for some other languages when using @code{gcc}, notably in
8775 the case of C and C++, it is possible to use
8776 use @code{gcc} without a @code{-c} switch to
8777 compile and link in one step. In the case of GNAT, you
8778 cannot use this approach, because the binder must be run
8779 and @code{gcc} cannot be used to run the GNAT binder.
8782 @geindex -fcallgraph-info (gcc)
8787 @item @code{-fcallgraph-info[=su,da]}
8789 Makes the compiler output callgraph information for the program, on a
8790 per-file basis. The information is generated in the VCG format. It can
8791 be decorated with additional, per-node and/or per-edge information, if a
8792 list of comma-separated markers is additionally specified. When the
8793 @code{su} marker is specified, the callgraph is decorated with stack usage
8794 information; it is equivalent to @code{-fstack-usage}. When the @code{da}
8795 marker is specified, the callgraph is decorated with information about
8796 dynamically allocated objects.
8799 @geindex -fdump-scos (gcc)
8804 @item @code{-fdump-scos}
8806 Generates SCO (Source Coverage Obligation) information in the ALI file.
8807 This information is used by advanced coverage tools. See unit @code{SCOs}
8808 in the compiler sources for details in files @code{scos.ads} and
8812 @geindex -flto (gcc)
8817 @item @code{-flto[=@emph{n}]}
8819 Enables Link Time Optimization. This switch must be used in conjunction
8820 with the @code{-Ox} switches (but not with the @code{-gnatn} switch
8821 since it is a full replacement for the latter) and instructs the compiler
8822 to defer most optimizations until the link stage. The advantage of this
8823 approach is that the compiler can do a whole-program analysis and choose
8824 the best interprocedural optimization strategy based on a complete view
8825 of the program, instead of a fragmentary view with the usual approach.
8826 This can also speed up the compilation of big programs and reduce the
8827 size of the executable, compared with a traditional per-unit compilation
8828 with inlining across units enabled by the @code{-gnatn} switch.
8829 The drawback of this approach is that it may require more memory and that
8830 the debugging information generated by -g with it might be hardly usable.
8831 The switch, as well as the accompanying @code{-Ox} switches, must be
8832 specified both for the compilation and the link phases.
8833 If the @code{n} parameter is specified, the optimization and final code
8834 generation at link time are executed using @code{n} parallel jobs by
8835 means of an installed @code{make} program.
8838 @geindex -fno-inline (gcc)
8843 @item @code{-fno-inline}
8845 Suppresses all inlining, unless requested with pragma @code{Inline_Always}. The
8846 effect is enforced regardless of other optimization or inlining switches.
8847 Note that inlining can also be suppressed on a finer-grained basis with
8848 pragma @code{No_Inline}.
8851 @geindex -fno-inline-functions (gcc)
8856 @item @code{-fno-inline-functions}
8858 Suppresses automatic inlining of subprograms, which is enabled
8859 if @code{-O3} is used.
8862 @geindex -fno-inline-small-functions (gcc)
8867 @item @code{-fno-inline-small-functions}
8869 Suppresses automatic inlining of small subprograms, which is enabled
8870 if @code{-O2} is used.
8873 @geindex -fno-inline-functions-called-once (gcc)
8878 @item @code{-fno-inline-functions-called-once}
8880 Suppresses inlining of subprograms local to the unit and called once
8881 from within it, which is enabled if @code{-O1} is used.
8884 @geindex -fno-ivopts (gcc)
8889 @item @code{-fno-ivopts}
8891 Suppresses high-level loop induction variable optimizations, which are
8892 enabled if @code{-O1} is used. These optimizations are generally
8893 profitable but, for some specific cases of loops with numerous uses
8894 of the iteration variable that follow a common pattern, they may end
8895 up destroying the regularity that could be exploited at a lower level
8896 and thus producing inferior code.
8899 @geindex -fno-strict-aliasing (gcc)
8904 @item @code{-fno-strict-aliasing}
8906 Causes the compiler to avoid assumptions regarding non-aliasing
8907 of objects of different types. See
8908 @ref{f3,,Optimization and Strict Aliasing} for details.
8911 @geindex -fno-strict-overflow (gcc)
8916 @item @code{-fno-strict-overflow}
8918 Causes the compiler to avoid assumptions regarding the rules of signed
8919 integer overflow. These rules specify that signed integer overflow will
8920 result in a Constraint_Error exception at run time and are enforced in
8921 default mode by the compiler, so this switch should not be necessary in
8922 normal operating mode. It might be useful in conjunction with @code{-gnato0}
8923 for very peculiar cases of low-level programming.
8926 @geindex -fstack-check (gcc)
8931 @item @code{-fstack-check}
8933 Activates stack checking.
8934 See @ref{f4,,Stack Overflow Checking} for details.
8937 @geindex -fstack-usage (gcc)
8942 @item @code{-fstack-usage}
8944 Makes the compiler output stack usage information for the program, on a
8945 per-subprogram basis. See @ref{f5,,Static Stack Usage Analysis} for details.
8955 Generate debugging information. This information is stored in the object
8956 file and copied from there to the final executable file by the linker,
8957 where it can be read by the debugger. You must use the
8958 @code{-g} switch if you plan on using the debugger.
8961 @geindex -gnat05 (gcc)
8966 @item @code{-gnat05}
8968 Allow full Ada 2005 features.
8971 @geindex -gnat12 (gcc)
8976 @item @code{-gnat12}
8978 Allow full Ada 2012 features.
8981 @geindex -gnat83 (gcc)
8983 @geindex -gnat2005 (gcc)
8988 @item @code{-gnat2005}
8990 Allow full Ada 2005 features (same as @code{-gnat05})
8993 @geindex -gnat2012 (gcc)
8998 @item @code{-gnat2012}
9000 Allow full Ada 2012 features (same as @code{-gnat12})
9002 @item @code{-gnat83}
9004 Enforce Ada 83 restrictions.
9007 @geindex -gnat95 (gcc)
9012 @item @code{-gnat95}
9014 Enforce Ada 95 restrictions.
9016 Note: for compatibility with some Ada 95 compilers which support only
9017 the @code{overriding} keyword of Ada 2005, the @code{-gnatd.D} switch can
9018 be used along with @code{-gnat95} to achieve a similar effect with GNAT.
9020 @code{-gnatd.D} instructs GNAT to consider @code{overriding} as a keyword
9021 and handle its associated semantic checks, even in Ada 95 mode.
9024 @geindex -gnata (gcc)
9031 Assertions enabled. @code{Pragma Assert} and @code{pragma Debug} to be
9032 activated. Note that these pragmas can also be controlled using the
9033 configuration pragmas @code{Assertion_Policy} and @code{Debug_Policy}.
9034 It also activates pragmas @code{Check}, @code{Precondition}, and
9035 @code{Postcondition}. Note that these pragmas can also be controlled
9036 using the configuration pragma @code{Check_Policy}. In Ada 2012, it
9037 also activates all assertions defined in the RM as aspects: preconditions,
9038 postconditions, type invariants and (sub)type predicates. In all Ada modes,
9039 corresponding pragmas for type invariants and (sub)type predicates are
9040 also activated. The default is that all these assertions are disabled,
9041 and have no effect, other than being checked for syntactic validity, and
9042 in the case of subtype predicates, constructions such as membership tests
9043 still test predicates even if assertions are turned off.
9046 @geindex -gnatA (gcc)
9053 Avoid processing @code{gnat.adc}. If a @code{gnat.adc} file is present,
9057 @geindex -gnatb (gcc)
9064 Generate brief messages to @code{stderr} even if verbose mode set.
9067 @geindex -gnatB (gcc)
9074 Assume no invalid (bad) values except for 'Valid attribute use
9075 (@ref{f6,,Validity Checking}).
9078 @geindex -gnatc (gcc)
9085 Check syntax and semantics only (no code generation attempted). When the
9086 compiler is invoked by @code{gnatmake}, if the switch @code{-gnatc} is
9087 only given to the compiler (after @code{-cargs} or in package Compiler of
9088 the project file, @code{gnatmake} will fail because it will not find the
9089 object file after compilation. If @code{gnatmake} is called with
9090 @code{-gnatc} as a builder switch (before @code{-cargs} or in package
9091 Builder of the project file) then @code{gnatmake} will not fail because
9092 it will not look for the object files after compilation, and it will not try
9096 @geindex -gnatC (gcc)
9103 Generate CodePeer intermediate format (no code generation attempted).
9104 This switch will generate an intermediate representation suitable for
9105 use by CodePeer (@code{.scil} files). This switch is not compatible with
9106 code generation (it will, among other things, disable some switches such
9107 as -gnatn, and enable others such as -gnata).
9110 @geindex -gnatd (gcc)
9117 Specify debug options for the compiler. The string of characters after
9118 the @code{-gnatd} specify the specific debug options. The possible
9119 characters are 0-9, a-z, A-Z, optionally preceded by a dot. See
9120 compiler source file @code{debug.adb} for details of the implemented
9121 debug options. Certain debug options are relevant to applications
9122 programmers, and these are documented at appropriate points in this
9126 @geindex -gnatD[nn] (gcc)
9133 Create expanded source files for source level debugging. This switch
9134 also suppresses generation of cross-reference information
9135 (see @code{-gnatx}). Note that this switch is not allowed if a previous
9136 -gnatR switch has been given, since these two switches are not compatible.
9139 @geindex -gnateA (gcc)
9144 @item @code{-gnateA}
9146 Check that the actual parameters of a subprogram call are not aliases of one
9147 another. To qualify as aliasing, the actuals must denote objects of a composite
9148 type, their memory locations must be identical or overlapping, and at least one
9149 of the corresponding formal parameters must be of mode OUT or IN OUT.
9152 type Rec_Typ is record
9153 Data : Integer := 0;
9156 function Self (Val : Rec_Typ) return Rec_Typ is
9161 procedure Detect_Aliasing (Val_1 : in out Rec_Typ; Val_2 : Rec_Typ) is
9164 end Detect_Aliasing;
9168 Detect_Aliasing (Obj, Obj);
9169 Detect_Aliasing (Obj, Self (Obj));
9172 In the example above, the first call to @code{Detect_Aliasing} fails with a
9173 @code{Program_Error} at run time because the actuals for @code{Val_1} and
9174 @code{Val_2} denote the same object. The second call executes without raising
9175 an exception because @code{Self(Obj)} produces an anonymous object which does
9176 not share the memory location of @code{Obj}.
9179 @geindex -gnatec (gcc)
9184 @item @code{-gnatec=@emph{path}}
9186 Specify a configuration pragma file
9187 (the equal sign is optional)
9188 (@ref{79,,The Configuration Pragmas Files}).
9191 @geindex -gnateC (gcc)
9196 @item @code{-gnateC}
9198 Generate CodePeer messages in a compiler-like format. This switch is only
9199 effective if @code{-gnatcC} is also specified and requires an installation
9203 @geindex -gnated (gcc)
9208 @item @code{-gnated}
9210 Disable atomic synchronization
9213 @geindex -gnateD (gcc)
9218 @item @code{-gnateDsymbol[=@emph{value}]}
9220 Defines a symbol, associated with @code{value}, for preprocessing.
9221 (@ref{18,,Integrated Preprocessing}).
9224 @geindex -gnateE (gcc)
9229 @item @code{-gnateE}
9231 Generate extra information in exception messages. In particular, display
9232 extra column information and the value and range associated with index and
9233 range check failures, and extra column information for access checks.
9234 In cases where the compiler is able to determine at compile time that
9235 a check will fail, it gives a warning, and the extra information is not
9236 produced at run time.
9239 @geindex -gnatef (gcc)
9244 @item @code{-gnatef}
9246 Display full source path name in brief error messages.
9249 @geindex -gnateF (gcc)
9254 @item @code{-gnateF}
9256 Check for overflow on all floating-point operations, including those
9257 for unconstrained predefined types. See description of pragma
9258 @code{Check_Float_Overflow} in GNAT RM.
9261 @geindex -gnateg (gcc)
9268 The @code{-gnatc} switch must always be specified before this switch, e.g.
9269 @code{-gnatceg}. Generate a C header from the Ada input file. See
9270 @ref{ca,,Generating C Headers for Ada Specifications} for more
9274 @geindex -gnateG (gcc)
9279 @item @code{-gnateG}
9281 Save result of preprocessing in a text file.
9284 @geindex -gnatei (gcc)
9289 @item @code{-gnatei@emph{nnn}}
9291 Set maximum number of instantiations during compilation of a single unit to
9292 @code{nnn}. This may be useful in increasing the default maximum of 8000 for
9293 the rare case when a single unit legitimately exceeds this limit.
9296 @geindex -gnateI (gcc)
9301 @item @code{-gnateI@emph{nnn}}
9303 Indicates that the source is a multi-unit source and that the index of the
9304 unit to compile is @code{nnn}. @code{nnn} needs to be a positive number and need
9305 to be a valid index in the multi-unit source.
9308 @geindex -gnatel (gcc)
9313 @item @code{-gnatel}
9315 This switch can be used with the static elaboration model to issue info
9317 where implicit @code{pragma Elaborate} and @code{pragma Elaborate_All}
9318 are generated. This is useful in diagnosing elaboration circularities
9319 caused by these implicit pragmas when using the static elaboration
9320 model. See See the section in this guide on elaboration checking for
9321 further details. These messages are not generated by default, and are
9322 intended only for temporary use when debugging circularity problems.
9325 @geindex -gnatel (gcc)
9330 @item @code{-gnateL}
9332 This switch turns off the info messages about implicit elaboration pragmas.
9335 @geindex -gnatem (gcc)
9340 @item @code{-gnatem=@emph{path}}
9342 Specify a mapping file
9343 (the equal sign is optional)
9344 (@ref{f7,,Units to Sources Mapping Files}).
9347 @geindex -gnatep (gcc)
9352 @item @code{-gnatep=@emph{file}}
9354 Specify a preprocessing data file
9355 (the equal sign is optional)
9356 (@ref{18,,Integrated Preprocessing}).
9359 @geindex -gnateP (gcc)
9364 @item @code{-gnateP}
9366 Turn categorization dependency errors into warnings.
9367 Ada requires that units that WITH one another have compatible categories, for
9368 example a Pure unit cannot WITH a Preelaborate unit. If this switch is used,
9369 these errors become warnings (which can be ignored, or suppressed in the usual
9370 manner). This can be useful in some specialized circumstances such as the
9371 temporary use of special test software.
9374 @geindex -gnateS (gcc)
9379 @item @code{-gnateS}
9381 Synonym of @code{-fdump-scos}, kept for backwards compatibility.
9384 @geindex -gnatet=file (gcc)
9389 @item @code{-gnatet=@emph{path}}
9391 Generate target dependent information. The format of the output file is
9392 described in the section about switch @code{-gnateT}.
9395 @geindex -gnateT (gcc)
9400 @item @code{-gnateT=@emph{path}}
9402 Read target dependent information, such as endianness or sizes and alignments
9403 of base type. If this switch is passed, the default target dependent
9404 information of the compiler is replaced by the one read from the input file.
9405 This is used by tools other than the compiler, e.g. to do
9406 semantic analysis of programs that will run on some other target than
9407 the machine on which the tool is run.
9409 The following target dependent values should be defined,
9410 where @code{Nat} denotes a natural integer value, @code{Pos} denotes a
9411 positive integer value, and fields marked with a question mark are
9412 boolean fields, where a value of 0 is False, and a value of 1 is True:
9415 Bits_BE : Nat; -- Bits stored big-endian?
9416 Bits_Per_Unit : Pos; -- Bits in a storage unit
9417 Bits_Per_Word : Pos; -- Bits in a word
9418 Bytes_BE : Nat; -- Bytes stored big-endian?
9419 Char_Size : Pos; -- Standard.Character'Size
9420 Double_Float_Alignment : Nat; -- Alignment of double float
9421 Double_Scalar_Alignment : Nat; -- Alignment of double length scalar
9422 Double_Size : Pos; -- Standard.Long_Float'Size
9423 Float_Size : Pos; -- Standard.Float'Size
9424 Float_Words_BE : Nat; -- Float words stored big-endian?
9425 Int_Size : Pos; -- Standard.Integer'Size
9426 Long_Double_Size : Pos; -- Standard.Long_Long_Float'Size
9427 Long_Long_Size : Pos; -- Standard.Long_Long_Integer'Size
9428 Long_Size : Pos; -- Standard.Long_Integer'Size
9429 Maximum_Alignment : Pos; -- Maximum permitted alignment
9430 Max_Unaligned_Field : Pos; -- Maximum size for unaligned bit field
9431 Pointer_Size : Pos; -- System.Address'Size
9432 Short_Enums : Nat; -- Foreign enums use short size?
9433 Short_Size : Pos; -- Standard.Short_Integer'Size
9434 Strict_Alignment : Nat; -- Strict alignment?
9435 System_Allocator_Alignment : Nat; -- Alignment for malloc calls
9436 Wchar_T_Size : Pos; -- Interfaces.C.wchar_t'Size
9437 Words_BE : Nat; -- Words stored big-endian?
9440 @code{Bits_Per_Unit} is the number of bits in a storage unit, the equivalent of
9441 GCC macro @code{BITS_PER_UNIT} documented as follows: @cite{Define this macro to be the number of bits in an addressable storage unit (byte); normally 8.}
9443 @code{Bits_Per_Word} is the number of bits in a machine word, the equivalent of
9444 GCC macro @code{BITS_PER_WORD} documented as follows: @cite{Number of bits in a word; normally 32.}
9446 @code{Double_Scalar_Alignment} is the alignment for a scalar whose size is two
9447 machine words. It should be the same as the alignment for C @code{long_long} on
9450 @code{Maximum_Alignment} is the maximum alignment that the compiler might choose
9451 by default for a type or object, which is also the maximum alignment that can
9452 be specified in GNAT. It is computed for GCC backends as @code{BIGGEST_ALIGNMENT
9453 / BITS_PER_UNIT} where GCC macro @code{BIGGEST_ALIGNMENT} is documented as
9454 follows: @cite{Biggest alignment that any data type can require on this machine@comma{} in bits.}
9456 @code{Max_Unaligned_Field} is the maximum size for unaligned bit field, which is
9457 64 for the majority of GCC targets (but can be different on some targets like
9460 @code{Strict_Alignment} is the equivalent of GCC macro @code{STRICT_ALIGNMENT}
9461 documented as follows: @cite{Define this macro to be the value 1 if instructions will fail to work if given data not on the nominal alignment. If instructions will merely go slower in that case@comma{} define this macro as 0.}
9463 @code{System_Allocator_Alignment} is the guaranteed alignment of data returned
9464 by calls to @code{malloc}.
9466 The format of the input file is as follows. First come the values of
9467 the variables defined above, with one line per value:
9473 where @code{name} is the name of the parameter, spelled out in full,
9474 and cased as in the above list, and @code{value} is an unsigned decimal
9475 integer. Two or more blanks separates the name from the value.
9477 All the variables must be present, in alphabetical order (i.e. the
9478 same order as the list above).
9480 Then there is a blank line to separate the two parts of the file. Then
9481 come the lines showing the floating-point types to be registered, with
9482 one line per registered mode:
9485 name digs float_rep size alignment
9488 where @code{name} is the string name of the type (which can have
9489 single spaces embedded in the name (e.g. long double), @code{digs} is
9490 the number of digits for the floating-point type, @code{float_rep} is
9491 the float representation (I/V/A for IEEE-754-Binary, Vax_Native,
9492 AAMP), @code{size} is the size in bits, @code{alignment} is the
9493 alignment in bits. The name is followed by at least two blanks, fields
9494 are separated by at least one blank, and a LF character immediately
9495 follows the alignment field.
9497 Here is an example of a target parameterization file:
9505 Double_Float_Alignment 0
9506 Double_Scalar_Alignment 0
9511 Long_Double_Size 128
9514 Maximum_Alignment 16
9515 Max_Unaligned_Field 64
9519 System_Allocator_Alignment 16
9525 long double 18 I 80 128
9530 @geindex -gnateu (gcc)
9535 @item @code{-gnateu}
9537 Ignore unrecognized validity, warning, and style switches that
9538 appear after this switch is given. This may be useful when
9539 compiling sources developed on a later version of the compiler
9540 with an earlier version. Of course the earlier version must
9541 support this switch.
9544 @geindex -gnateV (gcc)
9549 @item @code{-gnateV}
9551 Check that all actual parameters of a subprogram call are valid according to
9552 the rules of validity checking (@ref{f6,,Validity Checking}).
9555 @geindex -gnateY (gcc)
9560 @item @code{-gnateY}
9562 Ignore all STYLE_CHECKS pragmas. Full legality checks
9563 are still carried out, but the pragmas have no effect
9564 on what style checks are active. This allows all style
9565 checking options to be controlled from the command line.
9568 @geindex -gnatE (gcc)
9575 Full dynamic elaboration checks.
9578 @geindex -gnatf (gcc)
9585 Full errors. Multiple errors per line, all undefined references, do not
9586 attempt to suppress cascaded errors.
9589 @geindex -gnatF (gcc)
9596 Externals names are folded to all uppercase.
9599 @geindex -gnatg (gcc)
9606 Internal GNAT implementation mode. This should not be used for applications
9607 programs, it is intended only for use by the compiler and its run-time
9608 library. For documentation, see the GNAT sources. Note that @code{-gnatg}
9609 implies @code{-gnatw.ge} and @code{-gnatyg} so that all standard
9610 warnings and all standard style options are turned on. All warnings and style
9611 messages are treated as errors.
9614 @geindex -gnatG[nn] (gcc)
9619 @item @code{-gnatG=nn}
9621 List generated expanded code in source form.
9624 @geindex -gnath (gcc)
9631 Output usage information. The output is written to @code{stdout}.
9634 @geindex -gnatH (gcc)
9641 Legacy elaboration-checking mode enabled. When this switch is in effect, the
9642 pre-18.x access-before-elaboration model becomes the de facto model.
9645 @geindex -gnati (gcc)
9650 @item @code{-gnati@emph{c}}
9652 Identifier character set (@code{c} = 1/2/3/4/8/9/p/f/n/w).
9653 For details of the possible selections for @code{c},
9654 see @ref{48,,Character Set Control}.
9657 @geindex -gnatI (gcc)
9664 Ignore representation clauses. When this switch is used,
9665 representation clauses are treated as comments. This is useful
9666 when initially porting code where you want to ignore rep clause
9667 problems, and also for compiling foreign code (particularly
9668 for use with ASIS). The representation clauses that are ignored
9669 are: enumeration_representation_clause, record_representation_clause,
9670 and attribute_definition_clause for the following attributes:
9671 Address, Alignment, Bit_Order, Component_Size, Machine_Radix,
9672 Object_Size, Scalar_Storage_Order, Size, Small, Stream_Size,
9673 and Value_Size. Pragma Default_Scalar_Storage_Order is also ignored.
9674 Note that this option should be used only for compiling -- the
9675 code is likely to malfunction at run time.
9677 Note that when @code{-gnatct} is used to generate trees for input
9678 into ASIS tools, these representation clauses are removed
9679 from the tree and ignored. This means that the tool will not see them.
9682 @geindex -gnatjnn (gcc)
9687 @item @code{-gnatj@emph{nn}}
9689 Reformat error messages to fit on @code{nn} character lines
9692 @geindex -gnatJ (gcc)
9699 Permissive elaboration-checking mode enabled. When this switch is in effect,
9700 the post-18.x access-before-elaboration model ignores potential issues with:
9709 Activations of tasks defined in instances
9715 Calls from within an instance to its enclosing context
9718 Calls through generic formal parameters
9721 Calls to subprograms defined in instances
9727 Indirect calls using 'Access
9736 Synchronous task suspension
9739 and does not emit compile-time diagnostics or run-time checks.
9742 @geindex -gnatk (gcc)
9747 @item @code{-gnatk=@emph{n}}
9749 Limit file names to @code{n} (1-999) characters (@code{k} = krunch).
9752 @geindex -gnatl (gcc)
9759 Output full source listing with embedded error messages.
9762 @geindex -gnatL (gcc)
9769 Used in conjunction with -gnatG or -gnatD to intersperse original
9770 source lines (as comment lines with line numbers) in the expanded
9774 @geindex -gnatm (gcc)
9779 @item @code{-gnatm=@emph{n}}
9781 Limit number of detected error or warning messages to @code{n}
9782 where @code{n} is in the range 1..999999. The default setting if
9783 no switch is given is 9999. If the number of warnings reaches this
9784 limit, then a message is output and further warnings are suppressed,
9785 but the compilation is continued. If the number of error messages
9786 reaches this limit, then a message is output and the compilation
9787 is abandoned. The equal sign here is optional. A value of zero
9788 means that no limit applies.
9791 @geindex -gnatn (gcc)
9796 @item @code{-gnatn[12]}
9798 Activate inlining across units for subprograms for which pragma @code{Inline}
9799 is specified. This inlining is performed by the GCC back-end. An optional
9800 digit sets the inlining level: 1 for moderate inlining across units
9801 or 2 for full inlining across units. If no inlining level is specified,
9802 the compiler will pick it based on the optimization level.
9805 @geindex -gnatN (gcc)
9812 Activate front end inlining for subprograms for which
9813 pragma @code{Inline} is specified. This inlining is performed
9814 by the front end and will be visible in the
9815 @code{-gnatG} output.
9817 When using a gcc-based back end (in practice this means using any version
9818 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
9819 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
9820 Historically front end inlining was more extensive than the gcc back end
9821 inlining, but that is no longer the case.
9824 @geindex -gnato0 (gcc)
9829 @item @code{-gnato0}
9831 Suppresses overflow checking. This causes the behavior of the compiler to
9832 match the default for older versions where overflow checking was suppressed
9833 by default. This is equivalent to having
9834 @code{pragma Suppress (Overflow_Check)} in a configuration pragma file.
9837 @geindex -gnato?? (gcc)
9842 @item @code{-gnato??}
9844 Set default mode for handling generation of code to avoid intermediate
9845 arithmetic overflow. Here @code{??} is two digits, a
9846 single digit, or nothing. Each digit is one of the digits @code{1}
9850 @multitable {xxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
9865 All intermediate overflows checked against base type (@code{STRICT})
9873 Minimize intermediate overflows (@code{MINIMIZED})
9881 Eliminate intermediate overflows (@code{ELIMINATED})
9886 If only one digit appears, then it applies to all
9887 cases; if two digits are given, then the first applies outside
9888 assertions, pre/postconditions, and type invariants, and the second
9889 applies within assertions, pre/postconditions, and type invariants.
9891 If no digits follow the @code{-gnato}, then it is equivalent to
9893 causing all intermediate overflows to be handled in strict
9896 This switch also causes arithmetic overflow checking to be performed
9897 (as though @code{pragma Unsuppress (Overflow_Check)} had been specified).
9899 The default if no option @code{-gnato} is given is that overflow handling
9900 is in @code{STRICT} mode (computations done using the base type), and that
9901 overflow checking is enabled.
9903 Note that division by zero is a separate check that is not
9904 controlled by this switch (divide-by-zero checking is on by default).
9906 See also @ref{f8,,Specifying the Desired Mode}.
9909 @geindex -gnatp (gcc)
9916 Suppress all checks. See @ref{f9,,Run-Time Checks} for details. This switch
9917 has no effect if cancelled by a subsequent @code{-gnat-p} switch.
9920 @geindex -gnat-p (gcc)
9925 @item @code{-gnat-p}
9927 Cancel effect of previous @code{-gnatp} switch.
9930 @geindex -gnatP (gcc)
9937 Enable polling. This is required on some systems (notably Windows NT) to
9938 obtain asynchronous abort and asynchronous transfer of control capability.
9939 See @code{Pragma_Polling} in the @cite{GNAT_Reference_Manual} for full
9943 @geindex -gnatq (gcc)
9950 Don't quit. Try semantics, even if parse errors.
9953 @geindex -gnatQ (gcc)
9960 Don't quit. Generate @code{ALI} and tree files even if illegalities.
9961 Note that code generation is still suppressed in the presence of any
9962 errors, so even with @code{-gnatQ} no object file is generated.
9965 @geindex -gnatr (gcc)
9972 Treat pragma Restrictions as Restriction_Warnings.
9975 @geindex -gnatR (gcc)
9980 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
9982 Output representation information for declared types, objects and
9983 subprograms. Note that this switch is not allowed if a previous
9984 @code{-gnatD} switch has been given, since these two switches
9988 @geindex -gnats (gcc)
9998 @geindex -gnatS (gcc)
10003 @item @code{-gnatS}
10005 Print package Standard.
10008 @geindex -gnatt (gcc)
10013 @item @code{-gnatt}
10015 Generate tree output file.
10018 @geindex -gnatT (gcc)
10023 @item @code{-gnatT@emph{nnn}}
10025 All compiler tables start at @code{nnn} times usual starting size.
10028 @geindex -gnatu (gcc)
10033 @item @code{-gnatu}
10035 List units for this compilation.
10038 @geindex -gnatU (gcc)
10043 @item @code{-gnatU}
10045 Tag all error messages with the unique string 'error:'
10048 @geindex -gnatv (gcc)
10053 @item @code{-gnatv}
10055 Verbose mode. Full error output with source lines to @code{stdout}.
10058 @geindex -gnatV (gcc)
10063 @item @code{-gnatV}
10065 Control level of validity checking (@ref{f6,,Validity Checking}).
10068 @geindex -gnatw (gcc)
10073 @item @code{-gnatw@emph{xxx}}
10076 @code{xxx} is a string of option letters that denotes
10077 the exact warnings that
10078 are enabled or disabled (@ref{fa,,Warning Message Control}).
10081 @geindex -gnatW (gcc)
10086 @item @code{-gnatW@emph{e}}
10088 Wide character encoding method
10089 (@code{e}=n/h/u/s/e/8).
10092 @geindex -gnatx (gcc)
10097 @item @code{-gnatx}
10099 Suppress generation of cross-reference information.
10102 @geindex -gnatX (gcc)
10107 @item @code{-gnatX}
10109 Enable GNAT implementation extensions and latest Ada version.
10112 @geindex -gnaty (gcc)
10117 @item @code{-gnaty}
10119 Enable built-in style checks (@ref{fb,,Style Checking}).
10122 @geindex -gnatz (gcc)
10127 @item @code{-gnatz@emph{m}}
10129 Distribution stub generation and compilation
10130 (@code{m}=r/c for receiver/caller stubs).
10138 @item @code{-I@emph{dir}}
10142 Direct GNAT to search the @code{dir} directory for source files needed by
10143 the current compilation
10144 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10156 Except for the source file named in the command line, do not look for source
10157 files in the directory containing the source file named in the command line
10158 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
10166 @item @code{-o @emph{file}}
10168 This switch is used in @code{gcc} to redirect the generated object file
10169 and its associated ALI file. Beware of this switch with GNAT, because it may
10170 cause the object file and ALI file to have different names which in turn
10171 may confuse the binder and the linker.
10174 @geindex -nostdinc (gcc)
10179 @item @code{-nostdinc}
10181 Inhibit the search of the default location for the GNAT Run Time
10182 Library (RTL) source files.
10185 @geindex -nostdlib (gcc)
10190 @item @code{-nostdlib}
10192 Inhibit the search of the default location for the GNAT Run Time
10193 Library (RTL) ALI files.
10201 @item @code{-O[@emph{n}]}
10203 @code{n} controls the optimization level:
10206 @multitable {xxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
10221 No optimization, the default setting if no @code{-O} appears
10229 Normal optimization, the default if you specify @code{-O} without an
10230 operand. A good compromise between code quality and compilation
10239 Extensive optimization, may improve execution time, possibly at
10240 the cost of substantially increased compilation time.
10248 Same as @code{-O2}, and also includes inline expansion for small
10249 subprograms in the same unit.
10257 Optimize space usage
10262 See also @ref{fc,,Optimization Levels}.
10265 @geindex -pass-exit-codes (gcc)
10270 @item @code{-pass-exit-codes}
10272 Catch exit codes from the compiler and use the most meaningful as
10276 @geindex --RTS (gcc)
10281 @item @code{--RTS=@emph{rts-path}}
10283 Specifies the default location of the run-time library. Same meaning as the
10284 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
10294 Used in place of @code{-c} to
10295 cause the assembler source file to be
10296 generated, using @code{.s} as the extension,
10297 instead of the object file.
10298 This may be useful if you need to examine the generated assembly code.
10301 @geindex -fverbose-asm (gcc)
10306 @item @code{-fverbose-asm}
10308 Used in conjunction with @code{-S}
10309 to cause the generated assembly code file to be annotated with variable
10310 names, making it significantly easier to follow.
10320 Show commands generated by the @code{gcc} driver. Normally used only for
10321 debugging purposes or if you need to be sure what version of the
10322 compiler you are executing.
10330 @item @code{-V @emph{ver}}
10332 Execute @code{ver} version of the compiler. This is the @code{gcc}
10333 version, not the GNAT version.
10343 Turn off warnings generated by the back end of the compiler. Use of
10344 this switch also causes the default for front end warnings to be set
10345 to suppress (as though @code{-gnatws} had appeared at the start of
10349 @geindex Combining GNAT switches
10351 You may combine a sequence of GNAT switches into a single switch. For
10352 example, the combined switch
10361 is equivalent to specifying the following sequence of switches:
10366 -gnato -gnatf -gnati3
10370 The following restrictions apply to the combination of switches
10377 The switch @code{-gnatc} if combined with other switches must come
10378 first in the string.
10381 The switch @code{-gnats} if combined with other switches must come
10382 first in the string.
10386 @code{-gnatzc} and @code{-gnatzr} may not be combined with any other
10387 switches, and only one of them may appear in the command line.
10390 The switch @code{-gnat-p} may not be combined with any other switch.
10393 Once a 'y' appears in the string (that is a use of the @code{-gnaty}
10394 switch), then all further characters in the switch are interpreted
10395 as style modifiers (see description of @code{-gnaty}).
10398 Once a 'd' appears in the string (that is a use of the @code{-gnatd}
10399 switch), then all further characters in the switch are interpreted
10400 as debug flags (see description of @code{-gnatd}).
10403 Once a 'w' appears in the string (that is a use of the @code{-gnatw}
10404 switch), then all further characters in the switch are interpreted
10405 as warning mode modifiers (see description of @code{-gnatw}).
10408 Once a 'V' appears in the string (that is a use of the @code{-gnatV}
10409 switch), then all further characters in the switch are interpreted
10410 as validity checking options (@ref{f6,,Validity Checking}).
10413 Option 'em', 'ec', 'ep', 'l=' and 'R' must be the last options in
10414 a combined list of options.
10417 @node Output and Error Message Control,Warning Message Control,Alphabetical List of All Switches,Compiler Switches
10418 @anchor{gnat_ugn/building_executable_programs_with_gnat id14}@anchor{fd}@anchor{gnat_ugn/building_executable_programs_with_gnat output-and-error-message-control}@anchor{fe}
10419 @subsection Output and Error Message Control
10424 The standard default format for error messages is called 'brief format'.
10425 Brief format messages are written to @code{stderr} (the standard error
10426 file) and have the following form:
10429 e.adb:3:04: Incorrect spelling of keyword "function"
10430 e.adb:4:20: ";" should be "is"
10433 The first integer after the file name is the line number in the file,
10434 and the second integer is the column number within the line.
10435 @code{GPS} can parse the error messages
10436 and point to the referenced character.
10437 The following switches provide control over the error message
10440 @geindex -gnatv (gcc)
10445 @item @code{-gnatv}
10447 The @code{v} stands for verbose.
10448 The effect of this setting is to write long-format error
10449 messages to @code{stdout} (the standard output file.
10450 The same program compiled with the
10451 @code{-gnatv} switch would generate:
10454 3. funcion X (Q : Integer)
10456 >>> Incorrect spelling of keyword "function"
10459 >>> ";" should be "is"
10462 The vertical bar indicates the location of the error, and the @code{>>>}
10463 prefix can be used to search for error messages. When this switch is
10464 used the only source lines output are those with errors.
10467 @geindex -gnatl (gcc)
10472 @item @code{-gnatl}
10474 The @code{l} stands for list.
10475 This switch causes a full listing of
10476 the file to be generated. In the case where a body is
10477 compiled, the corresponding spec is also listed, along
10478 with any subunits. Typical output from compiling a package
10479 body @code{p.adb} might look like:
10484 1. package body p is
10486 3. procedure a is separate;
10497 2. pragma Elaborate_Body
10518 When you specify the @code{-gnatv} or @code{-gnatl} switches and
10519 standard output is redirected, a brief summary is written to
10520 @code{stderr} (standard error) giving the number of error messages and
10521 warning messages generated.
10524 @geindex -gnatl=fname (gcc)
10529 @item @code{-gnatl=@emph{fname}}
10531 This has the same effect as @code{-gnatl} except that the output is
10532 written to a file instead of to standard output. If the given name
10533 @code{fname} does not start with a period, then it is the full name
10534 of the file to be written. If @code{fname} is an extension, it is
10535 appended to the name of the file being compiled. For example, if
10536 file @code{xyz.adb} is compiled with @code{-gnatl=.lst},
10537 then the output is written to file xyz.adb.lst.
10540 @geindex -gnatU (gcc)
10545 @item @code{-gnatU}
10547 This switch forces all error messages to be preceded by the unique
10548 string 'error:'. This means that error messages take a few more
10549 characters in space, but allows easy searching for and identification
10553 @geindex -gnatb (gcc)
10558 @item @code{-gnatb}
10560 The @code{b} stands for brief.
10561 This switch causes GNAT to generate the
10562 brief format error messages to @code{stderr} (the standard error
10563 file) as well as the verbose
10564 format message or full listing (which as usual is written to
10565 @code{stdout} (the standard output file).
10568 @geindex -gnatm (gcc)
10573 @item @code{-gnatm=@emph{n}}
10575 The @code{m} stands for maximum.
10576 @code{n} is a decimal integer in the
10577 range of 1 to 999999 and limits the number of error or warning
10578 messages to be generated. For example, using
10579 @code{-gnatm2} might yield
10582 e.adb:3:04: Incorrect spelling of keyword "function"
10583 e.adb:5:35: missing ".."
10584 fatal error: maximum number of errors detected
10585 compilation abandoned
10588 The default setting if
10589 no switch is given is 9999. If the number of warnings reaches this
10590 limit, then a message is output and further warnings are suppressed,
10591 but the compilation is continued. If the number of error messages
10592 reaches this limit, then a message is output and the compilation
10593 is abandoned. A value of zero means that no limit applies.
10595 Note that the equal sign is optional, so the switches
10596 @code{-gnatm2} and @code{-gnatm=2} are equivalent.
10599 @geindex -gnatf (gcc)
10604 @item @code{-gnatf}
10606 @geindex Error messages
10607 @geindex suppressing
10609 The @code{f} stands for full.
10610 Normally, the compiler suppresses error messages that are likely to be
10611 redundant. This switch causes all error
10612 messages to be generated. In particular, in the case of
10613 references to undefined variables. If a given variable is referenced
10614 several times, the normal format of messages is
10617 e.adb:7:07: "V" is undefined (more references follow)
10620 where the parenthetical comment warns that there are additional
10621 references to the variable @code{V}. Compiling the same program with the
10622 @code{-gnatf} switch yields
10625 e.adb:7:07: "V" is undefined
10626 e.adb:8:07: "V" is undefined
10627 e.adb:8:12: "V" is undefined
10628 e.adb:8:16: "V" is undefined
10629 e.adb:9:07: "V" is undefined
10630 e.adb:9:12: "V" is undefined
10633 The @code{-gnatf} switch also generates additional information for
10634 some error messages. Some examples are:
10640 Details on possibly non-portable unchecked conversion
10643 List possible interpretations for ambiguous calls
10646 Additional details on incorrect parameters
10650 @geindex -gnatjnn (gcc)
10655 @item @code{-gnatjnn}
10657 In normal operation mode (or if @code{-gnatj0} is used), then error messages
10658 with continuation lines are treated as though the continuation lines were
10659 separate messages (and so a warning with two continuation lines counts as
10660 three warnings, and is listed as three separate messages).
10662 If the @code{-gnatjnn} switch is used with a positive value for nn, then
10663 messages are output in a different manner. A message and all its continuation
10664 lines are treated as a unit, and count as only one warning or message in the
10665 statistics totals. Furthermore, the message is reformatted so that no line
10666 is longer than nn characters.
10669 @geindex -gnatq (gcc)
10674 @item @code{-gnatq}
10676 The @code{q} stands for quit (really 'don't quit').
10677 In normal operation mode, the compiler first parses the program and
10678 determines if there are any syntax errors. If there are, appropriate
10679 error messages are generated and compilation is immediately terminated.
10681 GNAT to continue with semantic analysis even if syntax errors have been
10682 found. This may enable the detection of more errors in a single run. On
10683 the other hand, the semantic analyzer is more likely to encounter some
10684 internal fatal error when given a syntactically invalid tree.
10687 @geindex -gnatQ (gcc)
10692 @item @code{-gnatQ}
10694 In normal operation mode, the @code{ALI} file is not generated if any
10695 illegalities are detected in the program. The use of @code{-gnatQ} forces
10696 generation of the @code{ALI} file. This file is marked as being in
10697 error, so it cannot be used for binding purposes, but it does contain
10698 reasonably complete cross-reference information, and thus may be useful
10699 for use by tools (e.g., semantic browsing tools or integrated development
10700 environments) that are driven from the @code{ALI} file. This switch
10701 implies @code{-gnatq}, since the semantic phase must be run to get a
10702 meaningful ALI file.
10704 In addition, if @code{-gnatt} is also specified, then the tree file is
10705 generated even if there are illegalities. It may be useful in this case
10706 to also specify @code{-gnatq} to ensure that full semantic processing
10707 occurs. The resulting tree file can be processed by ASIS, for the purpose
10708 of providing partial information about illegal units, but if the error
10709 causes the tree to be badly malformed, then ASIS may crash during the
10712 When @code{-gnatQ} is used and the generated @code{ALI} file is marked as
10713 being in error, @code{gnatmake} will attempt to recompile the source when it
10714 finds such an @code{ALI} file, including with switch @code{-gnatc}.
10716 Note that @code{-gnatQ} has no effect if @code{-gnats} is specified,
10717 since ALI files are never generated if @code{-gnats} is set.
10720 @node Warning Message Control,Debugging and Assertion Control,Output and Error Message Control,Compiler Switches
10721 @anchor{gnat_ugn/building_executable_programs_with_gnat warning-message-control}@anchor{fa}@anchor{gnat_ugn/building_executable_programs_with_gnat id15}@anchor{ff}
10722 @subsection Warning Message Control
10725 @geindex Warning messages
10727 In addition to error messages, which correspond to illegalities as defined
10728 in the Ada Reference Manual, the compiler detects two kinds of warning
10731 First, the compiler considers some constructs suspicious and generates a
10732 warning message to alert you to a possible error. Second, if the
10733 compiler detects a situation that is sure to raise an exception at
10734 run time, it generates a warning message. The following shows an example
10735 of warning messages:
10738 e.adb:4:24: warning: creation of object may raise Storage_Error
10739 e.adb:10:17: warning: static value out of range
10740 e.adb:10:17: warning: "Constraint_Error" will be raised at run time
10743 GNAT considers a large number of situations as appropriate
10744 for the generation of warning messages. As always, warnings are not
10745 definite indications of errors. For example, if you do an out-of-range
10746 assignment with the deliberate intention of raising a
10747 @code{Constraint_Error} exception, then the warning that may be
10748 issued does not indicate an error. Some of the situations for which GNAT
10749 issues warnings (at least some of the time) are given in the following
10750 list. This list is not complete, and new warnings are often added to
10751 subsequent versions of GNAT. The list is intended to give a general idea
10752 of the kinds of warnings that are generated.
10758 Possible infinitely recursive calls
10761 Out-of-range values being assigned
10764 Possible order of elaboration problems
10767 Size not a multiple of alignment for a record type
10770 Assertions (pragma Assert) that are sure to fail
10776 Address clauses with possibly unaligned values, or where an attempt is
10777 made to overlay a smaller variable with a larger one.
10780 Fixed-point type declarations with a null range
10783 Direct_IO or Sequential_IO instantiated with a type that has access values
10786 Variables that are never assigned a value
10789 Variables that are referenced before being initialized
10792 Task entries with no corresponding @code{accept} statement
10795 Duplicate accepts for the same task entry in a @code{select}
10798 Objects that take too much storage
10801 Unchecked conversion between types of differing sizes
10804 Missing @code{return} statement along some execution path in a function
10807 Incorrect (unrecognized) pragmas
10810 Incorrect external names
10813 Allocation from empty storage pool
10816 Potentially blocking operation in protected type
10819 Suspicious parenthesization of expressions
10822 Mismatching bounds in an aggregate
10825 Attempt to return local value by reference
10828 Premature instantiation of a generic body
10831 Attempt to pack aliased components
10834 Out of bounds array subscripts
10837 Wrong length on string assignment
10840 Violations of style rules if style checking is enabled
10843 Unused @emph{with} clauses
10846 @code{Bit_Order} usage that does not have any effect
10849 @code{Standard.Duration} used to resolve universal fixed expression
10852 Dereference of possibly null value
10855 Declaration that is likely to cause storage error
10858 Internal GNAT unit @emph{with}ed by application unit
10861 Values known to be out of range at compile time
10864 Unreferenced or unmodified variables. Note that a special
10865 exemption applies to variables which contain any of the substrings
10866 @code{DISCARD, DUMMY, IGNORE, JUNK, UNUSED}, in any casing. Such variables
10867 are considered likely to be intentionally used in a situation where
10868 otherwise a warning would be given, so warnings of this kind are
10869 always suppressed for such variables.
10872 Address overlays that could clobber memory
10875 Unexpected initialization when address clause present
10878 Bad alignment for address clause
10881 Useless type conversions
10884 Redundant assignment statements and other redundant constructs
10887 Useless exception handlers
10890 Accidental hiding of name by child unit
10893 Access before elaboration detected at compile time
10896 A range in a @code{for} loop that is known to be null or might be null
10899 The following section lists compiler switches that are available
10900 to control the handling of warning messages. It is also possible
10901 to exercise much finer control over what warnings are issued and
10902 suppressed using the GNAT pragma Warnings (see the description
10903 of the pragma in the @cite{GNAT_Reference_manual}).
10905 @geindex -gnatwa (gcc)
10910 @item @code{-gnatwa}
10912 @emph{Activate most optional warnings.}
10914 This switch activates most optional warning messages. See the remaining list
10915 in this section for details on optional warning messages that can be
10916 individually controlled. The warnings that are not turned on by this
10923 @code{-gnatwd} (implicit dereferencing)
10926 @code{-gnatw.d} (tag warnings with -gnatw switch)
10929 @code{-gnatwh} (hiding)
10932 @code{-gnatw.h} (holes in record layouts)
10935 @code{-gnatw.j} (late primitives of tagged types)
10938 @code{-gnatw.k} (redefinition of names in standard)
10941 @code{-gnatwl} (elaboration warnings)
10944 @code{-gnatw.l} (inherited aspects)
10947 @code{-gnatw.n} (atomic synchronization)
10950 @code{-gnatwo} (address clause overlay)
10953 @code{-gnatw.o} (values set by out parameters ignored)
10956 @code{-gnatw.q} (questionable layout of record types)
10959 @code{-gnatw.s} (overridden size clause)
10962 @code{-gnatwt} (tracking of deleted conditional code)
10965 @code{-gnatw.u} (unordered enumeration)
10968 @code{-gnatw.w} (use of Warnings Off)
10971 @code{-gnatw.y} (reasons for package needing body)
10974 All other optional warnings are turned on.
10977 @geindex -gnatwA (gcc)
10982 @item @code{-gnatwA}
10984 @emph{Suppress all optional errors.}
10986 This switch suppresses all optional warning messages, see remaining list
10987 in this section for details on optional warning messages that can be
10988 individually controlled. Note that unlike switch @code{-gnatws}, the
10989 use of switch @code{-gnatwA} does not suppress warnings that are
10990 normally given unconditionally and cannot be individually controlled
10991 (for example, the warning about a missing exit path in a function).
10992 Also, again unlike switch @code{-gnatws}, warnings suppressed by
10993 the use of switch @code{-gnatwA} can be individually turned back
10994 on. For example the use of switch @code{-gnatwA} followed by
10995 switch @code{-gnatwd} will suppress all optional warnings except
10996 the warnings for implicit dereferencing.
10999 @geindex -gnatw.a (gcc)
11004 @item @code{-gnatw.a}
11006 @emph{Activate warnings on failing assertions.}
11008 @geindex Assert failures
11010 This switch activates warnings for assertions where the compiler can tell at
11011 compile time that the assertion will fail. Note that this warning is given
11012 even if assertions are disabled. The default is that such warnings are
11016 @geindex -gnatw.A (gcc)
11021 @item @code{-gnatw.A}
11023 @emph{Suppress warnings on failing assertions.}
11025 @geindex Assert failures
11027 This switch suppresses warnings for assertions where the compiler can tell at
11028 compile time that the assertion will fail.
11031 @geindex -gnatwb (gcc)
11036 @item @code{-gnatwb}
11038 @emph{Activate warnings on bad fixed values.}
11040 @geindex Bad fixed values
11042 @geindex Fixed-point Small value
11044 @geindex Small value
11046 This switch activates warnings for static fixed-point expressions whose
11047 value is not an exact multiple of Small. Such values are implementation
11048 dependent, since an implementation is free to choose either of the multiples
11049 that surround the value. GNAT always chooses the closer one, but this is not
11050 required behavior, and it is better to specify a value that is an exact
11051 multiple, ensuring predictable execution. The default is that such warnings
11055 @geindex -gnatwB (gcc)
11060 @item @code{-gnatwB}
11062 @emph{Suppress warnings on bad fixed values.}
11064 This switch suppresses warnings for static fixed-point expressions whose
11065 value is not an exact multiple of Small.
11068 @geindex -gnatw.b (gcc)
11073 @item @code{-gnatw.b}
11075 @emph{Activate warnings on biased representation.}
11077 @geindex Biased representation
11079 This switch activates warnings when a size clause, value size clause, component
11080 clause, or component size clause forces the use of biased representation for an
11081 integer type (e.g. representing a range of 10..11 in a single bit by using 0/1
11082 to represent 10/11). The default is that such warnings are generated.
11085 @geindex -gnatwB (gcc)
11090 @item @code{-gnatw.B}
11092 @emph{Suppress warnings on biased representation.}
11094 This switch suppresses warnings for representation clauses that force the use
11095 of biased representation.
11098 @geindex -gnatwc (gcc)
11103 @item @code{-gnatwc}
11105 @emph{Activate warnings on conditionals.}
11107 @geindex Conditionals
11110 This switch activates warnings for conditional expressions used in
11111 tests that are known to be True or False at compile time. The default
11112 is that such warnings are not generated.
11113 Note that this warning does
11114 not get issued for the use of boolean variables or constants whose
11115 values are known at compile time, since this is a standard technique
11116 for conditional compilation in Ada, and this would generate too many
11117 false positive warnings.
11119 This warning option also activates a special test for comparisons using
11120 the operators '>=' and' <='.
11121 If the compiler can tell that only the equality condition is possible,
11122 then it will warn that the '>' or '<' part of the test
11123 is useless and that the operator could be replaced by '='.
11124 An example would be comparing a @code{Natural} variable <= 0.
11126 This warning option also generates warnings if
11127 one or both tests is optimized away in a membership test for integer
11128 values if the result can be determined at compile time. Range tests on
11129 enumeration types are not included, since it is common for such tests
11130 to include an end point.
11132 This warning can also be turned on using @code{-gnatwa}.
11135 @geindex -gnatwC (gcc)
11140 @item @code{-gnatwC}
11142 @emph{Suppress warnings on conditionals.}
11144 This switch suppresses warnings for conditional expressions used in
11145 tests that are known to be True or False at compile time.
11148 @geindex -gnatw.c (gcc)
11153 @item @code{-gnatw.c}
11155 @emph{Activate warnings on missing component clauses.}
11157 @geindex Component clause
11160 This switch activates warnings for record components where a record
11161 representation clause is present and has component clauses for the
11162 majority, but not all, of the components. A warning is given for each
11163 component for which no component clause is present.
11166 @geindex -gnatwC (gcc)
11171 @item @code{-gnatw.C}
11173 @emph{Suppress warnings on missing component clauses.}
11175 This switch suppresses warnings for record components that are
11176 missing a component clause in the situation described above.
11179 @geindex -gnatwd (gcc)
11184 @item @code{-gnatwd}
11186 @emph{Activate warnings on implicit dereferencing.}
11188 If this switch is set, then the use of a prefix of an access type
11189 in an indexed component, slice, or selected component without an
11190 explicit @code{.all} will generate a warning. With this warning
11191 enabled, access checks occur only at points where an explicit
11192 @code{.all} appears in the source code (assuming no warnings are
11193 generated as a result of this switch). The default is that such
11194 warnings are not generated.
11197 @geindex -gnatwD (gcc)
11202 @item @code{-gnatwD}
11204 @emph{Suppress warnings on implicit dereferencing.}
11206 @geindex Implicit dereferencing
11208 @geindex Dereferencing
11211 This switch suppresses warnings for implicit dereferences in
11212 indexed components, slices, and selected components.
11215 @geindex -gnatw.d (gcc)
11220 @item @code{-gnatw.d}
11222 @emph{Activate tagging of warning and info messages.}
11224 If this switch is set, then warning messages are tagged, with one of the
11234 Used to tag warnings controlled by the switch @code{-gnatwx} where x
11239 Used to tag warnings controlled by the switch @code{-gnatw.x} where x
11244 Used to tag elaboration information (info) messages generated when the
11245 static model of elaboration is used and the @code{-gnatel} switch is set.
11248 @emph{[restriction warning]}
11249 Used to tag warning messages for restriction violations, activated by use
11250 of the pragma @code{Restriction_Warnings}.
11253 @emph{[warning-as-error]}
11254 Used to tag warning messages that have been converted to error messages by
11255 use of the pragma Warning_As_Error. Note that such warnings are prefixed by
11256 the string "error: " rather than "warning: ".
11259 @emph{[enabled by default]}
11260 Used to tag all other warnings that are always given by default, unless
11261 warnings are completely suppressed using pragma @emph{Warnings(Off)} or
11262 the switch @code{-gnatws}.
11267 @geindex -gnatw.d (gcc)
11272 @item @code{-gnatw.D}
11274 @emph{Deactivate tagging of warning and info messages messages.}
11276 If this switch is set, then warning messages return to the default
11277 mode in which warnings and info messages are not tagged as described above for
11281 @geindex -gnatwe (gcc)
11284 @geindex treat as error
11289 @item @code{-gnatwe}
11291 @emph{Treat warnings and style checks as errors.}
11293 This switch causes warning messages and style check messages to be
11295 The warning string still appears, but the warning messages are counted
11296 as errors, and prevent the generation of an object file. Note that this
11297 is the only -gnatw switch that affects the handling of style check messages.
11298 Note also that this switch has no effect on info (information) messages, which
11299 are not treated as errors if this switch is present.
11302 @geindex -gnatw.e (gcc)
11307 @item @code{-gnatw.e}
11309 @emph{Activate every optional warning.}
11312 @geindex activate every optional warning
11314 This switch activates all optional warnings, including those which
11315 are not activated by @code{-gnatwa}. The use of this switch is not
11316 recommended for normal use. If you turn this switch on, it is almost
11317 certain that you will get large numbers of useless warnings. The
11318 warnings that are excluded from @code{-gnatwa} are typically highly
11319 specialized warnings that are suitable for use only in code that has
11320 been specifically designed according to specialized coding rules.
11323 @geindex -gnatwE (gcc)
11326 @geindex treat as error
11331 @item @code{-gnatwE}
11333 @emph{Treat all run-time exception warnings as errors.}
11335 This switch causes warning messages regarding errors that will be raised
11336 during run-time execution to be treated as errors.
11339 @geindex -gnatwf (gcc)
11344 @item @code{-gnatwf}
11346 @emph{Activate warnings on unreferenced formals.}
11349 @geindex unreferenced
11351 This switch causes a warning to be generated if a formal parameter
11352 is not referenced in the body of the subprogram. This warning can
11353 also be turned on using @code{-gnatwu}. The
11354 default is that these warnings are not generated.
11357 @geindex -gnatwF (gcc)
11362 @item @code{-gnatwF}
11364 @emph{Suppress warnings on unreferenced formals.}
11366 This switch suppresses warnings for unreferenced formal
11367 parameters. Note that the
11368 combination @code{-gnatwu} followed by @code{-gnatwF} has the
11369 effect of warning on unreferenced entities other than subprogram
11373 @geindex -gnatwg (gcc)
11378 @item @code{-gnatwg}
11380 @emph{Activate warnings on unrecognized pragmas.}
11383 @geindex unrecognized
11385 This switch causes a warning to be generated if an unrecognized
11386 pragma is encountered. Apart from issuing this warning, the
11387 pragma is ignored and has no effect. The default
11388 is that such warnings are issued (satisfying the Ada Reference
11389 Manual requirement that such warnings appear).
11392 @geindex -gnatwG (gcc)
11397 @item @code{-gnatwG}
11399 @emph{Suppress warnings on unrecognized pragmas.}
11401 This switch suppresses warnings for unrecognized pragmas.
11404 @geindex -gnatw.g (gcc)
11409 @item @code{-gnatw.g}
11411 @emph{Warnings used for GNAT sources.}
11413 This switch sets the warning categories that are used by the standard
11414 GNAT style. Currently this is equivalent to
11415 @code{-gnatwAao.q.s.CI.V.X.Z}
11416 but more warnings may be added in the future without advanced notice.
11419 @geindex -gnatwh (gcc)
11424 @item @code{-gnatwh}
11426 @emph{Activate warnings on hiding.}
11428 @geindex Hiding of Declarations
11430 This switch activates warnings on hiding declarations that are considered
11431 potentially confusing. Not all cases of hiding cause warnings; for example an
11432 overriding declaration hides an implicit declaration, which is just normal
11433 code. The default is that warnings on hiding are not generated.
11436 @geindex -gnatwH (gcc)
11441 @item @code{-gnatwH}
11443 @emph{Suppress warnings on hiding.}
11445 This switch suppresses warnings on hiding declarations.
11448 @geindex -gnatw.h (gcc)
11453 @item @code{-gnatw.h}
11455 @emph{Activate warnings on holes/gaps in records.}
11457 @geindex Record Representation (gaps)
11459 This switch activates warnings on component clauses in record
11460 representation clauses that leave holes (gaps) in the record layout.
11461 If this warning option is active, then record representation clauses
11462 should specify a contiguous layout, adding unused fill fields if needed.
11465 @geindex -gnatw.H (gcc)
11470 @item @code{-gnatw.H}
11472 @emph{Suppress warnings on holes/gaps in records.}
11474 This switch suppresses warnings on component clauses in record
11475 representation clauses that leave holes (haps) in the record layout.
11478 @geindex -gnatwi (gcc)
11483 @item @code{-gnatwi}
11485 @emph{Activate warnings on implementation units.}
11487 This switch activates warnings for a @emph{with} of an internal GNAT
11488 implementation unit, defined as any unit from the @code{Ada},
11489 @code{Interfaces}, @code{GNAT},
11491 hierarchies that is not
11492 documented in either the Ada Reference Manual or the GNAT
11493 Programmer's Reference Manual. Such units are intended only
11494 for internal implementation purposes and should not be @emph{with}ed
11495 by user programs. The default is that such warnings are generated
11498 @geindex -gnatwI (gcc)
11503 @item @code{-gnatwI}
11505 @emph{Disable warnings on implementation units.}
11507 This switch disables warnings for a @emph{with} of an internal GNAT
11508 implementation unit.
11511 @geindex -gnatw.i (gcc)
11516 @item @code{-gnatw.i}
11518 @emph{Activate warnings on overlapping actuals.}
11520 This switch enables a warning on statically detectable overlapping actuals in
11521 a subprogram call, when one of the actuals is an in-out parameter, and the
11522 types of the actuals are not by-copy types. This warning is off by default.
11525 @geindex -gnatw.I (gcc)
11530 @item @code{-gnatw.I}
11532 @emph{Disable warnings on overlapping actuals.}
11534 This switch disables warnings on overlapping actuals in a call..
11537 @geindex -gnatwj (gcc)
11542 @item @code{-gnatwj}
11544 @emph{Activate warnings on obsolescent features (Annex J).}
11547 @geindex obsolescent
11549 @geindex Obsolescent features
11551 If this warning option is activated, then warnings are generated for
11552 calls to subprograms marked with @code{pragma Obsolescent} and
11553 for use of features in Annex J of the Ada Reference Manual. In the
11554 case of Annex J, not all features are flagged. In particular use
11555 of the renamed packages (like @code{Text_IO}) and use of package
11556 @code{ASCII} are not flagged, since these are very common and
11557 would generate many annoying positive warnings. The default is that
11558 such warnings are not generated.
11560 In addition to the above cases, warnings are also generated for
11561 GNAT features that have been provided in past versions but which
11562 have been superseded (typically by features in the new Ada standard).
11563 For example, @code{pragma Ravenscar} will be flagged since its
11564 function is replaced by @code{pragma Profile(Ravenscar)}, and
11565 @code{pragma Interface_Name} will be flagged since its function
11566 is replaced by @code{pragma Import}.
11568 Note that this warning option functions differently from the
11569 restriction @code{No_Obsolescent_Features} in two respects.
11570 First, the restriction applies only to annex J features.
11571 Second, the restriction does flag uses of package @code{ASCII}.
11574 @geindex -gnatwJ (gcc)
11579 @item @code{-gnatwJ}
11581 @emph{Suppress warnings on obsolescent features (Annex J).}
11583 This switch disables warnings on use of obsolescent features.
11586 @geindex -gnatw.j (gcc)
11591 @item @code{-gnatw.j}
11593 @emph{Activate warnings on late declarations of tagged type primitives.}
11595 This switch activates warnings on visible primitives added to a
11596 tagged type after deriving a private extension from it.
11599 @geindex -gnatw.J (gcc)
11604 @item @code{-gnatw.J}
11606 @emph{Suppress warnings on late declarations of tagged type primitives.}
11608 This switch suppresses warnings on visible primitives added to a
11609 tagged type after deriving a private extension from it.
11612 @geindex -gnatwk (gcc)
11617 @item @code{-gnatwk}
11619 @emph{Activate warnings on variables that could be constants.}
11621 This switch activates warnings for variables that are initialized but
11622 never modified, and then could be declared constants. The default is that
11623 such warnings are not given.
11626 @geindex -gnatwK (gcc)
11631 @item @code{-gnatwK}
11633 @emph{Suppress warnings on variables that could be constants.}
11635 This switch disables warnings on variables that could be declared constants.
11638 @geindex -gnatw.k (gcc)
11643 @item @code{-gnatw.k}
11645 @emph{Activate warnings on redefinition of names in standard.}
11647 This switch activates warnings for declarations that declare a name that
11648 is defined in package Standard. Such declarations can be confusing,
11649 especially since the names in package Standard continue to be directly
11650 visible, meaning that use visibiliy on such redeclared names does not
11651 work as expected. Names of discriminants and components in records are
11652 not included in this check.
11655 @geindex -gnatwK (gcc)
11660 @item @code{-gnatw.K}
11662 @emph{Suppress warnings on redefinition of names in standard.}
11664 This switch activates warnings for declarations that declare a name that
11665 is defined in package Standard.
11668 @geindex -gnatwl (gcc)
11673 @item @code{-gnatwl}
11675 @emph{Activate warnings for elaboration pragmas.}
11677 @geindex Elaboration
11680 This switch activates warnings for possible elaboration problems,
11681 including suspicious use
11682 of @code{Elaborate} pragmas, when using the static elaboration model, and
11683 possible situations that may raise @code{Program_Error} when using the
11684 dynamic elaboration model.
11685 See the section in this guide on elaboration checking for further details.
11686 The default is that such warnings
11690 @geindex -gnatwL (gcc)
11695 @item @code{-gnatwL}
11697 @emph{Suppress warnings for elaboration pragmas.}
11699 This switch suppresses warnings for possible elaboration problems.
11702 @geindex -gnatw.l (gcc)
11707 @item @code{-gnatw.l}
11709 @emph{List inherited aspects.}
11711 This switch causes the compiler to list inherited invariants,
11712 preconditions, and postconditions from Type_Invariant'Class, Invariant'Class,
11713 Pre'Class, and Post'Class aspects. Also list inherited subtype predicates.
11716 @geindex -gnatw.L (gcc)
11721 @item @code{-gnatw.L}
11723 @emph{Suppress listing of inherited aspects.}
11725 This switch suppresses listing of inherited aspects.
11728 @geindex -gnatwm (gcc)
11733 @item @code{-gnatwm}
11735 @emph{Activate warnings on modified but unreferenced variables.}
11737 This switch activates warnings for variables that are assigned (using
11738 an initialization value or with one or more assignment statements) but
11739 whose value is never read. The warning is suppressed for volatile
11740 variables and also for variables that are renamings of other variables
11741 or for which an address clause is given.
11742 The default is that these warnings are not given.
11745 @geindex -gnatwM (gcc)
11750 @item @code{-gnatwM}
11752 @emph{Disable warnings on modified but unreferenced variables.}
11754 This switch disables warnings for variables that are assigned or
11755 initialized, but never read.
11758 @geindex -gnatw.m (gcc)
11763 @item @code{-gnatw.m}
11765 @emph{Activate warnings on suspicious modulus values.}
11767 This switch activates warnings for modulus values that seem suspicious.
11768 The cases caught are where the size is the same as the modulus (e.g.
11769 a modulus of 7 with a size of 7 bits), and modulus values of 32 or 64
11770 with no size clause. The guess in both cases is that 2**x was intended
11771 rather than x. In addition expressions of the form 2*x for small x
11772 generate a warning (the almost certainly accurate guess being that
11773 2**x was intended). The default is that these warnings are given.
11776 @geindex -gnatw.M (gcc)
11781 @item @code{-gnatw.M}
11783 @emph{Disable warnings on suspicious modulus values.}
11785 This switch disables warnings for suspicious modulus values.
11788 @geindex -gnatwn (gcc)
11793 @item @code{-gnatwn}
11795 @emph{Set normal warnings mode.}
11797 This switch sets normal warning mode, in which enabled warnings are
11798 issued and treated as warnings rather than errors. This is the default
11799 mode. the switch @code{-gnatwn} can be used to cancel the effect of
11800 an explicit @code{-gnatws} or
11801 @code{-gnatwe}. It also cancels the effect of the
11802 implicit @code{-gnatwe} that is activated by the
11803 use of @code{-gnatg}.
11806 @geindex -gnatw.n (gcc)
11808 @geindex Atomic Synchronization
11814 @item @code{-gnatw.n}
11816 @emph{Activate warnings on atomic synchronization.}
11818 This switch actives warnings when an access to an atomic variable
11819 requires the generation of atomic synchronization code. These
11820 warnings are off by default.
11823 @geindex -gnatw.N (gcc)
11828 @item @code{-gnatw.N}
11830 @emph{Suppress warnings on atomic synchronization.}
11832 @geindex Atomic Synchronization
11835 This switch suppresses warnings when an access to an atomic variable
11836 requires the generation of atomic synchronization code.
11839 @geindex -gnatwo (gcc)
11841 @geindex Address Clauses
11847 @item @code{-gnatwo}
11849 @emph{Activate warnings on address clause overlays.}
11851 This switch activates warnings for possibly unintended initialization
11852 effects of defining address clauses that cause one variable to overlap
11853 another. The default is that such warnings are generated.
11856 @geindex -gnatwO (gcc)
11861 @item @code{-gnatwO}
11863 @emph{Suppress warnings on address clause overlays.}
11865 This switch suppresses warnings on possibly unintended initialization
11866 effects of defining address clauses that cause one variable to overlap
11870 @geindex -gnatw.o (gcc)
11875 @item @code{-gnatw.o}
11877 @emph{Activate warnings on modified but unreferenced out parameters.}
11879 This switch activates warnings for variables that are modified by using
11880 them as actuals for a call to a procedure with an out mode formal, where
11881 the resulting assigned value is never read. It is applicable in the case
11882 where there is more than one out mode formal. If there is only one out
11883 mode formal, the warning is issued by default (controlled by -gnatwu).
11884 The warning is suppressed for volatile
11885 variables and also for variables that are renamings of other variables
11886 or for which an address clause is given.
11887 The default is that these warnings are not given.
11890 @geindex -gnatw.O (gcc)
11895 @item @code{-gnatw.O}
11897 @emph{Disable warnings on modified but unreferenced out parameters.}
11899 This switch suppresses warnings for variables that are modified by using
11900 them as actuals for a call to a procedure with an out mode formal, where
11901 the resulting assigned value is never read.
11904 @geindex -gnatwp (gcc)
11912 @item @code{-gnatwp}
11914 @emph{Activate warnings on ineffective pragma Inlines.}
11916 This switch activates warnings for failure of front end inlining
11917 (activated by @code{-gnatN}) to inline a particular call. There are
11918 many reasons for not being able to inline a call, including most
11919 commonly that the call is too complex to inline. The default is
11920 that such warnings are not given.
11921 Warnings on ineffective inlining by the gcc back-end can be activated
11922 separately, using the gcc switch -Winline.
11925 @geindex -gnatwP (gcc)
11930 @item @code{-gnatwP}
11932 @emph{Suppress warnings on ineffective pragma Inlines.}
11934 This switch suppresses warnings on ineffective pragma Inlines. If the
11935 inlining mechanism cannot inline a call, it will simply ignore the
11939 @geindex -gnatw.p (gcc)
11941 @geindex Parameter order
11947 @item @code{-gnatw.p}
11949 @emph{Activate warnings on parameter ordering.}
11951 This switch activates warnings for cases of suspicious parameter
11952 ordering when the list of arguments are all simple identifiers that
11953 match the names of the formals, but are in a different order. The
11954 warning is suppressed if any use of named parameter notation is used,
11955 so this is the appropriate way to suppress a false positive (and
11956 serves to emphasize that the "misordering" is deliberate). The
11957 default is that such warnings are not given.
11960 @geindex -gnatw.P (gcc)
11965 @item @code{-gnatw.P}
11967 @emph{Suppress warnings on parameter ordering.}
11969 This switch suppresses warnings on cases of suspicious parameter
11973 @geindex -gnatwq (gcc)
11975 @geindex Parentheses
11981 @item @code{-gnatwq}
11983 @emph{Activate warnings on questionable missing parentheses.}
11985 This switch activates warnings for cases where parentheses are not used and
11986 the result is potential ambiguity from a readers point of view. For example
11987 (not a > b) when a and b are modular means ((not a) > b) and very likely the
11988 programmer intended (not (a > b)). Similarly (-x mod 5) means (-(x mod 5)) and
11989 quite likely ((-x) mod 5) was intended. In such situations it seems best to
11990 follow the rule of always parenthesizing to make the association clear, and
11991 this warning switch warns if such parentheses are not present. The default
11992 is that these warnings are given.
11995 @geindex -gnatwQ (gcc)
12000 @item @code{-gnatwQ}
12002 @emph{Suppress warnings on questionable missing parentheses.}
12004 This switch suppresses warnings for cases where the association is not
12005 clear and the use of parentheses is preferred.
12008 @geindex -gnatw.q (gcc)
12016 @item @code{-gnatw.q}
12018 @emph{Activate warnings on questionable layout of record types.}
12020 This switch activates warnings for cases where the default layout of
12021 a record type, that is to say the layout of its components in textual
12022 order of the source code, would very likely cause inefficiencies in
12023 the code generated by the compiler, both in terms of space and speed
12024 during execution. One warning is issued for each problematic component
12025 without representation clause in the nonvariant part and then in each
12026 variant recursively, if any.
12028 The purpose of these warnings is neither to prescribe an optimal layout
12029 nor to force the use of representation clauses, but rather to get rid of
12030 the most blatant inefficiencies in the layout. Therefore, the default
12031 layout is matched against the following synthetic ordered layout and
12032 the deviations are flagged on a component-by-component basis:
12038 first all components or groups of components whose length is fixed
12039 and a multiple of the storage unit,
12042 then the remaining components whose length is fixed and not a multiple
12043 of the storage unit,
12046 then the remaining components whose length doesn't depend on discriminants
12047 (that is to say, with variable but uniform length for all objects),
12050 then all components whose length depends on discriminants,
12053 finally the variant part (if any),
12056 for the nonvariant part and for each variant recursively, if any.
12058 The exact wording of the warning depends on whether the compiler is allowed
12059 to reorder the components in the record type or precluded from doing it by
12060 means of pragma @code{No_Component_Reordering}.
12062 The default is that these warnings are not given.
12065 @geindex -gnatw.Q (gcc)
12070 @item @code{-gnatw.Q}
12072 @emph{Suppress warnings on questionable layout of record types.}
12074 This switch suppresses warnings for cases where the default layout of
12075 a record type would very likely cause inefficiencies.
12078 @geindex -gnatwr (gcc)
12083 @item @code{-gnatwr}
12085 @emph{Activate warnings on redundant constructs.}
12087 This switch activates warnings for redundant constructs. The following
12088 is the current list of constructs regarded as redundant:
12094 Assignment of an item to itself.
12097 Type conversion that converts an expression to its own type.
12100 Use of the attribute @code{Base} where @code{typ'Base} is the same
12104 Use of pragma @code{Pack} when all components are placed by a record
12105 representation clause.
12108 Exception handler containing only a reraise statement (raise with no
12109 operand) which has no effect.
12112 Use of the operator abs on an operand that is known at compile time
12116 Comparison of an object or (unary or binary) operation of boolean type to
12117 an explicit True value.
12120 The default is that warnings for redundant constructs are not given.
12123 @geindex -gnatwR (gcc)
12128 @item @code{-gnatwR}
12130 @emph{Suppress warnings on redundant constructs.}
12132 This switch suppresses warnings for redundant constructs.
12135 @geindex -gnatw.r (gcc)
12140 @item @code{-gnatw.r}
12142 @emph{Activate warnings for object renaming function.}
12144 This switch activates warnings for an object renaming that renames a
12145 function call, which is equivalent to a constant declaration (as
12146 opposed to renaming the function itself). The default is that these
12147 warnings are given.
12150 @geindex -gnatwT (gcc)
12155 @item @code{-gnatw.R}
12157 @emph{Suppress warnings for object renaming function.}
12159 This switch suppresses warnings for object renaming function.
12162 @geindex -gnatws (gcc)
12167 @item @code{-gnatws}
12169 @emph{Suppress all warnings.}
12171 This switch completely suppresses the
12172 output of all warning messages from the GNAT front end, including
12173 both warnings that can be controlled by switches described in this
12174 section, and those that are normally given unconditionally. The
12175 effect of this suppress action can only be cancelled by a subsequent
12176 use of the switch @code{-gnatwn}.
12178 Note that switch @code{-gnatws} does not suppress
12179 warnings from the @code{gcc} back end.
12180 To suppress these back end warnings as well, use the switch @code{-w}
12181 in addition to @code{-gnatws}. Also this switch has no effect on the
12182 handling of style check messages.
12185 @geindex -gnatw.s (gcc)
12187 @geindex Record Representation (component sizes)
12192 @item @code{-gnatw.s}
12194 @emph{Activate warnings on overridden size clauses.}
12196 This switch activates warnings on component clauses in record
12197 representation clauses where the length given overrides that
12198 specified by an explicit size clause for the component type. A
12199 warning is similarly given in the array case if a specified
12200 component size overrides an explicit size clause for the array
12204 @geindex -gnatw.S (gcc)
12209 @item @code{-gnatw.S}
12211 @emph{Suppress warnings on overridden size clauses.}
12213 This switch suppresses warnings on component clauses in record
12214 representation clauses that override size clauses, and similar
12215 warnings when an array component size overrides a size clause.
12218 @geindex -gnatwt (gcc)
12220 @geindex Deactivated code
12223 @geindex Deleted code
12229 @item @code{-gnatwt}
12231 @emph{Activate warnings for tracking of deleted conditional code.}
12233 This switch activates warnings for tracking of code in conditionals (IF and
12234 CASE statements) that is detected to be dead code which cannot be executed, and
12235 which is removed by the front end. This warning is off by default. This may be
12236 useful for detecting deactivated code in certified applications.
12239 @geindex -gnatwT (gcc)
12244 @item @code{-gnatwT}
12246 @emph{Suppress warnings for tracking of deleted conditional code.}
12248 This switch suppresses warnings for tracking of deleted conditional code.
12251 @geindex -gnatw.t (gcc)
12256 @item @code{-gnatw.t}
12258 @emph{Activate warnings on suspicious contracts.}
12260 This switch activates warnings on suspicious contracts. This includes
12261 warnings on suspicious postconditions (whether a pragma @code{Postcondition} or a
12262 @code{Post} aspect in Ada 2012) and suspicious contract cases (pragma or aspect
12263 @code{Contract_Cases}). A function postcondition or contract case is suspicious
12264 when no postcondition or contract case for this function mentions the result
12265 of the function. A procedure postcondition or contract case is suspicious
12266 when it only refers to the pre-state of the procedure, because in that case
12267 it should rather be expressed as a precondition. This switch also controls
12268 warnings on suspicious cases of expressions typically found in contracts like
12269 quantified expressions and uses of Update attribute. The default is that such
12270 warnings are generated.
12273 @geindex -gnatw.T (gcc)
12278 @item @code{-gnatw.T}
12280 @emph{Suppress warnings on suspicious contracts.}
12282 This switch suppresses warnings on suspicious contracts.
12285 @geindex -gnatwu (gcc)
12290 @item @code{-gnatwu}
12292 @emph{Activate warnings on unused entities.}
12294 This switch activates warnings to be generated for entities that
12295 are declared but not referenced, and for units that are @emph{with}ed
12297 referenced. In the case of packages, a warning is also generated if
12298 no entities in the package are referenced. This means that if a with'ed
12299 package is referenced but the only references are in @code{use}
12300 clauses or @code{renames}
12301 declarations, a warning is still generated. A warning is also generated
12302 for a generic package that is @emph{with}ed but never instantiated.
12303 In the case where a package or subprogram body is compiled, and there
12304 is a @emph{with} on the corresponding spec
12305 that is only referenced in the body,
12306 a warning is also generated, noting that the
12307 @emph{with} can be moved to the body. The default is that
12308 such warnings are not generated.
12309 This switch also activates warnings on unreferenced formals
12310 (it includes the effect of @code{-gnatwf}).
12313 @geindex -gnatwU (gcc)
12318 @item @code{-gnatwU}
12320 @emph{Suppress warnings on unused entities.}
12322 This switch suppresses warnings for unused entities and packages.
12323 It also turns off warnings on unreferenced formals (and thus includes
12324 the effect of @code{-gnatwF}).
12327 @geindex -gnatw.u (gcc)
12332 @item @code{-gnatw.u}
12334 @emph{Activate warnings on unordered enumeration types.}
12336 This switch causes enumeration types to be considered as conceptually
12337 unordered, unless an explicit pragma @code{Ordered} is given for the type.
12338 The effect is to generate warnings in clients that use explicit comparisons
12339 or subranges, since these constructs both treat objects of the type as
12340 ordered. (A @emph{client} is defined as a unit that is other than the unit in
12341 which the type is declared, or its body or subunits.) Please refer to
12342 the description of pragma @code{Ordered} in the
12343 @cite{GNAT Reference Manual} for further details.
12344 The default is that such warnings are not generated.
12347 @geindex -gnatw.U (gcc)
12352 @item @code{-gnatw.U}
12354 @emph{Deactivate warnings on unordered enumeration types.}
12356 This switch causes all enumeration types to be considered as ordered, so
12357 that no warnings are given for comparisons or subranges for any type.
12360 @geindex -gnatwv (gcc)
12362 @geindex Unassigned variable warnings
12367 @item @code{-gnatwv}
12369 @emph{Activate warnings on unassigned variables.}
12371 This switch activates warnings for access to variables which
12372 may not be properly initialized. The default is that
12373 such warnings are generated.
12376 @geindex -gnatwV (gcc)
12381 @item @code{-gnatwV}
12383 @emph{Suppress warnings on unassigned variables.}
12385 This switch suppresses warnings for access to variables which
12386 may not be properly initialized.
12387 For variables of a composite type, the warning can also be suppressed in
12388 Ada 2005 by using a default initialization with a box. For example, if
12389 Table is an array of records whose components are only partially uninitialized,
12390 then the following code:
12393 Tab : Table := (others => <>);
12396 will suppress warnings on subsequent statements that access components
12400 @geindex -gnatw.v (gcc)
12402 @geindex bit order warnings
12407 @item @code{-gnatw.v}
12409 @emph{Activate info messages for non-default bit order.}
12411 This switch activates messages (labeled "info", they are not warnings,
12412 just informational messages) about the effects of non-default bit-order
12413 on records to which a component clause is applied. The effect of specifying
12414 non-default bit ordering is a bit subtle (and changed with Ada 2005), so
12415 these messages, which are given by default, are useful in understanding the
12416 exact consequences of using this feature.
12419 @geindex -gnatw.V (gcc)
12424 @item @code{-gnatw.V}
12426 @emph{Suppress info messages for non-default bit order.}
12428 This switch suppresses information messages for the effects of specifying
12429 non-default bit order on record components with component clauses.
12432 @geindex -gnatww (gcc)
12434 @geindex String indexing warnings
12439 @item @code{-gnatww}
12441 @emph{Activate warnings on wrong low bound assumption.}
12443 This switch activates warnings for indexing an unconstrained string parameter
12444 with a literal or S'Length. This is a case where the code is assuming that the
12445 low bound is one, which is in general not true (for example when a slice is
12446 passed). The default is that such warnings are generated.
12449 @geindex -gnatwW (gcc)
12454 @item @code{-gnatwW}
12456 @emph{Suppress warnings on wrong low bound assumption.}
12458 This switch suppresses warnings for indexing an unconstrained string parameter
12459 with a literal or S'Length. Note that this warning can also be suppressed
12460 in a particular case by adding an assertion that the lower bound is 1,
12461 as shown in the following example:
12464 procedure K (S : String) is
12465 pragma Assert (S'First = 1);
12470 @geindex -gnatw.w (gcc)
12472 @geindex Warnings Off control
12477 @item @code{-gnatw.w}
12479 @emph{Activate warnings on Warnings Off pragmas.}
12481 This switch activates warnings for use of @code{pragma Warnings (Off, entity)}
12482 where either the pragma is entirely useless (because it suppresses no
12483 warnings), or it could be replaced by @code{pragma Unreferenced} or
12484 @code{pragma Unmodified}.
12485 Also activates warnings for the case of
12486 Warnings (Off, String), where either there is no matching
12487 Warnings (On, String), or the Warnings (Off) did not suppress any warning.
12488 The default is that these warnings are not given.
12491 @geindex -gnatw.W (gcc)
12496 @item @code{-gnatw.W}
12498 @emph{Suppress warnings on unnecessary Warnings Off pragmas.}
12500 This switch suppresses warnings for use of @code{pragma Warnings (Off, ...)}.
12503 @geindex -gnatwx (gcc)
12505 @geindex Export/Import pragma warnings
12510 @item @code{-gnatwx}
12512 @emph{Activate warnings on Export/Import pragmas.}
12514 This switch activates warnings on Export/Import pragmas when
12515 the compiler detects a possible conflict between the Ada and
12516 foreign language calling sequences. For example, the use of
12517 default parameters in a convention C procedure is dubious
12518 because the C compiler cannot supply the proper default, so
12519 a warning is issued. The default is that such warnings are
12523 @geindex -gnatwX (gcc)
12528 @item @code{-gnatwX}
12530 @emph{Suppress warnings on Export/Import pragmas.}
12532 This switch suppresses warnings on Export/Import pragmas.
12533 The sense of this is that you are telling the compiler that
12534 you know what you are doing in writing the pragma, and it
12535 should not complain at you.
12538 @geindex -gnatwm (gcc)
12543 @item @code{-gnatw.x}
12545 @emph{Activate warnings for No_Exception_Propagation mode.}
12547 This switch activates warnings for exception usage when pragma Restrictions
12548 (No_Exception_Propagation) is in effect. Warnings are given for implicit or
12549 explicit exception raises which are not covered by a local handler, and for
12550 exception handlers which do not cover a local raise. The default is that
12551 these warnings are given for units that contain exception handlers.
12553 @item @code{-gnatw.X}
12555 @emph{Disable warnings for No_Exception_Propagation mode.}
12557 This switch disables warnings for exception usage when pragma Restrictions
12558 (No_Exception_Propagation) is in effect.
12561 @geindex -gnatwy (gcc)
12563 @geindex Ada compatibility issues warnings
12568 @item @code{-gnatwy}
12570 @emph{Activate warnings for Ada compatibility issues.}
12572 For the most part, newer versions of Ada are upwards compatible
12573 with older versions. For example, Ada 2005 programs will almost
12574 always work when compiled as Ada 2012.
12575 However there are some exceptions (for example the fact that
12576 @code{some} is now a reserved word in Ada 2012). This
12577 switch activates several warnings to help in identifying
12578 and correcting such incompatibilities. The default is that
12579 these warnings are generated. Note that at one point Ada 2005
12580 was called Ada 0Y, hence the choice of character.
12583 @geindex -gnatwY (gcc)
12585 @geindex Ada compatibility issues warnings
12590 @item @code{-gnatwY}
12592 @emph{Disable warnings for Ada compatibility issues.}
12594 This switch suppresses the warnings intended to help in identifying
12595 incompatibilities between Ada language versions.
12598 @geindex -gnatw.y (gcc)
12600 @geindex Package spec needing body
12605 @item @code{-gnatw.y}
12607 @emph{Activate information messages for why package spec needs body.}
12609 There are a number of cases in which a package spec needs a body.
12610 For example, the use of pragma Elaborate_Body, or the declaration
12611 of a procedure specification requiring a completion. This switch
12612 causes information messages to be output showing why a package
12613 specification requires a body. This can be useful in the case of
12614 a large package specification which is unexpectedly requiring a
12615 body. The default is that such information messages are not output.
12618 @geindex -gnatw.Y (gcc)
12620 @geindex No information messages for why package spec needs body
12625 @item @code{-gnatw.Y}
12627 @emph{Disable information messages for why package spec needs body.}
12629 This switch suppresses the output of information messages showing why
12630 a package specification needs a body.
12633 @geindex -gnatwz (gcc)
12635 @geindex Unchecked_Conversion warnings
12640 @item @code{-gnatwz}
12642 @emph{Activate warnings on unchecked conversions.}
12644 This switch activates warnings for unchecked conversions
12645 where the types are known at compile time to have different
12646 sizes. The default is that such warnings are generated. Warnings are also
12647 generated for subprogram pointers with different conventions.
12650 @geindex -gnatwZ (gcc)
12655 @item @code{-gnatwZ}
12657 @emph{Suppress warnings on unchecked conversions.}
12659 This switch suppresses warnings for unchecked conversions
12660 where the types are known at compile time to have different
12661 sizes or conventions.
12664 @geindex -gnatw.z (gcc)
12666 @geindex Size/Alignment warnings
12671 @item @code{-gnatw.z}
12673 @emph{Activate warnings for size not a multiple of alignment.}
12675 This switch activates warnings for cases of record types with
12676 specified @code{Size} and @code{Alignment} attributes where the
12677 size is not a multiple of the alignment, resulting in an object
12678 size that is greater than the specified size. The default
12679 is that such warnings are generated.
12682 @geindex -gnatw.Z (gcc)
12684 @geindex Size/Alignment warnings
12689 @item @code{-gnatw.Z}
12691 @emph{Suppress warnings for size not a multiple of alignment.}
12693 This switch suppresses warnings for cases of record types with
12694 specified @code{Size} and @code{Alignment} attributes where the
12695 size is not a multiple of the alignment, resulting in an object
12696 size that is greater than the specified size.
12697 The warning can also be
12698 suppressed by giving an explicit @code{Object_Size} value.
12701 @geindex -Wunused (gcc)
12706 @item @code{-Wunused}
12708 The warnings controlled by the @code{-gnatw} switch are generated by
12709 the front end of the compiler. The GCC back end can provide
12710 additional warnings and they are controlled by the @code{-W} switch.
12711 For example, @code{-Wunused} activates back end
12712 warnings for entities that are declared but not referenced.
12715 @geindex -Wuninitialized (gcc)
12720 @item @code{-Wuninitialized}
12722 Similarly, @code{-Wuninitialized} activates
12723 the back end warning for uninitialized variables. This switch must be
12724 used in conjunction with an optimization level greater than zero.
12727 @geindex -Wstack-usage (gcc)
12732 @item @code{-Wstack-usage=@emph{len}}
12734 Warn if the stack usage of a subprogram might be larger than @code{len} bytes.
12735 See @ref{f5,,Static Stack Usage Analysis} for details.
12738 @geindex -Wall (gcc)
12745 This switch enables most warnings from the GCC back end.
12746 The code generator detects a number of warning situations that are missed
12747 by the GNAT front end, and this switch can be used to activate them.
12748 The use of this switch also sets the default front end warning mode to
12749 @code{-gnatwa}, that is, most front end warnings activated as well.
12759 Conversely, this switch suppresses warnings from the GCC back end.
12760 The use of this switch also sets the default front end warning mode to
12761 @code{-gnatws}, that is, front end warnings suppressed as well.
12764 @geindex -Werror (gcc)
12769 @item @code{-Werror}
12771 This switch causes warnings from the GCC back end to be treated as
12772 errors. The warning string still appears, but the warning messages are
12773 counted as errors, and prevent the generation of an object file.
12776 A string of warning parameters can be used in the same parameter. For example:
12782 will turn on all optional warnings except for unrecognized pragma warnings,
12783 and also specify that warnings should be treated as errors.
12785 When no switch @code{-gnatw} is used, this is equivalent to:
12932 @node Debugging and Assertion Control,Validity Checking,Warning Message Control,Compiler Switches
12933 @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-and-assertion-control}@anchor{100}@anchor{gnat_ugn/building_executable_programs_with_gnat id16}@anchor{101}
12934 @subsection Debugging and Assertion Control
12937 @geindex -gnata (gcc)
12942 @item @code{-gnata}
12948 @geindex Assertions
12950 @geindex Precondition
12952 @geindex Postcondition
12954 @geindex Type invariants
12956 @geindex Subtype predicates
12958 The @code{-gnata} option is equivalent to the following @code{Assertion_Policy} pragma:
12961 pragma Assertion_Policy (Check);
12964 Which is a shorthand for:
12967 pragma Assertion_Policy
12969 Static_Predicate => Check,
12970 Dynamic_Predicate => Check,
12972 Pre'Class => Check,
12974 Post'Class => Check,
12975 Type_Invariant => Check,
12976 Type_Invariant'Class => Check);
12979 The pragmas @code{Assert} and @code{Debug} normally have no effect and
12980 are ignored. This switch, where @code{a} stands for 'assert', causes
12981 pragmas @code{Assert} and @code{Debug} to be activated. This switch also
12982 causes preconditions, postconditions, subtype predicates, and
12983 type invariants to be activated.
12985 The pragmas have the form:
12988 pragma Assert (<Boolean-expression> [, <static-string-expression>])
12989 pragma Debug (<procedure call>)
12990 pragma Type_Invariant (<type-local-name>, <Boolean-expression>)
12991 pragma Predicate (<type-local-name>, <Boolean-expression>)
12992 pragma Precondition (<Boolean-expression>, <string-expression>)
12993 pragma Postcondition (<Boolean-expression>, <string-expression>)
12996 The aspects have the form:
12999 with [Pre|Post|Type_Invariant|Dynamic_Predicate|Static_Predicate]
13000 => <Boolean-expression>;
13003 The @code{Assert} pragma causes @code{Boolean-expression} to be tested.
13004 If the result is @code{True}, the pragma has no effect (other than
13005 possible side effects from evaluating the expression). If the result is
13006 @code{False}, the exception @code{Assert_Failure} declared in the package
13007 @code{System.Assertions} is raised (passing @code{static-string-expression}, if
13008 present, as the message associated with the exception). If no string
13009 expression is given, the default is a string containing the file name and
13010 line number of the pragma.
13012 The @code{Debug} pragma causes @code{procedure} to be called. Note that
13013 @code{pragma Debug} may appear within a declaration sequence, allowing
13014 debugging procedures to be called between declarations.
13016 For the aspect specification, the @code{Boolean-expression} is evaluated.
13017 If the result is @code{True}, the aspect has no effect. If the result
13018 is @code{False}, the exception @code{Assert_Failure} is raised.
13021 @node Validity Checking,Style Checking,Debugging and Assertion Control,Compiler Switches
13022 @anchor{gnat_ugn/building_executable_programs_with_gnat validity-checking}@anchor{f6}@anchor{gnat_ugn/building_executable_programs_with_gnat id17}@anchor{102}
13023 @subsection Validity Checking
13026 @geindex Validity Checking
13028 The Ada Reference Manual defines the concept of invalid values (see
13029 RM 13.9.1). The primary source of invalid values is uninitialized
13030 variables. A scalar variable that is left uninitialized may contain
13031 an invalid value; the concept of invalid does not apply to access or
13034 It is an error to read an invalid value, but the RM does not require
13035 run-time checks to detect such errors, except for some minimal
13036 checking to prevent erroneous execution (i.e. unpredictable
13037 behavior). This corresponds to the @code{-gnatVd} switch below,
13038 which is the default. For example, by default, if the expression of a
13039 case statement is invalid, it will raise Constraint_Error rather than
13040 causing a wild jump, and if an array index on the left-hand side of an
13041 assignment is invalid, it will raise Constraint_Error rather than
13042 overwriting an arbitrary memory location.
13044 The @code{-gnatVa} may be used to enable additional validity checks,
13045 which are not required by the RM. These checks are often very
13046 expensive (which is why the RM does not require them). These checks
13047 are useful in tracking down uninitialized variables, but they are
13048 not usually recommended for production builds, and in particular
13049 we do not recommend using these extra validity checking options in
13050 combination with optimization, since this can confuse the optimizer.
13051 If performance is a consideration, leading to the need to optimize,
13052 then the validity checking options should not be used.
13054 The other @code{-gnatV@emph{x}} switches below allow finer-grained
13055 control; you can enable whichever validity checks you desire. However,
13056 for most debugging purposes, @code{-gnatVa} is sufficient, and the
13057 default @code{-gnatVd} (i.e. standard Ada behavior) is usually
13058 sufficient for non-debugging use.
13060 The @code{-gnatB} switch tells the compiler to assume that all
13061 values are valid (that is, within their declared subtype range)
13062 except in the context of a use of the Valid attribute. This means
13063 the compiler can generate more efficient code, since the range
13064 of values is better known at compile time. However, an uninitialized
13065 variable can cause wild jumps and memory corruption in this mode.
13067 The @code{-gnatV@emph{x}} switch allows control over the validity
13068 checking mode as described below.
13069 The @code{x} argument is a string of letters that
13070 indicate validity checks that are performed or not performed in addition
13071 to the default checks required by Ada as described above.
13073 @geindex -gnatVa (gcc)
13078 @item @code{-gnatVa}
13080 @emph{All validity checks.}
13082 All validity checks are turned on.
13083 That is, @code{-gnatVa} is
13084 equivalent to @code{gnatVcdfimorst}.
13087 @geindex -gnatVc (gcc)
13092 @item @code{-gnatVc}
13094 @emph{Validity checks for copies.}
13096 The right hand side of assignments, and the initializing values of
13097 object declarations are validity checked.
13100 @geindex -gnatVd (gcc)
13105 @item @code{-gnatVd}
13107 @emph{Default (RM) validity checks.}
13109 Some validity checks are done by default following normal Ada semantics
13110 (RM 13.9.1 (9-11)).
13111 A check is done in case statements that the expression is within the range
13112 of the subtype. If it is not, Constraint_Error is raised.
13113 For assignments to array components, a check is done that the expression used
13114 as index is within the range. If it is not, Constraint_Error is raised.
13115 Both these validity checks may be turned off using switch @code{-gnatVD}.
13116 They are turned on by default. If @code{-gnatVD} is specified, a subsequent
13117 switch @code{-gnatVd} will leave the checks turned on.
13118 Switch @code{-gnatVD} should be used only if you are sure that all such
13119 expressions have valid values. If you use this switch and invalid values
13120 are present, then the program is erroneous, and wild jumps or memory
13121 overwriting may occur.
13124 @geindex -gnatVe (gcc)
13129 @item @code{-gnatVe}
13131 @emph{Validity checks for elementary components.}
13133 In the absence of this switch, assignments to record or array components are
13134 not validity checked, even if validity checks for assignments generally
13135 (@code{-gnatVc}) are turned on. In Ada, assignment of composite values do not
13136 require valid data, but assignment of individual components does. So for
13137 example, there is a difference between copying the elements of an array with a
13138 slice assignment, compared to assigning element by element in a loop. This
13139 switch allows you to turn off validity checking for components, even when they
13140 are assigned component by component.
13143 @geindex -gnatVf (gcc)
13148 @item @code{-gnatVf}
13150 @emph{Validity checks for floating-point values.}
13152 In the absence of this switch, validity checking occurs only for discrete
13153 values. If @code{-gnatVf} is specified, then validity checking also applies
13154 for floating-point values, and NaNs and infinities are considered invalid,
13155 as well as out of range values for constrained types. Note that this means
13156 that standard IEEE infinity mode is not allowed. The exact contexts
13157 in which floating-point values are checked depends on the setting of other
13158 options. For example, @code{-gnatVif} or @code{-gnatVfi}
13159 (the order does not matter) specifies that floating-point parameters of mode
13160 @code{in} should be validity checked.
13163 @geindex -gnatVi (gcc)
13168 @item @code{-gnatVi}
13170 @emph{Validity checks for `@w{`}in`@w{`} mode parameters.}
13172 Arguments for parameters of mode @code{in} are validity checked in function
13173 and procedure calls at the point of call.
13176 @geindex -gnatVm (gcc)
13181 @item @code{-gnatVm}
13183 @emph{Validity checks for `@w{`}in out`@w{`} mode parameters.}
13185 Arguments for parameters of mode @code{in out} are validity checked in
13186 procedure calls at the point of call. The @code{'m'} here stands for
13187 modify, since this concerns parameters that can be modified by the call.
13188 Note that there is no specific option to test @code{out} parameters,
13189 but any reference within the subprogram will be tested in the usual
13190 manner, and if an invalid value is copied back, any reference to it
13191 will be subject to validity checking.
13194 @geindex -gnatVn (gcc)
13199 @item @code{-gnatVn}
13201 @emph{No validity checks.}
13203 This switch turns off all validity checking, including the default checking
13204 for case statements and left hand side subscripts. Note that the use of
13205 the switch @code{-gnatp} suppresses all run-time checks, including
13206 validity checks, and thus implies @code{-gnatVn}. When this switch
13207 is used, it cancels any other @code{-gnatV} previously issued.
13210 @geindex -gnatVo (gcc)
13215 @item @code{-gnatVo}
13217 @emph{Validity checks for operator and attribute operands.}
13219 Arguments for predefined operators and attributes are validity checked.
13220 This includes all operators in package @code{Standard},
13221 the shift operators defined as intrinsic in package @code{Interfaces}
13222 and operands for attributes such as @code{Pos}. Checks are also made
13223 on individual component values for composite comparisons, and on the
13224 expressions in type conversions and qualified expressions. Checks are
13225 also made on explicit ranges using @code{..} (e.g., slices, loops etc).
13228 @geindex -gnatVp (gcc)
13233 @item @code{-gnatVp}
13235 @emph{Validity checks for parameters.}
13237 This controls the treatment of parameters within a subprogram (as opposed
13238 to @code{-gnatVi} and @code{-gnatVm} which control validity testing
13239 of parameters on a call. If either of these call options is used, then
13240 normally an assumption is made within a subprogram that the input arguments
13241 have been validity checking at the point of call, and do not need checking
13242 again within a subprogram). If @code{-gnatVp} is set, then this assumption
13243 is not made, and parameters are not assumed to be valid, so their validity
13244 will be checked (or rechecked) within the subprogram.
13247 @geindex -gnatVr (gcc)
13252 @item @code{-gnatVr}
13254 @emph{Validity checks for function returns.}
13256 The expression in @code{return} statements in functions is validity
13260 @geindex -gnatVs (gcc)
13265 @item @code{-gnatVs}
13267 @emph{Validity checks for subscripts.}
13269 All subscripts expressions are checked for validity, whether they appear
13270 on the right side or left side (in default mode only left side subscripts
13271 are validity checked).
13274 @geindex -gnatVt (gcc)
13279 @item @code{-gnatVt}
13281 @emph{Validity checks for tests.}
13283 Expressions used as conditions in @code{if}, @code{while} or @code{exit}
13284 statements are checked, as well as guard expressions in entry calls.
13287 The @code{-gnatV} switch may be followed by a string of letters
13288 to turn on a series of validity checking options.
13289 For example, @code{-gnatVcr}
13290 specifies that in addition to the default validity checking, copies and
13291 function return expressions are to be validity checked.
13292 In order to make it easier to specify the desired combination of effects,
13293 the upper case letters @code{CDFIMORST} may
13294 be used to turn off the corresponding lower case option.
13295 Thus @code{-gnatVaM} turns on all validity checking options except for
13296 checking of @code{in out} parameters.
13298 The specification of additional validity checking generates extra code (and
13299 in the case of @code{-gnatVa} the code expansion can be substantial).
13300 However, these additional checks can be very useful in detecting
13301 uninitialized variables, incorrect use of unchecked conversion, and other
13302 errors leading to invalid values. The use of pragma @code{Initialize_Scalars}
13303 is useful in conjunction with the extra validity checking, since this
13304 ensures that wherever possible uninitialized variables have invalid values.
13306 See also the pragma @code{Validity_Checks} which allows modification of
13307 the validity checking mode at the program source level, and also allows for
13308 temporary disabling of validity checks.
13310 @node Style Checking,Run-Time Checks,Validity Checking,Compiler Switches
13311 @anchor{gnat_ugn/building_executable_programs_with_gnat id18}@anchor{103}@anchor{gnat_ugn/building_executable_programs_with_gnat style-checking}@anchor{fb}
13312 @subsection Style Checking
13315 @geindex Style checking
13317 @geindex -gnaty (gcc)
13319 The @code{-gnatyx} switch causes the compiler to
13320 enforce specified style rules. A limited set of style rules has been used
13321 in writing the GNAT sources themselves. This switch allows user programs
13322 to activate all or some of these checks. If the source program fails a
13323 specified style check, an appropriate message is given, preceded by
13324 the character sequence '(style)'. This message does not prevent
13325 successful compilation (unless the @code{-gnatwe} switch is used).
13327 Note that this is by no means intended to be a general facility for
13328 checking arbitrary coding standards. It is simply an embedding of the
13329 style rules we have chosen for the GNAT sources. If you are starting
13330 a project which does not have established style standards, you may
13331 find it useful to adopt the entire set of GNAT coding standards, or
13332 some subset of them.
13335 The string @code{x} is a sequence of letters or digits
13336 indicating the particular style
13337 checks to be performed. The following checks are defined:
13339 @geindex -gnaty[0-9] (gcc)
13344 @item @code{-gnaty0}
13346 @emph{Specify indentation level.}
13348 If a digit from 1-9 appears
13349 in the string after @code{-gnaty}
13350 then proper indentation is checked, with the digit indicating the
13351 indentation level required. A value of zero turns off this style check.
13352 The general style of required indentation is as specified by
13353 the examples in the Ada Reference Manual. Full line comments must be
13354 aligned with the @code{--} starting on a column that is a multiple of
13355 the alignment level, or they may be aligned the same way as the following
13356 non-blank line (this is useful when full line comments appear in the middle
13357 of a statement, or they may be aligned with the source line on the previous
13361 @geindex -gnatya (gcc)
13366 @item @code{-gnatya}
13368 @emph{Check attribute casing.}
13370 Attribute names, including the case of keywords such as @code{digits}
13371 used as attributes names, must be written in mixed case, that is, the
13372 initial letter and any letter following an underscore must be uppercase.
13373 All other letters must be lowercase.
13376 @geindex -gnatyA (gcc)
13381 @item @code{-gnatyA}
13383 @emph{Use of array index numbers in array attributes.}
13385 When using the array attributes First, Last, Range,
13386 or Length, the index number must be omitted for one-dimensional arrays
13387 and is required for multi-dimensional arrays.
13390 @geindex -gnatyb (gcc)
13395 @item @code{-gnatyb}
13397 @emph{Blanks not allowed at statement end.}
13399 Trailing blanks are not allowed at the end of statements. The purpose of this
13400 rule, together with h (no horizontal tabs), is to enforce a canonical format
13401 for the use of blanks to separate source tokens.
13404 @geindex -gnatyB (gcc)
13409 @item @code{-gnatyB}
13411 @emph{Check Boolean operators.}
13413 The use of AND/OR operators is not permitted except in the cases of modular
13414 operands, array operands, and simple stand-alone boolean variables or
13415 boolean constants. In all other cases @code{and then}/@cite{or else} are
13419 @geindex -gnatyc (gcc)
13424 @item @code{-gnatyc}
13426 @emph{Check comments, double space.}
13428 Comments must meet the following set of rules:
13434 The @code{--} that starts the column must either start in column one,
13435 or else at least one blank must precede this sequence.
13438 Comments that follow other tokens on a line must have at least one blank
13439 following the @code{--} at the start of the comment.
13442 Full line comments must have at least two blanks following the
13443 @code{--} that starts the comment, with the following exceptions.
13446 A line consisting only of the @code{--} characters, possibly preceded
13447 by blanks is permitted.
13450 A comment starting with @code{--x} where @code{x} is a special character
13452 This allows proper processing of the output from specialized tools
13453 such as @code{gnatprep} (where @code{--!} is used) and in earlier versions of the SPARK
13455 language (where @code{--#} is used). For the purposes of this rule, a
13456 special character is defined as being in one of the ASCII ranges
13457 @code{16#21#...16#2F#} or @code{16#3A#...16#3F#}.
13458 Note that this usage is not permitted
13459 in GNAT implementation units (i.e., when @code{-gnatg} is used).
13462 A line consisting entirely of minus signs, possibly preceded by blanks, is
13463 permitted. This allows the construction of box comments where lines of minus
13464 signs are used to form the top and bottom of the box.
13467 A comment that starts and ends with @code{--} is permitted as long as at
13468 least one blank follows the initial @code{--}. Together with the preceding
13469 rule, this allows the construction of box comments, as shown in the following
13473 ---------------------------
13474 -- This is a box comment --
13475 -- with two text lines. --
13476 ---------------------------
13481 @geindex -gnatyC (gcc)
13486 @item @code{-gnatyC}
13488 @emph{Check comments, single space.}
13490 This is identical to @code{c} except that only one space
13491 is required following the @code{--} of a comment instead of two.
13494 @geindex -gnatyd (gcc)
13499 @item @code{-gnatyd}
13501 @emph{Check no DOS line terminators present.}
13503 All lines must be terminated by a single ASCII.LF
13504 character (in particular the DOS line terminator sequence CR/LF is not
13508 @geindex -gnatye (gcc)
13513 @item @code{-gnatye}
13515 @emph{Check end/exit labels.}
13517 Optional labels on @code{end} statements ending subprograms and on
13518 @code{exit} statements exiting named loops, are required to be present.
13521 @geindex -gnatyf (gcc)
13526 @item @code{-gnatyf}
13528 @emph{No form feeds or vertical tabs.}
13530 Neither form feeds nor vertical tab characters are permitted
13531 in the source text.
13534 @geindex -gnatyg (gcc)
13539 @item @code{-gnatyg}
13541 @emph{GNAT style mode.}
13543 The set of style check switches is set to match that used by the GNAT sources.
13544 This may be useful when developing code that is eventually intended to be
13545 incorporated into GNAT. Currently this is equivalent to @code{-gnatwydISux})
13546 but additional style switches may be added to this set in the future without
13550 @geindex -gnatyh (gcc)
13555 @item @code{-gnatyh}
13557 @emph{No horizontal tabs.}
13559 Horizontal tab characters are not permitted in the source text.
13560 Together with the b (no blanks at end of line) check, this
13561 enforces a canonical form for the use of blanks to separate
13565 @geindex -gnatyi (gcc)
13570 @item @code{-gnatyi}
13572 @emph{Check if-then layout.}
13574 The keyword @code{then} must appear either on the same
13575 line as corresponding @code{if}, or on a line on its own, lined
13576 up under the @code{if}.
13579 @geindex -gnatyI (gcc)
13584 @item @code{-gnatyI}
13586 @emph{check mode IN keywords.}
13588 Mode @code{in} (the default mode) is not
13589 allowed to be given explicitly. @code{in out} is fine,
13590 but not @code{in} on its own.
13593 @geindex -gnatyk (gcc)
13598 @item @code{-gnatyk}
13600 @emph{Check keyword casing.}
13602 All keywords must be in lower case (with the exception of keywords
13603 such as @code{digits} used as attribute names to which this check
13607 @geindex -gnatyl (gcc)
13612 @item @code{-gnatyl}
13614 @emph{Check layout.}
13616 Layout of statement and declaration constructs must follow the
13617 recommendations in the Ada Reference Manual, as indicated by the
13618 form of the syntax rules. For example an @code{else} keyword must
13619 be lined up with the corresponding @code{if} keyword.
13621 There are two respects in which the style rule enforced by this check
13622 option are more liberal than those in the Ada Reference Manual. First
13623 in the case of record declarations, it is permissible to put the
13624 @code{record} keyword on the same line as the @code{type} keyword, and
13625 then the @code{end} in @code{end record} must line up under @code{type}.
13626 This is also permitted when the type declaration is split on two lines.
13627 For example, any of the following three layouts is acceptable:
13648 Second, in the case of a block statement, a permitted alternative
13649 is to put the block label on the same line as the @code{declare} or
13650 @code{begin} keyword, and then line the @code{end} keyword up under
13651 the block label. For example both the following are permitted:
13668 The same alternative format is allowed for loops. For example, both of
13669 the following are permitted:
13672 Clear : while J < 10 loop
13683 @geindex -gnatyLnnn (gcc)
13688 @item @code{-gnatyL}
13690 @emph{Set maximum nesting level.}
13692 The maximum level of nesting of constructs (including subprograms, loops,
13693 blocks, packages, and conditionals) may not exceed the given value
13694 @emph{nnn}. A value of zero disconnects this style check.
13697 @geindex -gnatym (gcc)
13702 @item @code{-gnatym}
13704 @emph{Check maximum line length.}
13706 The length of source lines must not exceed 79 characters, including
13707 any trailing blanks. The value of 79 allows convenient display on an
13708 80 character wide device or window, allowing for possible special
13709 treatment of 80 character lines. Note that this count is of
13710 characters in the source text. This means that a tab character counts
13711 as one character in this count and a wide character sequence counts as
13712 a single character (however many bytes are needed in the encoding).
13715 @geindex -gnatyMnnn (gcc)
13720 @item @code{-gnatyM}
13722 @emph{Set maximum line length.}
13724 The length of lines must not exceed the
13725 given value @emph{nnn}. The maximum value that can be specified is 32767.
13726 If neither style option for setting the line length is used, then the
13727 default is 255. This also controls the maximum length of lexical elements,
13728 where the only restriction is that they must fit on a single line.
13731 @geindex -gnatyn (gcc)
13736 @item @code{-gnatyn}
13738 @emph{Check casing of entities in Standard.}
13740 Any identifier from Standard must be cased
13741 to match the presentation in the Ada Reference Manual (for example,
13742 @code{Integer} and @code{ASCII.NUL}).
13745 @geindex -gnatyN (gcc)
13750 @item @code{-gnatyN}
13752 @emph{Turn off all style checks.}
13754 All style check options are turned off.
13757 @geindex -gnatyo (gcc)
13762 @item @code{-gnatyo}
13764 @emph{Check order of subprogram bodies.}
13766 All subprogram bodies in a given scope
13767 (e.g., a package body) must be in alphabetical order. The ordering
13768 rule uses normal Ada rules for comparing strings, ignoring casing
13769 of letters, except that if there is a trailing numeric suffix, then
13770 the value of this suffix is used in the ordering (e.g., Junk2 comes
13774 @geindex -gnatyO (gcc)
13779 @item @code{-gnatyO}
13781 @emph{Check that overriding subprograms are explicitly marked as such.}
13783 This applies to all subprograms of a derived type that override a primitive
13784 operation of the type, for both tagged and untagged types. In particular,
13785 the declaration of a primitive operation of a type extension that overrides
13786 an inherited operation must carry an overriding indicator. Another case is
13787 the declaration of a function that overrides a predefined operator (such
13788 as an equality operator).
13791 @geindex -gnatyp (gcc)
13796 @item @code{-gnatyp}
13798 @emph{Check pragma casing.}
13800 Pragma names must be written in mixed case, that is, the
13801 initial letter and any letter following an underscore must be uppercase.
13802 All other letters must be lowercase. An exception is that SPARK_Mode is
13803 allowed as an alternative for Spark_Mode.
13806 @geindex -gnatyr (gcc)
13811 @item @code{-gnatyr}
13813 @emph{Check references.}
13815 All identifier references must be cased in the same way as the
13816 corresponding declaration. No specific casing style is imposed on
13817 identifiers. The only requirement is for consistency of references
13821 @geindex -gnatys (gcc)
13826 @item @code{-gnatys}
13828 @emph{Check separate specs.}
13830 Separate declarations ('specs') are required for subprograms (a
13831 body is not allowed to serve as its own declaration). The only
13832 exception is that parameterless library level procedures are
13833 not required to have a separate declaration. This exception covers
13834 the most frequent form of main program procedures.
13837 @geindex -gnatyS (gcc)
13842 @item @code{-gnatyS}
13844 @emph{Check no statements after then/else.}
13846 No statements are allowed
13847 on the same line as a @code{then} or @code{else} keyword following the
13848 keyword in an @code{if} statement. @code{or else} and @code{and then} are not
13849 affected, and a special exception allows a pragma to appear after @code{else}.
13852 @geindex -gnatyt (gcc)
13857 @item @code{-gnatyt}
13859 @emph{Check token spacing.}
13861 The following token spacing rules are enforced:
13867 The keywords @code{abs} and @code{not} must be followed by a space.
13870 The token @code{=>} must be surrounded by spaces.
13873 The token @code{<>} must be preceded by a space or a left parenthesis.
13876 Binary operators other than @code{**} must be surrounded by spaces.
13877 There is no restriction on the layout of the @code{**} binary operator.
13880 Colon must be surrounded by spaces.
13883 Colon-equal (assignment, initialization) must be surrounded by spaces.
13886 Comma must be the first non-blank character on the line, or be
13887 immediately preceded by a non-blank character, and must be followed
13891 If the token preceding a left parenthesis ends with a letter or digit, then
13892 a space must separate the two tokens.
13895 If the token following a right parenthesis starts with a letter or digit, then
13896 a space must separate the two tokens.
13899 A right parenthesis must either be the first non-blank character on
13900 a line, or it must be preceded by a non-blank character.
13903 A semicolon must not be preceded by a space, and must not be followed by
13904 a non-blank character.
13907 A unary plus or minus may not be followed by a space.
13910 A vertical bar must be surrounded by spaces.
13913 Exactly one blank (and no other white space) must appear between
13914 a @code{not} token and a following @code{in} token.
13917 @geindex -gnatyu (gcc)
13922 @item @code{-gnatyu}
13924 @emph{Check unnecessary blank lines.}
13926 Unnecessary blank lines are not allowed. A blank line is considered
13927 unnecessary if it appears at the end of the file, or if more than
13928 one blank line occurs in sequence.
13931 @geindex -gnatyx (gcc)
13936 @item @code{-gnatyx}
13938 @emph{Check extra parentheses.}
13940 Unnecessary extra level of parentheses (C-style) are not allowed
13941 around conditions in @code{if} statements, @code{while} statements and
13942 @code{exit} statements.
13945 @geindex -gnatyy (gcc)
13950 @item @code{-gnatyy}
13952 @emph{Set all standard style check options.}
13954 This is equivalent to @code{gnaty3aAbcefhiklmnprst}, that is all checking
13955 options enabled with the exception of @code{-gnatyB}, @code{-gnatyd},
13956 @code{-gnatyI}, @code{-gnatyLnnn}, @code{-gnatyo}, @code{-gnatyO},
13957 @code{-gnatyS}, @code{-gnatyu}, and @code{-gnatyx}.
13960 @geindex -gnaty- (gcc)
13965 @item @code{-gnaty-}
13967 @emph{Remove style check options.}
13969 This causes any subsequent options in the string to act as canceling the
13970 corresponding style check option. To cancel maximum nesting level control,
13971 use the @code{L} parameter without any integer value after that, because any
13972 digit following @emph{-} in the parameter string of the @code{-gnaty}
13973 option will be treated as canceling the indentation check. The same is true
13974 for the @code{M} parameter. @code{y} and @code{N} parameters are not
13975 allowed after @emph{-}.
13978 @geindex -gnaty+ (gcc)
13983 @item @code{-gnaty+}
13985 @emph{Enable style check options.}
13987 This causes any subsequent options in the string to enable the corresponding
13988 style check option. That is, it cancels the effect of a previous -,
13992 @c end of switch description (leave this comment to ease automatic parsing for
13996 In the above rules, appearing in column one is always permitted, that is,
13997 counts as meeting either a requirement for a required preceding space,
13998 or as meeting a requirement for no preceding space.
14000 Appearing at the end of a line is also always permitted, that is, counts
14001 as meeting either a requirement for a following space, or as meeting
14002 a requirement for no following space.
14004 If any of these style rules is violated, a message is generated giving
14005 details on the violation. The initial characters of such messages are
14006 always '@cite{(style)}'. Note that these messages are treated as warning
14007 messages, so they normally do not prevent the generation of an object
14008 file. The @code{-gnatwe} switch can be used to treat warning messages,
14009 including style messages, as fatal errors.
14011 The switch @code{-gnaty} on its own (that is not
14012 followed by any letters or digits) is equivalent
14013 to the use of @code{-gnatyy} as described above, that is all
14014 built-in standard style check options are enabled.
14016 The switch @code{-gnatyN} clears any previously set style checks.
14018 @node Run-Time Checks,Using gcc for Syntax Checking,Style Checking,Compiler Switches
14019 @anchor{gnat_ugn/building_executable_programs_with_gnat run-time-checks}@anchor{f9}@anchor{gnat_ugn/building_executable_programs_with_gnat id19}@anchor{104}
14020 @subsection Run-Time Checks
14023 @geindex Division by zero
14025 @geindex Access before elaboration
14028 @geindex division by zero
14031 @geindex access before elaboration
14034 @geindex stack overflow checking
14036 By default, the following checks are suppressed: stack overflow
14037 checks, and checks for access before elaboration on subprogram
14038 calls. All other checks, including overflow checks, range checks and
14039 array bounds checks, are turned on by default. The following @code{gcc}
14040 switches refine this default behavior.
14042 @geindex -gnatp (gcc)
14047 @item @code{-gnatp}
14049 @geindex Suppressing checks
14052 @geindex suppressing
14054 This switch causes the unit to be compiled
14055 as though @code{pragma Suppress (All_checks)}
14056 had been present in the source. Validity checks are also eliminated (in
14057 other words @code{-gnatp} also implies @code{-gnatVn}.
14058 Use this switch to improve the performance
14059 of the code at the expense of safety in the presence of invalid data or
14062 Note that when checks are suppressed, the compiler is allowed, but not
14063 required, to omit the checking code. If the run-time cost of the
14064 checking code is zero or near-zero, the compiler will generate it even
14065 if checks are suppressed. In particular, if the compiler can prove
14066 that a certain check will necessarily fail, it will generate code to
14067 do an unconditional 'raise', even if checks are suppressed. The
14068 compiler warns in this case. Another case in which checks may not be
14069 eliminated is when they are embedded in certain run-time routines such
14070 as math library routines.
14072 Of course, run-time checks are omitted whenever the compiler can prove
14073 that they will not fail, whether or not checks are suppressed.
14075 Note that if you suppress a check that would have failed, program
14076 execution is erroneous, which means the behavior is totally
14077 unpredictable. The program might crash, or print wrong answers, or
14078 do anything else. It might even do exactly what you wanted it to do
14079 (and then it might start failing mysteriously next week or next
14080 year). The compiler will generate code based on the assumption that
14081 the condition being checked is true, which can result in erroneous
14082 execution if that assumption is wrong.
14084 The checks subject to suppression include all the checks defined by the Ada
14085 standard, the additional implementation defined checks @code{Alignment_Check},
14086 @code{Duplicated_Tag_Check}, @code{Predicate_Check}, @code{Container_Checks}, @code{Tampering_Check},
14087 and @code{Validity_Check}, as well as any checks introduced using @code{pragma Check_Name}.
14088 Note that @code{Atomic_Synchronization} is not automatically suppressed by use of this option.
14090 If the code depends on certain checks being active, you can use
14091 pragma @code{Unsuppress} either as a configuration pragma or as
14092 a local pragma to make sure that a specified check is performed
14093 even if @code{gnatp} is specified.
14095 The @code{-gnatp} switch has no effect if a subsequent
14096 @code{-gnat-p} switch appears.
14099 @geindex -gnat-p (gcc)
14101 @geindex Suppressing checks
14104 @geindex suppressing
14111 @item @code{-gnat-p}
14113 This switch cancels the effect of a previous @code{gnatp} switch.
14116 @geindex -gnato?? (gcc)
14118 @geindex Overflow checks
14120 @geindex Overflow mode
14128 @item @code{-gnato??}
14130 This switch controls the mode used for computing intermediate
14131 arithmetic integer operations, and also enables overflow checking.
14132 For a full description of overflow mode and checking control, see
14133 the 'Overflow Check Handling in GNAT' appendix in this
14136 Overflow checks are always enabled by this switch. The argument
14137 controls the mode, using the codes
14142 @item @emph{1 = STRICT}
14144 In STRICT mode, intermediate operations are always done using the
14145 base type, and overflow checking ensures that the result is within
14146 the base type range.
14148 @item @emph{2 = MINIMIZED}
14150 In MINIMIZED mode, overflows in intermediate operations are avoided
14151 where possible by using a larger integer type for the computation
14152 (typically @code{Long_Long_Integer}). Overflow checking ensures that
14153 the result fits in this larger integer type.
14155 @item @emph{3 = ELIMINATED}
14157 In ELIMINATED mode, overflows in intermediate operations are avoided
14158 by using multi-precision arithmetic. In this case, overflow checking
14159 has no effect on intermediate operations (since overflow is impossible).
14162 If two digits are present after @code{-gnato} then the first digit
14163 sets the mode for expressions outside assertions, and the second digit
14164 sets the mode for expressions within assertions. Here assertions is used
14165 in the technical sense (which includes for example precondition and
14166 postcondition expressions).
14168 If one digit is present, the corresponding mode is applicable to both
14169 expressions within and outside assertion expressions.
14171 If no digits are present, the default is to enable overflow checks
14172 and set STRICT mode for both kinds of expressions. This is compatible
14173 with the use of @code{-gnato} in previous versions of GNAT.
14175 @geindex Machine_Overflows
14177 Note that the @code{-gnato??} switch does not affect the code generated
14178 for any floating-point operations; it applies only to integer semantics.
14179 For floating-point, GNAT has the @code{Machine_Overflows}
14180 attribute set to @code{False} and the normal mode of operation is to
14181 generate IEEE NaN and infinite values on overflow or invalid operations
14182 (such as dividing 0.0 by 0.0).
14184 The reason that we distinguish overflow checking from other kinds of
14185 range constraint checking is that a failure of an overflow check, unlike
14186 for example the failure of a range check, can result in an incorrect
14187 value, but cannot cause random memory destruction (like an out of range
14188 subscript), or a wild jump (from an out of range case value). Overflow
14189 checking is also quite expensive in time and space, since in general it
14190 requires the use of double length arithmetic.
14192 Note again that the default is @code{-gnato11} (equivalent to @code{-gnato1}),
14193 so overflow checking is performed in STRICT mode by default.
14196 @geindex -gnatE (gcc)
14198 @geindex Elaboration checks
14201 @geindex elaboration
14206 @item @code{-gnatE}
14208 Enables dynamic checks for access-before-elaboration
14209 on subprogram calls and generic instantiations.
14210 Note that @code{-gnatE} is not necessary for safety, because in the
14211 default mode, GNAT ensures statically that the checks would not fail.
14212 For full details of the effect and use of this switch,
14213 @ref{1c,,Compiling with gcc}.
14216 @geindex -fstack-check (gcc)
14218 @geindex Stack Overflow Checking
14221 @geindex stack overflow checking
14226 @item @code{-fstack-check}
14228 Activates stack overflow checking. For full details of the effect and use of
14229 this switch see @ref{f4,,Stack Overflow Checking}.
14232 @geindex Unsuppress
14234 The setting of these switches only controls the default setting of the
14235 checks. You may modify them using either @code{Suppress} (to remove
14236 checks) or @code{Unsuppress} (to add back suppressed checks) pragmas in
14237 the program source.
14239 @node Using gcc for Syntax Checking,Using gcc for Semantic Checking,Run-Time Checks,Compiler Switches
14240 @anchor{gnat_ugn/building_executable_programs_with_gnat id20}@anchor{105}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-syntax-checking}@anchor{106}
14241 @subsection Using @code{gcc} for Syntax Checking
14244 @geindex -gnats (gcc)
14249 @item @code{-gnats}
14251 The @code{s} stands for 'syntax'.
14253 Run GNAT in syntax checking only mode. For
14254 example, the command
14257 $ gcc -c -gnats x.adb
14260 compiles file @code{x.adb} in syntax-check-only mode. You can check a
14261 series of files in a single command
14262 , and can use wild cards to specify such a group of files.
14263 Note that you must specify the @code{-c} (compile
14264 only) flag in addition to the @code{-gnats} flag.
14266 You may use other switches in conjunction with @code{-gnats}. In
14267 particular, @code{-gnatl} and @code{-gnatv} are useful to control the
14268 format of any generated error messages.
14270 When the source file is empty or contains only empty lines and/or comments,
14271 the output is a warning:
14274 $ gcc -c -gnats -x ada toto.txt
14275 toto.txt:1:01: warning: empty file, contains no compilation units
14279 Otherwise, the output is simply the error messages, if any. No object file or
14280 ALI file is generated by a syntax-only compilation. Also, no units other
14281 than the one specified are accessed. For example, if a unit @code{X}
14282 @emph{with}s a unit @code{Y}, compiling unit @code{X} in syntax
14283 check only mode does not access the source file containing unit
14286 @geindex Multiple units
14287 @geindex syntax checking
14289 Normally, GNAT allows only a single unit in a source file. However, this
14290 restriction does not apply in syntax-check-only mode, and it is possible
14291 to check a file containing multiple compilation units concatenated
14292 together. This is primarily used by the @code{gnatchop} utility
14293 (@ref{36,,Renaming Files with gnatchop}).
14296 @node Using gcc for Semantic Checking,Compiling Different Versions of Ada,Using gcc for Syntax Checking,Compiler Switches
14297 @anchor{gnat_ugn/building_executable_programs_with_gnat id21}@anchor{107}@anchor{gnat_ugn/building_executable_programs_with_gnat using-gcc-for-semantic-checking}@anchor{108}
14298 @subsection Using @code{gcc} for Semantic Checking
14301 @geindex -gnatc (gcc)
14306 @item @code{-gnatc}
14308 The @code{c} stands for 'check'.
14309 Causes the compiler to operate in semantic check mode,
14310 with full checking for all illegalities specified in the
14311 Ada Reference Manual, but without generation of any object code
14312 (no object file is generated).
14314 Because dependent files must be accessed, you must follow the GNAT
14315 semantic restrictions on file structuring to operate in this mode:
14321 The needed source files must be accessible
14322 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}).
14325 Each file must contain only one compilation unit.
14328 The file name and unit name must match (@ref{52,,File Naming Rules}).
14331 The output consists of error messages as appropriate. No object file is
14332 generated. An @code{ALI} file is generated for use in the context of
14333 cross-reference tools, but this file is marked as not being suitable
14334 for binding (since no object file is generated).
14335 The checking corresponds exactly to the notion of
14336 legality in the Ada Reference Manual.
14338 Any unit can be compiled in semantics-checking-only mode, including
14339 units that would not normally be compiled (subunits,
14340 and specifications where a separate body is present).
14343 @node Compiling Different Versions of Ada,Character Set Control,Using gcc for Semantic Checking,Compiler Switches
14344 @anchor{gnat_ugn/building_executable_programs_with_gnat compiling-different-versions-of-ada}@anchor{6}@anchor{gnat_ugn/building_executable_programs_with_gnat id22}@anchor{109}
14345 @subsection Compiling Different Versions of Ada
14348 The switches described in this section allow you to explicitly specify
14349 the version of the Ada language that your programs are written in.
14350 The default mode is Ada 2012,
14351 but you can also specify Ada 95, Ada 2005 mode, or
14352 indicate Ada 83 compatibility mode.
14354 @geindex Compatibility with Ada 83
14356 @geindex -gnat83 (gcc)
14359 @geindex Ada 83 tests
14361 @geindex Ada 83 mode
14366 @item @code{-gnat83} (Ada 83 Compatibility Mode)
14368 Although GNAT is primarily an Ada 95 / Ada 2005 compiler, this switch
14369 specifies that the program is to be compiled in Ada 83 mode. With
14370 @code{-gnat83}, GNAT rejects most post-Ada 83 extensions and applies Ada 83
14371 semantics where this can be done easily.
14372 It is not possible to guarantee this switch does a perfect
14373 job; some subtle tests, such as are
14374 found in earlier ACVC tests (and that have been removed from the ACATS suite
14375 for Ada 95), might not compile correctly.
14376 Nevertheless, this switch may be useful in some circumstances, for example
14377 where, due to contractual reasons, existing code needs to be maintained
14378 using only Ada 83 features.
14380 With few exceptions (most notably the need to use @code{<>} on
14382 @geindex Generic formal parameters
14383 generic formal parameters,
14384 the use of the new Ada 95 / Ada 2005
14385 reserved words, and the use of packages
14386 with optional bodies), it is not necessary to specify the
14387 @code{-gnat83} switch when compiling Ada 83 programs, because, with rare
14388 exceptions, Ada 95 and Ada 2005 are upwardly compatible with Ada 83. Thus
14389 a correct Ada 83 program is usually also a correct program
14390 in these later versions of the language standard. For further information
14391 please refer to the @emph{Compatibility and Porting Guide} chapter in the
14392 @cite{GNAT Reference Manual}.
14395 @geindex -gnat95 (gcc)
14397 @geindex Ada 95 mode
14402 @item @code{-gnat95} (Ada 95 mode)
14404 This switch directs the compiler to implement the Ada 95 version of the
14406 Since Ada 95 is almost completely upwards
14407 compatible with Ada 83, Ada 83 programs may generally be compiled using
14408 this switch (see the description of the @code{-gnat83} switch for further
14409 information about Ada 83 mode).
14410 If an Ada 2005 program is compiled in Ada 95 mode,
14411 uses of the new Ada 2005 features will cause error
14412 messages or warnings.
14414 This switch also can be used to cancel the effect of a previous
14415 @code{-gnat83}, @code{-gnat05/2005}, or @code{-gnat12/2012}
14416 switch earlier in the command line.
14419 @geindex -gnat05 (gcc)
14421 @geindex -gnat2005 (gcc)
14423 @geindex Ada 2005 mode
14428 @item @code{-gnat05} or @code{-gnat2005} (Ada 2005 mode)
14430 This switch directs the compiler to implement the Ada 2005 version of the
14431 language, as documented in the official Ada standards document.
14432 Since Ada 2005 is almost completely upwards
14433 compatible with Ada 95 (and thus also with Ada 83), Ada 83 and Ada 95 programs
14434 may generally be compiled using this switch (see the description of the
14435 @code{-gnat83} and @code{-gnat95} switches for further
14439 @geindex -gnat12 (gcc)
14441 @geindex -gnat2012 (gcc)
14443 @geindex Ada 2012 mode
14448 @item @code{-gnat12} or @code{-gnat2012} (Ada 2012 mode)
14450 This switch directs the compiler to implement the Ada 2012 version of the
14451 language (also the default).
14452 Since Ada 2012 is almost completely upwards
14453 compatible with Ada 2005 (and thus also with Ada 83, and Ada 95),
14454 Ada 83 and Ada 95 programs
14455 may generally be compiled using this switch (see the description of the
14456 @code{-gnat83}, @code{-gnat95}, and @code{-gnat05/2005} switches
14457 for further information).
14460 @geindex -gnatX (gcc)
14462 @geindex Ada language extensions
14464 @geindex GNAT extensions
14469 @item @code{-gnatX} (Enable GNAT Extensions)
14471 This switch directs the compiler to implement the latest version of the
14472 language (currently Ada 2012) and also to enable certain GNAT implementation
14473 extensions that are not part of any Ada standard. For a full list of these
14474 extensions, see the GNAT reference manual.
14477 @node Character Set Control,File Naming Control,Compiling Different Versions of Ada,Compiler Switches
14478 @anchor{gnat_ugn/building_executable_programs_with_gnat id23}@anchor{10a}@anchor{gnat_ugn/building_executable_programs_with_gnat character-set-control}@anchor{48}
14479 @subsection Character Set Control
14482 @geindex -gnati (gcc)
14487 @item @code{-gnati@emph{c}}
14489 Normally GNAT recognizes the Latin-1 character set in source program
14490 identifiers, as described in the Ada Reference Manual.
14492 GNAT to recognize alternate character sets in identifiers. @code{c} is a
14493 single character indicating the character set, as follows:
14496 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14503 ISO 8859-1 (Latin-1) identifiers
14511 ISO 8859-2 (Latin-2) letters allowed in identifiers
14519 ISO 8859-3 (Latin-3) letters allowed in identifiers
14527 ISO 8859-4 (Latin-4) letters allowed in identifiers
14535 ISO 8859-5 (Cyrillic) letters allowed in identifiers
14543 ISO 8859-15 (Latin-9) letters allowed in identifiers
14551 IBM PC letters (code page 437) allowed in identifiers
14559 IBM PC letters (code page 850) allowed in identifiers
14567 Full upper-half codes allowed in identifiers
14575 No upper-half codes allowed in identifiers
14583 Wide-character codes (that is, codes greater than 255)
14584 allowed in identifiers
14589 See @ref{3e,,Foreign Language Representation} for full details on the
14590 implementation of these character sets.
14593 @geindex -gnatW (gcc)
14598 @item @code{-gnatW@emph{e}}
14600 Specify the method of encoding for wide characters.
14601 @code{e} is one of the following:
14604 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14611 Hex encoding (brackets coding also recognized)
14619 Upper half encoding (brackets encoding also recognized)
14627 Shift/JIS encoding (brackets encoding also recognized)
14635 EUC encoding (brackets encoding also recognized)
14643 UTF-8 encoding (brackets encoding also recognized)
14651 Brackets encoding only (default value)
14656 For full details on these encoding
14657 methods see @ref{4e,,Wide_Character Encodings}.
14658 Note that brackets coding is always accepted, even if one of the other
14659 options is specified, so for example @code{-gnatW8} specifies that both
14660 brackets and UTF-8 encodings will be recognized. The units that are
14661 with'ed directly or indirectly will be scanned using the specified
14662 representation scheme, and so if one of the non-brackets scheme is
14663 used, it must be used consistently throughout the program. However,
14664 since brackets encoding is always recognized, it may be conveniently
14665 used in standard libraries, allowing these libraries to be used with
14666 any of the available coding schemes.
14668 Note that brackets encoding only applies to program text. Within comments,
14669 brackets are considered to be normal graphic characters, and bracket sequences
14670 are never recognized as wide characters.
14672 If no @code{-gnatW?} parameter is present, then the default
14673 representation is normally Brackets encoding only. However, if the
14674 first three characters of the file are 16#EF# 16#BB# 16#BF# (the standard
14675 byte order mark or BOM for UTF-8), then these three characters are
14676 skipped and the default representation for the file is set to UTF-8.
14678 Note that the wide character representation that is specified (explicitly
14679 or by default) for the main program also acts as the default encoding used
14680 for Wide_Text_IO files if not specifically overridden by a WCEM form
14684 When no @code{-gnatW?} is specified, then characters (other than wide
14685 characters represented using brackets notation) are treated as 8-bit
14686 Latin-1 codes. The codes recognized are the Latin-1 graphic characters,
14687 and ASCII format effectors (CR, LF, HT, VT). Other lower half control
14688 characters in the range 16#00#..16#1F# are not accepted in program text
14689 or in comments. Upper half control characters (16#80#..16#9F#) are rejected
14690 in program text, but allowed and ignored in comments. Note in particular
14691 that the Next Line (NEL) character whose encoding is 16#85# is not recognized
14692 as an end of line in this default mode. If your source program contains
14693 instances of the NEL character used as a line terminator,
14694 you must use UTF-8 encoding for the whole
14695 source program. In default mode, all lines must be ended by a standard
14696 end of line sequence (CR, CR/LF, or LF).
14698 Note that the convention of simply accepting all upper half characters in
14699 comments means that programs that use standard ASCII for program text, but
14700 UTF-8 encoding for comments are accepted in default mode, providing that the
14701 comments are ended by an appropriate (CR, or CR/LF, or LF) line terminator.
14702 This is a common mode for many programs with foreign language comments.
14704 @node File Naming Control,Subprogram Inlining Control,Character Set Control,Compiler Switches
14705 @anchor{gnat_ugn/building_executable_programs_with_gnat file-naming-control}@anchor{10b}@anchor{gnat_ugn/building_executable_programs_with_gnat id24}@anchor{10c}
14706 @subsection File Naming Control
14709 @geindex -gnatk (gcc)
14714 @item @code{-gnatk@emph{n}}
14716 Activates file name 'krunching'. @code{n}, a decimal integer in the range
14717 1-999, indicates the maximum allowable length of a file name (not
14718 including the @code{.ads} or @code{.adb} extension). The default is not
14719 to enable file name krunching.
14721 For the source file naming rules, @ref{52,,File Naming Rules}.
14724 @node Subprogram Inlining Control,Auxiliary Output Control,File Naming Control,Compiler Switches
14725 @anchor{gnat_ugn/building_executable_programs_with_gnat subprogram-inlining-control}@anchor{10d}@anchor{gnat_ugn/building_executable_programs_with_gnat id25}@anchor{10e}
14726 @subsection Subprogram Inlining Control
14729 @geindex -gnatn (gcc)
14734 @item @code{-gnatn[12]}
14736 The @code{n} here is intended to suggest the first syllable of the word 'inline'.
14737 GNAT recognizes and processes @code{Inline} pragmas. However, for inlining to
14738 actually occur, optimization must be enabled and, by default, inlining of
14739 subprograms across units is not performed. If you want to additionally
14740 enable inlining of subprograms specified by pragma @code{Inline} across units,
14741 you must also specify this switch.
14743 In the absence of this switch, GNAT does not attempt inlining across units
14744 and does not access the bodies of subprograms for which @code{pragma Inline} is
14745 specified if they are not in the current unit.
14747 You can optionally specify the inlining level: 1 for moderate inlining across
14748 units, which is a good compromise between compilation times and performances
14749 at run time, or 2 for full inlining across units, which may bring about
14750 longer compilation times. If no inlining level is specified, the compiler will
14751 pick it based on the optimization level: 1 for @code{-O1}, @code{-O2} or
14752 @code{-Os} and 2 for @code{-O3}.
14754 If you specify this switch the compiler will access these bodies,
14755 creating an extra source dependency for the resulting object file, and
14756 where possible, the call will be inlined.
14757 For further details on when inlining is possible
14758 see @ref{10f,,Inlining of Subprograms}.
14761 @geindex -gnatN (gcc)
14766 @item @code{-gnatN}
14768 This switch activates front-end inlining which also
14769 generates additional dependencies.
14771 When using a gcc-based back end (in practice this means using any version
14772 of GNAT other than the JGNAT, .NET or GNAAMP versions), then the use of
14773 @code{-gnatN} is deprecated, and the use of @code{-gnatn} is preferred.
14774 Historically front end inlining was more extensive than the gcc back end
14775 inlining, but that is no longer the case.
14778 @node Auxiliary Output Control,Debugging Control,Subprogram Inlining Control,Compiler Switches
14779 @anchor{gnat_ugn/building_executable_programs_with_gnat auxiliary-output-control}@anchor{110}@anchor{gnat_ugn/building_executable_programs_with_gnat id26}@anchor{111}
14780 @subsection Auxiliary Output Control
14783 @geindex -gnatt (gcc)
14785 @geindex Writing internal trees
14787 @geindex Internal trees
14788 @geindex writing to file
14793 @item @code{-gnatt}
14795 Causes GNAT to write the internal tree for a unit to a file (with the
14796 extension @code{.adt}.
14797 This not normally required, but is used by separate analysis tools.
14799 these tools do the necessary compilations automatically, so you should
14800 not have to specify this switch in normal operation.
14801 Note that the combination of switches @code{-gnatct}
14802 generates a tree in the form required by ASIS applications.
14805 @geindex -gnatu (gcc)
14810 @item @code{-gnatu}
14812 Print a list of units required by this compilation on @code{stdout}.
14813 The listing includes all units on which the unit being compiled depends
14814 either directly or indirectly.
14817 @geindex -pass-exit-codes (gcc)
14822 @item @code{-pass-exit-codes}
14824 If this switch is not used, the exit code returned by @code{gcc} when
14825 compiling multiple files indicates whether all source files have
14826 been successfully used to generate object files or not.
14828 When @code{-pass-exit-codes} is used, @code{gcc} exits with an extended
14829 exit status and allows an integrated development environment to better
14830 react to a compilation failure. Those exit status are:
14833 @multitable {xxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
14840 There was an error in at least one source file.
14848 At least one source file did not generate an object file.
14856 The compiler died unexpectedly (internal error for example).
14864 An object file has been generated for every source file.
14870 @node Debugging Control,Exception Handling Control,Auxiliary Output Control,Compiler Switches
14871 @anchor{gnat_ugn/building_executable_programs_with_gnat debugging-control}@anchor{112}@anchor{gnat_ugn/building_executable_programs_with_gnat id27}@anchor{113}
14872 @subsection Debugging Control
14877 @geindex Debugging options
14880 @geindex -gnatd (gcc)
14885 @item @code{-gnatd@emph{x}}
14887 Activate internal debugging switches. @code{x} is a letter or digit, or
14888 string of letters or digits, which specifies the type of debugging
14889 outputs desired. Normally these are used only for internal development
14890 or system debugging purposes. You can find full documentation for these
14891 switches in the body of the @code{Debug} unit in the compiler source
14892 file @code{debug.adb}.
14895 @geindex -gnatG (gcc)
14900 @item @code{-gnatG[=@emph{nn}]}
14902 This switch causes the compiler to generate auxiliary output containing
14903 a pseudo-source listing of the generated expanded code. Like most Ada
14904 compilers, GNAT works by first transforming the high level Ada code into
14905 lower level constructs. For example, tasking operations are transformed
14906 into calls to the tasking run-time routines. A unique capability of GNAT
14907 is to list this expanded code in a form very close to normal Ada source.
14908 This is very useful in understanding the implications of various Ada
14909 usage on the efficiency of the generated code. There are many cases in
14910 Ada (e.g., the use of controlled types), where simple Ada statements can
14911 generate a lot of run-time code. By using @code{-gnatG} you can identify
14912 these cases, and consider whether it may be desirable to modify the coding
14913 approach to improve efficiency.
14915 The optional parameter @code{nn} if present after -gnatG specifies an
14916 alternative maximum line length that overrides the normal default of 72.
14917 This value is in the range 40-999999, values less than 40 being silently
14918 reset to 40. The equal sign is optional.
14920 The format of the output is very similar to standard Ada source, and is
14921 easily understood by an Ada programmer. The following special syntactic
14922 additions correspond to low level features used in the generated code that
14923 do not have any exact analogies in pure Ada source form. The following
14924 is a partial list of these special constructions. See the spec
14925 of package @code{Sprint} in file @code{sprint.ads} for a full list.
14927 @geindex -gnatL (gcc)
14929 If the switch @code{-gnatL} is used in conjunction with
14930 @code{-gnatG}, then the original source lines are interspersed
14931 in the expanded source (as comment lines with the original line number).
14936 @item @code{new @emph{xxx} [storage_pool = @emph{yyy}]}
14938 Shows the storage pool being used for an allocator.
14940 @item @code{at end @emph{procedure-name};}
14942 Shows the finalization (cleanup) procedure for a scope.
14944 @item @code{(if @emph{expr} then @emph{expr} else @emph{expr})}
14946 Conditional expression equivalent to the @code{x?y:z} construction in C.
14948 @item @code{@emph{target}^(@emph{source})}
14950 A conversion with floating-point truncation instead of rounding.
14952 @item @code{@emph{target}?(@emph{source})}
14954 A conversion that bypasses normal Ada semantic checking. In particular
14955 enumeration types and fixed-point types are treated simply as integers.
14957 @item @code{@emph{target}?^(@emph{source})}
14959 Combines the above two cases.
14962 @code{@emph{x} #/ @emph{y}}
14964 @code{@emph{x} #mod @emph{y}}
14966 @code{@emph{x} # @emph{y}}
14971 @item @code{@emph{x} #rem @emph{y}}
14973 A division or multiplication of fixed-point values which are treated as
14974 integers without any kind of scaling.
14976 @item @code{free @emph{expr} [storage_pool = @emph{xxx}]}
14978 Shows the storage pool associated with a @code{free} statement.
14980 @item @code{[subtype or type declaration]}
14982 Used to list an equivalent declaration for an internally generated
14983 type that is referenced elsewhere in the listing.
14985 @item @code{freeze @emph{type-name} [@emph{actions}]}
14987 Shows the point at which @code{type-name} is frozen, with possible
14988 associated actions to be performed at the freeze point.
14990 @item @code{reference @emph{itype}}
14992 Reference (and hence definition) to internal type @code{itype}.
14994 @item @code{@emph{function-name}! (@emph{arg}, @emph{arg}, @emph{arg})}
14996 Intrinsic function call.
14998 @item @code{@emph{label-name} : label}
15000 Declaration of label @code{labelname}.
15002 @item @code{#$ @emph{subprogram-name}}
15004 An implicit call to a run-time support routine
15005 (to meet the requirement of H.3.1(9) in a
15006 convenient manner).
15008 @item @code{@emph{expr} && @emph{expr} && @emph{expr} ... && @emph{expr}}
15010 A multiple concatenation (same effect as @code{expr} & @code{expr} &
15011 @code{expr}, but handled more efficiently).
15013 @item @code{[constraint_error]}
15015 Raise the @code{Constraint_Error} exception.
15017 @item @code{@emph{expression}'reference}
15019 A pointer to the result of evaluating @{expression@}.
15021 @item @code{@emph{target-type}!(@emph{source-expression})}
15023 An unchecked conversion of @code{source-expression} to @code{target-type}.
15025 @item @code{[@emph{numerator}/@emph{denominator}]}
15027 Used to represent internal real literals (that) have no exact
15028 representation in base 2-16 (for example, the result of compile time
15029 evaluation of the expression 1.0/27.0).
15033 @geindex -gnatD (gcc)
15038 @item @code{-gnatD[=nn]}
15040 When used in conjunction with @code{-gnatG}, this switch causes
15041 the expanded source, as described above for
15042 @code{-gnatG} to be written to files with names
15043 @code{xxx.dg}, where @code{xxx} is the normal file name,
15044 instead of to the standard output file. For
15045 example, if the source file name is @code{hello.adb}, then a file
15046 @code{hello.adb.dg} will be written. The debugging
15047 information generated by the @code{gcc} @code{-g} switch
15048 will refer to the generated @code{xxx.dg} file. This allows
15049 you to do source level debugging using the generated code which is
15050 sometimes useful for complex code, for example to find out exactly
15051 which part of a complex construction raised an exception. This switch
15052 also suppresses generation of cross-reference information (see
15053 @code{-gnatx}) since otherwise the cross-reference information
15054 would refer to the @code{.dg} file, which would cause
15055 confusion since this is not the original source file.
15057 Note that @code{-gnatD} actually implies @code{-gnatG}
15058 automatically, so it is not necessary to give both options.
15059 In other words @code{-gnatD} is equivalent to @code{-gnatDG}).
15061 @geindex -gnatL (gcc)
15063 If the switch @code{-gnatL} is used in conjunction with
15064 @code{-gnatDG}, then the original source lines are interspersed
15065 in the expanded source (as comment lines with the original line number).
15067 The optional parameter @code{nn} if present after -gnatD specifies an
15068 alternative maximum line length that overrides the normal default of 72.
15069 This value is in the range 40-999999, values less than 40 being silently
15070 reset to 40. The equal sign is optional.
15073 @geindex -gnatr (gcc)
15075 @geindex pragma Restrictions
15080 @item @code{-gnatr}
15082 This switch causes pragma Restrictions to be treated as Restriction_Warnings
15083 so that violation of restrictions causes warnings rather than illegalities.
15084 This is useful during the development process when new restrictions are added
15085 or investigated. The switch also causes pragma Profile to be treated as
15086 Profile_Warnings, and pragma Restricted_Run_Time and pragma Ravenscar set
15087 restriction warnings rather than restrictions.
15090 @geindex -gnatR (gcc)
15095 @item @code{-gnatR[0|1|2|3|4][e][j][m][s]}
15097 This switch controls output from the compiler of a listing showing
15098 representation information for declared types, objects and subprograms.
15099 For @code{-gnatR0}, no information is output (equivalent to omitting
15100 the @code{-gnatR} switch). For @code{-gnatR1} (which is the default,
15101 so @code{-gnatR} with no parameter has the same effect), size and
15102 alignment information is listed for declared array and record types.
15104 For @code{-gnatR2}, size and alignment information is listed for all
15105 declared types and objects. The @code{Linker_Section} is also listed for any
15106 entity for which the @code{Linker_Section} is set explicitly or implicitly (the
15107 latter case occurs for objects of a type for which a @code{Linker_Section}
15110 For @code{-gnatR3}, symbolic expressions for values that are computed
15111 at run time for records are included. These symbolic expressions have
15112 a mostly obvious format with #n being used to represent the value of the
15113 n'th discriminant. See source files @code{repinfo.ads/adb} in the
15114 GNAT sources for full details on the format of @code{-gnatR3} output.
15116 For @code{-gnatR4}, information for relevant compiler-generated types
15117 is also listed, i.e. when they are structurally part of other declared
15120 If the switch is followed by an @code{e} (e.g. @code{-gnatR2e}), then
15121 extended representation information for record sub-components of records
15124 If the switch is followed by an @code{m} (e.g. @code{-gnatRm}), then
15125 subprogram conventions and parameter passing mechanisms for all the
15126 subprograms are included.
15128 If the switch is followed by a @code{j} (e.g., @code{-gnatRj}), then
15129 the output is in the JSON data interchange format specified by the
15130 ECMA-404 standard. The semantic description of this JSON output is
15131 available in the specification of the Repinfo unit present in the
15134 If the switch is followed by an @code{s} (e.g., @code{-gnatR3s}), then
15135 the output is to a file with the name @code{file.rep} where file is
15136 the name of the corresponding source file, except if @cite{j`} is also
15137 specified, in which case the file name is @code{file.json}.
15139 Note that it is possible for record components to have zero size. In
15140 this case, the component clause uses an obvious extension of permitted
15141 Ada syntax, for example @code{at 0 range 0 .. -1}.
15144 @geindex -gnatS (gcc)
15149 @item @code{-gnatS}
15151 The use of the switch @code{-gnatS} for an
15152 Ada compilation will cause the compiler to output a
15153 representation of package Standard in a form very
15154 close to standard Ada. It is not quite possible to
15155 do this entirely in standard Ada (since new
15156 numeric base types cannot be created in standard
15157 Ada), but the output is easily
15158 readable to any Ada programmer, and is useful to
15159 determine the characteristics of target dependent
15160 types in package Standard.
15163 @geindex -gnatx (gcc)
15168 @item @code{-gnatx}
15170 Normally the compiler generates full cross-referencing information in
15171 the @code{ALI} file. This information is used by a number of tools,
15172 including @code{gnatfind} and @code{gnatxref}. The @code{-gnatx} switch
15173 suppresses this information. This saves some space and may slightly
15174 speed up compilation, but means that these tools cannot be used.
15177 @node Exception Handling Control,Units to Sources Mapping Files,Debugging Control,Compiler Switches
15178 @anchor{gnat_ugn/building_executable_programs_with_gnat id28}@anchor{114}@anchor{gnat_ugn/building_executable_programs_with_gnat exception-handling-control}@anchor{115}
15179 @subsection Exception Handling Control
15182 GNAT uses two methods for handling exceptions at run time. The
15183 @code{setjmp/longjmp} method saves the context when entering
15184 a frame with an exception handler. Then when an exception is
15185 raised, the context can be restored immediately, without the
15186 need for tracing stack frames. This method provides very fast
15187 exception propagation, but introduces significant overhead for
15188 the use of exception handlers, even if no exception is raised.
15190 The other approach is called 'zero cost' exception handling.
15191 With this method, the compiler builds static tables to describe
15192 the exception ranges. No dynamic code is required when entering
15193 a frame containing an exception handler. When an exception is
15194 raised, the tables are used to control a back trace of the
15195 subprogram invocation stack to locate the required exception
15196 handler. This method has considerably poorer performance for
15197 the propagation of exceptions, but there is no overhead for
15198 exception handlers if no exception is raised. Note that in this
15199 mode and in the context of mixed Ada and C/C++ programming,
15200 to propagate an exception through a C/C++ code, the C/C++ code
15201 must be compiled with the @code{-funwind-tables} GCC's
15204 The following switches may be used to control which of the
15205 two exception handling methods is used.
15207 @geindex --RTS=sjlj (gnatmake)
15212 @item @code{--RTS=sjlj}
15214 This switch causes the setjmp/longjmp run-time (when available) to be used
15215 for exception handling. If the default
15216 mechanism for the target is zero cost exceptions, then
15217 this switch can be used to modify this default, and must be
15218 used for all units in the partition.
15219 This option is rarely used. One case in which it may be
15220 advantageous is if you have an application where exception
15221 raising is common and the overall performance of the
15222 application is improved by favoring exception propagation.
15225 @geindex --RTS=zcx (gnatmake)
15227 @geindex Zero Cost Exceptions
15232 @item @code{--RTS=zcx}
15234 This switch causes the zero cost approach to be used
15235 for exception handling. If this is the default mechanism for the
15236 target (see below), then this switch is unneeded. If the default
15237 mechanism for the target is setjmp/longjmp exceptions, then
15238 this switch can be used to modify this default, and must be
15239 used for all units in the partition.
15240 This option can only be used if the zero cost approach
15241 is available for the target in use, otherwise it will generate an error.
15244 The same option @code{--RTS} must be used both for @code{gcc}
15245 and @code{gnatbind}. Passing this option to @code{gnatmake}
15246 (@ref{dc,,Switches for gnatmake}) will ensure the required consistency
15247 through the compilation and binding steps.
15249 @node Units to Sources Mapping Files,Code Generation Control,Exception Handling Control,Compiler Switches
15250 @anchor{gnat_ugn/building_executable_programs_with_gnat id29}@anchor{116}@anchor{gnat_ugn/building_executable_programs_with_gnat units-to-sources-mapping-files}@anchor{f7}
15251 @subsection Units to Sources Mapping Files
15254 @geindex -gnatem (gcc)
15259 @item @code{-gnatem=@emph{path}}
15261 A mapping file is a way to communicate to the compiler two mappings:
15262 from unit names to file names (without any directory information) and from
15263 file names to path names (with full directory information). These mappings
15264 are used by the compiler to short-circuit the path search.
15266 The use of mapping files is not required for correct operation of the
15267 compiler, but mapping files can improve efficiency, particularly when
15268 sources are read over a slow network connection. In normal operation,
15269 you need not be concerned with the format or use of mapping files,
15270 and the @code{-gnatem} switch is not a switch that you would use
15271 explicitly. It is intended primarily for use by automatic tools such as
15272 @code{gnatmake} running under the project file facility. The
15273 description here of the format of mapping files is provided
15274 for completeness and for possible use by other tools.
15276 A mapping file is a sequence of sets of three lines. In each set, the
15277 first line is the unit name, in lower case, with @code{%s} appended
15278 for specs and @code{%b} appended for bodies; the second line is the
15279 file name; and the third line is the path name.
15286 /gnat/project1/sources/main.2.ada
15289 When the switch @code{-gnatem} is specified, the compiler will
15290 create in memory the two mappings from the specified file. If there is
15291 any problem (nonexistent file, truncated file or duplicate entries),
15292 no mapping will be created.
15294 Several @code{-gnatem} switches may be specified; however, only the
15295 last one on the command line will be taken into account.
15297 When using a project file, @code{gnatmake} creates a temporary
15298 mapping file and communicates it to the compiler using this switch.
15301 @node Code Generation Control,,Units to Sources Mapping Files,Compiler Switches
15302 @anchor{gnat_ugn/building_executable_programs_with_gnat code-generation-control}@anchor{117}@anchor{gnat_ugn/building_executable_programs_with_gnat id30}@anchor{118}
15303 @subsection Code Generation Control
15306 The GCC technology provides a wide range of target dependent
15307 @code{-m} switches for controlling
15308 details of code generation with respect to different versions of
15309 architectures. This includes variations in instruction sets (e.g.,
15310 different members of the power pc family), and different requirements
15311 for optimal arrangement of instructions (e.g., different members of
15312 the x86 family). The list of available @code{-m} switches may be
15313 found in the GCC documentation.
15315 Use of these @code{-m} switches may in some cases result in improved
15318 The GNAT technology is tested and qualified without any
15319 @code{-m} switches,
15320 so generally the most reliable approach is to avoid the use of these
15321 switches. However, we generally expect most of these switches to work
15322 successfully with GNAT, and many customers have reported successful
15323 use of these options.
15325 Our general advice is to avoid the use of @code{-m} switches unless
15326 special needs lead to requirements in this area. In particular,
15327 there is no point in using @code{-m} switches to improve performance
15328 unless you actually see a performance improvement.
15330 @node Linker Switches,Binding with gnatbind,Compiler Switches,Building Executable Programs with GNAT
15331 @anchor{gnat_ugn/building_executable_programs_with_gnat linker-switches}@anchor{119}@anchor{gnat_ugn/building_executable_programs_with_gnat id31}@anchor{11a}
15332 @section Linker Switches
15335 Linker switches can be specified after @code{-largs} builder switch.
15337 @geindex -fuse-ld=name
15342 @item @code{-fuse-ld=@emph{name}}
15344 Linker to be used. The default is @code{bfd} for @code{ld.bfd},
15345 the alternative being @code{gold} for @code{ld.gold}. The later is
15346 a more recent and faster linker, but only available on GNU/Linux
15350 @node Binding with gnatbind,Linking with gnatlink,Linker Switches,Building Executable Programs with GNAT
15351 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-gnatbind}@anchor{1d}@anchor{gnat_ugn/building_executable_programs_with_gnat id32}@anchor{11b}
15352 @section Binding with @code{gnatbind}
15357 This chapter describes the GNAT binder, @code{gnatbind}, which is used
15358 to bind compiled GNAT objects.
15360 The @code{gnatbind} program performs four separate functions:
15366 Checks that a program is consistent, in accordance with the rules in
15367 Chapter 10 of the Ada Reference Manual. In particular, error
15368 messages are generated if a program uses inconsistent versions of a
15372 Checks that an acceptable order of elaboration exists for the program
15373 and issues an error message if it cannot find an order of elaboration
15374 that satisfies the rules in Chapter 10 of the Ada Language Manual.
15377 Generates a main program incorporating the given elaboration order.
15378 This program is a small Ada package (body and spec) that
15379 must be subsequently compiled
15380 using the GNAT compiler. The necessary compilation step is usually
15381 performed automatically by @code{gnatlink}. The two most important
15382 functions of this program
15383 are to call the elaboration routines of units in an appropriate order
15384 and to call the main program.
15387 Determines the set of object files required by the given main program.
15388 This information is output in the forms of comments in the generated program,
15389 to be read by the @code{gnatlink} utility used to link the Ada application.
15393 * Running gnatbind::
15394 * Switches for gnatbind::
15395 * Command-Line Access::
15396 * Search Paths for gnatbind::
15397 * Examples of gnatbind Usage::
15401 @node Running gnatbind,Switches for gnatbind,,Binding with gnatbind
15402 @anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatbind}@anchor{11c}@anchor{gnat_ugn/building_executable_programs_with_gnat id33}@anchor{11d}
15403 @subsection Running @code{gnatbind}
15406 The form of the @code{gnatbind} command is
15409 $ gnatbind [ switches ] mainprog[.ali] [ switches ]
15412 where @code{mainprog.adb} is the Ada file containing the main program
15413 unit body. @code{gnatbind} constructs an Ada
15414 package in two files whose names are
15415 @code{b~mainprog.ads}, and @code{b~mainprog.adb}.
15416 For example, if given the
15417 parameter @code{hello.ali}, for a main program contained in file
15418 @code{hello.adb}, the binder output files would be @code{b~hello.ads}
15419 and @code{b~hello.adb}.
15421 When doing consistency checking, the binder takes into consideration
15422 any source files it can locate. For example, if the binder determines
15423 that the given main program requires the package @code{Pack}, whose
15425 file is @code{pack.ali} and whose corresponding source spec file is
15426 @code{pack.ads}, it attempts to locate the source file @code{pack.ads}
15427 (using the same search path conventions as previously described for the
15428 @code{gcc} command). If it can locate this source file, it checks that
15430 or source checksums of the source and its references to in @code{ALI} files
15431 match. In other words, any @code{ALI} files that mentions this spec must have
15432 resulted from compiling this version of the source file (or in the case
15433 where the source checksums match, a version close enough that the
15434 difference does not matter).
15436 @geindex Source files
15437 @geindex use by binder
15439 The effect of this consistency checking, which includes source files, is
15440 that the binder ensures that the program is consistent with the latest
15441 version of the source files that can be located at bind time. Editing a
15442 source file without compiling files that depend on the source file cause
15443 error messages to be generated by the binder.
15445 For example, suppose you have a main program @code{hello.adb} and a
15446 package @code{P}, from file @code{p.ads} and you perform the following
15453 Enter @code{gcc -c hello.adb} to compile the main program.
15456 Enter @code{gcc -c p.ads} to compile package @code{P}.
15459 Edit file @code{p.ads}.
15462 Enter @code{gnatbind hello}.
15465 At this point, the file @code{p.ali} contains an out-of-date time stamp
15466 because the file @code{p.ads} has been edited. The attempt at binding
15467 fails, and the binder generates the following error messages:
15470 error: "hello.adb" must be recompiled ("p.ads" has been modified)
15471 error: "p.ads" has been modified and must be recompiled
15474 Now both files must be recompiled as indicated, and then the bind can
15475 succeed, generating a main program. You need not normally be concerned
15476 with the contents of this file, but for reference purposes a sample
15477 binder output file is given in @ref{e,,Example of Binder Output File}.
15479 In most normal usage, the default mode of @code{gnatbind} which is to
15480 generate the main package in Ada, as described in the previous section.
15481 In particular, this means that any Ada programmer can read and understand
15482 the generated main program. It can also be debugged just like any other
15483 Ada code provided the @code{-g} switch is used for
15484 @code{gnatbind} and @code{gnatlink}.
15486 @node Switches for gnatbind,Command-Line Access,Running gnatbind,Binding with gnatbind
15487 @anchor{gnat_ugn/building_executable_programs_with_gnat id34}@anchor{11e}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatbind}@anchor{11f}
15488 @subsection Switches for @code{gnatbind}
15491 The following switches are available with @code{gnatbind}; details will
15492 be presented in subsequent sections.
15494 @geindex --version (gnatbind)
15499 @item @code{--version}
15501 Display Copyright and version, then exit disregarding all other options.
15504 @geindex --help (gnatbind)
15509 @item @code{--help}
15511 If @code{--version} was not used, display usage, then exit disregarding
15515 @geindex -a (gnatbind)
15522 Indicates that, if supported by the platform, the adainit procedure should
15523 be treated as an initialisation routine by the linker (a constructor). This
15524 is intended to be used by the Project Manager to automatically initialize
15525 shared Stand-Alone Libraries.
15528 @geindex -aO (gnatbind)
15535 Specify directory to be searched for ALI files.
15538 @geindex -aI (gnatbind)
15545 Specify directory to be searched for source file.
15548 @geindex -A (gnatbind)
15553 @item @code{-A[=@emph{filename}]}
15555 Output ALI list (to standard output or to the named file).
15558 @geindex -b (gnatbind)
15565 Generate brief messages to @code{stderr} even if verbose mode set.
15568 @geindex -c (gnatbind)
15575 Check only, no generation of binder output file.
15578 @geindex -dnn[k|m] (gnatbind)
15583 @item @code{-d@emph{nn}[k|m]}
15585 This switch can be used to change the default task stack size value
15586 to a specified size @code{nn}, which is expressed in bytes by default, or
15587 in kilobytes when suffixed with @code{k} or in megabytes when suffixed
15589 In the absence of a @code{[k|m]} suffix, this switch is equivalent,
15590 in effect, to completing all task specs with
15593 pragma Storage_Size (nn);
15596 When they do not already have such a pragma.
15599 @geindex -D (gnatbind)
15604 @item @code{-D@emph{nn}[k|m]}
15606 Set the default secondary stack size to @code{nn}. The suffix indicates whether
15607 the size is in bytes (no suffix), kilobytes (@code{k} suffix) or megabytes
15610 The secondary stack holds objects of unconstrained types that are returned by
15611 functions, for example unconstrained Strings. The size of the secondary stack
15612 can be dynamic or fixed depending on the target.
15614 For most targets, the secondary stack grows on demand and is implemented as
15615 a chain of blocks in the heap. In this case, the default secondary stack size
15616 determines the initial size of the secondary stack for each task and the
15617 smallest amount the secondary stack can grow by.
15619 For Ravenscar, ZFP, and Cert run-times the size of the secondary stack is
15620 fixed. This switch can be used to change the default size of these stacks.
15621 The default secondary stack size can be overridden on a per-task basis if
15622 individual tasks have different secondary stack requirements. This is
15623 achieved through the Secondary_Stack_Size aspect that takes the size of the
15624 secondary stack in bytes.
15627 @geindex -e (gnatbind)
15634 Output complete list of elaboration-order dependencies.
15637 @geindex -Ea (gnatbind)
15644 Store tracebacks in exception occurrences when the target supports it.
15645 The "a" is for "address"; tracebacks will contain hexadecimal addresses,
15646 unless symbolic tracebacks are enabled.
15648 See also the packages @code{GNAT.Traceback} and
15649 @code{GNAT.Traceback.Symbolic} for more information.
15650 Note that on x86 ports, you must not use @code{-fomit-frame-pointer}
15654 @geindex -Es (gnatbind)
15661 Store tracebacks in exception occurrences when the target supports it.
15662 The "s" is for "symbolic"; symbolic tracebacks are enabled.
15665 @geindex -E (gnatbind)
15672 Currently the same as @code{-Ea}.
15675 @geindex -f (gnatbind)
15680 @item @code{-f@emph{elab-order}}
15682 Force elaboration order.
15685 @geindex -F (gnatbind)
15692 Force the checks of elaboration flags. @code{gnatbind} does not normally
15693 generate checks of elaboration flags for the main executable, except when
15694 a Stand-Alone Library is used. However, there are cases when this cannot be
15695 detected by gnatbind. An example is importing an interface of a Stand-Alone
15696 Library through a pragma Import and only specifying through a linker switch
15697 this Stand-Alone Library. This switch is used to guarantee that elaboration
15698 flag checks are generated.
15701 @geindex -h (gnatbind)
15708 Output usage (help) information.
15710 @geindex -H32 (gnatbind)
15714 Use 32-bit allocations for @code{__gnat_malloc} (and thus for access types).
15715 For further details see @ref{120,,Dynamic Allocation Control}.
15717 @geindex -H64 (gnatbind)
15719 @geindex __gnat_malloc
15723 Use 64-bit allocations for @code{__gnat_malloc} (and thus for access types).
15724 For further details see @ref{120,,Dynamic Allocation Control}.
15726 @geindex -I (gnatbind)
15730 Specify directory to be searched for source and ALI files.
15732 @geindex -I- (gnatbind)
15736 Do not look for sources in the current directory where @code{gnatbind} was
15737 invoked, and do not look for ALI files in the directory containing the
15738 ALI file named in the @code{gnatbind} command line.
15740 @geindex -l (gnatbind)
15744 Output chosen elaboration order.
15746 @geindex -L (gnatbind)
15748 @item @code{-L@emph{xxx}}
15750 Bind the units for library building. In this case the @code{adainit} and
15751 @code{adafinal} procedures (@ref{b4,,Binding with Non-Ada Main Programs})
15752 are renamed to @code{@emph{xxx}init} and
15753 @code{@emph{xxx}final}.
15755 (@ref{15,,GNAT and Libraries}, for more details.)
15757 @geindex -M (gnatbind)
15759 @item @code{-M@emph{xyz}}
15761 Rename generated main program from main to xyz. This option is
15762 supported on cross environments only.
15764 @geindex -m (gnatbind)
15766 @item @code{-m@emph{n}}
15768 Limit number of detected errors or warnings to @code{n}, where @code{n} is
15769 in the range 1..999999. The default value if no switch is
15770 given is 9999. If the number of warnings reaches this limit, then a
15771 message is output and further warnings are suppressed, the bind
15772 continues in this case. If the number of errors reaches this
15773 limit, then a message is output and the bind is abandoned.
15774 A value of zero means that no limit is enforced. The equal
15777 @geindex -n (gnatbind)
15783 @geindex -nostdinc (gnatbind)
15785 @item @code{-nostdinc}
15787 Do not look for sources in the system default directory.
15789 @geindex -nostdlib (gnatbind)
15791 @item @code{-nostdlib}
15793 Do not look for library files in the system default directory.
15795 @geindex --RTS (gnatbind)
15797 @item @code{--RTS=@emph{rts-path}}
15799 Specifies the default location of the run-time library. Same meaning as the
15800 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
15802 @geindex -o (gnatbind)
15804 @item @code{-o @emph{file}}
15806 Name the output file @code{file} (default is @code{b~`xxx}.adb`).
15807 Note that if this option is used, then linking must be done manually,
15808 gnatlink cannot be used.
15810 @geindex -O (gnatbind)
15812 @item @code{-O[=@emph{filename}]}
15814 Output object list (to standard output or to the named file).
15816 @geindex -p (gnatbind)
15820 Pessimistic (worst-case) elaboration order.
15822 @geindex -P (gnatbind)
15826 Generate binder file suitable for CodePeer.
15828 @geindex -R (gnatbind)
15832 Output closure source list, which includes all non-run-time units that are
15833 included in the bind.
15835 @geindex -Ra (gnatbind)
15839 Like @code{-R} but the list includes run-time units.
15841 @geindex -s (gnatbind)
15845 Require all source files to be present.
15847 @geindex -S (gnatbind)
15849 @item @code{-S@emph{xxx}}
15851 Specifies the value to be used when detecting uninitialized scalar
15852 objects with pragma Initialize_Scalars.
15853 The @code{xxx} string specified with the switch is one of:
15859 @code{in} for an invalid value.
15861 If zero is invalid for the discrete type in question,
15862 then the scalar value is set to all zero bits.
15863 For signed discrete types, the largest possible negative value of
15864 the underlying scalar is set (i.e. a one bit followed by all zero bits).
15865 For unsigned discrete types, the underlying scalar value is set to all
15866 one bits. For floating-point types, a NaN value is set
15867 (see body of package System.Scalar_Values for exact values).
15870 @code{lo} for low value.
15872 If zero is invalid for the discrete type in question,
15873 then the scalar value is set to all zero bits.
15874 For signed discrete types, the largest possible negative value of
15875 the underlying scalar is set (i.e. a one bit followed by all zero bits).
15876 For unsigned discrete types, the underlying scalar value is set to all
15877 zero bits. For floating-point, a small value is set
15878 (see body of package System.Scalar_Values for exact values).
15881 @code{hi} for high value.
15883 If zero is invalid for the discrete type in question,
15884 then the scalar value is set to all one bits.
15885 For signed discrete types, the largest possible positive value of
15886 the underlying scalar is set (i.e. a zero bit followed by all one bits).
15887 For unsigned discrete types, the underlying scalar value is set to all
15888 one bits. For floating-point, a large value is set
15889 (see body of package System.Scalar_Values for exact values).
15892 @code{xx} for hex value (two hex digits).
15894 The underlying scalar is set to a value consisting of repeated bytes, whose
15895 value corresponds to the given value. For example if @code{BF} is given,
15896 then a 32-bit scalar value will be set to the bit patterm @code{16#BFBFBFBF#}.
15899 @geindex GNAT_INIT_SCALARS
15901 In addition, you can specify @code{-Sev} to indicate that the value is
15902 to be set at run time. In this case, the program will look for an environment
15903 variable of the form @code{GNAT_INIT_SCALARS=@emph{yy}}, where @code{yy} is one
15904 of @code{in/lo/hi/@emph{xx}} with the same meanings as above.
15905 If no environment variable is found, or if it does not have a valid value,
15906 then the default is @code{in} (invalid values).
15909 @geindex -static (gnatbind)
15914 @item @code{-static}
15916 Link against a static GNAT run-time.
15918 @geindex -shared (gnatbind)
15920 @item @code{-shared}
15922 Link against a shared GNAT run-time when available.
15924 @geindex -t (gnatbind)
15928 Tolerate time stamp and other consistency errors.
15930 @geindex -T (gnatbind)
15932 @item @code{-T@emph{n}}
15934 Set the time slice value to @code{n} milliseconds. If the system supports
15935 the specification of a specific time slice value, then the indicated value
15936 is used. If the system does not support specific time slice values, but
15937 does support some general notion of round-robin scheduling, then any
15938 nonzero value will activate round-robin scheduling.
15940 A value of zero is treated specially. It turns off time
15941 slicing, and in addition, indicates to the tasking run-time that the
15942 semantics should match as closely as possible the Annex D
15943 requirements of the Ada RM, and in particular sets the default
15944 scheduling policy to @code{FIFO_Within_Priorities}.
15946 @geindex -u (gnatbind)
15948 @item @code{-u@emph{n}}
15950 Enable dynamic stack usage, with @code{n} results stored and displayed
15951 at program termination. A result is generated when a task
15952 terminates. Results that can't be stored are displayed on the fly, at
15953 task termination. This option is currently not supported on Itanium
15954 platforms. (See @ref{121,,Dynamic Stack Usage Analysis} for details.)
15956 @geindex -v (gnatbind)
15960 Verbose mode. Write error messages, header, summary output to
15963 @geindex -V (gnatbind)
15965 @item @code{-V@emph{key}=@emph{value}}
15967 Store the given association of @code{key} to @code{value} in the bind environment.
15968 Values stored this way can be retrieved at run time using
15969 @code{GNAT.Bind_Environment}.
15971 @geindex -w (gnatbind)
15973 @item @code{-w@emph{x}}
15975 Warning mode; @code{x} = s/e for suppress/treat as error.
15977 @geindex -Wx (gnatbind)
15979 @item @code{-Wx@emph{e}}
15981 Override default wide character encoding for standard Text_IO files.
15983 @geindex -x (gnatbind)
15987 Exclude source files (check object consistency only).
15989 @geindex -Xnnn (gnatbind)
15991 @item @code{-X@emph{nnn}}
15993 Set default exit status value, normally 0 for POSIX compliance.
15995 @geindex -y (gnatbind)
15999 Enable leap seconds support in @code{Ada.Calendar} and its children.
16001 @geindex -z (gnatbind)
16005 No main subprogram.
16008 You may obtain this listing of switches by running @code{gnatbind} with
16012 * Consistency-Checking Modes::
16013 * Binder Error Message Control::
16014 * Elaboration Control::
16016 * Dynamic Allocation Control::
16017 * Binding with Non-Ada Main Programs::
16018 * Binding Programs with No Main Subprogram::
16022 @node Consistency-Checking Modes,Binder Error Message Control,,Switches for gnatbind
16023 @anchor{gnat_ugn/building_executable_programs_with_gnat consistency-checking-modes}@anchor{122}@anchor{gnat_ugn/building_executable_programs_with_gnat id35}@anchor{123}
16024 @subsubsection Consistency-Checking Modes
16027 As described earlier, by default @code{gnatbind} checks
16028 that object files are consistent with one another and are consistent
16029 with any source files it can locate. The following switches control binder
16034 @geindex -s (gnatbind)
16042 Require source files to be present. In this mode, the binder must be
16043 able to locate all source files that are referenced, in order to check
16044 their consistency. In normal mode, if a source file cannot be located it
16045 is simply ignored. If you specify this switch, a missing source
16048 @geindex -Wx (gnatbind)
16050 @item @code{-Wx@emph{e}}
16052 Override default wide character encoding for standard Text_IO files.
16053 Normally the default wide character encoding method used for standard
16054 [Wide_[Wide_]]Text_IO files is taken from the encoding specified for
16055 the main source input (see description of switch
16056 @code{-gnatWx} for the compiler). The
16057 use of this switch for the binder (which has the same set of
16058 possible arguments) overrides this default as specified.
16060 @geindex -x (gnatbind)
16064 Exclude source files. In this mode, the binder only checks that ALI
16065 files are consistent with one another. Source files are not accessed.
16066 The binder runs faster in this mode, and there is still a guarantee that
16067 the resulting program is self-consistent.
16068 If a source file has been edited since it was last compiled, and you
16069 specify this switch, the binder will not detect that the object
16070 file is out of date with respect to the source file. Note that this is the
16071 mode that is automatically used by @code{gnatmake} because in this
16072 case the checking against sources has already been performed by
16073 @code{gnatmake} in the course of compilation (i.e., before binding).
16076 @node Binder Error Message Control,Elaboration Control,Consistency-Checking Modes,Switches for gnatbind
16077 @anchor{gnat_ugn/building_executable_programs_with_gnat id36}@anchor{124}@anchor{gnat_ugn/building_executable_programs_with_gnat binder-error-message-control}@anchor{125}
16078 @subsubsection Binder Error Message Control
16081 The following switches provide control over the generation of error
16082 messages from the binder:
16086 @geindex -v (gnatbind)
16094 Verbose mode. In the normal mode, brief error messages are generated to
16095 @code{stderr}. If this switch is present, a header is written
16096 to @code{stdout} and any error messages are directed to @code{stdout}.
16097 All that is written to @code{stderr} is a brief summary message.
16099 @geindex -b (gnatbind)
16103 Generate brief error messages to @code{stderr} even if verbose mode is
16104 specified. This is relevant only when used with the
16107 @geindex -m (gnatbind)
16109 @item @code{-m@emph{n}}
16111 Limits the number of error messages to @code{n}, a decimal integer in the
16112 range 1-999. The binder terminates immediately if this limit is reached.
16114 @geindex -M (gnatbind)
16116 @item @code{-M@emph{xxx}}
16118 Renames the generated main program from @code{main} to @code{xxx}.
16119 This is useful in the case of some cross-building environments, where
16120 the actual main program is separate from the one generated
16121 by @code{gnatbind}.
16123 @geindex -ws (gnatbind)
16129 Suppress all warning messages.
16131 @geindex -we (gnatbind)
16135 Treat any warning messages as fatal errors.
16137 @geindex -t (gnatbind)
16139 @geindex Time stamp checks
16142 @geindex Binder consistency checks
16144 @geindex Consistency checks
16149 The binder performs a number of consistency checks including:
16155 Check that time stamps of a given source unit are consistent
16158 Check that checksums of a given source unit are consistent
16161 Check that consistent versions of @code{GNAT} were used for compilation
16164 Check consistency of configuration pragmas as required
16167 Normally failure of such checks, in accordance with the consistency
16168 requirements of the Ada Reference Manual, causes error messages to be
16169 generated which abort the binder and prevent the output of a binder
16170 file and subsequent link to obtain an executable.
16172 The @code{-t} switch converts these error messages
16173 into warnings, so that
16174 binding and linking can continue to completion even in the presence of such
16175 errors. The result may be a failed link (due to missing symbols), or a
16176 non-functional executable which has undefined semantics.
16180 This means that @code{-t} should be used only in unusual situations,
16186 @node Elaboration Control,Output Control,Binder Error Message Control,Switches for gnatbind
16187 @anchor{gnat_ugn/building_executable_programs_with_gnat id37}@anchor{126}@anchor{gnat_ugn/building_executable_programs_with_gnat elaboration-control}@anchor{127}
16188 @subsubsection Elaboration Control
16191 The following switches provide additional control over the elaboration
16192 order. For full details see @ref{f,,Elaboration Order Handling in GNAT}.
16194 @geindex -f (gnatbind)
16199 @item @code{-f@emph{elab-order}}
16201 Force elaboration order.
16203 @code{elab-order} should be the name of a "forced elaboration order file", that
16204 is, a text file containing library item names, one per line. A name of the
16205 form "some.unit%s" or "some.unit (spec)" denotes the spec of Some.Unit. A
16206 name of the form "some.unit%b" or "some.unit (body)" denotes the body of
16207 Some.Unit. Each pair of lines is taken to mean that there is an elaboration
16208 dependence of the second line on the first. For example, if the file
16218 then the spec of This will be elaborated before the body of This, and the
16219 body of This will be elaborated before the spec of That, and the spec of That
16220 will be elaborated before the body of That. The first and last of these three
16221 dependences are already required by Ada rules, so this file is really just
16222 forcing the body of This to be elaborated before the spec of That.
16224 The given order must be consistent with Ada rules, or else @code{gnatbind} will
16225 give elaboration cycle errors. For example, if you say x (body) should be
16226 elaborated before x (spec), there will be a cycle, because Ada rules require
16227 x (spec) to be elaborated before x (body); you can't have the spec and body
16228 both elaborated before each other.
16230 If you later add "with That;" to the body of This, there will be a cycle, in
16231 which case you should erase either "this (body)" or "that (spec)" from the
16232 above forced elaboration order file.
16234 Blank lines and Ada-style comments are ignored. Unit names that do not exist
16235 in the program are ignored. Units in the GNAT predefined library are also
16238 @geindex -p (gnatbind)
16242 Normally the binder attempts to choose an elaboration order that is
16243 likely to minimize the likelihood of an elaboration order error resulting
16244 in raising a @code{Program_Error} exception. This switch reverses the
16245 action of the binder, and requests that it deliberately choose an order
16246 that is likely to maximize the likelihood of an elaboration error.
16247 This is useful in ensuring portability and avoiding dependence on
16248 accidental fortuitous elaboration ordering.
16250 Normally it only makes sense to use the @code{-p}
16252 elaboration checking is used (@code{-gnatE} switch used for compilation).
16253 This is because in the default static elaboration mode, all necessary
16254 @code{Elaborate} and @code{Elaborate_All} pragmas are implicitly inserted.
16255 These implicit pragmas are still respected by the binder in
16256 @code{-p} mode, so a
16257 safe elaboration order is assured.
16259 Note that @code{-p} is not intended for
16260 production use; it is more for debugging/experimental use.
16263 @node Output Control,Dynamic Allocation Control,Elaboration Control,Switches for gnatbind
16264 @anchor{gnat_ugn/building_executable_programs_with_gnat output-control}@anchor{128}@anchor{gnat_ugn/building_executable_programs_with_gnat id38}@anchor{129}
16265 @subsubsection Output Control
16268 The following switches allow additional control over the output
16269 generated by the binder.
16273 @geindex -c (gnatbind)
16281 Check only. Do not generate the binder output file. In this mode the
16282 binder performs all error checks but does not generate an output file.
16284 @geindex -e (gnatbind)
16288 Output complete list of elaboration-order dependencies, showing the
16289 reason for each dependency. This output can be rather extensive but may
16290 be useful in diagnosing problems with elaboration order. The output is
16291 written to @code{stdout}.
16293 @geindex -h (gnatbind)
16297 Output usage information. The output is written to @code{stdout}.
16299 @geindex -K (gnatbind)
16303 Output linker options to @code{stdout}. Includes library search paths,
16304 contents of pragmas Ident and Linker_Options, and libraries added
16305 by @code{gnatbind}.
16307 @geindex -l (gnatbind)
16311 Output chosen elaboration order. The output is written to @code{stdout}.
16313 @geindex -O (gnatbind)
16317 Output full names of all the object files that must be linked to provide
16318 the Ada component of the program. The output is written to @code{stdout}.
16319 This list includes the files explicitly supplied and referenced by the user
16320 as well as implicitly referenced run-time unit files. The latter are
16321 omitted if the corresponding units reside in shared libraries. The
16322 directory names for the run-time units depend on the system configuration.
16324 @geindex -o (gnatbind)
16326 @item @code{-o @emph{file}}
16328 Set name of output file to @code{file} instead of the normal
16329 @code{b~`mainprog}.adb` default. Note that @code{file} denote the Ada
16330 binder generated body filename.
16331 Note that if this option is used, then linking must be done manually.
16332 It is not possible to use gnatlink in this case, since it cannot locate
16335 @geindex -r (gnatbind)
16339 Generate list of @code{pragma Restrictions} that could be applied to
16340 the current unit. This is useful for code audit purposes, and also may
16341 be used to improve code generation in some cases.
16344 @node Dynamic Allocation Control,Binding with Non-Ada Main Programs,Output Control,Switches for gnatbind
16345 @anchor{gnat_ugn/building_executable_programs_with_gnat dynamic-allocation-control}@anchor{120}@anchor{gnat_ugn/building_executable_programs_with_gnat id39}@anchor{12a}
16346 @subsubsection Dynamic Allocation Control
16349 The heap control switches -- @code{-H32} and @code{-H64} --
16350 determine whether dynamic allocation uses 32-bit or 64-bit memory.
16351 They only affect compiler-generated allocations via @code{__gnat_malloc};
16352 explicit calls to @code{malloc} and related functions from the C
16353 run-time library are unaffected.
16360 Allocate memory on 32-bit heap
16364 Allocate memory on 64-bit heap. This is the default
16365 unless explicitly overridden by a @code{'Size} clause on the access type.
16368 These switches are only effective on VMS platforms.
16370 @node Binding with Non-Ada Main Programs,Binding Programs with No Main Subprogram,Dynamic Allocation Control,Switches for gnatbind
16371 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-with-non-ada-main-programs}@anchor{b4}@anchor{gnat_ugn/building_executable_programs_with_gnat id40}@anchor{12b}
16372 @subsubsection Binding with Non-Ada Main Programs
16375 The description so far has assumed that the main
16376 program is in Ada, and that the task of the binder is to generate a
16377 corresponding function @code{main} that invokes this Ada main
16378 program. GNAT also supports the building of executable programs where
16379 the main program is not in Ada, but some of the called routines are
16380 written in Ada and compiled using GNAT (@ref{44,,Mixed Language Programming}).
16381 The following switch is used in this situation:
16385 @geindex -n (gnatbind)
16393 No main program. The main program is not in Ada.
16396 In this case, most of the functions of the binder are still required,
16397 but instead of generating a main program, the binder generates a file
16398 containing the following callable routines:
16407 @item @code{adainit}
16409 You must call this routine to initialize the Ada part of the program by
16410 calling the necessary elaboration routines. A call to @code{adainit} is
16411 required before the first call to an Ada subprogram.
16413 Note that it is assumed that the basic execution environment must be setup
16414 to be appropriate for Ada execution at the point where the first Ada
16415 subprogram is called. In particular, if the Ada code will do any
16416 floating-point operations, then the FPU must be setup in an appropriate
16417 manner. For the case of the x86, for example, full precision mode is
16418 required. The procedure GNAT.Float_Control.Reset may be used to ensure
16419 that the FPU is in the right state.
16427 @item @code{adafinal}
16429 You must call this routine to perform any library-level finalization
16430 required by the Ada subprograms. A call to @code{adafinal} is required
16431 after the last call to an Ada subprogram, and before the program
16436 @geindex -n (gnatbind)
16439 @geindex multiple input files
16441 If the @code{-n} switch
16442 is given, more than one ALI file may appear on
16443 the command line for @code{gnatbind}. The normal @code{closure}
16444 calculation is performed for each of the specified units. Calculating
16445 the closure means finding out the set of units involved by tracing
16446 @emph{with} references. The reason it is necessary to be able to
16447 specify more than one ALI file is that a given program may invoke two or
16448 more quite separate groups of Ada units.
16450 The binder takes the name of its output file from the last specified ALI
16451 file, unless overridden by the use of the @code{-o file}.
16453 @geindex -o (gnatbind)
16455 The output is an Ada unit in source form that can be compiled with GNAT.
16456 This compilation occurs automatically as part of the @code{gnatlink}
16459 Currently the GNAT run-time requires a FPU using 80 bits mode
16460 precision. Under targets where this is not the default it is required to
16461 call GNAT.Float_Control.Reset before using floating point numbers (this
16462 include float computation, float input and output) in the Ada code. A
16463 side effect is that this could be the wrong mode for the foreign code
16464 where floating point computation could be broken after this call.
16466 @node Binding Programs with No Main Subprogram,,Binding with Non-Ada Main Programs,Switches for gnatbind
16467 @anchor{gnat_ugn/building_executable_programs_with_gnat binding-programs-with-no-main-subprogram}@anchor{12c}@anchor{gnat_ugn/building_executable_programs_with_gnat id41}@anchor{12d}
16468 @subsubsection Binding Programs with No Main Subprogram
16471 It is possible to have an Ada program which does not have a main
16472 subprogram. This program will call the elaboration routines of all the
16473 packages, then the finalization routines.
16475 The following switch is used to bind programs organized in this manner:
16479 @geindex -z (gnatbind)
16487 Normally the binder checks that the unit name given on the command line
16488 corresponds to a suitable main subprogram. When this switch is used,
16489 a list of ALI files can be given, and the execution of the program
16490 consists of elaboration of these units in an appropriate order. Note
16491 that the default wide character encoding method for standard Text_IO
16492 files is always set to Brackets if this switch is set (you can use
16494 @code{-Wx} to override this default).
16497 @node Command-Line Access,Search Paths for gnatbind,Switches for gnatbind,Binding with gnatbind
16498 @anchor{gnat_ugn/building_executable_programs_with_gnat id42}@anchor{12e}@anchor{gnat_ugn/building_executable_programs_with_gnat command-line-access}@anchor{12f}
16499 @subsection Command-Line Access
16502 The package @code{Ada.Command_Line} provides access to the command-line
16503 arguments and program name. In order for this interface to operate
16504 correctly, the two variables
16515 are declared in one of the GNAT library routines. These variables must
16516 be set from the actual @code{argc} and @code{argv} values passed to the
16517 main program. With no @emph{n} present, @code{gnatbind}
16518 generates the C main program to automatically set these variables.
16519 If the @emph{n} switch is used, there is no automatic way to
16520 set these variables. If they are not set, the procedures in
16521 @code{Ada.Command_Line} will not be available, and any attempt to use
16522 them will raise @code{Constraint_Error}. If command line access is
16523 required, your main program must set @code{gnat_argc} and
16524 @code{gnat_argv} from the @code{argc} and @code{argv} values passed to
16527 @node Search Paths for gnatbind,Examples of gnatbind Usage,Command-Line Access,Binding with gnatbind
16528 @anchor{gnat_ugn/building_executable_programs_with_gnat search-paths-for-gnatbind}@anchor{8c}@anchor{gnat_ugn/building_executable_programs_with_gnat id43}@anchor{130}
16529 @subsection Search Paths for @code{gnatbind}
16532 The binder takes the name of an ALI file as its argument and needs to
16533 locate source files as well as other ALI files to verify object consistency.
16535 For source files, it follows exactly the same search rules as @code{gcc}
16536 (see @ref{89,,Search Paths and the Run-Time Library (RTL)}). For ALI files the
16537 directories searched are:
16543 The directory containing the ALI file named in the command line, unless
16544 the switch @code{-I-} is specified.
16547 All directories specified by @code{-I}
16548 switches on the @code{gnatbind}
16549 command line, in the order given.
16551 @geindex ADA_PRJ_OBJECTS_FILE
16554 Each of the directories listed in the text file whose name is given
16556 @geindex ADA_PRJ_OBJECTS_FILE
16557 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16558 @code{ADA_PRJ_OBJECTS_FILE} environment variable.
16560 @geindex ADA_PRJ_OBJECTS_FILE
16561 @geindex environment variable; ADA_PRJ_OBJECTS_FILE
16562 @code{ADA_PRJ_OBJECTS_FILE} is normally set by gnatmake or by the gnat
16563 driver when project files are used. It should not normally be set
16566 @geindex ADA_OBJECTS_PATH
16569 Each of the directories listed in the value of the
16570 @geindex ADA_OBJECTS_PATH
16571 @geindex environment variable; ADA_OBJECTS_PATH
16572 @code{ADA_OBJECTS_PATH} environment variable.
16573 Construct this value
16576 @geindex environment variable; PATH
16577 @code{PATH} environment variable: a list of directory
16578 names separated by colons (semicolons when working with the NT version
16582 The content of the @code{ada_object_path} file which is part of the GNAT
16583 installation tree and is used to store standard libraries such as the
16584 GNAT Run-Time Library (RTL) unless the switch @code{-nostdlib} is
16585 specified. See @ref{87,,Installing a library}
16588 @geindex -I (gnatbind)
16590 @geindex -aI (gnatbind)
16592 @geindex -aO (gnatbind)
16594 In the binder the switch @code{-I}
16595 is used to specify both source and
16596 library file paths. Use @code{-aI}
16597 instead if you want to specify
16598 source paths only, and @code{-aO}
16599 if you want to specify library paths
16600 only. This means that for the binder
16601 @code{-I@emph{dir}} is equivalent to
16602 @code{-aI@emph{dir}}
16603 @code{-aO`@emph{dir}}.
16604 The binder generates the bind file (a C language source file) in the
16605 current working directory.
16611 @geindex Interfaces
16615 The packages @code{Ada}, @code{System}, and @code{Interfaces} and their
16616 children make up the GNAT Run-Time Library, together with the package
16617 GNAT and its children, which contain a set of useful additional
16618 library functions provided by GNAT. The sources for these units are
16619 needed by the compiler and are kept together in one directory. The ALI
16620 files and object files generated by compiling the RTL are needed by the
16621 binder and the linker and are kept together in one directory, typically
16622 different from the directory containing the sources. In a normal
16623 installation, you need not specify these directory names when compiling
16624 or binding. Either the environment variables or the built-in defaults
16625 cause these files to be found.
16627 Besides simplifying access to the RTL, a major use of search paths is
16628 in compiling sources from multiple directories. This can make
16629 development environments much more flexible.
16631 @node Examples of gnatbind Usage,,Search Paths for gnatbind,Binding with gnatbind
16632 @anchor{gnat_ugn/building_executable_programs_with_gnat id44}@anchor{131}@anchor{gnat_ugn/building_executable_programs_with_gnat examples-of-gnatbind-usage}@anchor{132}
16633 @subsection Examples of @code{gnatbind} Usage
16636 Here are some examples of @code{gnatbind} invovations:
16644 The main program @code{Hello} (source program in @code{hello.adb}) is
16645 bound using the standard switch settings. The generated main program is
16646 @code{b~hello.adb}. This is the normal, default use of the binder.
16649 gnatbind hello -o mainprog.adb
16652 The main program @code{Hello} (source program in @code{hello.adb}) is
16653 bound using the standard switch settings. The generated main program is
16654 @code{mainprog.adb} with the associated spec in
16655 @code{mainprog.ads}. Note that you must specify the body here not the
16656 spec. Note that if this option is used, then linking must be done manually,
16657 since gnatlink will not be able to find the generated file.
16660 @node Linking with gnatlink,Using the GNU make Utility,Binding with gnatbind,Building Executable Programs with GNAT
16661 @anchor{gnat_ugn/building_executable_programs_with_gnat id45}@anchor{133}@anchor{gnat_ugn/building_executable_programs_with_gnat linking-with-gnatlink}@anchor{1e}
16662 @section Linking with @code{gnatlink}
16667 This chapter discusses @code{gnatlink}, a tool that links
16668 an Ada program and builds an executable file. This utility
16669 invokes the system linker (via the @code{gcc} command)
16670 with a correct list of object files and library references.
16671 @code{gnatlink} automatically determines the list of files and
16672 references for the Ada part of a program. It uses the binder file
16673 generated by the @code{gnatbind} to determine this list.
16676 * Running gnatlink::
16677 * Switches for gnatlink::
16681 @node Running gnatlink,Switches for gnatlink,,Linking with gnatlink
16682 @anchor{gnat_ugn/building_executable_programs_with_gnat id46}@anchor{134}@anchor{gnat_ugn/building_executable_programs_with_gnat running-gnatlink}@anchor{135}
16683 @subsection Running @code{gnatlink}
16686 The form of the @code{gnatlink} command is
16689 $ gnatlink [ switches ] mainprog [.ali]
16690 [ non-Ada objects ] [ linker options ]
16693 The arguments of @code{gnatlink} (switches, main @code{ALI} file,
16695 or linker options) may be in any order, provided that no non-Ada object may
16696 be mistaken for a main @code{ALI} file.
16697 Any file name @code{F} without the @code{.ali}
16698 extension will be taken as the main @code{ALI} file if a file exists
16699 whose name is the concatenation of @code{F} and @code{.ali}.
16701 @code{mainprog.ali} references the ALI file of the main program.
16702 The @code{.ali} extension of this file can be omitted. From this
16703 reference, @code{gnatlink} locates the corresponding binder file
16704 @code{b~mainprog.adb} and, using the information in this file along
16705 with the list of non-Ada objects and linker options, constructs a
16706 linker command file to create the executable.
16708 The arguments other than the @code{gnatlink} switches and the main
16709 @code{ALI} file are passed to the linker uninterpreted.
16710 They typically include the names of
16711 object files for units written in other languages than Ada and any library
16712 references required to resolve references in any of these foreign language
16713 units, or in @code{Import} pragmas in any Ada units.
16715 @code{linker options} is an optional list of linker specific
16717 The default linker called by gnatlink is @code{gcc} which in
16718 turn calls the appropriate system linker.
16720 One useful option for the linker is @code{-s}: it reduces the size of the
16721 executable by removing all symbol table and relocation information from the
16724 Standard options for the linker such as @code{-lmy_lib} or
16725 @code{-Ldir} can be added as is.
16726 For options that are not recognized by
16727 @code{gcc} as linker options, use the @code{gcc} switches
16728 @code{-Xlinker} or @code{-Wl,}.
16730 Refer to the GCC documentation for
16733 Here is an example showing how to generate a linker map:
16736 $ gnatlink my_prog -Wl,-Map,MAPFILE
16739 Using @code{linker options} it is possible to set the program stack and
16741 See @ref{136,,Setting Stack Size from gnatlink} and
16742 @ref{137,,Setting Heap Size from gnatlink}.
16744 @code{gnatlink} determines the list of objects required by the Ada
16745 program and prepends them to the list of objects passed to the linker.
16746 @code{gnatlink} also gathers any arguments set by the use of
16747 @code{pragma Linker_Options} and adds them to the list of arguments
16748 presented to the linker.
16750 @node Switches for gnatlink,,Running gnatlink,Linking with gnatlink
16751 @anchor{gnat_ugn/building_executable_programs_with_gnat id47}@anchor{138}@anchor{gnat_ugn/building_executable_programs_with_gnat switches-for-gnatlink}@anchor{139}
16752 @subsection Switches for @code{gnatlink}
16755 The following switches are available with the @code{gnatlink} utility:
16757 @geindex --version (gnatlink)
16762 @item @code{--version}
16764 Display Copyright and version, then exit disregarding all other options.
16767 @geindex --help (gnatlink)
16772 @item @code{--help}
16774 If @code{--version} was not used, display usage, then exit disregarding
16778 @geindex Command line length
16780 @geindex -f (gnatlink)
16787 On some targets, the command line length is limited, and @code{gnatlink}
16788 will generate a separate file for the linker if the list of object files
16790 The @code{-f} switch forces this file
16791 to be generated even if
16792 the limit is not exceeded. This is useful in some cases to deal with
16793 special situations where the command line length is exceeded.
16796 @geindex Debugging information
16799 @geindex -g (gnatlink)
16806 The option to include debugging information causes the Ada bind file (in
16807 other words, @code{b~mainprog.adb}) to be compiled with @code{-g}.
16808 In addition, the binder does not delete the @code{b~mainprog.adb},
16809 @code{b~mainprog.o} and @code{b~mainprog.ali} files.
16810 Without @code{-g}, the binder removes these files by default.
16813 @geindex -n (gnatlink)
16820 Do not compile the file generated by the binder. This may be used when
16821 a link is rerun with different options, but there is no need to recompile
16825 @geindex -v (gnatlink)
16832 Verbose mode. Causes additional information to be output, including a full
16833 list of the included object files.
16834 This switch option is most useful when you want
16835 to see what set of object files are being used in the link step.
16838 @geindex -v -v (gnatlink)
16845 Very verbose mode. Requests that the compiler operate in verbose mode when
16846 it compiles the binder file, and that the system linker run in verbose mode.
16849 @geindex -o (gnatlink)
16854 @item @code{-o @emph{exec-name}}
16856 @code{exec-name} specifies an alternate name for the generated
16857 executable program. If this switch is omitted, the executable has the same
16858 name as the main unit. For example, @code{gnatlink try.ali} creates
16859 an executable called @code{try}.
16862 @geindex -B (gnatlink)
16867 @item @code{-B@emph{dir}}
16869 Load compiler executables (for example, @code{gnat1}, the Ada compiler)
16870 from @code{dir} instead of the default location. Only use this switch
16871 when multiple versions of the GNAT compiler are available.
16872 See the @code{Directory Options} section in @cite{The_GNU_Compiler_Collection}
16873 for further details. You would normally use the @code{-b} or
16874 @code{-V} switch instead.
16877 @geindex -M (gnatlink)
16884 When linking an executable, create a map file. The name of the map file
16885 has the same name as the executable with extension ".map".
16888 @geindex -M= (gnatlink)
16893 @item @code{-M=@emph{mapfile}}
16895 When linking an executable, create a map file. The name of the map file is
16899 @geindex --GCC=compiler_name (gnatlink)
16904 @item @code{--GCC=@emph{compiler_name}}
16906 Program used for compiling the binder file. The default is
16907 @code{gcc}. You need to use quotes around @code{compiler_name} if
16908 @code{compiler_name} contains spaces or other separator characters.
16909 As an example @code{--GCC="foo -x -y"} will instruct @code{gnatlink} to
16910 use @code{foo -x -y} as your compiler. Note that switch @code{-c} is always
16911 inserted after your command name. Thus in the above example the compiler
16912 command that will be used by @code{gnatlink} will be @code{foo -c -x -y}.
16913 A limitation of this syntax is that the name and path name of the executable
16914 itself must not include any embedded spaces. If the compiler executable is
16915 different from the default one (gcc or <prefix>-gcc), then the back-end
16916 switches in the ALI file are not used to compile the binder generated source.
16917 For example, this is the case with @code{--GCC="foo -x -y"}. But the back end
16918 switches will be used for @code{--GCC="gcc -gnatv"}. If several
16919 @code{--GCC=compiler_name} are used, only the last @code{compiler_name}
16920 is taken into account. However, all the additional switches are also taken
16921 into account. Thus,
16922 @code{--GCC="foo -x -y" --GCC="bar -z -t"} is equivalent to
16923 @code{--GCC="bar -x -y -z -t"}.
16926 @geindex --LINK= (gnatlink)
16931 @item @code{--LINK=@emph{name}}
16933 @code{name} is the name of the linker to be invoked. This is especially
16934 useful in mixed language programs since languages such as C++ require
16935 their own linker to be used. When this switch is omitted, the default
16936 name for the linker is @code{gcc}. When this switch is used, the
16937 specified linker is called instead of @code{gcc} with exactly the same
16938 parameters that would have been passed to @code{gcc} so if the desired
16939 linker requires different parameters it is necessary to use a wrapper
16940 script that massages the parameters before invoking the real linker. It
16941 may be useful to control the exact invocation by using the verbose
16945 @node Using the GNU make Utility,,Linking with gnatlink,Building Executable Programs with GNAT
16946 @anchor{gnat_ugn/building_executable_programs_with_gnat using-the-gnu-make-utility}@anchor{1f}@anchor{gnat_ugn/building_executable_programs_with_gnat id48}@anchor{13a}
16947 @section Using the GNU @code{make} Utility
16950 @geindex make (GNU)
16953 This chapter offers some examples of makefiles that solve specific
16954 problems. It does not explain how to write a makefile, nor does it try to replace the
16955 @code{gnatmake} utility (@ref{1b,,Building with gnatmake}).
16957 All the examples in this section are specific to the GNU version of
16958 make. Although @code{make} is a standard utility, and the basic language
16959 is the same, these examples use some advanced features found only in
16963 * Using gnatmake in a Makefile::
16964 * Automatically Creating a List of Directories::
16965 * Generating the Command Line Switches::
16966 * Overcoming Command Line Length Limits::
16970 @node Using gnatmake in a Makefile,Automatically Creating a List of Directories,,Using the GNU make Utility
16971 @anchor{gnat_ugn/building_executable_programs_with_gnat using-gnatmake-in-a-makefile}@anchor{13b}@anchor{gnat_ugn/building_executable_programs_with_gnat id49}@anchor{13c}
16972 @subsection Using gnatmake in a Makefile
16975 @c index makefile (GNU make)
16977 Complex project organizations can be handled in a very powerful way by
16978 using GNU make combined with gnatmake. For instance, here is a Makefile
16979 which allows you to build each subsystem of a big project into a separate
16980 shared library. Such a makefile allows you to significantly reduce the link
16981 time of very big applications while maintaining full coherence at
16982 each step of the build process.
16984 The list of dependencies are handled automatically by
16985 @code{gnatmake}. The Makefile is simply used to call gnatmake in each of
16986 the appropriate directories.
16988 Note that you should also read the example on how to automatically
16989 create the list of directories
16990 (@ref{13d,,Automatically Creating a List of Directories})
16991 which might help you in case your project has a lot of subdirectories.
16994 ## This Makefile is intended to be used with the following directory
16996 ## - The sources are split into a series of csc (computer software components)
16997 ## Each of these csc is put in its own directory.
16998 ## Their name are referenced by the directory names.
16999 ## They will be compiled into shared library (although this would also work
17000 ## with static libraries
17001 ## - The main program (and possibly other packages that do not belong to any
17002 ## csc is put in the top level directory (where the Makefile is).
17003 ## toplevel_dir __ first_csc (sources) __ lib (will contain the library)
17004 ## \\_ second_csc (sources) __ lib (will contain the library)
17006 ## Although this Makefile is build for shared library, it is easy to modify
17007 ## to build partial link objects instead (modify the lines with -shared and
17010 ## With this makefile, you can change any file in the system or add any new
17011 ## file, and everything will be recompiled correctly (only the relevant shared
17012 ## objects will be recompiled, and the main program will be re-linked).
17014 # The list of computer software component for your project. This might be
17015 # generated automatically.
17018 # Name of the main program (no extension)
17021 # If we need to build objects with -fPIC, uncomment the following line
17024 # The following variable should give the directory containing libgnat.so
17025 # You can get this directory through 'gnatls -v'. This is usually the last
17026 # directory in the Object_Path.
17029 # The directories for the libraries
17030 # (This macro expands the list of CSC to the list of shared libraries, you
17031 # could simply use the expanded form:
17032 # LIB_DIR=aa/lib/libaa.so bb/lib/libbb.so cc/lib/libcc.so
17033 LIB_DIR=$@{foreach dir,$@{CSC_LIST@},$@{dir@}/lib/lib$@{dir@}.so@}
17035 $@{MAIN@}: objects $@{LIB_DIR@}
17036 gnatbind $@{MAIN@} $@{CSC_LIST:%=-aO%/lib@} -shared
17037 gnatlink $@{MAIN@} $@{CSC_LIST:%=-l%@}
17040 # recompile the sources
17041 gnatmake -c -i $@{MAIN@}.adb $@{NEED_FPIC@} $@{CSC_LIST:%=-I%@}
17043 # Note: In a future version of GNAT, the following commands will be simplified
17044 # by a new tool, gnatmlib
17046 mkdir -p $@{dir $@@ @}
17047 cd $@{dir $@@ @} && gcc -shared -o $@{notdir $@@ @} ../*.o -L$@{GLIB@} -lgnat
17048 cd $@{dir $@@ @} && cp -f ../*.ali .
17050 # The dependencies for the modules
17051 # Note that we have to force the expansion of *.o, since in some cases
17052 # make won't be able to do it itself.
17053 aa/lib/libaa.so: $@{wildcard aa/*.o@}
17054 bb/lib/libbb.so: $@{wildcard bb/*.o@}
17055 cc/lib/libcc.so: $@{wildcard cc/*.o@}
17057 # Make sure all of the shared libraries are in the path before starting the
17060 LD_LIBRARY_PATH=`pwd`/aa/lib:`pwd`/bb/lib:`pwd`/cc/lib ./$@{MAIN@}
17063 $@{RM@} -rf $@{CSC_LIST:%=%/lib@}
17064 $@{RM@} $@{CSC_LIST:%=%/*.ali@}
17065 $@{RM@} $@{CSC_LIST:%=%/*.o@}
17066 $@{RM@} *.o *.ali $@{MAIN@}
17069 @node Automatically Creating a List of Directories,Generating the Command Line Switches,Using gnatmake in a Makefile,Using the GNU make Utility
17070 @anchor{gnat_ugn/building_executable_programs_with_gnat id50}@anchor{13e}@anchor{gnat_ugn/building_executable_programs_with_gnat automatically-creating-a-list-of-directories}@anchor{13d}
17071 @subsection Automatically Creating a List of Directories
17074 In most makefiles, you will have to specify a list of directories, and
17075 store it in a variable. For small projects, it is often easier to
17076 specify each of them by hand, since you then have full control over what
17077 is the proper order for these directories, which ones should be
17080 However, in larger projects, which might involve hundreds of
17081 subdirectories, it might be more convenient to generate this list
17084 The example below presents two methods. The first one, although less
17085 general, gives you more control over the list. It involves wildcard
17086 characters, that are automatically expanded by @code{make}. Its
17087 shortcoming is that you need to explicitly specify some of the
17088 organization of your project, such as for instance the directory tree
17089 depth, whether some directories are found in a separate tree, etc.
17091 The second method is the most general one. It requires an external
17092 program, called @code{find}, which is standard on all Unix systems. All
17093 the directories found under a given root directory will be added to the
17097 # The examples below are based on the following directory hierarchy:
17098 # All the directories can contain any number of files
17099 # ROOT_DIRECTORY -> a -> aa -> aaa
17102 # -> b -> ba -> baa
17105 # This Makefile creates a variable called DIRS, that can be reused any time
17106 # you need this list (see the other examples in this section)
17108 # The root of your project's directory hierarchy
17112 # First method: specify explicitly the list of directories
17113 # This allows you to specify any subset of all the directories you need.
17116 DIRS := a/aa/ a/ab/ b/ba/
17119 # Second method: use wildcards
17120 # Note that the argument(s) to wildcard below should end with a '/'.
17121 # Since wildcards also return file names, we have to filter them out
17122 # to avoid duplicate directory names.
17123 # We thus use make's `@w{`}dir`@w{`} and `@w{`}sort`@w{`} functions.
17124 # It sets DIRs to the following value (note that the directories aaa and baa
17125 # are not given, unless you change the arguments to wildcard).
17126 # DIRS= ./a/a/ ./b/ ./a/aa/ ./a/ab/ ./a/ac/ ./b/ba/ ./b/bb/ ./b/bc/
17129 DIRS := $@{sort $@{dir $@{wildcard $@{ROOT_DIRECTORY@}/*/
17130 $@{ROOT_DIRECTORY@}/*/*/@}@}@}
17133 # Third method: use an external program
17134 # This command is much faster if run on local disks, avoiding NFS slowdowns.
17135 # This is the most complete command: it sets DIRs to the following value:
17136 # DIRS= ./a ./a/aa ./a/aa/aaa ./a/ab ./a/ac ./b ./b/ba ./b/ba/baa ./b/bb ./b/bc
17139 DIRS := $@{shell find $@{ROOT_DIRECTORY@} -type d -print@}
17142 @node Generating the Command Line Switches,Overcoming Command Line Length Limits,Automatically Creating a List of Directories,Using the GNU make Utility
17143 @anchor{gnat_ugn/building_executable_programs_with_gnat id51}@anchor{13f}@anchor{gnat_ugn/building_executable_programs_with_gnat generating-the-command-line-switches}@anchor{140}
17144 @subsection Generating the Command Line Switches
17147 Once you have created the list of directories as explained in the
17148 previous section (@ref{13d,,Automatically Creating a List of Directories}),
17149 you can easily generate the command line arguments to pass to gnatmake.
17151 For the sake of completeness, this example assumes that the source path
17152 is not the same as the object path, and that you have two separate lists
17156 # see "Automatically creating a list of directories" to create
17161 GNATMAKE_SWITCHES := $@{patsubst %,-aI%,$@{SOURCE_DIRS@}@}
17162 GNATMAKE_SWITCHES += $@{patsubst %,-aO%,$@{OBJECT_DIRS@}@}
17165 gnatmake $@{GNATMAKE_SWITCHES@} main_unit
17168 @node Overcoming Command Line Length Limits,,Generating the Command Line Switches,Using the GNU make Utility
17169 @anchor{gnat_ugn/building_executable_programs_with_gnat overcoming-command-line-length-limits}@anchor{141}@anchor{gnat_ugn/building_executable_programs_with_gnat id52}@anchor{142}
17170 @subsection Overcoming Command Line Length Limits
17173 One problem that might be encountered on big projects is that many
17174 operating systems limit the length of the command line. It is thus hard to give
17175 gnatmake the list of source and object directories.
17177 This example shows how you can set up environment variables, which will
17178 make @code{gnatmake} behave exactly as if the directories had been
17179 specified on the command line, but have a much higher length limit (or
17180 even none on most systems).
17182 It assumes that you have created a list of directories in your Makefile,
17183 using one of the methods presented in
17184 @ref{13d,,Automatically Creating a List of Directories}.
17185 For the sake of completeness, we assume that the object
17186 path (where the ALI files are found) is different from the sources patch.
17188 Note a small trick in the Makefile below: for efficiency reasons, we
17189 create two temporary variables (SOURCE_LIST and OBJECT_LIST), that are
17190 expanded immediately by @code{make}. This way we overcome the standard
17191 make behavior which is to expand the variables only when they are
17194 On Windows, if you are using the standard Windows command shell, you must
17195 replace colons with semicolons in the assignments to these variables.
17198 # In this example, we create both ADA_INCLUDE_PATH and ADA_OBJECTS_PATH.
17199 # This is the same thing as putting the -I arguments on the command line.
17200 # (the equivalent of using -aI on the command line would be to define
17201 # only ADA_INCLUDE_PATH, the equivalent of -aO is ADA_OBJECTS_PATH).
17202 # You can of course have different values for these variables.
17204 # Note also that we need to keep the previous values of these variables, since
17205 # they might have been set before running 'make' to specify where the GNAT
17206 # library is installed.
17208 # see "Automatically creating a list of directories" to create these
17214 space:=$@{empty@} $@{empty@}
17215 SOURCE_LIST := $@{subst $@{space@},:,$@{SOURCE_DIRS@}@}
17216 OBJECT_LIST := $@{subst $@{space@},:,$@{OBJECT_DIRS@}@}
17217 ADA_INCLUDE_PATH += $@{SOURCE_LIST@}
17218 ADA_OBJECTS_PATH += $@{OBJECT_LIST@}
17219 export ADA_INCLUDE_PATH
17220 export ADA_OBJECTS_PATH
17226 @node GNAT Utility Programs,GNAT and Program Execution,Building Executable Programs with GNAT,Top
17227 @anchor{gnat_ugn/gnat_utility_programs doc}@anchor{143}@anchor{gnat_ugn/gnat_utility_programs gnat-utility-programs}@anchor{b}@anchor{gnat_ugn/gnat_utility_programs id1}@anchor{144}
17228 @chapter GNAT Utility Programs
17231 This chapter describes a number of utility programs:
17238 @ref{20,,The File Cleanup Utility gnatclean}
17241 @ref{21,,The GNAT Library Browser gnatls}
17244 @ref{22,,The Cross-Referencing Tools gnatxref and gnatfind}
17247 @ref{23,,The Ada to HTML Converter gnathtml}
17250 Other GNAT utilities are described elsewhere in this manual:
17256 @ref{59,,Handling Arbitrary File Naming Conventions with gnatname}
17259 @ref{63,,File Name Krunching with gnatkr}
17262 @ref{36,,Renaming Files with gnatchop}
17265 @ref{17,,Preprocessing with gnatprep}
17269 * The File Cleanup Utility gnatclean::
17270 * The GNAT Library Browser gnatls::
17271 * The Cross-Referencing Tools gnatxref and gnatfind::
17272 * The Ada to HTML Converter gnathtml::
17276 @node The File Cleanup Utility gnatclean,The GNAT Library Browser gnatls,,GNAT Utility Programs
17277 @anchor{gnat_ugn/gnat_utility_programs id2}@anchor{145}@anchor{gnat_ugn/gnat_utility_programs the-file-cleanup-utility-gnatclean}@anchor{20}
17278 @section The File Cleanup Utility @code{gnatclean}
17281 @geindex File cleanup tool
17285 @code{gnatclean} is a tool that allows the deletion of files produced by the
17286 compiler, binder and linker, including ALI files, object files, tree files,
17287 expanded source files, library files, interface copy source files, binder
17288 generated files and executable files.
17291 * Running gnatclean::
17292 * Switches for gnatclean::
17296 @node Running gnatclean,Switches for gnatclean,,The File Cleanup Utility gnatclean
17297 @anchor{gnat_ugn/gnat_utility_programs running-gnatclean}@anchor{146}@anchor{gnat_ugn/gnat_utility_programs id3}@anchor{147}
17298 @subsection Running @code{gnatclean}
17301 The @code{gnatclean} command has the form:
17306 $ gnatclean switches names
17310 where @code{names} is a list of source file names. Suffixes @code{.ads} and
17311 @code{adb} may be omitted. If a project file is specified using switch
17312 @code{-P}, then @code{names} may be completely omitted.
17314 In normal mode, @code{gnatclean} delete the files produced by the compiler and,
17315 if switch @code{-c} is not specified, by the binder and
17316 the linker. In informative-only mode, specified by switch
17317 @code{-n}, the list of files that would have been deleted in
17318 normal mode is listed, but no file is actually deleted.
17320 @node Switches for gnatclean,,Running gnatclean,The File Cleanup Utility gnatclean
17321 @anchor{gnat_ugn/gnat_utility_programs id4}@anchor{148}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatclean}@anchor{149}
17322 @subsection Switches for @code{gnatclean}
17325 @code{gnatclean} recognizes the following switches:
17327 @geindex --version (gnatclean)
17332 @item @code{--version}
17334 Display Copyright and version, then exit disregarding all other options.
17337 @geindex --help (gnatclean)
17342 @item @code{--help}
17344 If @code{--version} was not used, display usage, then exit disregarding
17347 @item @code{--subdirs=@emph{subdir}}
17349 Actual object directory of each project file is the subdirectory subdir of the
17350 object directory specified or defaulted in the project file.
17352 @item @code{--unchecked-shared-lib-imports}
17354 By default, shared library projects are not allowed to import static library
17355 projects. When this switch is used on the command line, this restriction is
17359 @geindex -c (gnatclean)
17366 Only attempt to delete the files produced by the compiler, not those produced
17367 by the binder or the linker. The files that are not to be deleted are library
17368 files, interface copy files, binder generated files and executable files.
17371 @geindex -D (gnatclean)
17376 @item @code{-D @emph{dir}}
17378 Indicate that ALI and object files should normally be found in directory @code{dir}.
17381 @geindex -F (gnatclean)
17388 When using project files, if some errors or warnings are detected during
17389 parsing and verbose mode is not in effect (no use of switch
17390 -v), then error lines start with the full path name of the project
17391 file, rather than its simple file name.
17394 @geindex -h (gnatclean)
17401 Output a message explaining the usage of @code{gnatclean}.
17404 @geindex -n (gnatclean)
17411 Informative-only mode. Do not delete any files. Output the list of the files
17412 that would have been deleted if this switch was not specified.
17415 @geindex -P (gnatclean)
17420 @item @code{-P@emph{project}}
17422 Use project file @code{project}. Only one such switch can be used.
17423 When cleaning a project file, the files produced by the compilation of the
17424 immediate sources or inherited sources of the project files are to be
17425 deleted. This is not depending on the presence or not of executable names
17426 on the command line.
17429 @geindex -q (gnatclean)
17436 Quiet output. If there are no errors, do not output anything, except in
17437 verbose mode (switch -v) or in informative-only mode
17441 @geindex -r (gnatclean)
17448 When a project file is specified (using switch -P),
17449 clean all imported and extended project files, recursively. If this switch
17450 is not specified, only the files related to the main project file are to be
17451 deleted. This switch has no effect if no project file is specified.
17454 @geindex -v (gnatclean)
17464 @geindex -vP (gnatclean)
17469 @item @code{-vP@emph{x}}
17471 Indicates the verbosity of the parsing of GNAT project files.
17472 @ref{de,,Switches Related to Project Files}.
17475 @geindex -X (gnatclean)
17480 @item @code{-X@emph{name}=@emph{value}}
17482 Indicates that external variable @code{name} has the value @code{value}.
17483 The Project Manager will use this value for occurrences of
17484 @code{external(name)} when parsing the project file.
17485 See @ref{de,,Switches Related to Project Files}.
17488 @geindex -aO (gnatclean)
17493 @item @code{-aO@emph{dir}}
17495 When searching for ALI and object files, look in directory @code{dir}.
17498 @geindex -I (gnatclean)
17503 @item @code{-I@emph{dir}}
17505 Equivalent to @code{-aO@emph{dir}}.
17508 @geindex -I- (gnatclean)
17510 @geindex Source files
17511 @geindex suppressing search
17518 Do not look for ALI or object files in the directory
17519 where @code{gnatclean} was invoked.
17522 @node The GNAT Library Browser gnatls,The Cross-Referencing Tools gnatxref and gnatfind,The File Cleanup Utility gnatclean,GNAT Utility Programs
17523 @anchor{gnat_ugn/gnat_utility_programs the-gnat-library-browser-gnatls}@anchor{21}@anchor{gnat_ugn/gnat_utility_programs id5}@anchor{14a}
17524 @section The GNAT Library Browser @code{gnatls}
17527 @geindex Library browser
17531 @code{gnatls} is a tool that outputs information about compiled
17532 units. It gives the relationship between objects, unit names and source
17533 files. It can also be used to check the source dependencies of a unit
17534 as well as various characteristics.
17538 * Switches for gnatls::
17539 * Example of gnatls Usage::
17543 @node Running gnatls,Switches for gnatls,,The GNAT Library Browser gnatls
17544 @anchor{gnat_ugn/gnat_utility_programs id6}@anchor{14b}@anchor{gnat_ugn/gnat_utility_programs running-gnatls}@anchor{14c}
17545 @subsection Running @code{gnatls}
17548 The @code{gnatls} command has the form
17553 $ gnatls switches object_or_ali_file
17557 The main argument is the list of object or @code{ali} files
17558 (see @ref{42,,The Ada Library Information Files})
17559 for which information is requested.
17561 In normal mode, without additional option, @code{gnatls} produces a
17562 four-column listing. Each line represents information for a specific
17563 object. The first column gives the full path of the object, the second
17564 column gives the name of the principal unit in this object, the third
17565 column gives the status of the source and the fourth column gives the
17566 full path of the source representing this unit.
17567 Here is a simple example of use:
17573 ./demo1.o demo1 DIF demo1.adb
17574 ./demo2.o demo2 OK demo2.adb
17575 ./hello.o h1 OK hello.adb
17576 ./instr-child.o instr.child MOK instr-child.adb
17577 ./instr.o instr OK instr.adb
17578 ./tef.o tef DIF tef.adb
17579 ./text_io_example.o text_io_example OK text_io_example.adb
17580 ./tgef.o tgef DIF tgef.adb
17584 The first line can be interpreted as follows: the main unit which is
17586 object file @code{demo1.o} is demo1, whose main source is in
17587 @code{demo1.adb}. Furthermore, the version of the source used for the
17588 compilation of demo1 has been modified (DIF). Each source file has a status
17589 qualifier which can be:
17594 @item @emph{OK (unchanged)}
17596 The version of the source file used for the compilation of the
17597 specified unit corresponds exactly to the actual source file.
17599 @item @emph{MOK (slightly modified)}
17601 The version of the source file used for the compilation of the
17602 specified unit differs from the actual source file but not enough to
17603 require recompilation. If you use gnatmake with the option
17604 @code{-m} (minimal recompilation), a file marked
17605 MOK will not be recompiled.
17607 @item @emph{DIF (modified)}
17609 No version of the source found on the path corresponds to the source
17610 used to build this object.
17612 @item @emph{??? (file not found)}
17614 No source file was found for this unit.
17616 @item @emph{HID (hidden, unchanged version not first on PATH)}
17618 The version of the source that corresponds exactly to the source used
17619 for compilation has been found on the path but it is hidden by another
17620 version of the same source that has been modified.
17623 @node Switches for gnatls,Example of gnatls Usage,Running gnatls,The GNAT Library Browser gnatls
17624 @anchor{gnat_ugn/gnat_utility_programs id7}@anchor{14d}@anchor{gnat_ugn/gnat_utility_programs switches-for-gnatls}@anchor{14e}
17625 @subsection Switches for @code{gnatls}
17628 @code{gnatls} recognizes the following switches:
17630 @geindex --version (gnatls)
17635 @item @code{--version}
17637 Display Copyright and version, then exit disregarding all other options.
17640 @geindex --help (gnatls)
17645 @item @code{--help}
17647 If @code{--version} was not used, display usage, then exit disregarding
17651 @geindex -a (gnatls)
17658 Consider all units, including those of the predefined Ada library.
17659 Especially useful with @code{-d}.
17662 @geindex -d (gnatls)
17669 List sources from which specified units depend on.
17672 @geindex -h (gnatls)
17679 Output the list of options.
17682 @geindex -o (gnatls)
17689 Only output information about object files.
17692 @geindex -s (gnatls)
17699 Only output information about source files.
17702 @geindex -u (gnatls)
17709 Only output information about compilation units.
17712 @geindex -files (gnatls)
17717 @item @code{-files=@emph{file}}
17719 Take as arguments the files listed in text file @code{file}.
17720 Text file @code{file} may contain empty lines that are ignored.
17721 Each nonempty line should contain the name of an existing file.
17722 Several such switches may be specified simultaneously.
17725 @geindex -aO (gnatls)
17727 @geindex -aI (gnatls)
17729 @geindex -I (gnatls)
17731 @geindex -I- (gnatls)
17736 @item @code{-aO@emph{dir}}, @code{-aI@emph{dir}}, @code{-I@emph{dir}}, @code{-I-}, @code{-nostdinc}
17738 Source path manipulation. Same meaning as the equivalent @code{gnatmake}
17739 flags (@ref{dc,,Switches for gnatmake}).
17742 @geindex -aP (gnatls)
17747 @item @code{-aP@emph{dir}}
17749 Add @code{dir} at the beginning of the project search dir.
17752 @geindex --RTS (gnatls)
17757 @item @code{--RTS=@emph{rts-path}}
17759 Specifies the default location of the runtime library. Same meaning as the
17760 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
17763 @geindex -v (gnatls)
17770 Verbose mode. Output the complete source, object and project paths. Do not use
17771 the default column layout but instead use long format giving as much as
17772 information possible on each requested units, including special
17773 characteristics such as:
17779 @emph{Preelaborable}: The unit is preelaborable in the Ada sense.
17782 @emph{No_Elab_Code}: No elaboration code has been produced by the compiler for this unit.
17785 @emph{Pure}: The unit is pure in the Ada sense.
17788 @emph{Elaborate_Body}: The unit contains a pragma Elaborate_Body.
17791 @emph{Remote_Types}: The unit contains a pragma Remote_Types.
17794 @emph{Shared_Passive}: The unit contains a pragma Shared_Passive.
17797 @emph{Predefined}: This unit is part of the predefined environment and cannot be modified
17801 @emph{Remote_Call_Interface}: The unit contains a pragma Remote_Call_Interface.
17805 @node Example of gnatls Usage,,Switches for gnatls,The GNAT Library Browser gnatls
17806 @anchor{gnat_ugn/gnat_utility_programs id8}@anchor{14f}@anchor{gnat_ugn/gnat_utility_programs example-of-gnatls-usage}@anchor{150}
17807 @subsection Example of @code{gnatls} Usage
17810 Example of using the verbose switch. Note how the source and
17811 object paths are affected by the -I switch.
17816 $ gnatls -v -I.. demo1.o
17818 GNATLS 5.03w (20041123-34)
17819 Copyright 1997-2004 Free Software Foundation, Inc.
17821 Source Search Path:
17822 <Current_Directory>
17824 /home/comar/local/adainclude/
17826 Object Search Path:
17827 <Current_Directory>
17829 /home/comar/local/lib/gcc-lib/x86-linux/3.4.3/adalib/
17831 Project Search Path:
17832 <Current_Directory>
17833 /home/comar/local/lib/gnat/
17838 Kind => subprogram body
17839 Flags => No_Elab_Code
17840 Source => demo1.adb modified
17844 The following is an example of use of the dependency list.
17845 Note the use of the -s switch
17846 which gives a straight list of source files. This can be useful for
17847 building specialized scripts.
17852 $ gnatls -d demo2.o
17853 ./demo2.o demo2 OK demo2.adb
17859 $ gnatls -d -s -a demo1.o
17861 /home/comar/local/adainclude/ada.ads
17862 /home/comar/local/adainclude/a-finali.ads
17863 /home/comar/local/adainclude/a-filico.ads
17864 /home/comar/local/adainclude/a-stream.ads
17865 /home/comar/local/adainclude/a-tags.ads
17868 /home/comar/local/adainclude/gnat.ads
17869 /home/comar/local/adainclude/g-io.ads
17871 /home/comar/local/adainclude/system.ads
17872 /home/comar/local/adainclude/s-exctab.ads
17873 /home/comar/local/adainclude/s-finimp.ads
17874 /home/comar/local/adainclude/s-finroo.ads
17875 /home/comar/local/adainclude/s-secsta.ads
17876 /home/comar/local/adainclude/s-stalib.ads
17877 /home/comar/local/adainclude/s-stoele.ads
17878 /home/comar/local/adainclude/s-stratt.ads
17879 /home/comar/local/adainclude/s-tasoli.ads
17880 /home/comar/local/adainclude/s-unstyp.ads
17881 /home/comar/local/adainclude/unchconv.ads
17885 @node The Cross-Referencing Tools gnatxref and gnatfind,The Ada to HTML Converter gnathtml,The GNAT Library Browser gnatls,GNAT Utility Programs
17886 @anchor{gnat_ugn/gnat_utility_programs the-cross-referencing-tools-gnatxref-and-gnatfind}@anchor{22}@anchor{gnat_ugn/gnat_utility_programs id9}@anchor{151}
17887 @section The Cross-Referencing Tools @code{gnatxref} and @code{gnatfind}
17894 The compiler generates cross-referencing information (unless
17895 you set the @code{-gnatx} switch), which are saved in the @code{.ali} files.
17896 This information indicates where in the source each entity is declared and
17897 referenced. Note that entities in package Standard are not included, but
17898 entities in all other predefined units are included in the output.
17900 Before using any of these two tools, you need to compile successfully your
17901 application, so that GNAT gets a chance to generate the cross-referencing
17904 The two tools @code{gnatxref} and @code{gnatfind} take advantage of this
17905 information to provide the user with the capability to easily locate the
17906 declaration and references to an entity. These tools are quite similar,
17907 the difference being that @code{gnatfind} is intended for locating
17908 definitions and/or references to a specified entity or entities, whereas
17909 @code{gnatxref} is oriented to generating a full report of all
17912 To use these tools, you must not compile your application using the
17913 @code{-gnatx} switch on the @code{gnatmake} command line
17914 (see @ref{1b,,Building with gnatmake}). Otherwise, cross-referencing
17915 information will not be generated.
17918 * gnatxref Switches::
17919 * gnatfind Switches::
17920 * Configuration Files for gnatxref and gnatfind::
17921 * Regular Expressions in gnatfind and gnatxref::
17922 * Examples of gnatxref Usage::
17923 * Examples of gnatfind Usage::
17927 @node gnatxref Switches,gnatfind Switches,,The Cross-Referencing Tools gnatxref and gnatfind
17928 @anchor{gnat_ugn/gnat_utility_programs id10}@anchor{152}@anchor{gnat_ugn/gnat_utility_programs gnatxref-switches}@anchor{153}
17929 @subsection @code{gnatxref} Switches
17932 The command invocation for @code{gnatxref} is:
17937 $ gnatxref [ switches ] sourcefile1 [ sourcefile2 ... ]
17946 @item @code{sourcefile1} [, @code{sourcefile2} ...]
17948 identify the source files for which a report is to be generated. The
17949 @code{with}ed units will be processed too. You must provide at least one file.
17951 These file names are considered to be regular expressions, so for instance
17952 specifying @code{source*.adb} is the same as giving every file in the current
17953 directory whose name starts with @code{source} and whose extension is
17956 You shouldn't specify any directory name, just base names. @code{gnatxref}
17957 and @code{gnatfind} will be able to locate these files by themselves using
17958 the source path. If you specify directories, no result is produced.
17961 The following switches are available for @code{gnatxref}:
17963 @geindex --version (gnatxref)
17968 @item @code{--version}
17970 Display Copyright and version, then exit disregarding all other options.
17973 @geindex --help (gnatxref)
17978 @item @code{--help}
17980 If @code{--version} was not used, display usage, then exit disregarding
17984 @geindex -a (gnatxref)
17991 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
17992 the read-only files found in the library search path. Otherwise, these files
17993 will be ignored. This option can be used to protect Gnat sources or your own
17994 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
17995 much faster, and their output much smaller. Read-only here refers to access
17996 or permissions status in the file system for the current user.
17999 @geindex -aIDIR (gnatxref)
18004 @item @code{-aI@emph{DIR}}
18006 When looking for source files also look in directory DIR. The order in which
18007 source file search is undertaken is the same as for @code{gnatmake}.
18010 @geindex -aODIR (gnatxref)
18015 @item @code{aO@emph{DIR}}
18017 When -searching for library and object files, look in directory
18018 DIR. The order in which library files are searched is the same as for
18022 @geindex -nostdinc (gnatxref)
18027 @item @code{-nostdinc}
18029 Do not look for sources in the system default directory.
18032 @geindex -nostdlib (gnatxref)
18037 @item @code{-nostdlib}
18039 Do not look for library files in the system default directory.
18042 @geindex --ext (gnatxref)
18047 @item @code{--ext=@emph{extension}}
18049 Specify an alternate ali file extension. The default is @code{ali} and other
18050 extensions (e.g. @code{gli} for C/C++ sources) may be specified via this switch.
18051 Note that if this switch overrides the default, only the new extension will
18055 @geindex --RTS (gnatxref)
18060 @item @code{--RTS=@emph{rts-path}}
18062 Specifies the default location of the runtime library. Same meaning as the
18063 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18066 @geindex -d (gnatxref)
18073 If this switch is set @code{gnatxref} will output the parent type
18074 reference for each matching derived types.
18077 @geindex -f (gnatxref)
18084 If this switch is set, the output file names will be preceded by their
18085 directory (if the file was found in the search path). If this switch is
18086 not set, the directory will not be printed.
18089 @geindex -g (gnatxref)
18096 If this switch is set, information is output only for library-level
18097 entities, ignoring local entities. The use of this switch may accelerate
18098 @code{gnatfind} and @code{gnatxref}.
18101 @geindex -IDIR (gnatxref)
18106 @item @code{-I@emph{DIR}}
18108 Equivalent to @code{-aODIR -aIDIR}.
18111 @geindex -pFILE (gnatxref)
18116 @item @code{-p@emph{FILE}}
18118 Specify a configuration file to use to list the source and object directories.
18120 If a file is specified, then the content of the source directory and object
18121 directory lines are added as if they had been specified respectively
18122 by @code{-aI} and @code{-aO}.
18124 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18125 of this configuration file.
18129 Output only unused symbols. This may be really useful if you give your
18130 main compilation unit on the command line, as @code{gnatxref} will then
18131 display every unused entity and 'with'ed package.
18135 Instead of producing the default output, @code{gnatxref} will generate a
18136 @code{tags} file that can be used by vi. For examples how to use this
18137 feature, see @ref{155,,Examples of gnatxref Usage}. The tags file is output
18138 to the standard output, thus you will have to redirect it to a file.
18141 All these switches may be in any order on the command line, and may even
18142 appear after the file names. They need not be separated by spaces, thus
18143 you can say @code{gnatxref -ag} instead of @code{gnatxref -a -g}.
18145 @node gnatfind Switches,Configuration Files for gnatxref and gnatfind,gnatxref Switches,The Cross-Referencing Tools gnatxref and gnatfind
18146 @anchor{gnat_ugn/gnat_utility_programs id11}@anchor{156}@anchor{gnat_ugn/gnat_utility_programs gnatfind-switches}@anchor{157}
18147 @subsection @code{gnatfind} Switches
18150 The command invocation for @code{gnatfind} is:
18155 $ gnatfind [ switches ] pattern[:sourcefile[:line[:column]]]
18160 with the following iterpretation of the command arguments:
18165 @item @emph{pattern}
18167 An entity will be output only if it matches the regular expression found
18168 in @emph{pattern}, see @ref{158,,Regular Expressions in gnatfind and gnatxref}.
18170 Omitting the pattern is equivalent to specifying @code{*}, which
18171 will match any entity. Note that if you do not provide a pattern, you
18172 have to provide both a sourcefile and a line.
18174 Entity names are given in Latin-1, with uppercase/lowercase equivalence
18175 for matching purposes. At the current time there is no support for
18176 8-bit codes other than Latin-1, or for wide characters in identifiers.
18178 @item @emph{sourcefile}
18180 @code{gnatfind} will look for references, bodies or declarations
18181 of symbols referenced in @code{sourcefile}, at line @code{line}
18182 and column @code{column}. See @ref{159,,Examples of gnatfind Usage}
18183 for syntax examples.
18187 A decimal integer identifying the line number containing
18188 the reference to the entity (or entities) to be located.
18190 @item @emph{column}
18192 A decimal integer identifying the exact location on the
18193 line of the first character of the identifier for the
18194 entity reference. Columns are numbered from 1.
18196 @item @emph{file1 file2 ...}
18198 The search will be restricted to these source files. If none are given, then
18199 the search will be conducted for every library file in the search path.
18200 These files must appear only after the pattern or sourcefile.
18202 These file names are considered to be regular expressions, so for instance
18203 specifying @code{source*.adb} is the same as giving every file in the current
18204 directory whose name starts with @code{source} and whose extension is
18207 The location of the spec of the entity will always be displayed, even if it
18208 isn't in one of @code{file1}, @code{file2}, ... The
18209 occurrences of the entity in the separate units of the ones given on the
18210 command line will also be displayed.
18212 Note that if you specify at least one file in this part, @code{gnatfind} may
18213 sometimes not be able to find the body of the subprograms.
18216 At least one of 'sourcefile' or 'pattern' has to be present on
18219 The following switches are available:
18221 @geindex --version (gnatfind)
18226 @item @code{--version}
18228 Display Copyright and version, then exit disregarding all other options.
18231 @geindex --help (gnatfind)
18236 @item @code{--help}
18238 If @code{--version} was not used, display usage, then exit disregarding
18242 @geindex -a (gnatfind)
18249 If this switch is present, @code{gnatfind} and @code{gnatxref} will parse
18250 the read-only files found in the library search path. Otherwise, these files
18251 will be ignored. This option can be used to protect Gnat sources or your own
18252 libraries from being parsed, thus making @code{gnatfind} and @code{gnatxref}
18253 much faster, and their output much smaller. Read-only here refers to access
18254 or permission status in the file system for the current user.
18257 @geindex -aIDIR (gnatfind)
18262 @item @code{-aI@emph{DIR}}
18264 When looking for source files also look in directory DIR. The order in which
18265 source file search is undertaken is the same as for @code{gnatmake}.
18268 @geindex -aODIR (gnatfind)
18273 @item @code{-aO@emph{DIR}}
18275 When searching for library and object files, look in directory
18276 DIR. The order in which library files are searched is the same as for
18280 @geindex -nostdinc (gnatfind)
18285 @item @code{-nostdinc}
18287 Do not look for sources in the system default directory.
18290 @geindex -nostdlib (gnatfind)
18295 @item @code{-nostdlib}
18297 Do not look for library files in the system default directory.
18300 @geindex --ext (gnatfind)
18305 @item @code{--ext=@emph{extension}}
18307 Specify an alternate ali file extension. The default is @code{ali} and other
18308 extensions may be specified via this switch. Note that if this switch
18309 overrides the default, only the new extension will be considered.
18312 @geindex --RTS (gnatfind)
18317 @item @code{--RTS=@emph{rts-path}}
18319 Specifies the default location of the runtime library. Same meaning as the
18320 equivalent @code{gnatmake} flag (@ref{dc,,Switches for gnatmake}).
18323 @geindex -d (gnatfind)
18330 If this switch is set, then @code{gnatfind} will output the parent type
18331 reference for each matching derived types.
18334 @geindex -e (gnatfind)
18341 By default, @code{gnatfind} accept the simple regular expression set for
18342 @code{pattern}. If this switch is set, then the pattern will be
18343 considered as full Unix-style regular expression.
18346 @geindex -f (gnatfind)
18353 If this switch is set, the output file names will be preceded by their
18354 directory (if the file was found in the search path). If this switch is
18355 not set, the directory will not be printed.
18358 @geindex -g (gnatfind)
18365 If this switch is set, information is output only for library-level
18366 entities, ignoring local entities. The use of this switch may accelerate
18367 @code{gnatfind} and @code{gnatxref}.
18370 @geindex -IDIR (gnatfind)
18375 @item @code{-I@emph{DIR}}
18377 Equivalent to @code{-aODIR -aIDIR}.
18380 @geindex -pFILE (gnatfind)
18385 @item @code{-p@emph{FILE}}
18387 Specify a configuration file to use to list the source and object directories.
18389 If a file is specified, then the content of the source directory and object
18390 directory lines are added as if they had been specified respectively
18391 by @code{-aI} and @code{-aO}.
18393 See @ref{154,,Configuration Files for gnatxref and gnatfind} for the syntax
18394 of this configuration file.
18397 @geindex -r (gnatfind)
18404 By default, @code{gnatfind} will output only the information about the
18405 declaration, body or type completion of the entities. If this switch is
18406 set, the @code{gnatfind} will locate every reference to the entities in
18407 the files specified on the command line (or in every file in the search
18408 path if no file is given on the command line).
18411 @geindex -s (gnatfind)
18418 If this switch is set, then @code{gnatfind} will output the content
18419 of the Ada source file lines were the entity was found.
18422 @geindex -t (gnatfind)
18429 If this switch is set, then @code{gnatfind} will output the type hierarchy for
18430 the specified type. It act like -d option but recursively from parent
18431 type to parent type. When this switch is set it is not possible to
18432 specify more than one file.
18435 All these switches may be in any order on the command line, and may even
18436 appear after the file names. They need not be separated by spaces, thus
18437 you can say @code{gnatxref -ag} instead of
18438 @code{gnatxref -a -g}.
18440 As stated previously, @code{gnatfind} will search in every directory in the
18441 search path. You can force it to look only in the current directory if
18442 you specify @code{*} at the end of the command line.
18444 @node Configuration Files for gnatxref and gnatfind,Regular Expressions in gnatfind and gnatxref,gnatfind Switches,The Cross-Referencing Tools gnatxref and gnatfind
18445 @anchor{gnat_ugn/gnat_utility_programs configuration-files-for-gnatxref-and-gnatfind}@anchor{154}@anchor{gnat_ugn/gnat_utility_programs id12}@anchor{15a}
18446 @subsection Configuration Files for @code{gnatxref} and @code{gnatfind}
18449 Configuration files are used by @code{gnatxref} and @code{gnatfind} to specify
18450 the list of source and object directories to consider. They can be
18451 specified via the @code{-p} switch.
18453 The following lines can be included, in any order in the file:
18462 @item @emph{src_dir=DIR}
18464 [default: @code{"./"}].
18465 Specifies a directory where to look for source files. Multiple @code{src_dir}
18466 lines can be specified and they will be searched in the order they
18474 @item @emph{obj_dir=DIR}
18476 [default: @code{"./"}].
18477 Specifies a directory where to look for object and library files. Multiple
18478 @code{obj_dir} lines can be specified, and they will be searched in the order
18483 Any other line will be silently ignored.
18485 @node Regular Expressions in gnatfind and gnatxref,Examples of gnatxref Usage,Configuration Files for gnatxref and gnatfind,The Cross-Referencing Tools gnatxref and gnatfind
18486 @anchor{gnat_ugn/gnat_utility_programs id13}@anchor{15b}@anchor{gnat_ugn/gnat_utility_programs regular-expressions-in-gnatfind-and-gnatxref}@anchor{158}
18487 @subsection Regular Expressions in @code{gnatfind} and @code{gnatxref}
18490 As specified in the section about @code{gnatfind}, the pattern can be a
18491 regular expression. Two kinds of regular expressions
18501 @item @emph{Globbing pattern}
18503 These are the most common regular expression. They are the same as are
18504 generally used in a Unix shell command line, or in a DOS session.
18506 Here is a more formal grammar:
18510 term ::= elmt -- matches elmt
18511 term ::= elmt elmt -- concatenation (elmt then elmt)
18512 term ::= * -- any string of 0 or more characters
18513 term ::= ? -- matches any character
18514 term ::= [char @{char@}] -- matches any character listed
18515 term ::= [char - char] -- matches any character in range
18523 @item @emph{Full regular expression}
18525 The second set of regular expressions is much more powerful. This is the
18526 type of regular expressions recognized by utilities such as @code{grep}.
18528 The following is the form of a regular expression, expressed in same BNF
18529 style as is found in the Ada Reference Manual:
18532 regexp ::= term @{| term@} -- alternation (term or term ...)
18534 term ::= item @{item@} -- concatenation (item then item)
18536 item ::= elmt -- match elmt
18537 item ::= elmt * -- zero or more elmt's
18538 item ::= elmt + -- one or more elmt's
18539 item ::= elmt ? -- matches elmt or nothing
18541 elmt ::= nschar -- matches given character
18542 elmt ::= [nschar @{nschar@}] -- matches any character listed
18543 elmt ::= [^ nschar @{nschar@}] -- matches any character not listed
18544 elmt ::= [char - char] -- matches chars in given range
18545 elmt ::= \\ char -- matches given character
18546 elmt ::= . -- matches any single character
18547 elmt ::= ( regexp ) -- parens used for grouping
18549 char ::= any character, including special characters
18550 nschar ::= any character except ()[].*+?^
18553 Here are a few examples:
18560 @item @code{abcde|fghi}
18562 will match any of the two strings @code{abcde} and @code{fghi},
18566 will match any string like @code{abd}, @code{abcd}, @code{abccd},
18567 @code{abcccd}, and so on,
18569 @item @code{[a-z]+}
18571 will match any string which has only lowercase characters in it (and at
18572 least one character.
18578 @node Examples of gnatxref Usage,Examples of gnatfind Usage,Regular Expressions in gnatfind and gnatxref,The Cross-Referencing Tools gnatxref and gnatfind
18579 @anchor{gnat_ugn/gnat_utility_programs examples-of-gnatxref-usage}@anchor{155}@anchor{gnat_ugn/gnat_utility_programs id14}@anchor{15c}
18580 @subsection Examples of @code{gnatxref} Usage
18585 * Using gnatxref with vi::
18589 @node General Usage,Using gnatxref with vi,,Examples of gnatxref Usage
18590 @anchor{gnat_ugn/gnat_utility_programs general-usage}@anchor{15d}
18591 @subsubsection General Usage
18594 For the following examples, we will consider the following units:
18602 3: procedure Foo (B : in Integer);
18609 1: package body Main is
18610 2: procedure Foo (B : in Integer) is
18621 2: procedure Print (B : Integer);
18626 The first thing to do is to recompile your application (for instance, in
18627 that case just by doing a @code{gnatmake main}, so that GNAT generates
18628 the cross-referencing information.
18629 You can then issue any of the following commands:
18637 @code{gnatxref main.adb}
18638 @code{gnatxref} generates cross-reference information for main.adb
18639 and every unit 'with'ed by main.adb.
18641 The output would be:
18649 Decl: main.ads 3:20
18650 Body: main.adb 2:20
18651 Ref: main.adb 4:13 5:13 6:19
18654 Ref: main.adb 6:8 7:8
18664 Decl: main.ads 3:15
18665 Body: main.adb 2:15
18668 Body: main.adb 1:14
18671 Ref: main.adb 6:12 7:12
18675 This shows that the entity @code{Main} is declared in main.ads, line 2, column 9,
18676 its body is in main.adb, line 1, column 14 and is not referenced any where.
18678 The entity @code{Print} is declared in @code{bar.ads}, line 2, column 15 and it
18679 is referenced in @code{main.adb}, line 6 column 12 and line 7 column 12.
18682 @code{gnatxref package1.adb package2.ads}
18683 @code{gnatxref} will generates cross-reference information for
18684 @code{package1.adb}, @code{package2.ads} and any other package @code{with}ed by any
18689 @node Using gnatxref with vi,,General Usage,Examples of gnatxref Usage
18690 @anchor{gnat_ugn/gnat_utility_programs using-gnatxref-with-vi}@anchor{15e}
18691 @subsubsection Using @code{gnatxref} with @code{vi}
18694 @code{gnatxref} can generate a tags file output, which can be used
18695 directly from @code{vi}. Note that the standard version of @code{vi}
18696 will not work properly with overloaded symbols. Consider using another
18697 free implementation of @code{vi}, such as @code{vim}.
18702 $ gnatxref -v gnatfind.adb > tags
18706 The following command will generate the tags file for @code{gnatfind} itself
18707 (if the sources are in the search path!):
18712 $ gnatxref -v gnatfind.adb > tags
18716 From @code{vi}, you can then use the command @code{:tag @emph{entity}}
18717 (replacing @code{entity} by whatever you are looking for), and vi will
18718 display a new file with the corresponding declaration of entity.
18720 @node Examples of gnatfind Usage,,Examples of gnatxref Usage,The Cross-Referencing Tools gnatxref and gnatfind
18721 @anchor{gnat_ugn/gnat_utility_programs id15}@anchor{15f}@anchor{gnat_ugn/gnat_utility_programs examples-of-gnatfind-usage}@anchor{159}
18722 @subsection Examples of @code{gnatfind} Usage
18729 @code{gnatfind -f xyz:main.adb}
18730 Find declarations for all entities xyz referenced at least once in
18731 main.adb. The references are search in every library file in the search
18734 The directories will be printed as well (as the @code{-f}
18737 The output will look like:
18742 directory/main.ads:106:14: xyz <= declaration
18743 directory/main.adb:24:10: xyz <= body
18744 directory/foo.ads:45:23: xyz <= declaration
18748 I.e., one of the entities xyz found in main.adb is declared at
18749 line 12 of main.ads (and its body is in main.adb), and another one is
18750 declared at line 45 of foo.ads
18753 @code{gnatfind -fs xyz:main.adb}
18754 This is the same command as the previous one, but @code{gnatfind} will
18755 display the content of the Ada source file lines.
18757 The output will look like:
18760 directory/main.ads:106:14: xyz <= declaration
18762 directory/main.adb:24:10: xyz <= body
18764 directory/foo.ads:45:23: xyz <= declaration
18768 This can make it easier to find exactly the location your are looking
18772 @code{gnatfind -r "*x*":main.ads:123 foo.adb}
18773 Find references to all entities containing an x that are
18774 referenced on line 123 of main.ads.
18775 The references will be searched only in main.ads and foo.adb.
18778 @code{gnatfind main.ads:123}
18779 Find declarations and bodies for all entities that are referenced on
18780 line 123 of main.ads.
18782 This is the same as @code{gnatfind "*":main.adb:123`}
18785 @code{gnatfind mydir/main.adb:123:45}
18786 Find the declaration for the entity referenced at column 45 in
18787 line 123 of file main.adb in directory mydir. Note that it
18788 is usual to omit the identifier name when the column is given,
18789 since the column position identifies a unique reference.
18791 The column has to be the beginning of the identifier, and should not
18792 point to any character in the middle of the identifier.
18795 @node The Ada to HTML Converter gnathtml,,The Cross-Referencing Tools gnatxref and gnatfind,GNAT Utility Programs
18796 @anchor{gnat_ugn/gnat_utility_programs the-ada-to-html-converter-gnathtml}@anchor{23}@anchor{gnat_ugn/gnat_utility_programs id16}@anchor{160}
18797 @section The Ada to HTML Converter @code{gnathtml}
18802 @code{gnathtml} is a Perl script that allows Ada source files to be browsed using
18803 standard Web browsers. For installation information, see @ref{161,,Installing gnathtml}.
18805 Ada reserved keywords are highlighted in a bold font and Ada comments in
18806 a blue font. Unless your program was compiled with the gcc @code{-gnatx}
18807 switch to suppress the generation of cross-referencing information, user
18808 defined variables and types will appear in a different color; you will
18809 be able to click on any identifier and go to its declaration.
18812 * Invoking gnathtml::
18813 * Installing gnathtml::
18817 @node Invoking gnathtml,Installing gnathtml,,The Ada to HTML Converter gnathtml
18818 @anchor{gnat_ugn/gnat_utility_programs invoking-gnathtml}@anchor{162}@anchor{gnat_ugn/gnat_utility_programs id17}@anchor{163}
18819 @subsection Invoking @code{gnathtml}
18822 The command line is as follows:
18827 $ perl gnathtml.pl [ switches ] ada-files
18831 You can specify as many Ada files as you want. @code{gnathtml} will generate
18832 an html file for every ada file, and a global file called @code{index.htm}.
18833 This file is an index of every identifier defined in the files.
18835 The following switches are available:
18837 @geindex -83 (gnathtml)
18844 Only the Ada 83 subset of keywords will be highlighted.
18847 @geindex -cc (gnathtml)
18852 @item @code{cc @emph{color}}
18854 This option allows you to change the color used for comments. The default
18855 value is green. The color argument can be any name accepted by html.
18858 @geindex -d (gnathtml)
18865 If the Ada files depend on some other files (for instance through
18866 @code{with} clauses, the latter files will also be converted to html.
18867 Only the files in the user project will be converted to html, not the files
18868 in the run-time library itself.
18871 @geindex -D (gnathtml)
18878 This command is the same as @code{-d} above, but @code{gnathtml} will
18879 also look for files in the run-time library, and generate html files for them.
18882 @geindex -ext (gnathtml)
18887 @item @code{ext @emph{extension}}
18889 This option allows you to change the extension of the generated HTML files.
18890 If you do not specify an extension, it will default to @code{htm}.
18893 @geindex -f (gnathtml)
18900 By default, gnathtml will generate html links only for global entities
18901 ('with'ed units, global variables and types,...). If you specify
18902 @code{-f} on the command line, then links will be generated for local
18906 @geindex -l (gnathtml)
18911 @item @code{l @emph{number}}
18913 If this switch is provided and @code{number} is not 0, then
18914 @code{gnathtml} will number the html files every @code{number} line.
18917 @geindex -I (gnathtml)
18922 @item @code{I @emph{dir}}
18924 Specify a directory to search for library files (@code{.ALI} files) and
18925 source files. You can provide several -I switches on the command line,
18926 and the directories will be parsed in the order of the command line.
18929 @geindex -o (gnathtml)
18934 @item @code{o @emph{dir}}
18936 Specify the output directory for html files. By default, gnathtml will
18937 saved the generated html files in a subdirectory named @code{html/}.
18940 @geindex -p (gnathtml)
18945 @item @code{p @emph{file}}
18947 If you are using Emacs and the most recent Emacs Ada mode, which provides
18948 a full Integrated Development Environment for compiling, checking,
18949 running and debugging applications, you may use @code{.gpr} files
18950 to give the directories where Emacs can find sources and object files.
18952 Using this switch, you can tell gnathtml to use these files.
18953 This allows you to get an html version of your application, even if it
18954 is spread over multiple directories.
18957 @geindex -sc (gnathtml)
18962 @item @code{sc @emph{color}}
18964 This switch allows you to change the color used for symbol
18966 The default value is red. The color argument can be any name accepted by html.
18969 @geindex -t (gnathtml)
18974 @item @code{t @emph{file}}
18976 This switch provides the name of a file. This file contains a list of
18977 file names to be converted, and the effect is exactly as though they had
18978 appeared explicitly on the command line. This
18979 is the recommended way to work around the command line length limit on some
18983 @node Installing gnathtml,,Invoking gnathtml,The Ada to HTML Converter gnathtml
18984 @anchor{gnat_ugn/gnat_utility_programs installing-gnathtml}@anchor{161}@anchor{gnat_ugn/gnat_utility_programs id18}@anchor{164}
18985 @subsection Installing @code{gnathtml}
18988 @code{Perl} needs to be installed on your machine to run this script.
18989 @code{Perl} is freely available for almost every architecture and
18990 operating system via the Internet.
18992 On Unix systems, you may want to modify the first line of the script
18993 @code{gnathtml}, to explicitly specify where Perl
18994 is located. The syntax of this line is:
18999 #!full_path_name_to_perl
19003 Alternatively, you may run the script using the following command line:
19008 $ perl gnathtml.pl [ switches ] files
19012 @c -- +---------------------------------------------------------------------+
19014 @c -- | The following sections are present only in the PRO and GPL editions |
19016 @c -- +---------------------------------------------------------------------+
19026 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
19028 @node GNAT and Program Execution,Platform-Specific Information,GNAT Utility Programs,Top
19029 @anchor{gnat_ugn/gnat_and_program_execution gnat-and-program-execution}@anchor{c}@anchor{gnat_ugn/gnat_and_program_execution doc}@anchor{165}@anchor{gnat_ugn/gnat_and_program_execution id1}@anchor{166}
19030 @chapter GNAT and Program Execution
19033 This chapter covers several topics:
19039 @ref{167,,Running and Debugging Ada Programs}
19042 @ref{25,,Profiling}
19045 @ref{168,,Improving Performance}
19048 @ref{169,,Overflow Check Handling in GNAT}
19051 @ref{16a,,Performing Dimensionality Analysis in GNAT}
19054 @ref{16b,,Stack Related Facilities}
19057 @ref{16c,,Memory Management Issues}
19061 * Running and Debugging Ada Programs::
19063 * Improving Performance::
19064 * Overflow Check Handling in GNAT::
19065 * Performing Dimensionality Analysis in GNAT::
19066 * Stack Related Facilities::
19067 * Memory Management Issues::
19071 @node Running and Debugging Ada Programs,Profiling,,GNAT and Program Execution
19072 @anchor{gnat_ugn/gnat_and_program_execution id2}@anchor{167}@anchor{gnat_ugn/gnat_and_program_execution running-and-debugging-ada-programs}@anchor{24}
19073 @section Running and Debugging Ada Programs
19078 This section discusses how to debug Ada programs.
19080 An incorrect Ada program may be handled in three ways by the GNAT compiler:
19086 The illegality may be a violation of the static semantics of Ada. In
19087 that case GNAT diagnoses the constructs in the program that are illegal.
19088 It is then a straightforward matter for the user to modify those parts of
19092 The illegality may be a violation of the dynamic semantics of Ada. In
19093 that case the program compiles and executes, but may generate incorrect
19094 results, or may terminate abnormally with some exception.
19097 When presented with a program that contains convoluted errors, GNAT
19098 itself may terminate abnormally without providing full diagnostics on
19099 the incorrect user program.
19107 * The GNAT Debugger GDB::
19109 * Introduction to GDB Commands::
19110 * Using Ada Expressions::
19111 * Calling User-Defined Subprograms::
19112 * Using the next Command in a Function::
19113 * Stopping When Ada Exceptions Are Raised::
19115 * Debugging Generic Units::
19116 * Remote Debugging with gdbserver::
19117 * GNAT Abnormal Termination or Failure to Terminate::
19118 * Naming Conventions for GNAT Source Files::
19119 * Getting Internal Debugging Information::
19120 * Stack Traceback::
19121 * Pretty-Printers for the GNAT runtime::
19125 @node The GNAT Debugger GDB,Running GDB,,Running and Debugging Ada Programs
19126 @anchor{gnat_ugn/gnat_and_program_execution the-gnat-debugger-gdb}@anchor{16d}@anchor{gnat_ugn/gnat_and_program_execution id3}@anchor{16e}
19127 @subsection The GNAT Debugger GDB
19130 @code{GDB} is a general purpose, platform-independent debugger that
19131 can be used to debug mixed-language programs compiled with @code{gcc},
19132 and in particular is capable of debugging Ada programs compiled with
19133 GNAT. The latest versions of @code{GDB} are Ada-aware and can handle
19134 complex Ada data structures.
19136 See @cite{Debugging with GDB},
19137 for full details on the usage of @code{GDB}, including a section on
19138 its usage on programs. This manual should be consulted for full
19139 details. The section that follows is a brief introduction to the
19140 philosophy and use of @code{GDB}.
19142 When GNAT programs are compiled, the compiler optionally writes debugging
19143 information into the generated object file, including information on
19144 line numbers, and on declared types and variables. This information is
19145 separate from the generated code. It makes the object files considerably
19146 larger, but it does not add to the size of the actual executable that
19147 will be loaded into memory, and has no impact on run-time performance. The
19148 generation of debug information is triggered by the use of the
19149 @code{-g} switch in the @code{gcc} or @code{gnatmake} command
19150 used to carry out the compilations. It is important to emphasize that
19151 the use of these options does not change the generated code.
19153 The debugging information is written in standard system formats that
19154 are used by many tools, including debuggers and profilers. The format
19155 of the information is typically designed to describe C types and
19156 semantics, but GNAT implements a translation scheme which allows full
19157 details about Ada types and variables to be encoded into these
19158 standard C formats. Details of this encoding scheme may be found in
19159 the file exp_dbug.ads in the GNAT source distribution. However, the
19160 details of this encoding are, in general, of no interest to a user,
19161 since @code{GDB} automatically performs the necessary decoding.
19163 When a program is bound and linked, the debugging information is
19164 collected from the object files, and stored in the executable image of
19165 the program. Again, this process significantly increases the size of
19166 the generated executable file, but it does not increase the size of
19167 the executable program itself. Furthermore, if this program is run in
19168 the normal manner, it runs exactly as if the debug information were
19169 not present, and takes no more actual memory.
19171 However, if the program is run under control of @code{GDB}, the
19172 debugger is activated. The image of the program is loaded, at which
19173 point it is ready to run. If a run command is given, then the program
19174 will run exactly as it would have if @code{GDB} were not present. This
19175 is a crucial part of the @code{GDB} design philosophy. @code{GDB} is
19176 entirely non-intrusive until a breakpoint is encountered. If no
19177 breakpoint is ever hit, the program will run exactly as it would if no
19178 debugger were present. When a breakpoint is hit, @code{GDB} accesses
19179 the debugging information and can respond to user commands to inspect
19180 variables, and more generally to report on the state of execution.
19182 @node Running GDB,Introduction to GDB Commands,The GNAT Debugger GDB,Running and Debugging Ada Programs
19183 @anchor{gnat_ugn/gnat_and_program_execution id4}@anchor{16f}@anchor{gnat_ugn/gnat_and_program_execution running-gdb}@anchor{170}
19184 @subsection Running GDB
19187 This section describes how to initiate the debugger.
19189 The debugger can be launched from a @code{GPS} menu or
19190 directly from the command line. The description below covers the latter use.
19191 All the commands shown can be used in the @code{GPS} debug console window,
19192 but there are usually more GUI-based ways to achieve the same effect.
19194 The command to run @code{GDB} is
19203 where @code{program} is the name of the executable file. This
19204 activates the debugger and results in a prompt for debugger commands.
19205 The simplest command is simply @code{run}, which causes the program to run
19206 exactly as if the debugger were not present. The following section
19207 describes some of the additional commands that can be given to @code{GDB}.
19209 @node Introduction to GDB Commands,Using Ada Expressions,Running GDB,Running and Debugging Ada Programs
19210 @anchor{gnat_ugn/gnat_and_program_execution introduction-to-gdb-commands}@anchor{171}@anchor{gnat_ugn/gnat_and_program_execution id5}@anchor{172}
19211 @subsection Introduction to GDB Commands
19214 @code{GDB} contains a large repertoire of commands.
19215 See @cite{Debugging with GDB} for extensive documentation on the use
19216 of these commands, together with examples of their use. Furthermore,
19217 the command @emph{help} invoked from within GDB activates a simple help
19218 facility which summarizes the available commands and their options.
19219 In this section we summarize a few of the most commonly
19220 used commands to give an idea of what @code{GDB} is about. You should create
19221 a simple program with debugging information and experiment with the use of
19222 these @code{GDB} commands on the program as you read through the
19232 @item @code{set args @emph{arguments}}
19234 The @emph{arguments} list above is a list of arguments to be passed to
19235 the program on a subsequent run command, just as though the arguments
19236 had been entered on a normal invocation of the program. The @code{set args}
19237 command is not needed if the program does not require arguments.
19246 The @code{run} command causes execution of the program to start from
19247 the beginning. If the program is already running, that is to say if
19248 you are currently positioned at a breakpoint, then a prompt will ask
19249 for confirmation that you want to abandon the current execution and
19257 @item @code{breakpoint @emph{location}}
19259 The breakpoint command sets a breakpoint, that is to say a point at which
19260 execution will halt and @code{GDB} will await further
19261 commands. @emph{location} is
19262 either a line number within a file, given in the format @code{file:linenumber},
19263 or it is the name of a subprogram. If you request that a breakpoint be set on
19264 a subprogram that is overloaded, a prompt will ask you to specify on which of
19265 those subprograms you want to breakpoint. You can also
19266 specify that all of them should be breakpointed. If the program is run
19267 and execution encounters the breakpoint, then the program
19268 stops and @code{GDB} signals that the breakpoint was encountered by
19269 printing the line of code before which the program is halted.
19276 @item @code{catch exception @emph{name}}
19278 This command causes the program execution to stop whenever exception
19279 @code{name} is raised. If @code{name} is omitted, then the execution is
19280 suspended when any exception is raised.
19287 @item @code{print @emph{expression}}
19289 This will print the value of the given expression. Most simple
19290 Ada expression formats are properly handled by @code{GDB}, so the expression
19291 can contain function calls, variables, operators, and attribute references.
19298 @item @code{continue}
19300 Continues execution following a breakpoint, until the next breakpoint or the
19301 termination of the program.
19310 Executes a single line after a breakpoint. If the next statement
19311 is a subprogram call, execution continues into (the first statement of)
19312 the called subprogram.
19321 Executes a single line. If this line is a subprogram call, executes and
19322 returns from the call.
19331 Lists a few lines around the current source location. In practice, it
19332 is usually more convenient to have a separate edit window open with the
19333 relevant source file displayed. Successive applications of this command
19334 print subsequent lines. The command can be given an argument which is a
19335 line number, in which case it displays a few lines around the specified one.
19342 @item @code{backtrace}
19344 Displays a backtrace of the call chain. This command is typically
19345 used after a breakpoint has occurred, to examine the sequence of calls that
19346 leads to the current breakpoint. The display includes one line for each
19347 activation record (frame) corresponding to an active subprogram.
19356 At a breakpoint, @code{GDB} can display the values of variables local
19357 to the current frame. The command @code{up} can be used to
19358 examine the contents of other active frames, by moving the focus up
19359 the stack, that is to say from callee to caller, one frame at a time.
19368 Moves the focus of @code{GDB} down from the frame currently being
19369 examined to the frame of its callee (the reverse of the previous command),
19376 @item @code{frame @emph{n}}
19378 Inspect the frame with the given number. The value 0 denotes the frame
19379 of the current breakpoint, that is to say the top of the call stack.
19388 Kills the child process in which the program is running under GDB.
19389 This may be useful for several purposes:
19395 It allows you to recompile and relink your program, since on many systems
19396 you cannot regenerate an executable file while it is running in a process.
19399 You can run your program outside the debugger, on systems that do not
19400 permit executing a program outside GDB while breakpoints are set
19404 It allows you to debug a core dump rather than a running process.
19409 The above list is a very short introduction to the commands that
19410 @code{GDB} provides. Important additional capabilities, including conditional
19411 breakpoints, the ability to execute command sequences on a breakpoint,
19412 the ability to debug at the machine instruction level and many other
19413 features are described in detail in @cite{Debugging with GDB}.
19414 Note that most commands can be abbreviated
19415 (for example, c for continue, bt for backtrace).
19417 @node Using Ada Expressions,Calling User-Defined Subprograms,Introduction to GDB Commands,Running and Debugging Ada Programs
19418 @anchor{gnat_ugn/gnat_and_program_execution id6}@anchor{173}@anchor{gnat_ugn/gnat_and_program_execution using-ada-expressions}@anchor{174}
19419 @subsection Using Ada Expressions
19422 @geindex Ada expressions (in gdb)
19424 @code{GDB} supports a fairly large subset of Ada expression syntax, with some
19425 extensions. The philosophy behind the design of this subset is
19433 That @code{GDB} should provide basic literals and access to operations for
19434 arithmetic, dereferencing, field selection, indexing, and subprogram calls,
19435 leaving more sophisticated computations to subprograms written into the
19436 program (which therefore may be called from @code{GDB}).
19439 That type safety and strict adherence to Ada language restrictions
19440 are not particularly relevant in a debugging context.
19443 That brevity is important to the @code{GDB} user.
19447 Thus, for brevity, the debugger acts as if there were
19448 implicit @code{with} and @code{use} clauses in effect for all user-written
19449 packages, thus making it unnecessary to fully qualify most names with
19450 their packages, regardless of context. Where this causes ambiguity,
19451 @code{GDB} asks the user's intent.
19453 For details on the supported Ada syntax, see @cite{Debugging with GDB}.
19455 @node Calling User-Defined Subprograms,Using the next Command in a Function,Using Ada Expressions,Running and Debugging Ada Programs
19456 @anchor{gnat_ugn/gnat_and_program_execution id7}@anchor{175}@anchor{gnat_ugn/gnat_and_program_execution calling-user-defined-subprograms}@anchor{176}
19457 @subsection Calling User-Defined Subprograms
19460 An important capability of @code{GDB} is the ability to call user-defined
19461 subprograms while debugging. This is achieved simply by entering
19462 a subprogram call statement in the form:
19467 call subprogram-name (parameters)
19471 The keyword @code{call} can be omitted in the normal case where the
19472 @code{subprogram-name} does not coincide with any of the predefined
19473 @code{GDB} commands.
19475 The effect is to invoke the given subprogram, passing it the
19476 list of parameters that is supplied. The parameters can be expressions and
19477 can include variables from the program being debugged. The
19478 subprogram must be defined
19479 at the library level within your program, and @code{GDB} will call the
19480 subprogram within the environment of your program execution (which
19481 means that the subprogram is free to access or even modify variables
19482 within your program).
19484 The most important use of this facility is in allowing the inclusion of
19485 debugging routines that are tailored to particular data structures
19486 in your program. Such debugging routines can be written to provide a suitably
19487 high-level description of an abstract type, rather than a low-level dump
19488 of its physical layout. After all, the standard
19489 @code{GDB print} command only knows the physical layout of your
19490 types, not their abstract meaning. Debugging routines can provide information
19491 at the desired semantic level and are thus enormously useful.
19493 For example, when debugging GNAT itself, it is crucial to have access to
19494 the contents of the tree nodes used to represent the program internally.
19495 But tree nodes are represented simply by an integer value (which in turn
19496 is an index into a table of nodes).
19497 Using the @code{print} command on a tree node would simply print this integer
19498 value, which is not very useful. But the PN routine (defined in file
19499 treepr.adb in the GNAT sources) takes a tree node as input, and displays
19500 a useful high level representation of the tree node, which includes the
19501 syntactic category of the node, its position in the source, the integers
19502 that denote descendant nodes and parent node, as well as varied
19503 semantic information. To study this example in more detail, you might want to
19504 look at the body of the PN procedure in the stated file.
19506 Another useful application of this capability is to deal with situations of
19507 complex data which are not handled suitably by GDB. For example, if you specify
19508 Convention Fortran for a multi-dimensional array, GDB does not know that
19509 the ordering of array elements has been switched and will not properly
19510 address the array elements. In such a case, instead of trying to print the
19511 elements directly from GDB, you can write a callable procedure that prints
19512 the elements in the desired format.
19514 @node Using the next Command in a Function,Stopping When Ada Exceptions Are Raised,Calling User-Defined Subprograms,Running and Debugging Ada Programs
19515 @anchor{gnat_ugn/gnat_and_program_execution using-the-next-command-in-a-function}@anchor{177}@anchor{gnat_ugn/gnat_and_program_execution id8}@anchor{178}
19516 @subsection Using the @emph{next} Command in a Function
19519 When you use the @code{next} command in a function, the current source
19520 location will advance to the next statement as usual. A special case
19521 arises in the case of a @code{return} statement.
19523 Part of the code for a return statement is the 'epilogue' of the function.
19524 This is the code that returns to the caller. There is only one copy of
19525 this epilogue code, and it is typically associated with the last return
19526 statement in the function if there is more than one return. In some
19527 implementations, this epilogue is associated with the first statement
19530 The result is that if you use the @code{next} command from a return
19531 statement that is not the last return statement of the function you
19532 may see a strange apparent jump to the last return statement or to
19533 the start of the function. You should simply ignore this odd jump.
19534 The value returned is always that from the first return statement
19535 that was stepped through.
19537 @node Stopping When Ada Exceptions Are Raised,Ada Tasks,Using the next Command in a Function,Running and Debugging Ada Programs
19538 @anchor{gnat_ugn/gnat_and_program_execution stopping-when-ada-exceptions-are-raised}@anchor{179}@anchor{gnat_ugn/gnat_and_program_execution id9}@anchor{17a}
19539 @subsection Stopping When Ada Exceptions Are Raised
19542 @geindex Exceptions (in gdb)
19544 You can set catchpoints that stop the program execution when your program
19545 raises selected exceptions.
19554 @item @code{catch exception}
19556 Set a catchpoint that stops execution whenever (any task in the) program
19557 raises any exception.
19564 @item @code{catch exception @emph{name}}
19566 Set a catchpoint that stops execution whenever (any task in the) program
19567 raises the exception @emph{name}.
19574 @item @code{catch exception unhandled}
19576 Set a catchpoint that stops executing whenever (any task in the) program
19577 raises an exception for which there is no handler.
19584 @item @code{info exceptions}, @code{info exceptions @emph{regexp}}
19586 The @code{info exceptions} command permits the user to examine all defined
19587 exceptions within Ada programs. With a regular expression, @emph{regexp}, as
19588 argument, prints out only those exceptions whose name matches @emph{regexp}.
19592 @geindex Tasks (in gdb)
19594 @node Ada Tasks,Debugging Generic Units,Stopping When Ada Exceptions Are Raised,Running and Debugging Ada Programs
19595 @anchor{gnat_ugn/gnat_and_program_execution ada-tasks}@anchor{17b}@anchor{gnat_ugn/gnat_and_program_execution id10}@anchor{17c}
19596 @subsection Ada Tasks
19599 @code{GDB} allows the following task-related commands:
19608 @item @code{info tasks}
19610 This command shows a list of current Ada tasks, as in the following example:
19614 ID TID P-ID Thread Pri State Name
19615 1 8088000 0 807e000 15 Child Activation Wait main_task
19616 2 80a4000 1 80ae000 15 Accept/Select Wait b
19617 3 809a800 1 80a4800 15 Child Activation Wait a
19618 * 4 80ae800 3 80b8000 15 Running c
19621 In this listing, the asterisk before the first task indicates it to be the
19622 currently running task. The first column lists the task ID that is used
19623 to refer to tasks in the following commands.
19627 @geindex Breakpoints and tasks
19633 @code{break`@w{`}*linespec* `@w{`}task} @emph{taskid}, @code{break} @emph{linespec} @code{task} @emph{taskid} @code{if} ...
19637 These commands are like the @code{break ... thread ...}.
19638 @emph{linespec} specifies source lines.
19640 Use the qualifier @code{task @emph{taskid}} with a breakpoint command
19641 to specify that you only want @code{GDB} to stop the program when a
19642 particular Ada task reaches this breakpoint. @emph{taskid} is one of the
19643 numeric task identifiers assigned by @code{GDB}, shown in the first
19644 column of the @code{info tasks} display.
19646 If you do not specify @code{task @emph{taskid}} when you set a
19647 breakpoint, the breakpoint applies to @emph{all} tasks of your
19650 You can use the @code{task} qualifier on conditional breakpoints as
19651 well; in this case, place @code{task @emph{taskid}} before the
19652 breakpoint condition (before the @code{if}).
19656 @geindex Task switching (in gdb)
19662 @code{task @emph{taskno}}
19666 This command allows switching to the task referred by @emph{taskno}. In
19667 particular, this allows browsing of the backtrace of the specified
19668 task. It is advisable to switch back to the original task before
19669 continuing execution otherwise the scheduling of the program may be
19674 For more detailed information on the tasking support,
19675 see @cite{Debugging with GDB}.
19677 @geindex Debugging Generic Units
19681 @node Debugging Generic Units,Remote Debugging with gdbserver,Ada Tasks,Running and Debugging Ada Programs
19682 @anchor{gnat_ugn/gnat_and_program_execution debugging-generic-units}@anchor{17d}@anchor{gnat_ugn/gnat_and_program_execution id11}@anchor{17e}
19683 @subsection Debugging Generic Units
19686 GNAT always uses code expansion for generic instantiation. This means that
19687 each time an instantiation occurs, a complete copy of the original code is
19688 made, with appropriate substitutions of formals by actuals.
19690 It is not possible to refer to the original generic entities in
19691 @code{GDB}, but it is always possible to debug a particular instance of
19692 a generic, by using the appropriate expanded names. For example, if we have
19699 generic package k is
19700 procedure kp (v1 : in out integer);
19704 procedure kp (v1 : in out integer) is
19710 package k1 is new k;
19711 package k2 is new k;
19713 var : integer := 1;
19724 Then to break on a call to procedure kp in the k2 instance, simply
19730 (gdb) break g.k2.kp
19734 When the breakpoint occurs, you can step through the code of the
19735 instance in the normal manner and examine the values of local variables, as for
19738 @geindex Remote Debugging with gdbserver
19740 @node Remote Debugging with gdbserver,GNAT Abnormal Termination or Failure to Terminate,Debugging Generic Units,Running and Debugging Ada Programs
19741 @anchor{gnat_ugn/gnat_and_program_execution remote-debugging-with-gdbserver}@anchor{17f}@anchor{gnat_ugn/gnat_and_program_execution id12}@anchor{180}
19742 @subsection Remote Debugging with gdbserver
19745 On platforms where gdbserver is supported, it is possible to use this tool
19746 to debug your application remotely. This can be useful in situations
19747 where the program needs to be run on a target host that is different
19748 from the host used for development, particularly when the target has
19749 a limited amount of resources (either CPU and/or memory).
19751 To do so, start your program using gdbserver on the target machine.
19752 gdbserver then automatically suspends the execution of your program
19753 at its entry point, waiting for a debugger to connect to it. The
19754 following commands starts an application and tells gdbserver to
19755 wait for a connection with the debugger on localhost port 4444.
19760 $ gdbserver localhost:4444 program
19761 Process program created; pid = 5685
19762 Listening on port 4444
19766 Once gdbserver has started listening, we can tell the debugger to establish
19767 a connection with this gdbserver, and then start the same debugging session
19768 as if the program was being debugged on the same host, directly under
19769 the control of GDB.
19775 (gdb) target remote targethost:4444
19776 Remote debugging using targethost:4444
19777 0x00007f29936d0af0 in ?? () from /lib64/ld-linux-x86-64.so.
19779 Breakpoint 1 at 0x401f0c: file foo.adb, line 3.
19783 Breakpoint 1, foo () at foo.adb:4
19788 It is also possible to use gdbserver to attach to an already running
19789 program, in which case the execution of that program is simply suspended
19790 until the connection between the debugger and gdbserver is established.
19792 For more information on how to use gdbserver, see the @emph{Using the gdbserver Program}
19793 section in @cite{Debugging with GDB}.
19794 GNAT provides support for gdbserver on x86-linux, x86-windows and x86_64-linux.
19796 @geindex Abnormal Termination or Failure to Terminate
19798 @node GNAT Abnormal Termination or Failure to Terminate,Naming Conventions for GNAT Source Files,Remote Debugging with gdbserver,Running and Debugging Ada Programs
19799 @anchor{gnat_ugn/gnat_and_program_execution gnat-abnormal-termination-or-failure-to-terminate}@anchor{181}@anchor{gnat_ugn/gnat_and_program_execution id13}@anchor{182}
19800 @subsection GNAT Abnormal Termination or Failure to Terminate
19803 When presented with programs that contain serious errors in syntax
19805 GNAT may on rare occasions experience problems in operation, such
19807 segmentation fault or illegal memory access, raising an internal
19808 exception, terminating abnormally, or failing to terminate at all.
19809 In such cases, you can activate
19810 various features of GNAT that can help you pinpoint the construct in your
19811 program that is the likely source of the problem.
19813 The following strategies are presented in increasing order of
19814 difficulty, corresponding to your experience in using GNAT and your
19815 familiarity with compiler internals.
19821 Run @code{gcc} with the @code{-gnatf}. This first
19822 switch causes all errors on a given line to be reported. In its absence,
19823 only the first error on a line is displayed.
19825 The @code{-gnatdO} switch causes errors to be displayed as soon as they
19826 are encountered, rather than after compilation is terminated. If GNAT
19827 terminates prematurely or goes into an infinite loop, the last error
19828 message displayed may help to pinpoint the culprit.
19831 Run @code{gcc} with the @code{-v} (verbose) switch. In this
19832 mode, @code{gcc} produces ongoing information about the progress of the
19833 compilation and provides the name of each procedure as code is
19834 generated. This switch allows you to find which Ada procedure was being
19835 compiled when it encountered a code generation problem.
19838 @geindex -gnatdc switch
19844 Run @code{gcc} with the @code{-gnatdc} switch. This is a GNAT specific
19845 switch that does for the front-end what @code{-v} does
19846 for the back end. The system prints the name of each unit,
19847 either a compilation unit or nested unit, as it is being analyzed.
19850 Finally, you can start
19851 @code{gdb} directly on the @code{gnat1} executable. @code{gnat1} is the
19852 front-end of GNAT, and can be run independently (normally it is just
19853 called from @code{gcc}). You can use @code{gdb} on @code{gnat1} as you
19854 would on a C program (but @ref{16d,,The GNAT Debugger GDB} for caveats). The
19855 @code{where} command is the first line of attack; the variable
19856 @code{lineno} (seen by @code{print lineno}), used by the second phase of
19857 @code{gnat1} and by the @code{gcc} backend, indicates the source line at
19858 which the execution stopped, and @code{input_file name} indicates the name of
19862 @node Naming Conventions for GNAT Source Files,Getting Internal Debugging Information,GNAT Abnormal Termination or Failure to Terminate,Running and Debugging Ada Programs
19863 @anchor{gnat_ugn/gnat_and_program_execution naming-conventions-for-gnat-source-files}@anchor{183}@anchor{gnat_ugn/gnat_and_program_execution id14}@anchor{184}
19864 @subsection Naming Conventions for GNAT Source Files
19867 In order to examine the workings of the GNAT system, the following
19868 brief description of its organization may be helpful:
19874 Files with prefix @code{sc} contain the lexical scanner.
19877 All files prefixed with @code{par} are components of the parser. The
19878 numbers correspond to chapters of the Ada Reference Manual. For example,
19879 parsing of select statements can be found in @code{par-ch9.adb}.
19882 All files prefixed with @code{sem} perform semantic analysis. The
19883 numbers correspond to chapters of the Ada standard. For example, all
19884 issues involving context clauses can be found in @code{sem_ch10.adb}. In
19885 addition, some features of the language require sufficient special processing
19886 to justify their own semantic files: sem_aggr for aggregates, sem_disp for
19887 dynamic dispatching, etc.
19890 All files prefixed with @code{exp} perform normalization and
19891 expansion of the intermediate representation (abstract syntax tree, or AST).
19892 these files use the same numbering scheme as the parser and semantics files.
19893 For example, the construction of record initialization procedures is done in
19894 @code{exp_ch3.adb}.
19897 The files prefixed with @code{bind} implement the binder, which
19898 verifies the consistency of the compilation, determines an order of
19899 elaboration, and generates the bind file.
19902 The files @code{atree.ads} and @code{atree.adb} detail the low-level
19903 data structures used by the front-end.
19906 The files @code{sinfo.ads} and @code{sinfo.adb} detail the structure of
19907 the abstract syntax tree as produced by the parser.
19910 The files @code{einfo.ads} and @code{einfo.adb} detail the attributes of
19911 all entities, computed during semantic analysis.
19914 Library management issues are dealt with in files with prefix
19917 @geindex Annex A (in Ada Reference Manual)
19920 Ada files with the prefix @code{a-} are children of @code{Ada}, as
19921 defined in Annex A.
19923 @geindex Annex B (in Ada reference Manual)
19926 Files with prefix @code{i-} are children of @code{Interfaces}, as
19927 defined in Annex B.
19929 @geindex System (package in Ada Reference Manual)
19932 Files with prefix @code{s-} are children of @code{System}. This includes
19933 both language-defined children and GNAT run-time routines.
19935 @geindex GNAT (package)
19938 Files with prefix @code{g-} are children of @code{GNAT}. These are useful
19939 general-purpose packages, fully documented in their specs. All
19940 the other @code{.c} files are modifications of common @code{gcc} files.
19943 @node Getting Internal Debugging Information,Stack Traceback,Naming Conventions for GNAT Source Files,Running and Debugging Ada Programs
19944 @anchor{gnat_ugn/gnat_and_program_execution id15}@anchor{185}@anchor{gnat_ugn/gnat_and_program_execution getting-internal-debugging-information}@anchor{186}
19945 @subsection Getting Internal Debugging Information
19948 Most compilers have internal debugging switches and modes. GNAT
19949 does also, except GNAT internal debugging switches and modes are not
19950 secret. A summary and full description of all the compiler and binder
19951 debug flags are in the file @code{debug.adb}. You must obtain the
19952 sources of the compiler to see the full detailed effects of these flags.
19954 The switches that print the source of the program (reconstructed from
19955 the internal tree) are of general interest for user programs, as are the
19957 the full internal tree, and the entity table (the symbol table
19958 information). The reconstructed source provides a readable version of the
19959 program after the front-end has completed analysis and expansion,
19960 and is useful when studying the performance of specific constructs.
19961 For example, constraint checks are indicated, complex aggregates
19962 are replaced with loops and assignments, and tasking primitives
19963 are replaced with run-time calls.
19967 @geindex stack traceback
19969 @geindex stack unwinding
19971 @node Stack Traceback,Pretty-Printers for the GNAT runtime,Getting Internal Debugging Information,Running and Debugging Ada Programs
19972 @anchor{gnat_ugn/gnat_and_program_execution stack-traceback}@anchor{187}@anchor{gnat_ugn/gnat_and_program_execution id16}@anchor{188}
19973 @subsection Stack Traceback
19976 Traceback is a mechanism to display the sequence of subprogram calls that
19977 leads to a specified execution point in a program. Often (but not always)
19978 the execution point is an instruction at which an exception has been raised.
19979 This mechanism is also known as @emph{stack unwinding} because it obtains
19980 its information by scanning the run-time stack and recovering the activation
19981 records of all active subprograms. Stack unwinding is one of the most
19982 important tools for program debugging.
19984 The first entry stored in traceback corresponds to the deepest calling level,
19985 that is to say the subprogram currently executing the instruction
19986 from which we want to obtain the traceback.
19988 Note that there is no runtime performance penalty when stack traceback
19989 is enabled, and no exception is raised during program execution.
19992 @geindex non-symbolic
19995 * Non-Symbolic Traceback::
19996 * Symbolic Traceback::
20000 @node Non-Symbolic Traceback,Symbolic Traceback,,Stack Traceback
20001 @anchor{gnat_ugn/gnat_and_program_execution non-symbolic-traceback}@anchor{189}@anchor{gnat_ugn/gnat_and_program_execution id17}@anchor{18a}
20002 @subsubsection Non-Symbolic Traceback
20005 Note: this feature is not supported on all platforms. See
20006 @code{GNAT.Traceback} spec in @code{g-traceb.ads}
20007 for a complete list of supported platforms.
20009 @subsubheading Tracebacks From an Unhandled Exception
20012 A runtime non-symbolic traceback is a list of addresses of call instructions.
20013 To enable this feature you must use the @code{-E}
20014 @code{gnatbind} option. With this option a stack traceback is stored as part
20015 of exception information. You can retrieve this information using the
20016 @code{addr2line} tool.
20018 Here is a simple example:
20027 raise Constraint_Error;
20041 $ gnatmake stb -bargs -E
20044 Execution terminated by unhandled exception
20045 Exception name: CONSTRAINT_ERROR
20047 Call stack traceback locations:
20048 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20052 As we see the traceback lists a sequence of addresses for the unhandled
20053 exception @code{CONSTRAINT_ERROR} raised in procedure P1. It is easy to
20054 guess that this exception come from procedure P1. To translate these
20055 addresses into the source lines where the calls appear, the
20056 @code{addr2line} tool, described below, is invaluable. The use of this tool
20057 requires the program to be compiled with debug information.
20062 $ gnatmake -g stb -bargs -E
20065 Execution terminated by unhandled exception
20066 Exception name: CONSTRAINT_ERROR
20068 Call stack traceback locations:
20069 0x401373 0x40138b 0x40139c 0x401335 0x4011c4 0x4011f1 0x77e892a4
20071 $ addr2line --exe=stb 0x401373 0x40138b 0x40139c 0x401335 0x4011c4
20072 0x4011f1 0x77e892a4
20074 00401373 at d:/stb/stb.adb:5
20075 0040138B at d:/stb/stb.adb:10
20076 0040139C at d:/stb/stb.adb:14
20077 00401335 at d:/stb/b~stb.adb:104
20078 004011C4 at /build/.../crt1.c:200
20079 004011F1 at /build/.../crt1.c:222
20080 77E892A4 in ?? at ??:0
20084 The @code{addr2line} tool has several other useful options:
20089 @multitable {xxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
20096 to get the function name corresponding to any location
20100 @code{--demangle=gnat}
20104 to use the gnat decoding mode for the function names.
20105 Note that for binutils version 2.9.x the option is
20106 simply @code{--demangle}.
20112 $ addr2line --exe=stb --functions --demangle=gnat 0x401373 0x40138b
20113 0x40139c 0x401335 0x4011c4 0x4011f1
20115 00401373 in stb.p1 at d:/stb/stb.adb:5
20116 0040138B in stb.p2 at d:/stb/stb.adb:10
20117 0040139C in stb at d:/stb/stb.adb:14
20118 00401335 in main at d:/stb/b~stb.adb:104
20119 004011C4 in <__mingw_CRTStartup> at /build/.../crt1.c:200
20120 004011F1 in <mainCRTStartup> at /build/.../crt1.c:222
20124 From this traceback we can see that the exception was raised in
20125 @code{stb.adb} at line 5, which was reached from a procedure call in
20126 @code{stb.adb} at line 10, and so on. The @code{b~std.adb} is the binder file,
20127 which contains the call to the main program.
20128 @ref{11c,,Running gnatbind}. The remaining entries are assorted runtime routines,
20129 and the output will vary from platform to platform.
20131 It is also possible to use @code{GDB} with these traceback addresses to debug
20132 the program. For example, we can break at a given code location, as reported
20133 in the stack traceback:
20142 Furthermore, this feature is not implemented inside Windows DLL. Only
20143 the non-symbolic traceback is reported in this case.
20148 (gdb) break *0x401373
20149 Breakpoint 1 at 0x401373: file stb.adb, line 5.
20153 It is important to note that the stack traceback addresses
20154 do not change when debug information is included. This is particularly useful
20155 because it makes it possible to release software without debug information (to
20156 minimize object size), get a field report that includes a stack traceback
20157 whenever an internal bug occurs, and then be able to retrieve the sequence
20158 of calls with the same program compiled with debug information.
20160 @subsubheading Tracebacks From Exception Occurrences
20163 Non-symbolic tracebacks are obtained by using the @code{-E} binder argument.
20164 The stack traceback is attached to the exception information string, and can
20165 be retrieved in an exception handler within the Ada program, by means of the
20166 Ada facilities defined in @code{Ada.Exceptions}. Here is a simple example:
20172 with Ada.Exceptions;
20177 use Ada.Exceptions;
20185 Text_IO.Put_Line (Exception_Information (E));
20199 This program will output:
20206 Exception name: CONSTRAINT_ERROR
20207 Message: stb.adb:12
20208 Call stack traceback locations:
20209 0x4015e4 0x401633 0x401644 0x401461 0x4011c4 0x4011f1 0x77e892a4
20213 @subsubheading Tracebacks From Anywhere in a Program
20216 It is also possible to retrieve a stack traceback from anywhere in a
20217 program. For this you need to
20218 use the @code{GNAT.Traceback} API. This package includes a procedure called
20219 @code{Call_Chain} that computes a complete stack traceback, as well as useful
20220 display procedures described below. It is not necessary to use the
20221 @code{-E} @code{gnatbind} option in this case, because the stack traceback mechanism
20222 is invoked explicitly.
20224 In the following example we compute a traceback at a specific location in
20225 the program, and we display it using @code{GNAT.Debug_Utilities.Image} to
20226 convert addresses to strings:
20232 with GNAT.Traceback;
20233 with GNAT.Debug_Utilities;
20239 use GNAT.Traceback;
20242 TB : Tracebacks_Array (1 .. 10);
20243 -- We are asking for a maximum of 10 stack frames.
20245 -- Len will receive the actual number of stack frames returned.
20247 Call_Chain (TB, Len);
20249 Text_IO.Put ("In STB.P1 : ");
20251 for K in 1 .. Len loop
20252 Text_IO.Put (Debug_Utilities.Image (TB (K)));
20273 In STB.P1 : 16#0040_F1E4# 16#0040_14F2# 16#0040_170B# 16#0040_171C#
20274 16#0040_1461# 16#0040_11C4# 16#0040_11F1# 16#77E8_92A4#
20278 You can then get further information by invoking the @code{addr2line}
20279 tool as described earlier (note that the hexadecimal addresses
20280 need to be specified in C format, with a leading '0x').
20285 @node Symbolic Traceback,,Non-Symbolic Traceback,Stack Traceback
20286 @anchor{gnat_ugn/gnat_and_program_execution id18}@anchor{18b}@anchor{gnat_ugn/gnat_and_program_execution symbolic-traceback}@anchor{18c}
20287 @subsubsection Symbolic Traceback
20290 A symbolic traceback is a stack traceback in which procedure names are
20291 associated with each code location.
20293 Note that this feature is not supported on all platforms. See
20294 @code{GNAT.Traceback.Symbolic} spec in @code{g-trasym.ads} for a complete
20295 list of currently supported platforms.
20297 Note that the symbolic traceback requires that the program be compiled
20298 with debug information. If it is not compiled with debug information
20299 only the non-symbolic information will be valid.
20301 @subsubheading Tracebacks From Exception Occurrences
20304 Here is an example:
20310 with GNAT.Traceback.Symbolic;
20316 raise Constraint_Error;
20333 Ada.Text_IO.Put_Line (GNAT.Traceback.Symbolic.Symbolic_Traceback (E));
20338 $ gnatmake -g .\stb -bargs -E
20341 0040149F in stb.p1 at stb.adb:8
20342 004014B7 in stb.p2 at stb.adb:13
20343 004014CF in stb.p3 at stb.adb:18
20344 004015DD in ada.stb at stb.adb:22
20345 00401461 in main at b~stb.adb:168
20346 004011C4 in __mingw_CRTStartup at crt1.c:200
20347 004011F1 in mainCRTStartup at crt1.c:222
20348 77E892A4 in ?? at ??:0
20352 In the above example the @code{.\} syntax in the @code{gnatmake} command
20353 is currently required by @code{addr2line} for files that are in
20354 the current working directory.
20355 Moreover, the exact sequence of linker options may vary from platform
20357 The above @code{-largs} section is for Windows platforms. By contrast,
20358 under Unix there is no need for the @code{-largs} section.
20359 Differences across platforms are due to details of linker implementation.
20361 @subsubheading Tracebacks From Anywhere in a Program
20364 It is possible to get a symbolic stack traceback
20365 from anywhere in a program, just as for non-symbolic tracebacks.
20366 The first step is to obtain a non-symbolic
20367 traceback, and then call @code{Symbolic_Traceback} to compute the symbolic
20368 information. Here is an example:
20374 with GNAT.Traceback;
20375 with GNAT.Traceback.Symbolic;
20380 use GNAT.Traceback;
20381 use GNAT.Traceback.Symbolic;
20384 TB : Tracebacks_Array (1 .. 10);
20385 -- We are asking for a maximum of 10 stack frames.
20387 -- Len will receive the actual number of stack frames returned.
20389 Call_Chain (TB, Len);
20390 Text_IO.Put_Line (Symbolic_Traceback (TB (1 .. Len)));
20404 @subsubheading Automatic Symbolic Tracebacks
20407 Symbolic tracebacks may also be enabled by using the -Es switch to gnatbind (as
20408 in @code{gprbuild -g ... -bargs -Es}).
20409 This will cause the Exception_Information to contain a symbolic traceback,
20410 which will also be printed if an unhandled exception terminates the
20413 @node Pretty-Printers for the GNAT runtime,,Stack Traceback,Running and Debugging Ada Programs
20414 @anchor{gnat_ugn/gnat_and_program_execution id19}@anchor{18d}@anchor{gnat_ugn/gnat_and_program_execution pretty-printers-for-the-gnat-runtime}@anchor{18e}
20415 @subsection Pretty-Printers for the GNAT runtime
20418 As discussed in @cite{Calling User-Defined Subprograms}, GDB's
20419 @code{print} command only knows about the physical layout of program data
20420 structures and therefore normally displays only low-level dumps, which
20421 are often hard to understand.
20423 An example of this is when trying to display the contents of an Ada
20424 standard container, such as @code{Ada.Containers.Ordered_Maps.Map}:
20429 with Ada.Containers.Ordered_Maps;
20432 package Int_To_Nat is
20433 new Ada.Containers.Ordered_Maps (Integer, Natural);
20435 Map : Int_To_Nat.Map;
20437 Map.Insert (1, 10);
20438 Map.Insert (2, 20);
20439 Map.Insert (3, 30);
20441 Map.Clear; -- BREAK HERE
20446 When this program is built with debugging information and run under
20447 GDB up to the @code{Map.Clear} statement, trying to print @code{Map} will
20448 yield information that is only relevant to the developers of our standard
20470 Fortunately, GDB has a feature called pretty-printers@footnote{http://docs.adacore.com/gdb-docs/html/gdb.html#Pretty_002dPrinter-Introduction},
20471 which allows customizing how GDB displays data structures. The GDB
20472 shipped with GNAT embeds such pretty-printers for the most common
20473 containers in the standard library. To enable them, either run the
20474 following command manually under GDB or add it to your @code{.gdbinit} file:
20479 python import gnatdbg; gnatdbg.setup()
20483 Once this is done, GDB's @code{print} command will automatically use
20484 these pretty-printers when appropriate. Using the previous example:
20490 $1 = pp.int_to_nat.map of length 3 = @{
20498 Pretty-printers are invoked each time GDB tries to display a value,
20499 including when displaying the arguments of a called subprogram (in
20500 GDB's @code{backtrace} command) or when printing the value returned by a
20501 function (in GDB's @code{finish} command).
20503 To display a value without involving pretty-printers, @code{print} can be
20504 invoked with its @code{/r} option:
20515 Finer control of pretty-printers is also possible: see GDB's online documentation@footnote{http://docs.adacore.com/gdb-docs/html/gdb.html#Pretty_002dPrinter-Commands}
20516 for more information.
20520 @node Profiling,Improving Performance,Running and Debugging Ada Programs,GNAT and Program Execution
20521 @anchor{gnat_ugn/gnat_and_program_execution profiling}@anchor{25}@anchor{gnat_ugn/gnat_and_program_execution id20}@anchor{18f}
20525 This section describes how to use the the @code{gprof} profiler tool on Ada
20533 * Profiling an Ada Program with gprof::
20537 @node Profiling an Ada Program with gprof,,,Profiling
20538 @anchor{gnat_ugn/gnat_and_program_execution id21}@anchor{190}@anchor{gnat_ugn/gnat_and_program_execution profiling-an-ada-program-with-gprof}@anchor{191}
20539 @subsection Profiling an Ada Program with gprof
20542 This section is not meant to be an exhaustive documentation of @code{gprof}.
20543 Full documentation for it can be found in the @cite{GNU Profiler User's Guide}
20544 documentation that is part of this GNAT distribution.
20546 Profiling a program helps determine the parts of a program that are executed
20547 most often, and are therefore the most time-consuming.
20549 @code{gprof} is the standard GNU profiling tool; it has been enhanced to
20550 better handle Ada programs and multitasking.
20551 It is currently supported on the following platforms
20563 In order to profile a program using @code{gprof}, several steps are needed:
20569 Instrument the code, which requires a full recompilation of the project with the
20573 Execute the program under the analysis conditions, i.e. with the desired
20577 Analyze the results using the @code{gprof} tool.
20580 The following sections detail the different steps, and indicate how
20581 to interpret the results.
20584 * Compilation for profiling::
20585 * Program execution::
20587 * Interpretation of profiling results::
20591 @node Compilation for profiling,Program execution,,Profiling an Ada Program with gprof
20592 @anchor{gnat_ugn/gnat_and_program_execution id22}@anchor{192}@anchor{gnat_ugn/gnat_and_program_execution compilation-for-profiling}@anchor{193}
20593 @subsubsection Compilation for profiling
20597 @geindex for profiling
20599 @geindex -pg (gnatlink)
20600 @geindex for profiling
20602 In order to profile a program the first step is to tell the compiler
20603 to generate the necessary profiling information. The compiler switch to be used
20604 is @code{-pg}, which must be added to other compilation switches. This
20605 switch needs to be specified both during compilation and link stages, and can
20606 be specified once when using gnatmake:
20611 $ gnatmake -f -pg -P my_project
20615 Note that only the objects that were compiled with the @code{-pg} switch will
20616 be profiled; if you need to profile your whole project, use the @code{-f}
20617 gnatmake switch to force full recompilation.
20619 @node Program execution,Running gprof,Compilation for profiling,Profiling an Ada Program with gprof
20620 @anchor{gnat_ugn/gnat_and_program_execution program-execution}@anchor{194}@anchor{gnat_ugn/gnat_and_program_execution id23}@anchor{195}
20621 @subsubsection Program execution
20624 Once the program has been compiled for profiling, you can run it as usual.
20626 The only constraint imposed by profiling is that the program must terminate
20627 normally. An interrupted program (via a Ctrl-C, kill, etc.) will not be
20630 Once the program completes execution, a data file called @code{gmon.out} is
20631 generated in the directory where the program was launched from. If this file
20632 already exists, it will be overwritten.
20634 @node Running gprof,Interpretation of profiling results,Program execution,Profiling an Ada Program with gprof
20635 @anchor{gnat_ugn/gnat_and_program_execution running-gprof}@anchor{196}@anchor{gnat_ugn/gnat_and_program_execution id24}@anchor{197}
20636 @subsubsection Running gprof
20639 The @code{gprof} tool is called as follow:
20644 $ gprof my_prog gmon.out
20657 The complete form of the gprof command line is the following:
20662 $ gprof [switches] [executable [data-file]]
20666 @code{gprof} supports numerous switches. The order of these
20667 switch does not matter. The full list of options can be found in
20668 the GNU Profiler User's Guide documentation that comes with this documentation.
20670 The following is the subset of those switches that is most relevant:
20672 @geindex --demangle (gprof)
20677 @item @code{--demangle[=@emph{style}]}, @code{--no-demangle}
20679 These options control whether symbol names should be demangled when
20680 printing output. The default is to demangle C++ symbols. The
20681 @code{--no-demangle} option may be used to turn off demangling. Different
20682 compilers have different mangling styles. The optional demangling style
20683 argument can be used to choose an appropriate demangling style for your
20684 compiler, in particular Ada symbols generated by GNAT can be demangled using
20685 @code{--demangle=gnat}.
20688 @geindex -e (gprof)
20693 @item @code{-e @emph{function_name}}
20695 The @code{-e @emph{function}} option tells @code{gprof} not to print
20696 information about the function @code{function_name} (and its
20697 children...) in the call graph. The function will still be listed
20698 as a child of any functions that call it, but its index number will be
20699 shown as @code{[not printed]}. More than one @code{-e} option may be
20700 given; only one @code{function_name} may be indicated with each @code{-e}
20704 @geindex -E (gprof)
20709 @item @code{-E @emph{function_name}}
20711 The @code{-E @emph{function}} option works like the @code{-e} option, but
20712 execution time spent in the function (and children who were not called from
20713 anywhere else), will not be used to compute the percentages-of-time for
20714 the call graph. More than one @code{-E} option may be given; only one
20715 @code{function_name} may be indicated with each @code{-E`} option.
20718 @geindex -f (gprof)
20723 @item @code{-f @emph{function_name}}
20725 The @code{-f @emph{function}} option causes @code{gprof} to limit the
20726 call graph to the function @code{function_name} and its children (and
20727 their children...). More than one @code{-f} option may be given;
20728 only one @code{function_name} may be indicated with each @code{-f}
20732 @geindex -F (gprof)
20737 @item @code{-F @emph{function_name}}
20739 The @code{-F @emph{function}} option works like the @code{-f} option, but
20740 only time spent in the function and its children (and their
20741 children...) will be used to determine total-time and
20742 percentages-of-time for the call graph. More than one @code{-F} option
20743 may be given; only one @code{function_name} may be indicated with each
20744 @code{-F} option. The @code{-F} option overrides the @code{-E} option.
20747 @node Interpretation of profiling results,,Running gprof,Profiling an Ada Program with gprof
20748 @anchor{gnat_ugn/gnat_and_program_execution id25}@anchor{198}@anchor{gnat_ugn/gnat_and_program_execution interpretation-of-profiling-results}@anchor{199}
20749 @subsubsection Interpretation of profiling results
20752 The results of the profiling analysis are represented by two arrays: the
20753 'flat profile' and the 'call graph'. Full documentation of those outputs
20754 can be found in the GNU Profiler User's Guide.
20756 The flat profile shows the time spent in each function of the program, and how
20757 many time it has been called. This allows you to locate easily the most
20758 time-consuming functions.
20760 The call graph shows, for each subprogram, the subprograms that call it,
20761 and the subprograms that it calls. It also provides an estimate of the time
20762 spent in each of those callers/called subprograms.
20764 @node Improving Performance,Overflow Check Handling in GNAT,Profiling,GNAT and Program Execution
20765 @anchor{gnat_ugn/gnat_and_program_execution improving-performance}@anchor{26}@anchor{gnat_ugn/gnat_and_program_execution id26}@anchor{168}
20766 @section Improving Performance
20769 @geindex Improving performance
20771 This section presents several topics related to program performance.
20772 It first describes some of the tradeoffs that need to be considered
20773 and some of the techniques for making your program run faster.
20776 It then documents the unused subprogram/data elimination feature,
20777 which can reduce the size of program executables.
20780 * Performance Considerations::
20781 * Text_IO Suggestions::
20782 * Reducing Size of Executables with Unused Subprogram/Data Elimination::
20786 @node Performance Considerations,Text_IO Suggestions,,Improving Performance
20787 @anchor{gnat_ugn/gnat_and_program_execution performance-considerations}@anchor{19a}@anchor{gnat_ugn/gnat_and_program_execution id27}@anchor{19b}
20788 @subsection Performance Considerations
20791 The GNAT system provides a number of options that allow a trade-off
20798 performance of the generated code
20801 speed of compilation
20804 minimization of dependences and recompilation
20807 the degree of run-time checking.
20810 The defaults (if no options are selected) aim at improving the speed
20811 of compilation and minimizing dependences, at the expense of performance
20812 of the generated code:
20821 no inlining of subprogram calls
20824 all run-time checks enabled except overflow and elaboration checks
20827 These options are suitable for most program development purposes. This
20828 section describes how you can modify these choices, and also provides
20829 some guidelines on debugging optimized code.
20832 * Controlling Run-Time Checks::
20833 * Use of Restrictions::
20834 * Optimization Levels::
20835 * Debugging Optimized Code::
20836 * Inlining of Subprograms::
20837 * Floating_Point_Operations::
20838 * Vectorization of loops::
20839 * Other Optimization Switches::
20840 * Optimization and Strict Aliasing::
20841 * Aliased Variables and Optimization::
20842 * Atomic Variables and Optimization::
20843 * Passive Task Optimization::
20847 @node Controlling Run-Time Checks,Use of Restrictions,,Performance Considerations
20848 @anchor{gnat_ugn/gnat_and_program_execution id28}@anchor{19c}@anchor{gnat_ugn/gnat_and_program_execution controlling-run-time-checks}@anchor{19d}
20849 @subsubsection Controlling Run-Time Checks
20852 By default, GNAT generates all run-time checks, except stack overflow
20853 checks, and checks for access before elaboration on subprogram
20854 calls. The latter are not required in default mode, because all
20855 necessary checking is done at compile time.
20857 @geindex -gnatp (gcc)
20859 @geindex -gnato (gcc)
20861 The gnat switch, @code{-gnatp} allows this default to be modified. See
20862 @ref{f9,,Run-Time Checks}.
20864 Our experience is that the default is suitable for most development
20867 Elaboration checks are off by default, and also not needed by default, since
20868 GNAT uses a static elaboration analysis approach that avoids the need for
20869 run-time checking. This manual contains a full chapter discussing the issue
20870 of elaboration checks, and if the default is not satisfactory for your use,
20871 you should read this chapter.
20873 For validity checks, the minimal checks required by the Ada Reference
20874 Manual (for case statements and assignments to array elements) are on
20875 by default. These can be suppressed by use of the @code{-gnatVn} switch.
20876 Note that in Ada 83, there were no validity checks, so if the Ada 83 mode
20877 is acceptable (or when comparing GNAT performance with an Ada 83 compiler),
20878 it may be reasonable to routinely use @code{-gnatVn}. Validity checks
20879 are also suppressed entirely if @code{-gnatp} is used.
20881 @geindex Overflow checks
20888 @geindex Unsuppress
20890 @geindex pragma Suppress
20892 @geindex pragma Unsuppress
20894 Note that the setting of the switches controls the default setting of
20895 the checks. They may be modified using either @code{pragma Suppress} (to
20896 remove checks) or @code{pragma Unsuppress} (to add back suppressed
20897 checks) in the program source.
20899 @node Use of Restrictions,Optimization Levels,Controlling Run-Time Checks,Performance Considerations
20900 @anchor{gnat_ugn/gnat_and_program_execution id29}@anchor{19e}@anchor{gnat_ugn/gnat_and_program_execution use-of-restrictions}@anchor{19f}
20901 @subsubsection Use of Restrictions
20904 The use of pragma Restrictions allows you to control which features are
20905 permitted in your program. Apart from the obvious point that if you avoid
20906 relatively expensive features like finalization (enforceable by the use
20907 of pragma Restrictions (No_Finalization), the use of this pragma does not
20908 affect the generated code in most cases.
20910 One notable exception to this rule is that the possibility of task abort
20911 results in some distributed overhead, particularly if finalization or
20912 exception handlers are used. The reason is that certain sections of code
20913 have to be marked as non-abortable.
20915 If you use neither the @code{abort} statement, nor asynchronous transfer
20916 of control (@code{select ... then abort}), then this distributed overhead
20917 is removed, which may have a general positive effect in improving
20918 overall performance. Especially code involving frequent use of tasking
20919 constructs and controlled types will show much improved performance.
20920 The relevant restrictions pragmas are
20925 pragma Restrictions (No_Abort_Statements);
20926 pragma Restrictions (Max_Asynchronous_Select_Nesting => 0);
20930 It is recommended that these restriction pragmas be used if possible. Note
20931 that this also means that you can write code without worrying about the
20932 possibility of an immediate abort at any point.
20934 @node Optimization Levels,Debugging Optimized Code,Use of Restrictions,Performance Considerations
20935 @anchor{gnat_ugn/gnat_and_program_execution id30}@anchor{1a0}@anchor{gnat_ugn/gnat_and_program_execution optimization-levels}@anchor{fc}
20936 @subsubsection Optimization Levels
20941 Without any optimization option,
20942 the compiler's goal is to reduce the cost of
20943 compilation and to make debugging produce the expected results.
20944 Statements are independent: if you stop the program with a breakpoint between
20945 statements, you can then assign a new value to any variable or change
20946 the program counter to any other statement in the subprogram and get exactly
20947 the results you would expect from the source code.
20949 Turning on optimization makes the compiler attempt to improve the
20950 performance and/or code size at the expense of compilation time and
20951 possibly the ability to debug the program.
20953 If you use multiple
20954 -O options, with or without level numbers,
20955 the last such option is the one that is effective.
20957 The default is optimization off. This results in the fastest compile
20958 times, but GNAT makes absolutely no attempt to optimize, and the
20959 generated programs are considerably larger and slower than when
20960 optimization is enabled. You can use the
20961 @code{-O} switch (the permitted forms are @code{-O0}, @code{-O1}
20962 @code{-O2}, @code{-O3}, and @code{-Os})
20963 to @code{gcc} to control the optimization level:
20974 No optimization (the default);
20975 generates unoptimized code but has
20976 the fastest compilation time.
20978 Note that many other compilers do substantial optimization even
20979 if 'no optimization' is specified. With gcc, it is very unusual
20980 to use @code{-O0} for production if execution time is of any concern,
20981 since @code{-O0} means (almost) no optimization. This difference
20982 between gcc and other compilers should be kept in mind when
20983 doing performance comparisons.
20992 Moderate optimization;
20993 optimizes reasonably well but does not
20994 degrade compilation time significantly.
21004 generates highly optimized code and has
21005 the slowest compilation time.
21014 Full optimization as in @code{-O2};
21015 also uses more aggressive automatic inlining of subprograms within a unit
21016 (@ref{10f,,Inlining of Subprograms}) and attempts to vectorize loops.
21025 Optimize space usage (code and data) of resulting program.
21029 Higher optimization levels perform more global transformations on the
21030 program and apply more expensive analysis algorithms in order to generate
21031 faster and more compact code. The price in compilation time, and the
21032 resulting improvement in execution time,
21033 both depend on the particular application and the hardware environment.
21034 You should experiment to find the best level for your application.
21036 Since the precise set of optimizations done at each level will vary from
21037 release to release (and sometime from target to target), it is best to think
21038 of the optimization settings in general terms.
21039 See the @emph{Options That Control Optimization} section in
21040 @cite{Using the GNU Compiler Collection (GCC)}
21042 the @code{-O} settings and a number of @code{-f} options that
21043 individually enable or disable specific optimizations.
21045 Unlike some other compilation systems, @code{gcc} has
21046 been tested extensively at all optimization levels. There are some bugs
21047 which appear only with optimization turned on, but there have also been
21048 bugs which show up only in @emph{unoptimized} code. Selecting a lower
21049 level of optimization does not improve the reliability of the code
21050 generator, which in practice is highly reliable at all optimization
21053 Note regarding the use of @code{-O3}: The use of this optimization level
21054 ought not to be automatically preferred over that of level @code{-O2},
21055 since it often results in larger executables which may run more slowly.
21056 See further discussion of this point in @ref{10f,,Inlining of Subprograms}.
21058 @node Debugging Optimized Code,Inlining of Subprograms,Optimization Levels,Performance Considerations
21059 @anchor{gnat_ugn/gnat_and_program_execution debugging-optimized-code}@anchor{1a1}@anchor{gnat_ugn/gnat_and_program_execution id31}@anchor{1a2}
21060 @subsubsection Debugging Optimized Code
21063 @geindex Debugging optimized code
21065 @geindex Optimization and debugging
21067 Although it is possible to do a reasonable amount of debugging at
21068 nonzero optimization levels,
21069 the higher the level the more likely that
21070 source-level constructs will have been eliminated by optimization.
21071 For example, if a loop is strength-reduced, the loop
21072 control variable may be completely eliminated and thus cannot be
21073 displayed in the debugger.
21074 This can only happen at @code{-O2} or @code{-O3}.
21075 Explicit temporary variables that you code might be eliminated at
21076 level @code{-O1} or higher.
21080 The use of the @code{-g} switch,
21081 which is needed for source-level debugging,
21082 affects the size of the program executable on disk,
21083 and indeed the debugging information can be quite large.
21084 However, it has no effect on the generated code (and thus does not
21085 degrade performance)
21087 Since the compiler generates debugging tables for a compilation unit before
21088 it performs optimizations, the optimizing transformations may invalidate some
21089 of the debugging data. You therefore need to anticipate certain
21090 anomalous situations that may arise while debugging optimized code.
21091 These are the most common cases:
21097 @emph{The 'hopping Program Counter':} Repeated @code{step} or @code{next}
21099 the PC bouncing back and forth in the code. This may result from any of
21100 the following optimizations:
21106 @emph{Common subexpression elimination:} using a single instance of code for a
21107 quantity that the source computes several times. As a result you
21108 may not be able to stop on what looks like a statement.
21111 @emph{Invariant code motion:} moving an expression that does not change within a
21112 loop, to the beginning of the loop.
21115 @emph{Instruction scheduling:} moving instructions so as to
21116 overlap loads and stores (typically) with other code, or in
21117 general to move computations of values closer to their uses. Often
21118 this causes you to pass an assignment statement without the assignment
21119 happening and then later bounce back to the statement when the
21120 value is actually needed. Placing a breakpoint on a line of code
21121 and then stepping over it may, therefore, not always cause all the
21122 expected side-effects.
21126 @emph{The 'big leap':} More commonly known as @emph{cross-jumping}, in which
21127 two identical pieces of code are merged and the program counter suddenly
21128 jumps to a statement that is not supposed to be executed, simply because
21129 it (and the code following) translates to the same thing as the code
21130 that @emph{was} supposed to be executed. This effect is typically seen in
21131 sequences that end in a jump, such as a @code{goto}, a @code{return}, or
21132 a @code{break} in a C @code{switch} statement.
21135 @emph{The 'roving variable':} The symptom is an unexpected value in a variable.
21136 There are various reasons for this effect:
21142 In a subprogram prologue, a parameter may not yet have been moved to its
21146 A variable may be dead, and its register re-used. This is
21147 probably the most common cause.
21150 As mentioned above, the assignment of a value to a variable may
21154 A variable may be eliminated entirely by value propagation or
21155 other means. In this case, GCC may incorrectly generate debugging
21156 information for the variable
21159 In general, when an unexpected value appears for a local variable or parameter
21160 you should first ascertain if that value was actually computed by
21161 your program, as opposed to being incorrectly reported by the debugger.
21163 array elements in an object designated by an access value
21164 are generally less of a problem, once you have ascertained that the access
21166 Typically, this means checking variables in the preceding code and in the
21167 calling subprogram to verify that the value observed is explainable from other
21168 values (one must apply the procedure recursively to those
21169 other values); or re-running the code and stopping a little earlier
21170 (perhaps before the call) and stepping to better see how the variable obtained
21171 the value in question; or continuing to step @emph{from} the point of the
21172 strange value to see if code motion had simply moved the variable's
21176 In light of such anomalies, a recommended technique is to use @code{-O0}
21177 early in the software development cycle, when extensive debugging capabilities
21178 are most needed, and then move to @code{-O1} and later @code{-O2} as
21179 the debugger becomes less critical.
21180 Whether to use the @code{-g} switch in the release version is
21181 a release management issue.
21182 Note that if you use @code{-g} you can then use the @code{strip} program
21183 on the resulting executable,
21184 which removes both debugging information and global symbols.
21186 @node Inlining of Subprograms,Floating_Point_Operations,Debugging Optimized Code,Performance Considerations
21187 @anchor{gnat_ugn/gnat_and_program_execution id32}@anchor{1a3}@anchor{gnat_ugn/gnat_and_program_execution inlining-of-subprograms}@anchor{10f}
21188 @subsubsection Inlining of Subprograms
21191 A call to a subprogram in the current unit is inlined if all the
21192 following conditions are met:
21198 The optimization level is at least @code{-O1}.
21201 The called subprogram is suitable for inlining: It must be small enough
21202 and not contain something that @code{gcc} cannot support in inlined
21205 @geindex pragma Inline
21210 Any one of the following applies: @code{pragma Inline} is applied to the
21211 subprogram; the subprogram is local to the unit and called once from
21212 within it; the subprogram is small and optimization level @code{-O2} is
21213 specified; optimization level @code{-O3} is specified.
21216 Calls to subprograms in @emph{with}ed units are normally not inlined.
21217 To achieve actual inlining (that is, replacement of the call by the code
21218 in the body of the subprogram), the following conditions must all be true:
21224 The optimization level is at least @code{-O1}.
21227 The called subprogram is suitable for inlining: It must be small enough
21228 and not contain something that @code{gcc} cannot support in inlined
21232 There is a @code{pragma Inline} for the subprogram.
21235 The @code{-gnatn} switch is used on the command line.
21238 Even if all these conditions are met, it may not be possible for
21239 the compiler to inline the call, due to the length of the body,
21240 or features in the body that make it impossible for the compiler
21241 to do the inlining.
21243 Note that specifying the @code{-gnatn} switch causes additional
21244 compilation dependencies. Consider the following:
21266 With the default behavior (no @code{-gnatn} switch specified), the
21267 compilation of the @code{Main} procedure depends only on its own source,
21268 @code{main.adb}, and the spec of the package in file @code{r.ads}. This
21269 means that editing the body of @code{R} does not require recompiling
21272 On the other hand, the call @code{R.Q} is not inlined under these
21273 circumstances. If the @code{-gnatn} switch is present when @code{Main}
21274 is compiled, the call will be inlined if the body of @code{Q} is small
21275 enough, but now @code{Main} depends on the body of @code{R} in
21276 @code{r.adb} as well as on the spec. This means that if this body is edited,
21277 the main program must be recompiled. Note that this extra dependency
21278 occurs whether or not the call is in fact inlined by @code{gcc}.
21280 The use of front end inlining with @code{-gnatN} generates similar
21281 additional dependencies.
21283 @geindex -fno-inline (gcc)
21285 Note: The @code{-fno-inline} switch overrides all other conditions and ensures that
21286 no inlining occurs, unless requested with pragma Inline_Always for @code{gcc}
21287 back-ends. The extra dependences resulting from @code{-gnatn} will still be active,
21288 even if this switch is used to suppress the resulting inlining actions.
21290 @geindex -fno-inline-functions (gcc)
21292 Note: The @code{-fno-inline-functions} switch can be used to prevent
21293 automatic inlining of subprograms if @code{-O3} is used.
21295 @geindex -fno-inline-small-functions (gcc)
21297 Note: The @code{-fno-inline-small-functions} switch can be used to prevent
21298 automatic inlining of small subprograms if @code{-O2} is used.
21300 @geindex -fno-inline-functions-called-once (gcc)
21302 Note: The @code{-fno-inline-functions-called-once} switch
21303 can be used to prevent inlining of subprograms local to the unit
21304 and called once from within it if @code{-O1} is used.
21306 Note regarding the use of @code{-O3}: @code{-gnatn} is made up of two
21307 sub-switches @code{-gnatn1} and @code{-gnatn2} that can be directly
21308 specified in lieu of it, @code{-gnatn} being translated into one of them
21309 based on the optimization level. With @code{-O2} or below, @code{-gnatn}
21310 is equivalent to @code{-gnatn1} which activates pragma @code{Inline} with
21311 moderate inlining across modules. With @code{-O3}, @code{-gnatn} is
21312 equivalent to @code{-gnatn2} which activates pragma @code{Inline} with
21313 full inlining across modules. If you have used pragma @code{Inline} in
21314 appropriate cases, then it is usually much better to use @code{-O2}
21315 and @code{-gnatn} and avoid the use of @code{-O3} which has the additional
21316 effect of inlining subprograms you did not think should be inlined. We have
21317 found that the use of @code{-O3} may slow down the compilation and increase
21318 the code size by performing excessive inlining, leading to increased
21319 instruction cache pressure from the increased code size and thus minor
21320 performance improvements. So the bottom line here is that you should not
21321 automatically assume that @code{-O3} is better than @code{-O2}, and
21322 indeed you should use @code{-O3} only if tests show that it actually
21323 improves performance for your program.
21325 @node Floating_Point_Operations,Vectorization of loops,Inlining of Subprograms,Performance Considerations
21326 @anchor{gnat_ugn/gnat_and_program_execution floating-point-operations}@anchor{1a4}@anchor{gnat_ugn/gnat_and_program_execution id33}@anchor{1a5}
21327 @subsubsection Floating_Point_Operations
21330 @geindex Floating-Point Operations
21332 On almost all targets, GNAT maps Float and Long_Float to the 32-bit and
21333 64-bit standard IEEE floating-point representations, and operations will
21334 use standard IEEE arithmetic as provided by the processor. On most, but
21335 not all, architectures, the attribute Machine_Overflows is False for these
21336 types, meaning that the semantics of overflow is implementation-defined.
21337 In the case of GNAT, these semantics correspond to the normal IEEE
21338 treatment of infinities and NaN (not a number) values. For example,
21339 1.0 / 0.0 yields plus infinitiy and 0.0 / 0.0 yields a NaN. By
21340 avoiding explicit overflow checks, the performance is greatly improved
21341 on many targets. However, if required, floating-point overflow can be
21342 enabled by the use of the pragma Check_Float_Overflow.
21344 Another consideration that applies specifically to x86 32-bit
21345 architectures is which form of floating-point arithmetic is used.
21346 By default the operations use the old style x86 floating-point,
21347 which implements an 80-bit extended precision form (on these
21348 architectures the type Long_Long_Float corresponds to that form).
21349 In addition, generation of efficient code in this mode means that
21350 the extended precision form will be used for intermediate results.
21351 This may be helpful in improving the final precision of a complex
21352 expression. However it means that the results obtained on the x86
21353 will be different from those on other architectures, and for some
21354 algorithms, the extra intermediate precision can be detrimental.
21356 In addition to this old-style floating-point, all modern x86 chips
21357 implement an alternative floating-point operation model referred
21358 to as SSE2. In this model there is no extended form, and furthermore
21359 execution performance is significantly enhanced. To force GNAT to use
21360 this more modern form, use both of the switches:
21364 -msse2 -mfpmath=sse
21367 A unit compiled with these switches will automatically use the more
21368 efficient SSE2 instruction set for Float and Long_Float operations.
21369 Note that the ABI has the same form for both floating-point models,
21370 so it is permissible to mix units compiled with and without these
21373 @node Vectorization of loops,Other Optimization Switches,Floating_Point_Operations,Performance Considerations
21374 @anchor{gnat_ugn/gnat_and_program_execution id34}@anchor{1a6}@anchor{gnat_ugn/gnat_and_program_execution vectorization-of-loops}@anchor{1a7}
21375 @subsubsection Vectorization of loops
21378 @geindex Optimization Switches
21380 You can take advantage of the auto-vectorizer present in the @code{gcc}
21381 back end to vectorize loops with GNAT. The corresponding command line switch
21382 is @code{-ftree-vectorize} but, as it is enabled by default at @code{-O3}
21383 and other aggressive optimizations helpful for vectorization also are enabled
21384 by default at this level, using @code{-O3} directly is recommended.
21386 You also need to make sure that the target architecture features a supported
21387 SIMD instruction set. For example, for the x86 architecture, you should at
21388 least specify @code{-msse2} to get significant vectorization (but you don't
21389 need to specify it for x86-64 as it is part of the base 64-bit architecture).
21390 Similarly, for the PowerPC architecture, you should specify @code{-maltivec}.
21392 The preferred loop form for vectorization is the @code{for} iteration scheme.
21393 Loops with a @code{while} iteration scheme can also be vectorized if they are
21394 very simple, but the vectorizer will quickly give up otherwise. With either
21395 iteration scheme, the flow of control must be straight, in particular no
21396 @code{exit} statement may appear in the loop body. The loop may however
21397 contain a single nested loop, if it can be vectorized when considered alone:
21402 A : array (1..4, 1..4) of Long_Float;
21403 S : array (1..4) of Long_Float;
21407 for I in A'Range(1) loop
21408 for J in A'Range(2) loop
21409 S (I) := S (I) + A (I, J);
21416 The vectorizable operations depend on the targeted SIMD instruction set, but
21417 the adding and some of the multiplying operators are generally supported, as
21418 well as the logical operators for modular types. Note that compiling
21419 with @code{-gnatp} might well reveal cases where some checks do thwart
21422 Type conversions may also prevent vectorization if they involve semantics that
21423 are not directly supported by the code generator or the SIMD instruction set.
21424 A typical example is direct conversion from floating-point to integer types.
21425 The solution in this case is to use the following idiom:
21430 Integer (S'Truncation (F))
21434 if @code{S} is the subtype of floating-point object @code{F}.
21436 In most cases, the vectorizable loops are loops that iterate over arrays.
21437 All kinds of array types are supported, i.e. constrained array types with
21443 type Array_Type is array (1 .. 4) of Long_Float;
21447 constrained array types with dynamic bounds:
21452 type Array_Type is array (1 .. Q.N) of Long_Float;
21454 type Array_Type is array (Q.K .. 4) of Long_Float;
21456 type Array_Type is array (Q.K .. Q.N) of Long_Float;
21460 or unconstrained array types:
21465 type Array_Type is array (Positive range <>) of Long_Float;
21469 The quality of the generated code decreases when the dynamic aspect of the
21470 array type increases, the worst code being generated for unconstrained array
21471 types. This is so because, the less information the compiler has about the
21472 bounds of the array, the more fallback code it needs to generate in order to
21473 fix things up at run time.
21475 It is possible to specify that a given loop should be subject to vectorization
21476 preferably to other optimizations by means of pragma @code{Loop_Optimize}:
21481 pragma Loop_Optimize (Vector);
21485 placed immediately within the loop will convey the appropriate hint to the
21486 compiler for this loop.
21488 It is also possible to help the compiler generate better vectorized code
21489 for a given loop by asserting that there are no loop-carried dependencies
21490 in the loop. Consider for example the procedure:
21495 type Arr is array (1 .. 4) of Long_Float;
21497 procedure Add (X, Y : not null access Arr; R : not null access Arr) is
21499 for I in Arr'Range loop
21500 R(I) := X(I) + Y(I);
21506 By default, the compiler cannot unconditionally vectorize the loop because
21507 assigning to a component of the array designated by R in one iteration could
21508 change the value read from the components of the array designated by X or Y
21509 in a later iteration. As a result, the compiler will generate two versions
21510 of the loop in the object code, one vectorized and the other not vectorized,
21511 as well as a test to select the appropriate version at run time. This can
21512 be overcome by another hint:
21517 pragma Loop_Optimize (Ivdep);
21521 placed immediately within the loop will tell the compiler that it can safely
21522 omit the non-vectorized version of the loop as well as the run-time test.
21524 @node Other Optimization Switches,Optimization and Strict Aliasing,Vectorization of loops,Performance Considerations
21525 @anchor{gnat_ugn/gnat_and_program_execution other-optimization-switches}@anchor{1a8}@anchor{gnat_ugn/gnat_and_program_execution id35}@anchor{1a9}
21526 @subsubsection Other Optimization Switches
21529 @geindex Optimization Switches
21531 Since GNAT uses the @code{gcc} back end, all the specialized
21532 @code{gcc} optimization switches are potentially usable. These switches
21533 have not been extensively tested with GNAT but can generally be expected
21534 to work. Examples of switches in this category are @code{-funroll-loops}
21535 and the various target-specific @code{-m} options (in particular, it has
21536 been observed that @code{-march=xxx} can significantly improve performance
21537 on appropriate machines). For full details of these switches, see
21538 the @emph{Submodel Options} section in the @emph{Hardware Models and Configurations}
21539 chapter of @cite{Using the GNU Compiler Collection (GCC)}.
21541 @node Optimization and Strict Aliasing,Aliased Variables and Optimization,Other Optimization Switches,Performance Considerations
21542 @anchor{gnat_ugn/gnat_and_program_execution optimization-and-strict-aliasing}@anchor{f3}@anchor{gnat_ugn/gnat_and_program_execution id36}@anchor{1aa}
21543 @subsubsection Optimization and Strict Aliasing
21548 @geindex Strict Aliasing
21550 @geindex No_Strict_Aliasing
21552 The strong typing capabilities of Ada allow an optimizer to generate
21553 efficient code in situations where other languages would be forced to
21554 make worst case assumptions preventing such optimizations. Consider
21555 the following example:
21561 type Int1 is new Integer;
21562 type Int2 is new Integer;
21563 type Int1A is access Int1;
21564 type Int2A is access Int2;
21571 for J in Data'Range loop
21572 if Data (J) = Int1V.all then
21573 Int2V.all := Int2V.all + 1;
21581 In this example, since the variable @code{Int1V} can only access objects
21582 of type @code{Int1}, and @code{Int2V} can only access objects of type
21583 @code{Int2}, there is no possibility that the assignment to
21584 @code{Int2V.all} affects the value of @code{Int1V.all}. This means that
21585 the compiler optimizer can "know" that the value @code{Int1V.all} is constant
21586 for all iterations of the loop and avoid the extra memory reference
21587 required to dereference it each time through the loop.
21589 This kind of optimization, called strict aliasing analysis, is
21590 triggered by specifying an optimization level of @code{-O2} or
21591 higher or @code{-Os} and allows GNAT to generate more efficient code
21592 when access values are involved.
21594 However, although this optimization is always correct in terms of
21595 the formal semantics of the Ada Reference Manual, difficulties can
21596 arise if features like @code{Unchecked_Conversion} are used to break
21597 the typing system. Consider the following complete program example:
21603 type int1 is new integer;
21604 type int2 is new integer;
21605 type a1 is access int1;
21606 type a2 is access int2;
21611 function to_a2 (Input : a1) return a2;
21614 with Unchecked_Conversion;
21616 function to_a2 (Input : a1) return a2 is
21618 new Unchecked_Conversion (a1, a2);
21620 return to_a2u (Input);
21626 with Text_IO; use Text_IO;
21628 v1 : a1 := new int1;
21629 v2 : a2 := to_a2 (v1);
21633 put_line (int1'image (v1.all));
21638 This program prints out 0 in @code{-O0} or @code{-O1}
21639 mode, but it prints out 1 in @code{-O2} mode. That's
21640 because in strict aliasing mode, the compiler can and
21641 does assume that the assignment to @code{v2.all} could not
21642 affect the value of @code{v1.all}, since different types
21645 This behavior is not a case of non-conformance with the standard, since
21646 the Ada RM specifies that an unchecked conversion where the resulting
21647 bit pattern is not a correct value of the target type can result in an
21648 abnormal value and attempting to reference an abnormal value makes the
21649 execution of a program erroneous. That's the case here since the result
21650 does not point to an object of type @code{int2}. This means that the
21651 effect is entirely unpredictable.
21653 However, although that explanation may satisfy a language
21654 lawyer, in practice an applications programmer expects an
21655 unchecked conversion involving pointers to create true
21656 aliases and the behavior of printing 1 seems plain wrong.
21657 In this case, the strict aliasing optimization is unwelcome.
21659 Indeed the compiler recognizes this possibility, and the
21660 unchecked conversion generates a warning:
21665 p2.adb:5:07: warning: possible aliasing problem with type "a2"
21666 p2.adb:5:07: warning: use -fno-strict-aliasing switch for references
21667 p2.adb:5:07: warning: or use "pragma No_Strict_Aliasing (a2);"
21671 Unfortunately the problem is recognized when compiling the body of
21672 package @code{p2}, but the actual "bad" code is generated while
21673 compiling the body of @code{m} and this latter compilation does not see
21674 the suspicious @code{Unchecked_Conversion}.
21676 As implied by the warning message, there are approaches you can use to
21677 avoid the unwanted strict aliasing optimization in a case like this.
21679 One possibility is to simply avoid the use of @code{-O2}, but
21680 that is a bit drastic, since it throws away a number of useful
21681 optimizations that do not involve strict aliasing assumptions.
21683 A less drastic approach is to compile the program using the
21684 option @code{-fno-strict-aliasing}. Actually it is only the
21685 unit containing the dereferencing of the suspicious pointer
21686 that needs to be compiled. So in this case, if we compile
21687 unit @code{m} with this switch, then we get the expected
21688 value of zero printed. Analyzing which units might need
21689 the switch can be painful, so a more reasonable approach
21690 is to compile the entire program with options @code{-O2}
21691 and @code{-fno-strict-aliasing}. If the performance is
21692 satisfactory with this combination of options, then the
21693 advantage is that the entire issue of possible "wrong"
21694 optimization due to strict aliasing is avoided.
21696 To avoid the use of compiler switches, the configuration
21697 pragma @code{No_Strict_Aliasing} with no parameters may be
21698 used to specify that for all access types, the strict
21699 aliasing optimization should be suppressed.
21701 However, these approaches are still overkill, in that they causes
21702 all manipulations of all access values to be deoptimized. A more
21703 refined approach is to concentrate attention on the specific
21704 access type identified as problematic.
21706 First, if a careful analysis of uses of the pointer shows
21707 that there are no possible problematic references, then
21708 the warning can be suppressed by bracketing the
21709 instantiation of @code{Unchecked_Conversion} to turn
21715 pragma Warnings (Off);
21717 new Unchecked_Conversion (a1, a2);
21718 pragma Warnings (On);
21722 Of course that approach is not appropriate for this particular
21723 example, since indeed there is a problematic reference. In this
21724 case we can take one of two other approaches.
21726 The first possibility is to move the instantiation of unchecked
21727 conversion to the unit in which the type is declared. In
21728 this example, we would move the instantiation of
21729 @code{Unchecked_Conversion} from the body of package
21730 @code{p2} to the spec of package @code{p1}. Now the
21731 warning disappears. That's because any use of the
21732 access type knows there is a suspicious unchecked
21733 conversion, and the strict aliasing optimization
21734 is automatically suppressed for the type.
21736 If it is not practical to move the unchecked conversion to the same unit
21737 in which the destination access type is declared (perhaps because the
21738 source type is not visible in that unit), you may use pragma
21739 @code{No_Strict_Aliasing} for the type. This pragma must occur in the
21740 same declarative sequence as the declaration of the access type:
21745 type a2 is access int2;
21746 pragma No_Strict_Aliasing (a2);
21750 Here again, the compiler now knows that the strict aliasing optimization
21751 should be suppressed for any reference to type @code{a2} and the
21752 expected behavior is obtained.
21754 Finally, note that although the compiler can generate warnings for
21755 simple cases of unchecked conversions, there are tricker and more
21756 indirect ways of creating type incorrect aliases which the compiler
21757 cannot detect. Examples are the use of address overlays and unchecked
21758 conversions involving composite types containing access types as
21759 components. In such cases, no warnings are generated, but there can
21760 still be aliasing problems. One safe coding practice is to forbid the
21761 use of address clauses for type overlaying, and to allow unchecked
21762 conversion only for primitive types. This is not really a significant
21763 restriction since any possible desired effect can be achieved by
21764 unchecked conversion of access values.
21766 The aliasing analysis done in strict aliasing mode can certainly
21767 have significant benefits. We have seen cases of large scale
21768 application code where the time is increased by up to 5% by turning
21769 this optimization off. If you have code that includes significant
21770 usage of unchecked conversion, you might want to just stick with
21771 @code{-O1} and avoid the entire issue. If you get adequate
21772 performance at this level of optimization level, that's probably
21773 the safest approach. If tests show that you really need higher
21774 levels of optimization, then you can experiment with @code{-O2}
21775 and @code{-O2 -fno-strict-aliasing} to see how much effect this
21776 has on size and speed of the code. If you really need to use
21777 @code{-O2} with strict aliasing in effect, then you should
21778 review any uses of unchecked conversion of access types,
21779 particularly if you are getting the warnings described above.
21781 @node Aliased Variables and Optimization,Atomic Variables and Optimization,Optimization and Strict Aliasing,Performance Considerations
21782 @anchor{gnat_ugn/gnat_and_program_execution id37}@anchor{1ab}@anchor{gnat_ugn/gnat_and_program_execution aliased-variables-and-optimization}@anchor{1ac}
21783 @subsubsection Aliased Variables and Optimization
21788 There are scenarios in which programs may
21789 use low level techniques to modify variables
21790 that otherwise might be considered to be unassigned. For example,
21791 a variable can be passed to a procedure by reference, which takes
21792 the address of the parameter and uses the address to modify the
21793 variable's value, even though it is passed as an IN parameter.
21794 Consider the following example:
21800 Max_Length : constant Natural := 16;
21801 type Char_Ptr is access all Character;
21803 procedure Get_String(Buffer: Char_Ptr; Size : Integer);
21804 pragma Import (C, Get_String, "get_string");
21806 Name : aliased String (1 .. Max_Length) := (others => ' ');
21809 function Addr (S : String) return Char_Ptr is
21810 function To_Char_Ptr is
21811 new Ada.Unchecked_Conversion (System.Address, Char_Ptr);
21813 return To_Char_Ptr (S (S'First)'Address);
21817 Temp := Addr (Name);
21818 Get_String (Temp, Max_Length);
21823 where Get_String is a C function that uses the address in Temp to
21824 modify the variable @code{Name}. This code is dubious, and arguably
21825 erroneous, and the compiler would be entitled to assume that
21826 @code{Name} is never modified, and generate code accordingly.
21828 However, in practice, this would cause some existing code that
21829 seems to work with no optimization to start failing at high
21830 levels of optimzization.
21832 What the compiler does for such cases is to assume that marking
21833 a variable as aliased indicates that some "funny business" may
21834 be going on. The optimizer recognizes the aliased keyword and
21835 inhibits optimizations that assume the value cannot be assigned.
21836 This means that the above example will in fact "work" reliably,
21837 that is, it will produce the expected results.
21839 @node Atomic Variables and Optimization,Passive Task Optimization,Aliased Variables and Optimization,Performance Considerations
21840 @anchor{gnat_ugn/gnat_and_program_execution atomic-variables-and-optimization}@anchor{1ad}@anchor{gnat_ugn/gnat_and_program_execution id38}@anchor{1ae}
21841 @subsubsection Atomic Variables and Optimization
21846 There are two considerations with regard to performance when
21847 atomic variables are used.
21849 First, the RM only guarantees that access to atomic variables
21850 be atomic, it has nothing to say about how this is achieved,
21851 though there is a strong implication that this should not be
21852 achieved by explicit locking code. Indeed GNAT will never
21853 generate any locking code for atomic variable access (it will
21854 simply reject any attempt to make a variable or type atomic
21855 if the atomic access cannot be achieved without such locking code).
21857 That being said, it is important to understand that you cannot
21858 assume that the entire variable will always be accessed. Consider
21865 A,B,C,D : Character;
21868 for R'Alignment use 4;
21871 pragma Atomic (RV);
21878 You cannot assume that the reference to @code{RV.B}
21879 will read the entire 32-bit
21880 variable with a single load instruction. It is perfectly legitimate if
21881 the hardware allows it to do a byte read of just the B field. This read
21882 is still atomic, which is all the RM requires. GNAT can and does take
21883 advantage of this, depending on the architecture and optimization level.
21884 Any assumption to the contrary is non-portable and risky. Even if you
21885 examine the assembly language and see a full 32-bit load, this might
21886 change in a future version of the compiler.
21888 If your application requires that all accesses to @code{RV} in this
21889 example be full 32-bit loads, you need to make a copy for the access
21896 RV_Copy : constant R := RV;
21903 Now the reference to RV must read the whole variable.
21904 Actually one can imagine some compiler which figures
21905 out that the whole copy is not required (because only
21906 the B field is actually accessed), but GNAT
21907 certainly won't do that, and we don't know of any
21908 compiler that would not handle this right, and the
21909 above code will in practice work portably across
21910 all architectures (that permit the Atomic declaration).
21912 The second issue with atomic variables has to do with
21913 the possible requirement of generating synchronization
21914 code. For more details on this, consult the sections on
21915 the pragmas Enable/Disable_Atomic_Synchronization in the
21916 GNAT Reference Manual. If performance is critical, and
21917 such synchronization code is not required, it may be
21918 useful to disable it.
21920 @node Passive Task Optimization,,Atomic Variables and Optimization,Performance Considerations
21921 @anchor{gnat_ugn/gnat_and_program_execution passive-task-optimization}@anchor{1af}@anchor{gnat_ugn/gnat_and_program_execution id39}@anchor{1b0}
21922 @subsubsection Passive Task Optimization
21925 @geindex Passive Task
21927 A passive task is one which is sufficiently simple that
21928 in theory a compiler could recognize it an implement it
21929 efficiently without creating a new thread. The original design
21930 of Ada 83 had in mind this kind of passive task optimization, but
21931 only a few Ada 83 compilers attempted it. The problem was that
21932 it was difficult to determine the exact conditions under which
21933 the optimization was possible. The result is a very fragile
21934 optimization where a very minor change in the program can
21935 suddenly silently make a task non-optimizable.
21937 With the revisiting of this issue in Ada 95, there was general
21938 agreement that this approach was fundamentally flawed, and the
21939 notion of protected types was introduced. When using protected
21940 types, the restrictions are well defined, and you KNOW that the
21941 operations will be optimized, and furthermore this optimized
21942 performance is fully portable.
21944 Although it would theoretically be possible for GNAT to attempt to
21945 do this optimization, but it really doesn't make sense in the
21946 context of Ada 95, and none of the Ada 95 compilers implement
21947 this optimization as far as we know. In particular GNAT never
21948 attempts to perform this optimization.
21950 In any new Ada 95 code that is written, you should always
21951 use protected types in place of tasks that might be able to
21952 be optimized in this manner.
21953 Of course this does not help if you have legacy Ada 83 code
21954 that depends on this optimization, but it is unusual to encounter
21955 a case where the performance gains from this optimization
21958 Your program should work correctly without this optimization. If
21959 you have performance problems, then the most practical
21960 approach is to figure out exactly where these performance problems
21961 arise, and update those particular tasks to be protected types. Note
21962 that typically clients of the tasks who call entries, will not have
21963 to be modified, only the task definition itself.
21965 @node Text_IO Suggestions,Reducing Size of Executables with Unused Subprogram/Data Elimination,Performance Considerations,Improving Performance
21966 @anchor{gnat_ugn/gnat_and_program_execution text-io-suggestions}@anchor{1b1}@anchor{gnat_ugn/gnat_and_program_execution id40}@anchor{1b2}
21967 @subsection @code{Text_IO} Suggestions
21970 @geindex Text_IO and performance
21972 The @code{Ada.Text_IO} package has fairly high overheads due in part to
21973 the requirement of maintaining page and line counts. If performance
21974 is critical, a recommendation is to use @code{Stream_IO} instead of
21975 @code{Text_IO} for volume output, since this package has less overhead.
21977 If @code{Text_IO} must be used, note that by default output to the standard
21978 output and standard error files is unbuffered (this provides better
21979 behavior when output statements are used for debugging, or if the
21980 progress of a program is observed by tracking the output, e.g. by
21981 using the Unix @emph{tail -f} command to watch redirected output.
21983 If you are generating large volumes of output with @code{Text_IO} and
21984 performance is an important factor, use a designated file instead
21985 of the standard output file, or change the standard output file to
21986 be buffered using @code{Interfaces.C_Streams.setvbuf}.
21988 @node Reducing Size of Executables with Unused Subprogram/Data Elimination,,Text_IO Suggestions,Improving Performance
21989 @anchor{gnat_ugn/gnat_and_program_execution id41}@anchor{1b3}@anchor{gnat_ugn/gnat_and_program_execution reducing-size-of-executables-with-unused-subprogram-data-elimination}@anchor{1b4}
21990 @subsection Reducing Size of Executables with Unused Subprogram/Data Elimination
21993 @geindex Uunused subprogram/data elimination
21995 This section describes how you can eliminate unused subprograms and data from
21996 your executable just by setting options at compilation time.
21999 * About unused subprogram/data elimination::
22000 * Compilation options::
22001 * Example of unused subprogram/data elimination::
22005 @node About unused subprogram/data elimination,Compilation options,,Reducing Size of Executables with Unused Subprogram/Data Elimination
22006 @anchor{gnat_ugn/gnat_and_program_execution id42}@anchor{1b5}@anchor{gnat_ugn/gnat_and_program_execution about-unused-subprogram-data-elimination}@anchor{1b6}
22007 @subsubsection About unused subprogram/data elimination
22010 By default, an executable contains all code and data of its composing objects
22011 (directly linked or coming from statically linked libraries), even data or code
22012 never used by this executable.
22014 This feature will allow you to eliminate such unused code from your
22015 executable, making it smaller (in disk and in memory).
22017 This functionality is available on all Linux platforms except for the IA-64
22018 architecture and on all cross platforms using the ELF binary file format.
22019 In both cases GNU binutils version 2.16 or later are required to enable it.
22021 @node Compilation options,Example of unused subprogram/data elimination,About unused subprogram/data elimination,Reducing Size of Executables with Unused Subprogram/Data Elimination
22022 @anchor{gnat_ugn/gnat_and_program_execution id43}@anchor{1b7}@anchor{gnat_ugn/gnat_and_program_execution compilation-options}@anchor{1b8}
22023 @subsubsection Compilation options
22026 The operation of eliminating the unused code and data from the final executable
22027 is directly performed by the linker.
22029 @geindex -ffunction-sections (gcc)
22031 @geindex -fdata-sections (gcc)
22033 In order to do this, it has to work with objects compiled with the
22035 @code{-ffunction-sections} @code{-fdata-sections}.
22037 These options are usable with C and Ada files.
22038 They will place respectively each
22039 function or data in a separate section in the resulting object file.
22041 Once the objects and static libraries are created with these options, the
22042 linker can perform the dead code elimination. You can do this by setting
22043 the @code{-Wl,--gc-sections} option to gcc command or in the
22044 @code{-largs} section of @code{gnatmake}. This will perform a
22045 garbage collection of code and data never referenced.
22047 If the linker performs a partial link (@code{-r} linker option), then you
22048 will need to provide the entry point using the @code{-e} / @code{--entry}
22051 Note that objects compiled without the @code{-ffunction-sections} and
22052 @code{-fdata-sections} options can still be linked with the executable.
22053 However, no dead code elimination will be performed on those objects (they will
22056 The GNAT static library is now compiled with -ffunction-sections and
22057 -fdata-sections on some platforms. This allows you to eliminate the unused code
22058 and data of the GNAT library from your executable.
22060 @node Example of unused subprogram/data elimination,,Compilation options,Reducing Size of Executables with Unused Subprogram/Data Elimination
22061 @anchor{gnat_ugn/gnat_and_program_execution example-of-unused-subprogram-data-elimination}@anchor{1b9}@anchor{gnat_ugn/gnat_and_program_execution id44}@anchor{1ba}
22062 @subsubsection Example of unused subprogram/data elimination
22065 Here is a simple example:
22078 Used_Data : Integer;
22079 Unused_Data : Integer;
22081 procedure Used (Data : Integer);
22082 procedure Unused (Data : Integer);
22085 package body Aux is
22086 procedure Used (Data : Integer) is
22091 procedure Unused (Data : Integer) is
22093 Unused_Data := Data;
22099 @code{Unused} and @code{Unused_Data} are never referenced in this code
22100 excerpt, and hence they may be safely removed from the final executable.
22107 $ nm test | grep used
22108 020015f0 T aux__unused
22109 02005d88 B aux__unused_data
22110 020015cc T aux__used
22111 02005d84 B aux__used_data
22113 $ gnatmake test -cargs -fdata-sections -ffunction-sections \\
22114 -largs -Wl,--gc-sections
22116 $ nm test | grep used
22117 02005350 T aux__used
22118 0201ffe0 B aux__used_data
22122 It can be observed that the procedure @code{Unused} and the object
22123 @code{Unused_Data} are removed by the linker when using the
22124 appropriate options.
22126 @geindex Overflow checks
22128 @geindex Checks (overflow)
22131 @node Overflow Check Handling in GNAT,Performing Dimensionality Analysis in GNAT,Improving Performance,GNAT and Program Execution
22132 @anchor{gnat_ugn/gnat_and_program_execution id50}@anchor{169}@anchor{gnat_ugn/gnat_and_program_execution overflow-check-handling-in-gnat}@anchor{27}
22133 @section Overflow Check Handling in GNAT
22136 This section explains how to control the handling of overflow checks.
22140 * Management of Overflows in GNAT::
22141 * Specifying the Desired Mode::
22142 * Default Settings::
22143 * Implementation Notes::
22147 @node Background,Management of Overflows in GNAT,,Overflow Check Handling in GNAT
22148 @anchor{gnat_ugn/gnat_and_program_execution id51}@anchor{1bb}@anchor{gnat_ugn/gnat_and_program_execution background}@anchor{1bc}
22149 @subsection Background
22152 Overflow checks are checks that the compiler may make to ensure
22153 that intermediate results are not out of range. For example:
22164 If @code{A} has the value @code{Integer'Last}, then the addition may cause
22165 overflow since the result is out of range of the type @code{Integer}.
22166 In this case @code{Constraint_Error} will be raised if checks are
22169 A trickier situation arises in examples like the following:
22180 where @code{A} is @code{Integer'Last} and @code{C} is @code{-1}.
22181 Now the final result of the expression on the right hand side is
22182 @code{Integer'Last} which is in range, but the question arises whether the
22183 intermediate addition of @code{(A + 1)} raises an overflow error.
22185 The (perhaps surprising) answer is that the Ada language
22186 definition does not answer this question. Instead it leaves
22187 it up to the implementation to do one of two things if overflow
22188 checks are enabled.
22194 raise an exception (@code{Constraint_Error}), or
22197 yield the correct mathematical result which is then used in
22198 subsequent operations.
22201 If the compiler chooses the first approach, then the assignment of this
22202 example will indeed raise @code{Constraint_Error} if overflow checking is
22203 enabled, or result in erroneous execution if overflow checks are suppressed.
22205 But if the compiler
22206 chooses the second approach, then it can perform both additions yielding
22207 the correct mathematical result, which is in range, so no exception
22208 will be raised, and the right result is obtained, regardless of whether
22209 overflow checks are suppressed.
22211 Note that in the first example an
22212 exception will be raised in either case, since if the compiler
22213 gives the correct mathematical result for the addition, it will
22214 be out of range of the target type of the assignment, and thus
22215 fails the range check.
22217 This lack of specified behavior in the handling of overflow for
22218 intermediate results is a source of non-portability, and can thus
22219 be problematic when programs are ported. Most typically this arises
22220 in a situation where the original compiler did not raise an exception,
22221 and then the application is moved to a compiler where the check is
22222 performed on the intermediate result and an unexpected exception is
22225 Furthermore, when using Ada 2012's preconditions and other
22226 assertion forms, another issue arises. Consider:
22231 procedure P (A, B : Integer) with
22232 Pre => A + B <= Integer'Last;
22236 One often wants to regard arithmetic in a context like this from
22237 a mathematical point of view. So for example, if the two actual parameters
22238 for a call to @code{P} are both @code{Integer'Last}, then
22239 the precondition should be regarded as False. If we are executing
22240 in a mode with run-time checks enabled for preconditions, then we would
22241 like this precondition to fail, rather than raising an exception
22242 because of the intermediate overflow.
22244 However, the language definition leaves the specification of
22245 whether the above condition fails (raising @code{Assert_Error}) or
22246 causes an intermediate overflow (raising @code{Constraint_Error})
22247 up to the implementation.
22249 The situation is worse in a case such as the following:
22254 procedure Q (A, B, C : Integer) with
22255 Pre => A + B + C <= Integer'Last;
22264 Q (A => Integer'Last, B => 1, C => -1);
22268 From a mathematical point of view the precondition
22269 is True, but at run time we may (but are not guaranteed to) get an
22270 exception raised because of the intermediate overflow (and we really
22271 would prefer this precondition to be considered True at run time).
22273 @node Management of Overflows in GNAT,Specifying the Desired Mode,Background,Overflow Check Handling in GNAT
22274 @anchor{gnat_ugn/gnat_and_program_execution management-of-overflows-in-gnat}@anchor{1bd}@anchor{gnat_ugn/gnat_and_program_execution id52}@anchor{1be}
22275 @subsection Management of Overflows in GNAT
22278 To deal with the portability issue, and with the problem of
22279 mathematical versus run-time interpretation of the expressions in
22280 assertions, GNAT provides comprehensive control over the handling
22281 of intermediate overflow. GNAT can operate in three modes, and
22282 furthemore, permits separate selection of operating modes for
22283 the expressions within assertions (here the term 'assertions'
22284 is used in the technical sense, which includes preconditions and so forth)
22285 and for expressions appearing outside assertions.
22287 The three modes are:
22293 @emph{Use base type for intermediate operations} (@code{STRICT})
22295 In this mode, all intermediate results for predefined arithmetic
22296 operators are computed using the base type, and the result must
22297 be in range of the base type. If this is not the
22298 case then either an exception is raised (if overflow checks are
22299 enabled) or the execution is erroneous (if overflow checks are suppressed).
22300 This is the normal default mode.
22303 @emph{Most intermediate overflows avoided} (@code{MINIMIZED})
22305 In this mode, the compiler attempts to avoid intermediate overflows by
22306 using a larger integer type, typically @code{Long_Long_Integer},
22307 as the type in which arithmetic is
22308 performed for predefined arithmetic operators. This may be slightly more
22310 run time (compared to suppressing intermediate overflow checks), though
22311 the cost is negligible on modern 64-bit machines. For the examples given
22312 earlier, no intermediate overflows would have resulted in exceptions,
22313 since the intermediate results are all in the range of
22314 @code{Long_Long_Integer} (typically 64-bits on nearly all implementations
22315 of GNAT). In addition, if checks are enabled, this reduces the number of
22316 checks that must be made, so this choice may actually result in an
22317 improvement in space and time behavior.
22319 However, there are cases where @code{Long_Long_Integer} is not large
22320 enough, consider the following example:
22325 procedure R (A, B, C, D : Integer) with
22326 Pre => (A**2 * B**2) / (C**2 * D**2) <= 10;
22330 where @code{A} = @code{B} = @code{C} = @code{D} = @code{Integer'Last}.
22331 Now the intermediate results are
22332 out of the range of @code{Long_Long_Integer} even though the final result
22333 is in range and the precondition is True (from a mathematical point
22334 of view). In such a case, operating in this mode, an overflow occurs
22335 for the intermediate computation (which is why this mode
22336 says @emph{most} intermediate overflows are avoided). In this case,
22337 an exception is raised if overflow checks are enabled, and the
22338 execution is erroneous if overflow checks are suppressed.
22341 @emph{All intermediate overflows avoided} (@code{ELIMINATED})
22343 In this mode, the compiler avoids all intermediate overflows
22344 by using arbitrary precision arithmetic as required. In this
22345 mode, the above example with @code{A**2 * B**2} would
22346 not cause intermediate overflow, because the intermediate result
22347 would be evaluated using sufficient precision, and the result
22348 of evaluating the precondition would be True.
22350 This mode has the advantage of avoiding any intermediate
22351 overflows, but at the expense of significant run-time overhead,
22352 including the use of a library (included automatically in this
22353 mode) for multiple-precision arithmetic.
22355 This mode provides cleaner semantics for assertions, since now
22356 the run-time behavior emulates true arithmetic behavior for the
22357 predefined arithmetic operators, meaning that there is never a
22358 conflict between the mathematical view of the assertion, and its
22361 Note that in this mode, the behavior is unaffected by whether or
22362 not overflow checks are suppressed, since overflow does not occur.
22363 It is possible for gigantic intermediate expressions to raise
22364 @code{Storage_Error} as a result of attempting to compute the
22365 results of such expressions (e.g. @code{Integer'Last ** Integer'Last})
22366 but overflow is impossible.
22369 Note that these modes apply only to the evaluation of predefined
22370 arithmetic, membership, and comparison operators for signed integer
22373 For fixed-point arithmetic, checks can be suppressed. But if checks
22375 then fixed-point values are always checked for overflow against the
22376 base type for intermediate expressions (that is such checks always
22377 operate in the equivalent of @code{STRICT} mode).
22379 For floating-point, on nearly all architectures, @code{Machine_Overflows}
22380 is False, and IEEE infinities are generated, so overflow exceptions
22381 are never raised. If you want to avoid infinities, and check that
22382 final results of expressions are in range, then you can declare a
22383 constrained floating-point type, and range checks will be carried
22384 out in the normal manner (with infinite values always failing all
22387 @node Specifying the Desired Mode,Default Settings,Management of Overflows in GNAT,Overflow Check Handling in GNAT
22388 @anchor{gnat_ugn/gnat_and_program_execution specifying-the-desired-mode}@anchor{f8}@anchor{gnat_ugn/gnat_and_program_execution id53}@anchor{1bf}
22389 @subsection Specifying the Desired Mode
22392 @geindex pragma Overflow_Mode
22394 The desired mode of for handling intermediate overflow can be specified using
22395 either the @code{Overflow_Mode} pragma or an equivalent compiler switch.
22396 The pragma has the form
22401 pragma Overflow_Mode ([General =>] MODE [, [Assertions =>] MODE]);
22405 where @code{MODE} is one of
22411 @code{STRICT}: intermediate overflows checked (using base type)
22414 @code{MINIMIZED}: minimize intermediate overflows
22417 @code{ELIMINATED}: eliminate intermediate overflows
22420 The case is ignored, so @code{MINIMIZED}, @code{Minimized} and
22421 @code{minimized} all have the same effect.
22423 If only the @code{General} parameter is present, then the given @code{MODE} applies
22424 to expressions both within and outside assertions. If both arguments
22425 are present, then @code{General} applies to expressions outside assertions,
22426 and @code{Assertions} applies to expressions within assertions. For example:
22431 pragma Overflow_Mode
22432 (General => Minimized, Assertions => Eliminated);
22436 specifies that general expressions outside assertions be evaluated
22437 in 'minimize intermediate overflows' mode, and expressions within
22438 assertions be evaluated in 'eliminate intermediate overflows' mode.
22439 This is often a reasonable choice, avoiding excessive overhead
22440 outside assertions, but assuring a high degree of portability
22441 when importing code from another compiler, while incurring
22442 the extra overhead for assertion expressions to ensure that
22443 the behavior at run time matches the expected mathematical
22446 The @code{Overflow_Mode} pragma has the same scoping and placement
22447 rules as pragma @code{Suppress}, so it can occur either as a
22448 configuration pragma, specifying a default for the whole
22449 program, or in a declarative scope, where it applies to the
22450 remaining declarations and statements in that scope.
22452 Note that pragma @code{Overflow_Mode} does not affect whether
22453 overflow checks are enabled or suppressed. It only controls the
22454 method used to compute intermediate values. To control whether
22455 overflow checking is enabled or suppressed, use pragma @code{Suppress}
22456 or @code{Unsuppress} in the usual manner.
22458 @geindex -gnato? (gcc)
22460 @geindex -gnato?? (gcc)
22462 Additionally, a compiler switch @code{-gnato?} or @code{-gnato??}
22463 can be used to control the checking mode default (which can be subsequently
22464 overridden using pragmas).
22466 Here @code{?} is one of the digits @code{1} through @code{3}:
22471 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
22478 use base type for intermediate operations (@code{STRICT})
22486 minimize intermediate overflows (@code{MINIMIZED})
22494 eliminate intermediate overflows (@code{ELIMINATED})
22500 As with the pragma, if only one digit appears then it applies to all
22501 cases; if two digits are given, then the first applies outside
22502 assertions, and the second within assertions. Thus the equivalent
22503 of the example pragma above would be
22506 If no digits follow the @code{-gnato}, then it is equivalent to
22508 causing all intermediate operations to be computed using the base
22509 type (@code{STRICT} mode).
22511 @node Default Settings,Implementation Notes,Specifying the Desired Mode,Overflow Check Handling in GNAT
22512 @anchor{gnat_ugn/gnat_and_program_execution id54}@anchor{1c0}@anchor{gnat_ugn/gnat_and_program_execution default-settings}@anchor{1c1}
22513 @subsection Default Settings
22516 The default mode for overflow checks is
22525 which causes all computations both inside and outside assertions to use
22528 This retains compatibility with previous versions of
22529 GNAT which suppressed overflow checks by default and always
22530 used the base type for computation of intermediate results.
22532 @c Sphinx allows no emphasis within :index: role. As a workaround we
22533 @c point the index to "switch" and use emphasis for "-gnato".
22536 @geindex -gnato (gcc)
22537 switch @code{-gnato} (with no digits following)
22547 which causes overflow checking of all intermediate overflows
22548 both inside and outside assertions against the base type.
22550 The pragma @code{Suppress (Overflow_Check)} disables overflow
22551 checking, but it has no effect on the method used for computing
22552 intermediate results.
22554 The pragma @code{Unsuppress (Overflow_Check)} enables overflow
22555 checking, but it has no effect on the method used for computing
22556 intermediate results.
22558 @node Implementation Notes,,Default Settings,Overflow Check Handling in GNAT
22559 @anchor{gnat_ugn/gnat_and_program_execution id55}@anchor{1c2}@anchor{gnat_ugn/gnat_and_program_execution implementation-notes}@anchor{1c3}
22560 @subsection Implementation Notes
22563 In practice on typical 64-bit machines, the @code{MINIMIZED} mode is
22564 reasonably efficient, and can be generally used. It also helps
22565 to ensure compatibility with code imported from some other
22568 Setting all intermediate overflows checking (@code{CHECKED} mode)
22569 makes sense if you want to
22570 make sure that your code is compatible with any other possible
22571 Ada implementation. This may be useful in ensuring portability
22572 for code that is to be exported to some other compiler than GNAT.
22574 The Ada standard allows the reassociation of expressions at
22575 the same precedence level if no parentheses are present. For
22576 example, @code{A+B+C} parses as though it were @code{(A+B)+C}, but
22577 the compiler can reintepret this as @code{A+(B+C)}, possibly
22578 introducing or eliminating an overflow exception. The GNAT
22579 compiler never takes advantage of this freedom, and the
22580 expression @code{A+B+C} will be evaluated as @code{(A+B)+C}.
22581 If you need the other order, you can write the parentheses
22582 explicitly @code{A+(B+C)} and GNAT will respect this order.
22584 The use of @code{ELIMINATED} mode will cause the compiler to
22585 automatically include an appropriate arbitrary precision
22586 integer arithmetic package. The compiler will make calls
22587 to this package, though only in cases where it cannot be
22588 sure that @code{Long_Long_Integer} is sufficient to guard against
22589 intermediate overflows. This package does not use dynamic
22590 alllocation, but it does use the secondary stack, so an
22591 appropriate secondary stack package must be present (this
22592 is always true for standard full Ada, but may require
22593 specific steps for restricted run times such as ZFP).
22595 Although @code{ELIMINATED} mode causes expressions to use arbitrary
22596 precision arithmetic, avoiding overflow, the final result
22597 must be in an appropriate range. This is true even if the
22598 final result is of type @code{[Long_[Long_]]Integer'Base}, which
22599 still has the same bounds as its associated constrained
22602 Currently, the @code{ELIMINATED} mode is only available on target
22603 platforms for which @code{Long_Long_Integer} is 64-bits (nearly all GNAT
22606 @node Performing Dimensionality Analysis in GNAT,Stack Related Facilities,Overflow Check Handling in GNAT,GNAT and Program Execution
22607 @anchor{gnat_ugn/gnat_and_program_execution id56}@anchor{16a}@anchor{gnat_ugn/gnat_and_program_execution performing-dimensionality-analysis-in-gnat}@anchor{28}
22608 @section Performing Dimensionality Analysis in GNAT
22611 @geindex Dimensionality analysis
22613 The GNAT compiler supports dimensionality checking. The user can
22614 specify physical units for objects, and the compiler will verify that uses
22615 of these objects are compatible with their dimensions, in a fashion that is
22616 familiar to engineering practice. The dimensions of algebraic expressions
22617 (including powers with static exponents) are computed from their constituents.
22619 @geindex Dimension_System aspect
22621 @geindex Dimension aspect
22623 This feature depends on Ada 2012 aspect specifications, and is available from
22624 version 7.0.1 of GNAT onwards.
22625 The GNAT-specific aspect @code{Dimension_System}
22626 allows you to define a system of units; the aspect @code{Dimension}
22627 then allows the user to declare dimensioned quantities within a given system.
22628 (These aspects are described in the @emph{Implementation Defined Aspects}
22629 chapter of the @emph{GNAT Reference Manual}).
22631 The major advantage of this model is that it does not require the declaration of
22632 multiple operators for all possible combinations of types: it is only necessary
22633 to use the proper subtypes in object declarations.
22635 @geindex System.Dim.Mks package (GNAT library)
22637 @geindex MKS_Type type
22639 The simplest way to impose dimensionality checking on a computation is to make
22640 use of one of the instantiations of the package @code{System.Dim.Generic_Mks}, which
22641 are part of the GNAT library. This generic package defines a floating-point
22642 type @code{MKS_Type}, for which a sequence of dimension names are specified,
22643 together with their conventional abbreviations. The following should be read
22644 together with the full specification of the package, in file
22645 @code{s-digemk.ads}.
22649 @geindex s-digemk.ads file
22652 type Mks_Type is new Float_Type
22654 Dimension_System => (
22655 (Unit_Name => Meter, Unit_Symbol => 'm', Dim_Symbol => 'L'),
22656 (Unit_Name => Kilogram, Unit_Symbol => "kg", Dim_Symbol => 'M'),
22657 (Unit_Name => Second, Unit_Symbol => 's', Dim_Symbol => 'T'),
22658 (Unit_Name => Ampere, Unit_Symbol => 'A', Dim_Symbol => 'I'),
22659 (Unit_Name => Kelvin, Unit_Symbol => 'K', Dim_Symbol => "Theta"),
22660 (Unit_Name => Mole, Unit_Symbol => "mol", Dim_Symbol => 'N'),
22661 (Unit_Name => Candela, Unit_Symbol => "cd", Dim_Symbol => 'J'));
22665 The package then defines a series of subtypes that correspond to these
22666 conventional units. For example:
22671 subtype Length is Mks_Type
22673 Dimension => (Symbol => 'm', Meter => 1, others => 0);
22677 and similarly for @code{Mass}, @code{Time}, @code{Electric_Current},
22678 @code{Thermodynamic_Temperature}, @code{Amount_Of_Substance}, and
22679 @code{Luminous_Intensity} (the standard set of units of the SI system).
22681 The package also defines conventional names for values of each unit, for
22687 m : constant Length := 1.0;
22688 kg : constant Mass := 1.0;
22689 s : constant Time := 1.0;
22690 A : constant Electric_Current := 1.0;
22694 as well as useful multiples of these units:
22699 cm : constant Length := 1.0E-02;
22700 g : constant Mass := 1.0E-03;
22701 min : constant Time := 60.0;
22702 day : constant Time := 60.0 * 24.0 * min;
22707 There are three instantiations of @code{System.Dim.Generic_Mks} defined in the
22714 @code{System.Dim.Float_Mks} based on @code{Float} defined in @code{s-diflmk.ads}.
22717 @code{System.Dim.Long_Mks} based on @code{Long_Float} defined in @code{s-dilomk.ads}.
22720 @code{System.Dim.Mks} based on @code{Long_Long_Float} defined in @code{s-dimmks.ads}.
22723 Using one of these packages, you can then define a derived unit by providing
22724 the aspect that specifies its dimensions within the MKS system, as well as the
22725 string to be used for output of a value of that unit:
22730 subtype Acceleration is Mks_Type
22731 with Dimension => ("m/sec^2",
22738 Here is a complete example of use:
22743 with System.Dim.MKS; use System.Dim.Mks;
22744 with System.Dim.Mks_IO; use System.Dim.Mks_IO;
22745 with Text_IO; use Text_IO;
22746 procedure Free_Fall is
22747 subtype Acceleration is Mks_Type
22748 with Dimension => ("m/sec^2", 1, 0, -2, others => 0);
22749 G : constant acceleration := 9.81 * m / (s ** 2);
22750 T : Time := 10.0*s;
22754 Put ("Gravitational constant: ");
22755 Put (G, Aft => 2, Exp => 0); Put_Line ("");
22756 Distance := 0.5 * G * T ** 2;
22757 Put ("distance travelled in 10 seconds of free fall ");
22758 Put (Distance, Aft => 2, Exp => 0);
22764 Execution of this program yields:
22769 Gravitational constant: 9.81 m/sec^2
22770 distance travelled in 10 seconds of free fall 490.50 m
22774 However, incorrect assignments such as:
22780 Distance := 5.0 * kg;
22784 are rejected with the following diagnoses:
22790 >>> dimensions mismatch in assignment
22791 >>> left-hand side has dimension [L]
22792 >>> right-hand side is dimensionless
22794 Distance := 5.0 * kg:
22795 >>> dimensions mismatch in assignment
22796 >>> left-hand side has dimension [L]
22797 >>> right-hand side has dimension [M]
22801 The dimensions of an expression are properly displayed, even if there is
22802 no explicit subtype for it. If we add to the program:
22807 Put ("Final velocity: ");
22808 Put (G * T, Aft =>2, Exp =>0);
22813 then the output includes:
22818 Final velocity: 98.10 m.s**(-1)
22821 @geindex Dimensionable type
22823 @geindex Dimensioned subtype
22826 The type @code{Mks_Type} is said to be a @emph{dimensionable type} since it has a
22827 @code{Dimension_System} aspect, and the subtypes @code{Length}, @code{Mass}, etc.,
22828 are said to be @emph{dimensioned subtypes} since each one has a @code{Dimension}
22833 @geindex Dimension Vector (for a dimensioned subtype)
22835 @geindex Dimension aspect
22837 @geindex Dimension_System aspect
22840 The @code{Dimension} aspect of a dimensioned subtype @code{S} defines a mapping
22841 from the base type's Unit_Names to integer (or, more generally, rational)
22842 values. This mapping is the @emph{dimension vector} (also referred to as the
22843 @emph{dimensionality}) for that subtype, denoted by @code{DV(S)}, and thus for each
22844 object of that subtype. Intuitively, the value specified for each
22845 @code{Unit_Name} is the exponent associated with that unit; a zero value
22846 means that the unit is not used. For example:
22852 Acc : Acceleration;
22860 Here @code{DV(Acc)} = @code{DV(Acceleration)} =
22861 @code{(Meter=>1, Kilogram=>0, Second=>-2, Ampere=>0, Kelvin=>0, Mole=>0, Candela=>0)}.
22862 Symbolically, we can express this as @code{Meter / Second**2}.
22864 The dimension vector of an arithmetic expression is synthesized from the
22865 dimension vectors of its components, with compile-time dimensionality checks
22866 that help prevent mismatches such as using an @code{Acceleration} where a
22867 @code{Length} is required.
22869 The dimension vector of the result of an arithmetic expression @emph{expr}, or
22870 @code{DV(@emph{expr})}, is defined as follows, assuming conventional
22871 mathematical definitions for the vector operations that are used:
22877 If @emph{expr} is of the type @emph{universal_real}, or is not of a dimensioned subtype,
22878 then @emph{expr} is dimensionless; @code{DV(@emph{expr})} is the empty vector.
22881 @code{DV(@emph{op expr})}, where @emph{op} is a unary operator, is @code{DV(@emph{expr})}
22884 @code{DV(@emph{expr1 op expr2})} where @emph{op} is "+" or "-" is @code{DV(@emph{expr1})}
22885 provided that @code{DV(@emph{expr1})} = @code{DV(@emph{expr2})}.
22886 If this condition is not met then the construct is illegal.
22889 @code{DV(@emph{expr1} * @emph{expr2})} is @code{DV(@emph{expr1})} + @code{DV(@emph{expr2})},
22890 and @code{DV(@emph{expr1} / @emph{expr2})} = @code{DV(@emph{expr1})} - @code{DV(@emph{expr2})}.
22891 In this context if one of the @emph{expr}s is dimensionless then its empty
22892 dimension vector is treated as @code{(others => 0)}.
22895 @code{DV(@emph{expr} ** @emph{power})} is @emph{power} * @code{DV(@emph{expr})},
22896 provided that @emph{power} is a static rational value. If this condition is not
22897 met then the construct is illegal.
22900 Note that, by the above rules, it is illegal to use binary "+" or "-" to
22901 combine a dimensioned and dimensionless value. Thus an expression such as
22902 @code{acc-10.0} is illegal, where @code{acc} is an object of subtype
22903 @code{Acceleration}.
22905 The dimensionality checks for relationals use the same rules as
22906 for "+" and "-", except when comparing to a literal; thus
22924 and is thus illegal, but
22933 is accepted with a warning. Analogously a conditional expression requires the
22934 same dimension vector for each branch (with no exception for literals).
22936 The dimension vector of a type conversion @code{T(@emph{expr})} is defined
22937 as follows, based on the nature of @code{T}:
22943 If @code{T} is a dimensioned subtype then @code{DV(T(@emph{expr}))} is @code{DV(T)}
22944 provided that either @emph{expr} is dimensionless or
22945 @code{DV(T)} = @code{DV(@emph{expr})}. The conversion is illegal
22946 if @emph{expr} is dimensioned and @code{DV(@emph{expr})} /= @code{DV(T)}.
22947 Note that vector equality does not require that the corresponding
22948 Unit_Names be the same.
22950 As a consequence of the above rule, it is possible to convert between
22951 different dimension systems that follow the same international system
22952 of units, with the seven physical components given in the standard order
22953 (length, mass, time, etc.). Thus a length in meters can be converted to
22954 a length in inches (with a suitable conversion factor) but cannot be
22955 converted, for example, to a mass in pounds.
22958 If @code{T} is the base type for @emph{expr} (and the dimensionless root type of
22959 the dimension system), then @code{DV(T(@emph{expr}))} is @code{DV(expr)}.
22960 Thus, if @emph{expr} is of a dimensioned subtype of @code{T}, the conversion may
22961 be regarded as a "view conversion" that preserves dimensionality.
22963 This rule makes it possible to write generic code that can be instantiated
22964 with compatible dimensioned subtypes. The generic unit will contain
22965 conversions that will consequently be present in instantiations, but
22966 conversions to the base type will preserve dimensionality and make it
22967 possible to write generic code that is correct with respect to
22971 Otherwise (i.e., @code{T} is neither a dimensioned subtype nor a dimensionable
22972 base type), @code{DV(T(@emph{expr}))} is the empty vector. Thus a dimensioned
22973 value can be explicitly converted to a non-dimensioned subtype, which
22974 of course then escapes dimensionality analysis.
22977 The dimension vector for a type qualification @code{T'(@emph{expr})} is the same
22978 as for the type conversion @code{T(@emph{expr})}.
22980 An assignment statement
22989 requires @code{DV(Source)} = @code{DV(Target)}, and analogously for parameter
22990 passing (the dimension vector for the actual parameter must be equal to the
22991 dimension vector for the formal parameter).
22993 @node Stack Related Facilities,Memory Management Issues,Performing Dimensionality Analysis in GNAT,GNAT and Program Execution
22994 @anchor{gnat_ugn/gnat_and_program_execution id57}@anchor{16b}@anchor{gnat_ugn/gnat_and_program_execution stack-related-facilities}@anchor{29}
22995 @section Stack Related Facilities
22998 This section describes some useful tools associated with stack
22999 checking and analysis. In
23000 particular, it deals with dynamic and static stack usage measurements.
23003 * Stack Overflow Checking::
23004 * Static Stack Usage Analysis::
23005 * Dynamic Stack Usage Analysis::
23009 @node Stack Overflow Checking,Static Stack Usage Analysis,,Stack Related Facilities
23010 @anchor{gnat_ugn/gnat_and_program_execution id58}@anchor{1c4}@anchor{gnat_ugn/gnat_and_program_execution stack-overflow-checking}@anchor{f4}
23011 @subsection Stack Overflow Checking
23014 @geindex Stack Overflow Checking
23016 @geindex -fstack-check (gcc)
23018 For most operating systems, @code{gcc} does not perform stack overflow
23019 checking by default. This means that if the main environment task or
23020 some other task exceeds the available stack space, then unpredictable
23021 behavior will occur. Most native systems offer some level of protection by
23022 adding a guard page at the end of each task stack. This mechanism is usually
23023 not enough for dealing properly with stack overflow situations because
23024 a large local variable could "jump" above the guard page.
23025 Furthermore, when the
23026 guard page is hit, there may not be any space left on the stack for executing
23027 the exception propagation code. Enabling stack checking avoids
23030 To activate stack checking, compile all units with the @code{gcc} option
23031 @code{-fstack-check}. For example:
23036 $ gcc -c -fstack-check package1.adb
23040 Units compiled with this option will generate extra instructions to check
23041 that any use of the stack (for procedure calls or for declaring local
23042 variables in declare blocks) does not exceed the available stack space.
23043 If the space is exceeded, then a @code{Storage_Error} exception is raised.
23045 For declared tasks, the default stack size is defined by the GNAT runtime,
23046 whose size may be modified at bind time through the @code{-d} bind switch
23047 (@ref{11f,,Switches for gnatbind}). Task specific stack sizes may be set using the
23048 @code{Storage_Size} pragma.
23050 For the environment task, the stack size is determined by the operating system.
23051 Consequently, to modify the size of the environment task please refer to your
23052 operating system documentation.
23054 @node Static Stack Usage Analysis,Dynamic Stack Usage Analysis,Stack Overflow Checking,Stack Related Facilities
23055 @anchor{gnat_ugn/gnat_and_program_execution static-stack-usage-analysis}@anchor{f5}@anchor{gnat_ugn/gnat_and_program_execution id59}@anchor{1c5}
23056 @subsection Static Stack Usage Analysis
23059 @geindex Static Stack Usage Analysis
23061 @geindex -fstack-usage
23063 A unit compiled with @code{-fstack-usage} will generate an extra file
23065 the maximum amount of stack used, on a per-function basis.
23066 The file has the same
23067 basename as the target object file with a @code{.su} extension.
23068 Each line of this file is made up of three fields:
23074 The name of the function.
23080 One or more qualifiers: @code{static}, @code{dynamic}, @code{bounded}.
23083 The second field corresponds to the size of the known part of the function
23086 The qualifier @code{static} means that the function frame size
23088 It usually means that all local variables have a static size.
23089 In this case, the second field is a reliable measure of the function stack
23092 The qualifier @code{dynamic} means that the function frame size is not static.
23093 It happens mainly when some local variables have a dynamic size. When this
23094 qualifier appears alone, the second field is not a reliable measure
23095 of the function stack analysis. When it is qualified with @code{bounded}, it
23096 means that the second field is a reliable maximum of the function stack
23099 A unit compiled with @code{-Wstack-usage} will issue a warning for each
23100 subprogram whose stack usage might be larger than the specified amount of
23101 bytes. The wording is in keeping with the qualifier documented above.
23103 @node Dynamic Stack Usage Analysis,,Static Stack Usage Analysis,Stack Related Facilities
23104 @anchor{gnat_ugn/gnat_and_program_execution dynamic-stack-usage-analysis}@anchor{121}@anchor{gnat_ugn/gnat_and_program_execution id60}@anchor{1c6}
23105 @subsection Dynamic Stack Usage Analysis
23108 It is possible to measure the maximum amount of stack used by a task, by
23109 adding a switch to @code{gnatbind}, as:
23114 $ gnatbind -u0 file
23118 With this option, at each task termination, its stack usage is output on
23120 It is not always convenient to output the stack usage when the program
23121 is still running. Hence, it is possible to delay this output until program
23122 termination. for a given number of tasks specified as the argument of the
23123 @code{-u} option. For instance:
23128 $ gnatbind -u100 file
23132 will buffer the stack usage information of the first 100 tasks to terminate and
23133 output this info at program termination. Results are displayed in four
23139 Index | Task Name | Stack Size | Stack Usage
23149 @emph{Index} is a number associated with each task.
23152 @emph{Task Name} is the name of the task analyzed.
23155 @emph{Stack Size} is the maximum size for the stack.
23158 @emph{Stack Usage} is the measure done by the stack analyzer.
23159 In order to prevent overflow, the stack
23160 is not entirely analyzed, and it's not possible to know exactly how
23161 much has actually been used.
23164 By default the environment task stack, the stack that contains the main unit,
23165 is not processed. To enable processing of the environment task stack, the
23166 environment variable GNAT_STACK_LIMIT needs to be set to the maximum size of
23167 the environment task stack. This amount is given in kilobytes. For example:
23172 $ set GNAT_STACK_LIMIT 1600
23176 would specify to the analyzer that the environment task stack has a limit
23177 of 1.6 megabytes. Any stack usage beyond this will be ignored by the analysis.
23179 The package @code{GNAT.Task_Stack_Usage} provides facilities to get
23180 stack-usage reports at run time. See its body for the details.
23182 @node Memory Management Issues,,Stack Related Facilities,GNAT and Program Execution
23183 @anchor{gnat_ugn/gnat_and_program_execution id61}@anchor{16c}@anchor{gnat_ugn/gnat_and_program_execution memory-management-issues}@anchor{2a}
23184 @section Memory Management Issues
23187 This section describes some useful memory pools provided in the GNAT library
23188 and in particular the GNAT Debug Pool facility, which can be used to detect
23189 incorrect uses of access values (including 'dangling references').
23193 * Some Useful Memory Pools::
23194 * The GNAT Debug Pool Facility::
23198 @node Some Useful Memory Pools,The GNAT Debug Pool Facility,,Memory Management Issues
23199 @anchor{gnat_ugn/gnat_and_program_execution id62}@anchor{1c7}@anchor{gnat_ugn/gnat_and_program_execution some-useful-memory-pools}@anchor{1c8}
23200 @subsection Some Useful Memory Pools
23203 @geindex Memory Pool
23208 The @code{System.Pool_Global} package offers the Unbounded_No_Reclaim_Pool
23209 storage pool. Allocations use the standard system call @code{malloc} while
23210 deallocations use the standard system call @code{free}. No reclamation is
23211 performed when the pool goes out of scope. For performance reasons, the
23212 standard default Ada allocators/deallocators do not use any explicit storage
23213 pools but if they did, they could use this storage pool without any change in
23214 behavior. That is why this storage pool is used when the user
23215 manages to make the default implicit allocator explicit as in this example:
23220 type T1 is access Something;
23221 -- no Storage pool is defined for T2
23223 type T2 is access Something_Else;
23224 for T2'Storage_Pool use T1'Storage_Pool;
23225 -- the above is equivalent to
23226 for T2'Storage_Pool use System.Pool_Global.Global_Pool_Object;
23230 The @code{System.Pool_Local} package offers the @code{Unbounded_Reclaim_Pool} storage
23231 pool. The allocation strategy is similar to @code{Pool_Local}
23232 except that the all
23233 storage allocated with this pool is reclaimed when the pool object goes out of
23234 scope. This pool provides a explicit mechanism similar to the implicit one
23235 provided by several Ada 83 compilers for allocations performed through a local
23236 access type and whose purpose was to reclaim memory when exiting the
23237 scope of a given local access. As an example, the following program does not
23238 leak memory even though it does not perform explicit deallocation:
23243 with System.Pool_Local;
23244 procedure Pooloc1 is
23245 procedure Internal is
23246 type A is access Integer;
23247 X : System.Pool_Local.Unbounded_Reclaim_Pool;
23248 for A'Storage_Pool use X;
23251 for I in 1 .. 50 loop
23256 for I in 1 .. 100 loop
23263 The @code{System.Pool_Size} package implements the @code{Stack_Bounded_Pool} used when
23264 @code{Storage_Size} is specified for an access type.
23265 The whole storage for the pool is
23266 allocated at once, usually on the stack at the point where the access type is
23267 elaborated. It is automatically reclaimed when exiting the scope where the
23268 access type is defined. This package is not intended to be used directly by the
23269 user and it is implicitly used for each such declaration:
23274 type T1 is access Something;
23275 for T1'Storage_Size use 10_000;
23279 @node The GNAT Debug Pool Facility,,Some Useful Memory Pools,Memory Management Issues
23280 @anchor{gnat_ugn/gnat_and_program_execution id63}@anchor{1c9}@anchor{gnat_ugn/gnat_and_program_execution the-gnat-debug-pool-facility}@anchor{1ca}
23281 @subsection The GNAT Debug Pool Facility
23284 @geindex Debug Pool
23288 @geindex memory corruption
23290 The use of unchecked deallocation and unchecked conversion can easily
23291 lead to incorrect memory references. The problems generated by such
23292 references are usually difficult to tackle because the symptoms can be
23293 very remote from the origin of the problem. In such cases, it is
23294 very helpful to detect the problem as early as possible. This is the
23295 purpose of the Storage Pool provided by @code{GNAT.Debug_Pools}.
23297 In order to use the GNAT specific debugging pool, the user must
23298 associate a debug pool object with each of the access types that may be
23299 related to suspected memory problems. See Ada Reference Manual 13.11.
23304 type Ptr is access Some_Type;
23305 Pool : GNAT.Debug_Pools.Debug_Pool;
23306 for Ptr'Storage_Pool use Pool;
23310 @code{GNAT.Debug_Pools} is derived from a GNAT-specific kind of
23311 pool: the @code{Checked_Pool}. Such pools, like standard Ada storage pools,
23312 allow the user to redefine allocation and deallocation strategies. They
23313 also provide a checkpoint for each dereference, through the use of
23314 the primitive operation @code{Dereference} which is implicitly called at
23315 each dereference of an access value.
23317 Once an access type has been associated with a debug pool, operations on
23318 values of the type may raise four distinct exceptions,
23319 which correspond to four potential kinds of memory corruption:
23325 @code{GNAT.Debug_Pools.Accessing_Not_Allocated_Storage}
23328 @code{GNAT.Debug_Pools.Accessing_Deallocated_Storage}
23331 @code{GNAT.Debug_Pools.Freeing_Not_Allocated_Storage}
23334 @code{GNAT.Debug_Pools.Freeing_Deallocated_Storage}
23337 For types associated with a Debug_Pool, dynamic allocation is performed using
23338 the standard GNAT allocation routine. References to all allocated chunks of
23339 memory are kept in an internal dictionary. Several deallocation strategies are
23340 provided, whereupon the user can choose to release the memory to the system,
23341 keep it allocated for further invalid access checks, or fill it with an easily
23342 recognizable pattern for debug sessions. The memory pattern is the old IBM
23343 hexadecimal convention: @code{16#DEADBEEF#}.
23345 See the documentation in the file g-debpoo.ads for more information on the
23346 various strategies.
23348 Upon each dereference, a check is made that the access value denotes a
23349 properly allocated memory location. Here is a complete example of use of
23350 @code{Debug_Pools}, that includes typical instances of memory corruption:
23355 with Gnat.Io; use Gnat.Io;
23356 with Unchecked_Deallocation;
23357 with Unchecked_Conversion;
23358 with GNAT.Debug_Pools;
23359 with System.Storage_Elements;
23360 with Ada.Exceptions; use Ada.Exceptions;
23361 procedure Debug_Pool_Test is
23363 type T is access Integer;
23364 type U is access all T;
23366 P : GNAT.Debug_Pools.Debug_Pool;
23367 for T'Storage_Pool use P;
23369 procedure Free is new Unchecked_Deallocation (Integer, T);
23370 function UC is new Unchecked_Conversion (U, T);
23373 procedure Info is new GNAT.Debug_Pools.Print_Info(Put_Line);
23383 Put_Line (Integer'Image(B.all));
23385 when E : others => Put_Line ("raised: " & Exception_Name (E));
23390 when E : others => Put_Line ("raised: " & Exception_Name (E));
23394 Put_Line (Integer'Image(B.all));
23396 when E : others => Put_Line ("raised: " & Exception_Name (E));
23401 when E : others => Put_Line ("raised: " & Exception_Name (E));
23404 end Debug_Pool_Test;
23408 The debug pool mechanism provides the following precise diagnostics on the
23409 execution of this erroneous program:
23415 Total allocated bytes : 0
23416 Total deallocated bytes : 0
23417 Current Water Mark: 0
23421 Total allocated bytes : 8
23422 Total deallocated bytes : 0
23423 Current Water Mark: 8
23426 raised: GNAT.DEBUG_POOLS.ACCESSING_DEALLOCATED_STORAGE
23427 raised: GNAT.DEBUG_POOLS.FREEING_DEALLOCATED_STORAGE
23428 raised: GNAT.DEBUG_POOLS.ACCESSING_NOT_ALLOCATED_STORAGE
23429 raised: GNAT.DEBUG_POOLS.FREEING_NOT_ALLOCATED_STORAGE
23431 Total allocated bytes : 8
23432 Total deallocated bytes : 4
23433 Current Water Mark: 4
23439 @c -- Non-breaking space in running text
23440 @c -- E.g. Ada |nbsp| 95
23442 @node Platform-Specific Information,Example of Binder Output File,GNAT and Program Execution,Top
23443 @anchor{gnat_ugn/platform_specific_information platform-specific-information}@anchor{d}@anchor{gnat_ugn/platform_specific_information doc}@anchor{1cb}@anchor{gnat_ugn/platform_specific_information id1}@anchor{1cc}
23444 @chapter Platform-Specific Information
23447 This appendix contains information relating to the implementation
23448 of run-time libraries on various platforms and also covers
23449 topics related to the GNAT implementation on Windows and Mac OS.
23452 * Run-Time Libraries::
23453 * Specifying a Run-Time Library::
23454 * GNU/Linux Topics::
23455 * Microsoft Windows Topics::
23460 @node Run-Time Libraries,Specifying a Run-Time Library,,Platform-Specific Information
23461 @anchor{gnat_ugn/platform_specific_information id2}@anchor{1cd}@anchor{gnat_ugn/platform_specific_information run-time-libraries}@anchor{2b}
23462 @section Run-Time Libraries
23465 @geindex Tasking and threads libraries
23467 @geindex Threads libraries and tasking
23469 @geindex Run-time libraries (platform-specific information)
23471 The GNAT run-time implementation may vary with respect to both the
23472 underlying threads library and the exception-handling scheme.
23473 For threads support, the default run-time will bind to the thread
23474 package of the underlying operating system.
23476 For exception handling, either or both of two models are supplied:
23480 @geindex Zero-Cost Exceptions
23482 @geindex ZCX (Zero-Cost Exceptions)
23489 @strong{Zero-Cost Exceptions} ("ZCX"),
23490 which uses binder-generated tables that
23491 are interrogated at run time to locate a handler.
23493 @geindex setjmp/longjmp Exception Model
23495 @geindex SJLJ (setjmp/longjmp Exception Model)
23498 @strong{setjmp / longjmp} ('SJLJ'),
23499 which uses dynamically-set data to establish
23500 the set of handlers
23503 Most programs should experience a substantial speed improvement by
23504 being compiled with a ZCX run-time.
23505 This is especially true for
23506 tasking applications or applications with many exception handlers.@}
23508 This section summarizes which combinations of threads and exception support
23509 are supplied on various GNAT platforms.
23510 It then shows how to select a particular library either
23511 permanently or temporarily,
23512 explains the properties of (and tradeoffs among) the various threads
23513 libraries, and provides some additional
23514 information about several specific platforms.
23517 * Summary of Run-Time Configurations::
23521 @node Summary of Run-Time Configurations,,,Run-Time Libraries
23522 @anchor{gnat_ugn/platform_specific_information summary-of-run-time-configurations}@anchor{1ce}@anchor{gnat_ugn/platform_specific_information id3}@anchor{1cf}
23523 @subsection Summary of Run-Time Configurations
23527 @multitable {xxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxx} {xxxxxxxxxxxxxx}
23584 native Win32 threads
23596 native Win32 threads
23621 @node Specifying a Run-Time Library,GNU/Linux Topics,Run-Time Libraries,Platform-Specific Information
23622 @anchor{gnat_ugn/platform_specific_information specifying-a-run-time-library}@anchor{1d0}@anchor{gnat_ugn/platform_specific_information id4}@anchor{1d1}
23623 @section Specifying a Run-Time Library
23626 The @code{adainclude} subdirectory containing the sources of the GNAT
23627 run-time library, and the @code{adalib} subdirectory containing the
23628 @code{ALI} files and the static and/or shared GNAT library, are located
23629 in the gcc target-dependent area:
23634 target=$prefix/lib/gcc/gcc-*dumpmachine*/gcc-*dumpversion*/
23638 As indicated above, on some platforms several run-time libraries are supplied.
23639 These libraries are installed in the target dependent area and
23640 contain a complete source and binary subdirectory. The detailed description
23641 below explains the differences between the different libraries in terms of
23642 their thread support.
23644 The default run-time library (when GNAT is installed) is @emph{rts-native}.
23645 This default run-time is selected by the means of soft links.
23646 For example on x86-linux:
23649 @c -- $(target-dir)
23651 @c -- +--- adainclude----------+
23653 @c -- +--- adalib-----------+ |
23655 @c -- +--- rts-native | |
23657 @c -- | +--- adainclude <---+
23659 @c -- | +--- adalib <----+
23661 @c -- +--- rts-sjlj
23663 @c -- +--- adainclude
23671 _______/ / \ \_________________
23674 ADAINCLUDE ADALIB rts-native rts-sjlj
23679 +-------------> adainclude adalib adainclude adalib
23682 +---------------------+
23684 Run-Time Library Directory Structure
23685 (Upper-case names and dotted/dashed arrows represent soft links)
23688 If the @emph{rts-sjlj} library is to be selected on a permanent basis,
23689 these soft links can be modified with the following commands:
23695 $ rm -f adainclude adalib
23696 $ ln -s rts-sjlj/adainclude adainclude
23697 $ ln -s rts-sjlj/adalib adalib
23701 Alternatively, you can specify @code{rts-sjlj/adainclude} in the file
23702 @code{$target/ada_source_path} and @code{rts-sjlj/adalib} in
23703 @code{$target/ada_object_path}.
23705 @geindex --RTS option
23707 Selecting another run-time library temporarily can be
23708 achieved by using the @code{--RTS} switch, e.g., @code{--RTS=sjlj}
23709 @anchor{gnat_ugn/platform_specific_information choosing-the-scheduling-policy}@anchor{1d2}
23710 @geindex SCHED_FIFO scheduling policy
23712 @geindex SCHED_RR scheduling policy
23714 @geindex SCHED_OTHER scheduling policy
23717 * Choosing the Scheduling Policy::
23721 @node Choosing the Scheduling Policy,,,Specifying a Run-Time Library
23722 @anchor{gnat_ugn/platform_specific_information id5}@anchor{1d3}
23723 @subsection Choosing the Scheduling Policy
23726 When using a POSIX threads implementation, you have a choice of several
23727 scheduling policies: @code{SCHED_FIFO}, @code{SCHED_RR} and @code{SCHED_OTHER}.
23729 Typically, the default is @code{SCHED_OTHER}, while using @code{SCHED_FIFO}
23730 or @code{SCHED_RR} requires special (e.g., root) privileges.
23732 @geindex pragma Time_Slice
23734 @geindex -T0 option
23736 @geindex pragma Task_Dispatching_Policy
23738 By default, GNAT uses the @code{SCHED_OTHER} policy. To specify
23740 you can use one of the following:
23746 @code{pragma Time_Slice (0.0)}
23749 the corresponding binder option @code{-T0}
23752 @code{pragma Task_Dispatching_Policy (FIFO_Within_Priorities)}
23755 To specify @code{SCHED_RR},
23756 you should use @code{pragma Time_Slice} with a
23757 value greater than 0.0, or else use the corresponding @code{-T}
23760 To make sure a program is running as root, you can put something like
23761 this in a library package body in your application:
23766 function geteuid return Integer;
23767 pragma Import (C, geteuid, "geteuid");
23768 Ignore : constant Boolean :=
23769 (if geteuid = 0 then True else raise Program_Error with "must be root");
23773 It gets the effective user id, and if it's not 0 (i.e. root), it raises
23780 @node GNU/Linux Topics,Microsoft Windows Topics,Specifying a Run-Time Library,Platform-Specific Information
23781 @anchor{gnat_ugn/platform_specific_information id6}@anchor{1d4}@anchor{gnat_ugn/platform_specific_information gnu-linux-topics}@anchor{1d5}
23782 @section GNU/Linux Topics
23785 This section describes topics that are specific to GNU/Linux platforms.
23788 * Required Packages on GNU/Linux::
23792 @node Required Packages on GNU/Linux,,,GNU/Linux Topics
23793 @anchor{gnat_ugn/platform_specific_information id7}@anchor{1d6}@anchor{gnat_ugn/platform_specific_information required-packages-on-gnu-linux}@anchor{1d7}
23794 @subsection Required Packages on GNU/Linux
23797 GNAT requires the C library developer's package to be installed.
23798 The name of of that package depends on your GNU/Linux distribution:
23804 RedHat, SUSE: @code{glibc-devel};
23807 Debian, Ubuntu: @code{libc6-dev} (normally installed by default).
23810 If using the 32-bit version of GNAT on a 64-bit version of GNU/Linux,
23811 you'll need the 32-bit version of the following packages:
23817 RedHat, SUSE: @code{glibc.i686}, @code{glibc-devel.i686}, @code{ncurses-libs.i686}
23820 Debian, Ubuntu: @code{libc6:i386}, @code{libc6-dev:i386}, @code{lib32ncursesw5}
23823 Other GNU/Linux distributions might be choosing a different name
23824 for those packages.
23828 @node Microsoft Windows Topics,Mac OS Topics,GNU/Linux Topics,Platform-Specific Information
23829 @anchor{gnat_ugn/platform_specific_information microsoft-windows-topics}@anchor{2c}@anchor{gnat_ugn/platform_specific_information id8}@anchor{1d8}
23830 @section Microsoft Windows Topics
23833 This section describes topics that are specific to the Microsoft Windows
23841 * Using GNAT on Windows::
23842 * Using a network installation of GNAT::
23843 * CONSOLE and WINDOWS subsystems::
23844 * Temporary Files::
23845 * Disabling Command Line Argument Expansion::
23846 * Mixed-Language Programming on Windows::
23847 * Windows Specific Add-Ons::
23851 @node Using GNAT on Windows,Using a network installation of GNAT,,Microsoft Windows Topics
23852 @anchor{gnat_ugn/platform_specific_information using-gnat-on-windows}@anchor{1d9}@anchor{gnat_ugn/platform_specific_information id9}@anchor{1da}
23853 @subsection Using GNAT on Windows
23856 One of the strengths of the GNAT technology is that its tool set
23857 (@code{gcc}, @code{gnatbind}, @code{gnatlink}, @code{gnatmake}, the
23858 @code{gdb} debugger, etc.) is used in the same way regardless of the
23861 On Windows this tool set is complemented by a number of Microsoft-specific
23862 tools that have been provided to facilitate interoperability with Windows
23863 when this is required. With these tools:
23869 You can build applications using the @code{CONSOLE} or @code{WINDOWS}
23873 You can use any Dynamically Linked Library (DLL) in your Ada code (both
23874 relocatable and non-relocatable DLLs are supported).
23877 You can build Ada DLLs for use in other applications. These applications
23878 can be written in a language other than Ada (e.g., C, C++, etc). Again both
23879 relocatable and non-relocatable Ada DLLs are supported.
23882 You can include Windows resources in your Ada application.
23885 You can use or create COM/DCOM objects.
23888 Immediately below are listed all known general GNAT-for-Windows restrictions.
23889 Other restrictions about specific features like Windows Resources and DLLs
23890 are listed in separate sections below.
23896 It is not possible to use @code{GetLastError} and @code{SetLastError}
23897 when tasking, protected records, or exceptions are used. In these
23898 cases, in order to implement Ada semantics, the GNAT run-time system
23899 calls certain Win32 routines that set the last error variable to 0 upon
23900 success. It should be possible to use @code{GetLastError} and
23901 @code{SetLastError} when tasking, protected record, and exception
23902 features are not used, but it is not guaranteed to work.
23905 It is not possible to link against Microsoft C++ libraries except for
23906 import libraries. Interfacing must be done by the mean of DLLs.
23909 It is possible to link against Microsoft C libraries. Yet the preferred
23910 solution is to use C/C++ compiler that comes with GNAT, since it
23911 doesn't require having two different development environments and makes the
23912 inter-language debugging experience smoother.
23915 When the compilation environment is located on FAT32 drives, users may
23916 experience recompilations of the source files that have not changed if
23917 Daylight Saving Time (DST) state has changed since the last time files
23918 were compiled. NTFS drives do not have this problem.
23921 No components of the GNAT toolset use any entries in the Windows
23922 registry. The only entries that can be created are file associations and
23923 PATH settings, provided the user has chosen to create them at installation
23924 time, as well as some minimal book-keeping information needed to correctly
23925 uninstall or integrate different GNAT products.
23928 @node Using a network installation of GNAT,CONSOLE and WINDOWS subsystems,Using GNAT on Windows,Microsoft Windows Topics
23929 @anchor{gnat_ugn/platform_specific_information id10}@anchor{1db}@anchor{gnat_ugn/platform_specific_information using-a-network-installation-of-gnat}@anchor{1dc}
23930 @subsection Using a network installation of GNAT
23933 Make sure the system on which GNAT is installed is accessible from the
23934 current machine, i.e., the install location is shared over the network.
23935 Shared resources are accessed on Windows by means of UNC paths, which
23936 have the format @code{\\\\server\\sharename\\path}
23938 In order to use such a network installation, simply add the UNC path of the
23939 @code{bin} directory of your GNAT installation in front of your PATH. For
23940 example, if GNAT is installed in @code{\GNAT} directory of a share location
23941 called @code{c-drive} on a machine @code{LOKI}, the following command will
23947 $ path \\loki\c-drive\gnat\bin;%path%`
23951 Be aware that every compilation using the network installation results in the
23952 transfer of large amounts of data across the network and will likely cause
23953 serious performance penalty.
23955 @node CONSOLE and WINDOWS subsystems,Temporary Files,Using a network installation of GNAT,Microsoft Windows Topics
23956 @anchor{gnat_ugn/platform_specific_information id11}@anchor{1dd}@anchor{gnat_ugn/platform_specific_information console-and-windows-subsystems}@anchor{1de}
23957 @subsection CONSOLE and WINDOWS subsystems
23960 @geindex CONSOLE Subsystem
23962 @geindex WINDOWS Subsystem
23966 There are two main subsystems under Windows. The @code{CONSOLE} subsystem
23967 (which is the default subsystem) will always create a console when
23968 launching the application. This is not something desirable when the
23969 application has a Windows GUI. To get rid of this console the
23970 application must be using the @code{WINDOWS} subsystem. To do so
23971 the @code{-mwindows} linker option must be specified.
23976 $ gnatmake winprog -largs -mwindows
23980 @node Temporary Files,Disabling Command Line Argument Expansion,CONSOLE and WINDOWS subsystems,Microsoft Windows Topics
23981 @anchor{gnat_ugn/platform_specific_information id12}@anchor{1df}@anchor{gnat_ugn/platform_specific_information temporary-files}@anchor{1e0}
23982 @subsection Temporary Files
23985 @geindex Temporary files
23987 It is possible to control where temporary files gets created by setting
23990 @geindex environment variable; TMP
23991 @code{TMP} environment variable. The file will be created:
23997 Under the directory pointed to by the
23999 @geindex environment variable; TMP
24000 @code{TMP} environment variable if
24001 this directory exists.
24004 Under @code{c:\temp}, if the
24006 @geindex environment variable; TMP
24007 @code{TMP} environment variable is not
24008 set (or not pointing to a directory) and if this directory exists.
24011 Under the current working directory otherwise.
24014 This allows you to determine exactly where the temporary
24015 file will be created. This is particularly useful in networked
24016 environments where you may not have write access to some
24019 @node Disabling Command Line Argument Expansion,Mixed-Language Programming on Windows,Temporary Files,Microsoft Windows Topics
24020 @anchor{gnat_ugn/platform_specific_information disabling-command-line-argument-expansion}@anchor{1e1}
24021 @subsection Disabling Command Line Argument Expansion
24024 @geindex Command Line Argument Expansion
24026 By default, an executable compiled for the Windows platform will do
24027 the following postprocessing on the arguments passed on the command
24034 If the argument contains the characters @code{*} and/or @code{?}, then
24035 file expansion will be attempted. For example, if the current directory
24036 contains @code{a.txt} and @code{b.txt}, then when calling:
24039 $ my_ada_program *.txt
24042 The following arguments will effectively be passed to the main program
24043 (for example when using @code{Ada.Command_Line.Argument}):
24046 Ada.Command_Line.Argument (1) -> "a.txt"
24047 Ada.Command_Line.Argument (2) -> "b.txt"
24051 Filename expansion can be disabled for a given argument by using single
24052 quotes. Thus, calling:
24055 $ my_ada_program '*.txt'
24061 Ada.Command_Line.Argument (1) -> "*.txt"
24065 Note that if the program is launched from a shell such as Cygwin Bash
24066 then quote removal might be performed by the shell.
24068 In some contexts it might be useful to disable this feature (for example if
24069 the program performs its own argument expansion). In order to do this, a C
24070 symbol needs to be defined and set to @code{0}. You can do this by
24071 adding the following code fragment in one of your Ada units:
24074 Do_Argv_Expansion : Integer := 0;
24075 pragma Export (C, Do_Argv_Expansion, "__gnat_do_argv_expansion");
24078 The results of previous examples will be respectively:
24081 Ada.Command_Line.Argument (1) -> "*.txt"
24087 Ada.Command_Line.Argument (1) -> "'*.txt'"
24090 @node Mixed-Language Programming on Windows,Windows Specific Add-Ons,Disabling Command Line Argument Expansion,Microsoft Windows Topics
24091 @anchor{gnat_ugn/platform_specific_information id13}@anchor{1e2}@anchor{gnat_ugn/platform_specific_information mixed-language-programming-on-windows}@anchor{1e3}
24092 @subsection Mixed-Language Programming on Windows
24095 Developing pure Ada applications on Windows is no different than on
24096 other GNAT-supported platforms. However, when developing or porting an
24097 application that contains a mix of Ada and C/C++, the choice of your
24098 Windows C/C++ development environment conditions your overall
24099 interoperability strategy.
24101 If you use @code{gcc} or Microsoft C to compile the non-Ada part of
24102 your application, there are no Windows-specific restrictions that
24103 affect the overall interoperability with your Ada code. If you do want
24104 to use the Microsoft tools for your C++ code, you have two choices:
24110 Encapsulate your C++ code in a DLL to be linked with your Ada
24111 application. In this case, use the Microsoft or whatever environment to
24112 build the DLL and use GNAT to build your executable
24113 (@ref{1e4,,Using DLLs with GNAT}).
24116 Or you can encapsulate your Ada code in a DLL to be linked with the
24117 other part of your application. In this case, use GNAT to build the DLL
24118 (@ref{1e5,,Building DLLs with GNAT Project files}) and use the Microsoft
24119 or whatever environment to build your executable.
24122 In addition to the description about C main in
24123 @ref{44,,Mixed Language Programming} section, if the C main uses a
24124 stand-alone library it is required on x86-windows to
24125 setup the SEH context. For this the C main must looks like this:
24131 extern void adainit (void);
24132 extern void adafinal (void);
24133 extern void __gnat_initialize(void*);
24134 extern void call_to_ada (void);
24136 int main (int argc, char *argv[])
24140 /* Initialize the SEH context */
24141 __gnat_initialize (&SEH);
24145 /* Then call Ada services in the stand-alone library */
24154 Note that this is not needed on x86_64-windows where the Windows
24155 native SEH support is used.
24158 * Windows Calling Conventions::
24159 * Introduction to Dynamic Link Libraries (DLLs): Introduction to Dynamic Link Libraries DLLs.
24160 * Using DLLs with GNAT::
24161 * Building DLLs with GNAT Project files::
24162 * Building DLLs with GNAT::
24163 * Building DLLs with gnatdll::
24164 * Ada DLLs and Finalization::
24165 * Creating a Spec for Ada DLLs::
24166 * GNAT and Windows Resources::
24167 * Using GNAT DLLs from Microsoft Visual Studio Applications::
24168 * Debugging a DLL::
24169 * Setting Stack Size from gnatlink::
24170 * Setting Heap Size from gnatlink::
24174 @node Windows Calling Conventions,Introduction to Dynamic Link Libraries DLLs,,Mixed-Language Programming on Windows
24175 @anchor{gnat_ugn/platform_specific_information windows-calling-conventions}@anchor{1e6}@anchor{gnat_ugn/platform_specific_information id14}@anchor{1e7}
24176 @subsubsection Windows Calling Conventions
24183 This section pertain only to Win32. On Win64 there is a single native
24184 calling convention. All convention specifiers are ignored on this
24187 When a subprogram @code{F} (caller) calls a subprogram @code{G}
24188 (callee), there are several ways to push @code{G}'s parameters on the
24189 stack and there are several possible scenarios to clean up the stack
24190 upon @code{G}'s return. A calling convention is an agreed upon software
24191 protocol whereby the responsibilities between the caller (@code{F}) and
24192 the callee (@code{G}) are clearly defined. Several calling conventions
24193 are available for Windows:
24199 @code{C} (Microsoft defined)
24202 @code{Stdcall} (Microsoft defined)
24205 @code{Win32} (GNAT specific)
24208 @code{DLL} (GNAT specific)
24212 * C Calling Convention::
24213 * Stdcall Calling Convention::
24214 * Win32 Calling Convention::
24215 * DLL Calling Convention::
24219 @node C Calling Convention,Stdcall Calling Convention,,Windows Calling Conventions
24220 @anchor{gnat_ugn/platform_specific_information c-calling-convention}@anchor{1e8}@anchor{gnat_ugn/platform_specific_information id15}@anchor{1e9}
24221 @subsubsection @code{C} Calling Convention
24224 This is the default calling convention used when interfacing to C/C++
24225 routines compiled with either @code{gcc} or Microsoft Visual C++.
24227 In the @code{C} calling convention subprogram parameters are pushed on the
24228 stack by the caller from right to left. The caller itself is in charge of
24229 cleaning up the stack after the call. In addition, the name of a routine
24230 with @code{C} calling convention is mangled by adding a leading underscore.
24232 The name to use on the Ada side when importing (or exporting) a routine
24233 with @code{C} calling convention is the name of the routine. For
24234 instance the C function:
24239 int get_val (long);
24243 should be imported from Ada as follows:
24248 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24249 pragma Import (C, Get_Val, External_Name => "get_val");
24253 Note that in this particular case the @code{External_Name} parameter could
24254 have been omitted since, when missing, this parameter is taken to be the
24255 name of the Ada entity in lower case. When the @code{Link_Name} parameter
24256 is missing, as in the above example, this parameter is set to be the
24257 @code{External_Name} with a leading underscore.
24259 When importing a variable defined in C, you should always use the @code{C}
24260 calling convention unless the object containing the variable is part of a
24261 DLL (in which case you should use the @code{Stdcall} calling
24262 convention, @ref{1ea,,Stdcall Calling Convention}).
24264 @node Stdcall Calling Convention,Win32 Calling Convention,C Calling Convention,Windows Calling Conventions
24265 @anchor{gnat_ugn/platform_specific_information stdcall-calling-convention}@anchor{1ea}@anchor{gnat_ugn/platform_specific_information id16}@anchor{1eb}
24266 @subsubsection @code{Stdcall} Calling Convention
24269 This convention, which was the calling convention used for Pascal
24270 programs, is used by Microsoft for all the routines in the Win32 API for
24271 efficiency reasons. It must be used to import any routine for which this
24272 convention was specified.
24274 In the @code{Stdcall} calling convention subprogram parameters are pushed
24275 on the stack by the caller from right to left. The callee (and not the
24276 caller) is in charge of cleaning the stack on routine exit. In addition,
24277 the name of a routine with @code{Stdcall} calling convention is mangled by
24278 adding a leading underscore (as for the @code{C} calling convention) and a
24279 trailing @code{@@@emph{nn}}, where @code{nn} is the overall size (in
24280 bytes) of the parameters passed to the routine.
24282 The name to use on the Ada side when importing a C routine with a
24283 @code{Stdcall} calling convention is the name of the C routine. The leading
24284 underscore and trailing @code{@@@emph{nn}} are added automatically by
24285 the compiler. For instance the Win32 function:
24290 APIENTRY int get_val (long);
24294 should be imported from Ada as follows:
24299 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24300 pragma Import (Stdcall, Get_Val);
24301 -- On the x86 a long is 4 bytes, so the Link_Name is "_get_val@@4"
24305 As for the @code{C} calling convention, when the @code{External_Name}
24306 parameter is missing, it is taken to be the name of the Ada entity in lower
24307 case. If instead of writing the above import pragma you write:
24312 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24313 pragma Import (Stdcall, Get_Val, External_Name => "retrieve_val");
24317 then the imported routine is @code{_retrieve_val@@4}. However, if instead
24318 of specifying the @code{External_Name} parameter you specify the
24319 @code{Link_Name} as in the following example:
24324 function Get_Val (V : Interfaces.C.long) return Interfaces.C.int;
24325 pragma Import (Stdcall, Get_Val, Link_Name => "retrieve_val");
24329 then the imported routine is @code{retrieve_val}, that is, there is no
24330 decoration at all. No leading underscore and no Stdcall suffix
24331 @code{@@@emph{nn}}.
24333 This is especially important as in some special cases a DLL's entry
24334 point name lacks a trailing @code{@@@emph{nn}} while the exported
24335 name generated for a call has it.
24337 It is also possible to import variables defined in a DLL by using an
24338 import pragma for a variable. As an example, if a DLL contains a
24339 variable defined as:
24348 then, to access this variable from Ada you should write:
24353 My_Var : Interfaces.C.int;
24354 pragma Import (Stdcall, My_Var);
24358 Note that to ease building cross-platform bindings this convention
24359 will be handled as a @code{C} calling convention on non-Windows platforms.
24361 @node Win32 Calling Convention,DLL Calling Convention,Stdcall Calling Convention,Windows Calling Conventions
24362 @anchor{gnat_ugn/platform_specific_information win32-calling-convention}@anchor{1ec}@anchor{gnat_ugn/platform_specific_information id17}@anchor{1ed}
24363 @subsubsection @code{Win32} Calling Convention
24366 This convention, which is GNAT-specific is fully equivalent to the
24367 @code{Stdcall} calling convention described above.
24369 @node DLL Calling Convention,,Win32 Calling Convention,Windows Calling Conventions
24370 @anchor{gnat_ugn/platform_specific_information id18}@anchor{1ee}@anchor{gnat_ugn/platform_specific_information dll-calling-convention}@anchor{1ef}
24371 @subsubsection @code{DLL} Calling Convention
24374 This convention, which is GNAT-specific is fully equivalent to the
24375 @code{Stdcall} calling convention described above.
24377 @node Introduction to Dynamic Link Libraries DLLs,Using DLLs with GNAT,Windows Calling Conventions,Mixed-Language Programming on Windows
24378 @anchor{gnat_ugn/platform_specific_information id19}@anchor{1f0}@anchor{gnat_ugn/platform_specific_information introduction-to-dynamic-link-libraries-dlls}@anchor{1f1}
24379 @subsubsection Introduction to Dynamic Link Libraries (DLLs)
24384 A Dynamically Linked Library (DLL) is a library that can be shared by
24385 several applications running under Windows. A DLL can contain any number of
24386 routines and variables.
24388 One advantage of DLLs is that you can change and enhance them without
24389 forcing all the applications that depend on them to be relinked or
24390 recompiled. However, you should be aware than all calls to DLL routines are
24391 slower since, as you will understand below, such calls are indirect.
24393 To illustrate the remainder of this section, suppose that an application
24394 wants to use the services of a DLL @code{API.dll}. To use the services
24395 provided by @code{API.dll} you must statically link against the DLL or
24396 an import library which contains a jump table with an entry for each
24397 routine and variable exported by the DLL. In the Microsoft world this
24398 import library is called @code{API.lib}. When using GNAT this import
24399 library is called either @code{libAPI.dll.a}, @code{libapi.dll.a},
24400 @code{libAPI.a} or @code{libapi.a} (names are case insensitive).
24402 After you have linked your application with the DLL or the import library
24403 and you run your application, here is what happens:
24409 Your application is loaded into memory.
24412 The DLL @code{API.dll} is mapped into the address space of your
24413 application. This means that:
24419 The DLL will use the stack of the calling thread.
24422 The DLL will use the virtual address space of the calling process.
24425 The DLL will allocate memory from the virtual address space of the calling
24429 Handles (pointers) can be safely exchanged between routines in the DLL
24430 routines and routines in the application using the DLL.
24434 The entries in the jump table (from the import library @code{libAPI.dll.a}
24435 or @code{API.lib} or automatically created when linking against a DLL)
24436 which is part of your application are initialized with the addresses
24437 of the routines and variables in @code{API.dll}.
24440 If present in @code{API.dll}, routines @code{DllMain} or
24441 @code{DllMainCRTStartup} are invoked. These routines typically contain
24442 the initialization code needed for the well-being of the routines and
24443 variables exported by the DLL.
24446 There is an additional point which is worth mentioning. In the Windows
24447 world there are two kind of DLLs: relocatable and non-relocatable
24448 DLLs. Non-relocatable DLLs can only be loaded at a very specific address
24449 in the target application address space. If the addresses of two
24450 non-relocatable DLLs overlap and these happen to be used by the same
24451 application, a conflict will occur and the application will run
24452 incorrectly. Hence, when possible, it is always preferable to use and
24453 build relocatable DLLs. Both relocatable and non-relocatable DLLs are
24454 supported by GNAT. Note that the @code{-s} linker option (see GNU Linker
24455 User's Guide) removes the debugging symbols from the DLL but the DLL can
24456 still be relocated.
24458 As a side note, an interesting difference between Microsoft DLLs and
24459 Unix shared libraries, is the fact that on most Unix systems all public
24460 routines are exported by default in a Unix shared library, while under
24461 Windows it is possible (but not required) to list exported routines in
24462 a definition file (see @ref{1f2,,The Definition File}).
24464 @node Using DLLs with GNAT,Building DLLs with GNAT Project files,Introduction to Dynamic Link Libraries DLLs,Mixed-Language Programming on Windows
24465 @anchor{gnat_ugn/platform_specific_information id20}@anchor{1f3}@anchor{gnat_ugn/platform_specific_information using-dlls-with-gnat}@anchor{1e4}
24466 @subsubsection Using DLLs with GNAT
24469 To use the services of a DLL, say @code{API.dll}, in your Ada application
24476 The Ada spec for the routines and/or variables you want to access in
24477 @code{API.dll}. If not available this Ada spec must be built from the C/C++
24478 header files provided with the DLL.
24481 The import library (@code{libAPI.dll.a} or @code{API.lib}). As previously
24482 mentioned an import library is a statically linked library containing the
24483 import table which will be filled at load time to point to the actual
24484 @code{API.dll} routines. Sometimes you don't have an import library for the
24485 DLL you want to use. The following sections will explain how to build
24486 one. Note that this is optional.
24489 The actual DLL, @code{API.dll}.
24492 Once you have all the above, to compile an Ada application that uses the
24493 services of @code{API.dll} and whose main subprogram is @code{My_Ada_App},
24494 you simply issue the command
24499 $ gnatmake my_ada_app -largs -lAPI
24503 The argument @code{-largs -lAPI} at the end of the @code{gnatmake} command
24504 tells the GNAT linker to look for an import library. The linker will
24505 look for a library name in this specific order:
24511 @code{libAPI.dll.a}
24529 The first three are the GNU style import libraries. The third is the
24530 Microsoft style import libraries. The last two are the actual DLL names.
24532 Note that if the Ada package spec for @code{API.dll} contains the
24538 pragma Linker_Options ("-lAPI");
24542 you do not have to add @code{-largs -lAPI} at the end of the
24543 @code{gnatmake} command.
24545 If any one of the items above is missing you will have to create it
24546 yourself. The following sections explain how to do so using as an
24547 example a fictitious DLL called @code{API.dll}.
24550 * Creating an Ada Spec for the DLL Services::
24551 * Creating an Import Library::
24555 @node Creating an Ada Spec for the DLL Services,Creating an Import Library,,Using DLLs with GNAT
24556 @anchor{gnat_ugn/platform_specific_information id21}@anchor{1f4}@anchor{gnat_ugn/platform_specific_information creating-an-ada-spec-for-the-dll-services}@anchor{1f5}
24557 @subsubsection Creating an Ada Spec for the DLL Services
24560 A DLL typically comes with a C/C++ header file which provides the
24561 definitions of the routines and variables exported by the DLL. The Ada
24562 equivalent of this header file is a package spec that contains definitions
24563 for the imported entities. If the DLL you intend to use does not come with
24564 an Ada spec you have to generate one such spec yourself. For example if
24565 the header file of @code{API.dll} is a file @code{api.h} containing the
24566 following two definitions:
24576 then the equivalent Ada spec could be:
24581 with Interfaces.C.Strings;
24586 function Get (Str : C.Strings.Chars_Ptr) return C.int;
24589 pragma Import (C, Get);
24590 pragma Import (DLL, Some_Var);
24595 @node Creating an Import Library,,Creating an Ada Spec for the DLL Services,Using DLLs with GNAT
24596 @anchor{gnat_ugn/platform_specific_information id22}@anchor{1f6}@anchor{gnat_ugn/platform_specific_information creating-an-import-library}@anchor{1f7}
24597 @subsubsection Creating an Import Library
24600 @geindex Import library
24602 If a Microsoft-style import library @code{API.lib} or a GNAT-style
24603 import library @code{libAPI.dll.a} or @code{libAPI.a} is available
24604 with @code{API.dll} you can skip this section. You can also skip this
24605 section if @code{API.dll} or @code{libAPI.dll} is built with GNU tools
24606 as in this case it is possible to link directly against the
24607 DLL. Otherwise read on.
24609 @geindex Definition file
24610 @anchor{gnat_ugn/platform_specific_information the-definition-file}@anchor{1f2}
24611 @subsubheading The Definition File
24614 As previously mentioned, and unlike Unix systems, the list of symbols
24615 that are exported from a DLL must be provided explicitly in Windows.
24616 The main goal of a definition file is precisely that: list the symbols
24617 exported by a DLL. A definition file (usually a file with a @code{.def}
24618 suffix) has the following structure:
24623 [LIBRARY `@w{`}name`@w{`}]
24624 [DESCRIPTION `@w{`}string`@w{`}]
24626 `@w{`}symbol1`@w{`}
24627 `@w{`}symbol2`@w{`}
24635 @item @emph{LIBRARY name}
24637 This section, which is optional, gives the name of the DLL.
24639 @item @emph{DESCRIPTION string}
24641 This section, which is optional, gives a description string that will be
24642 embedded in the import library.
24644 @item @emph{EXPORTS}
24646 This section gives the list of exported symbols (procedures, functions or
24647 variables). For instance in the case of @code{API.dll} the @code{EXPORTS}
24648 section of @code{API.def} looks like:
24657 Note that you must specify the correct suffix (@code{@@@emph{nn}})
24658 (see @ref{1e6,,Windows Calling Conventions}) for a Stdcall
24659 calling convention function in the exported symbols list.
24661 There can actually be other sections in a definition file, but these
24662 sections are not relevant to the discussion at hand.
24663 @anchor{gnat_ugn/platform_specific_information create-def-file-automatically}@anchor{1f8}
24664 @subsubheading Creating a Definition File Automatically
24667 You can automatically create the definition file @code{API.def}
24668 (see @ref{1f2,,The Definition File}) from a DLL.
24669 For that use the @code{dlltool} program as follows:
24674 $ dlltool API.dll -z API.def --export-all-symbols
24677 Note that if some routines in the DLL have the @code{Stdcall} convention
24678 (@ref{1e6,,Windows Calling Conventions}) with stripped @code{@@@emph{nn}}
24679 suffix then you'll have to edit @code{api.def} to add it, and specify
24680 @code{-k} to @code{gnatdll} when creating the import library.
24682 Here are some hints to find the right @code{@@@emph{nn}} suffix.
24688 If you have the Microsoft import library (.lib), it is possible to get
24689 the right symbols by using Microsoft @code{dumpbin} tool (see the
24690 corresponding Microsoft documentation for further details).
24693 $ dumpbin /exports api.lib
24697 If you have a message about a missing symbol at link time the compiler
24698 tells you what symbol is expected. You just have to go back to the
24699 definition file and add the right suffix.
24702 @anchor{gnat_ugn/platform_specific_information gnat-style-import-library}@anchor{1f9}
24703 @subsubheading GNAT-Style Import Library
24706 To create a static import library from @code{API.dll} with the GNAT tools
24707 you should create the .def file, then use @code{gnatdll} tool
24708 (see @ref{1fa,,Using gnatdll}) as follows:
24713 $ gnatdll -e API.def -d API.dll
24716 @code{gnatdll} takes as input a definition file @code{API.def} and the
24717 name of the DLL containing the services listed in the definition file
24718 @code{API.dll}. The name of the static import library generated is
24719 computed from the name of the definition file as follows: if the
24720 definition file name is @code{xyz.def}, the import library name will
24721 be @code{libxyz.a}. Note that in the previous example option
24722 @code{-e} could have been removed because the name of the definition
24723 file (before the @code{.def} suffix) is the same as the name of the
24724 DLL (@ref{1fa,,Using gnatdll} for more information about @code{gnatdll}).
24726 @anchor{gnat_ugn/platform_specific_information msvs-style-import-library}@anchor{1fb}
24727 @subsubheading Microsoft-Style Import Library
24730 A Microsoft import library is needed only if you plan to make an
24731 Ada DLL available to applications developed with Microsoft
24732 tools (@ref{1e3,,Mixed-Language Programming on Windows}).
24734 To create a Microsoft-style import library for @code{API.dll} you
24735 should create the .def file, then build the actual import library using
24736 Microsoft's @code{lib} utility:
24741 $ lib -machine:IX86 -def:API.def -out:API.lib
24744 If you use the above command the definition file @code{API.def} must
24745 contain a line giving the name of the DLL:
24751 See the Microsoft documentation for further details about the usage of
24755 @node Building DLLs with GNAT Project files,Building DLLs with GNAT,Using DLLs with GNAT,Mixed-Language Programming on Windows
24756 @anchor{gnat_ugn/platform_specific_information id23}@anchor{1fc}@anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat-project-files}@anchor{1e5}
24757 @subsubsection Building DLLs with GNAT Project files
24763 There is nothing specific to Windows in the build process.
24764 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
24765 chapter of the @emph{GPRbuild User's Guide}.
24767 Due to a system limitation, it is not possible under Windows to create threads
24768 when inside the @code{DllMain} routine which is used for auto-initialization
24769 of shared libraries, so it is not possible to have library level tasks in SALs.
24771 @node Building DLLs with GNAT,Building DLLs with gnatdll,Building DLLs with GNAT Project files,Mixed-Language Programming on Windows
24772 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnat}@anchor{1fd}@anchor{gnat_ugn/platform_specific_information id24}@anchor{1fe}
24773 @subsubsection Building DLLs with GNAT
24779 This section explain how to build DLLs using the GNAT built-in DLL
24780 support. With the following procedure it is straight forward to build
24781 and use DLLs with GNAT.
24787 Building object files.
24788 The first step is to build all objects files that are to be included
24789 into the DLL. This is done by using the standard @code{gnatmake} tool.
24793 To build the DLL you must use the @code{gcc} @code{-shared} and
24794 @code{-shared-libgcc} options. It is quite simple to use this method:
24797 $ gcc -shared -shared-libgcc -o api.dll obj1.o obj2.o ...
24800 It is important to note that in this case all symbols found in the
24801 object files are automatically exported. It is possible to restrict
24802 the set of symbols to export by passing to @code{gcc} a definition
24803 file (see @ref{1f2,,The Definition File}).
24807 $ gcc -shared -shared-libgcc -o api.dll api.def obj1.o obj2.o ...
24810 If you use a definition file you must export the elaboration procedures
24811 for every package that required one. Elaboration procedures are named
24812 using the package name followed by "_E".
24815 Preparing DLL to be used.
24816 For the DLL to be used by client programs the bodies must be hidden
24817 from it and the .ali set with read-only attribute. This is very important
24818 otherwise GNAT will recompile all packages and will not actually use
24819 the code in the DLL. For example:
24823 $ copy *.ads *.ali api.dll apilib
24824 $ attrib +R apilib\\*.ali
24828 At this point it is possible to use the DLL by directly linking
24829 against it. Note that you must use the GNAT shared runtime when using
24830 GNAT shared libraries. This is achieved by using the @code{-shared} binder
24836 $ gnatmake main -Iapilib -bargs -shared -largs -Lapilib -lAPI
24840 @node Building DLLs with gnatdll,Ada DLLs and Finalization,Building DLLs with GNAT,Mixed-Language Programming on Windows
24841 @anchor{gnat_ugn/platform_specific_information building-dlls-with-gnatdll}@anchor{1ff}@anchor{gnat_ugn/platform_specific_information id25}@anchor{200}
24842 @subsubsection Building DLLs with gnatdll
24848 Note that it is preferred to use GNAT Project files
24849 (@ref{1e5,,Building DLLs with GNAT Project files}) or the built-in GNAT
24850 DLL support (@ref{1fd,,Building DLLs with GNAT}) or to build DLLs.
24852 This section explains how to build DLLs containing Ada code using
24853 @code{gnatdll}. These DLLs will be referred to as Ada DLLs in the
24854 remainder of this section.
24856 The steps required to build an Ada DLL that is to be used by Ada as well as
24857 non-Ada applications are as follows:
24863 You need to mark each Ada entity exported by the DLL with a @code{C} or
24864 @code{Stdcall} calling convention to avoid any Ada name mangling for the
24865 entities exported by the DLL
24866 (see @ref{201,,Exporting Ada Entities}). You can
24867 skip this step if you plan to use the Ada DLL only from Ada applications.
24870 Your Ada code must export an initialization routine which calls the routine
24871 @code{adainit} generated by @code{gnatbind} to perform the elaboration of
24872 the Ada code in the DLL (@ref{202,,Ada DLLs and Elaboration}). The initialization
24873 routine exported by the Ada DLL must be invoked by the clients of the DLL
24874 to initialize the DLL.
24877 When useful, the DLL should also export a finalization routine which calls
24878 routine @code{adafinal} generated by @code{gnatbind} to perform the
24879 finalization of the Ada code in the DLL (@ref{203,,Ada DLLs and Finalization}).
24880 The finalization routine exported by the Ada DLL must be invoked by the
24881 clients of the DLL when the DLL services are no further needed.
24884 You must provide a spec for the services exported by the Ada DLL in each
24885 of the programming languages to which you plan to make the DLL available.
24888 You must provide a definition file listing the exported entities
24889 (@ref{1f2,,The Definition File}).
24892 Finally you must use @code{gnatdll} to produce the DLL and the import
24893 library (@ref{1fa,,Using gnatdll}).
24896 Note that a relocatable DLL stripped using the @code{strip}
24897 binutils tool will not be relocatable anymore. To build a DLL without
24898 debug information pass @code{-largs -s} to @code{gnatdll}. This
24899 restriction does not apply to a DLL built using a Library Project.
24900 See the @emph{Library Projects} section in the @emph{GNAT Project Manager}
24901 chapter of the @emph{GPRbuild User's Guide}.
24903 @c Limitations_When_Using_Ada_DLLs_from Ada:
24906 * Limitations When Using Ada DLLs from Ada::
24907 * Exporting Ada Entities::
24908 * Ada DLLs and Elaboration::
24912 @node Limitations When Using Ada DLLs from Ada,Exporting Ada Entities,,Building DLLs with gnatdll
24913 @anchor{gnat_ugn/platform_specific_information limitations-when-using-ada-dlls-from-ada}@anchor{204}
24914 @subsubsection Limitations When Using Ada DLLs from Ada
24917 When using Ada DLLs from Ada applications there is a limitation users
24918 should be aware of. Because on Windows the GNAT run-time is not in a DLL of
24919 its own, each Ada DLL includes a part of the GNAT run-time. Specifically,
24920 each Ada DLL includes the services of the GNAT run-time that are necessary
24921 to the Ada code inside the DLL. As a result, when an Ada program uses an
24922 Ada DLL there are two independent GNAT run-times: one in the Ada DLL and
24923 one in the main program.
24925 It is therefore not possible to exchange GNAT run-time objects between the
24926 Ada DLL and the main Ada program. Example of GNAT run-time objects are file
24927 handles (e.g., @code{Text_IO.File_Type}), tasks types, protected objects
24930 It is completely safe to exchange plain elementary, array or record types,
24931 Windows object handles, etc.
24933 @node Exporting Ada Entities,Ada DLLs and Elaboration,Limitations When Using Ada DLLs from Ada,Building DLLs with gnatdll
24934 @anchor{gnat_ugn/platform_specific_information exporting-ada-entities}@anchor{201}@anchor{gnat_ugn/platform_specific_information id26}@anchor{205}
24935 @subsubsection Exporting Ada Entities
24938 @geindex Export table
24940 Building a DLL is a way to encapsulate a set of services usable from any
24941 application. As a result, the Ada entities exported by a DLL should be
24942 exported with the @code{C} or @code{Stdcall} calling conventions to avoid
24943 any Ada name mangling. As an example here is an Ada package
24944 @code{API}, spec and body, exporting two procedures, a function, and a
24950 with Interfaces.C; use Interfaces;
24952 Count : C.int := 0;
24953 function Factorial (Val : C.int) return C.int;
24955 procedure Initialize_API;
24956 procedure Finalize_API;
24957 -- Initialization & Finalization routines. More in the next section.
24959 pragma Export (C, Initialize_API);
24960 pragma Export (C, Finalize_API);
24961 pragma Export (C, Count);
24962 pragma Export (C, Factorial);
24967 package body API is
24968 function Factorial (Val : C.int) return C.int is
24971 Count := Count + 1;
24972 for K in 1 .. Val loop
24978 procedure Initialize_API is
24980 pragma Import (C, Adainit);
24983 end Initialize_API;
24985 procedure Finalize_API is
24986 procedure Adafinal;
24987 pragma Import (C, Adafinal);
24995 If the Ada DLL you are building will only be used by Ada applications
24996 you do not have to export Ada entities with a @code{C} or @code{Stdcall}
24997 convention. As an example, the previous package could be written as
25004 Count : Integer := 0;
25005 function Factorial (Val : Integer) return Integer;
25007 procedure Initialize_API;
25008 procedure Finalize_API;
25009 -- Initialization and Finalization routines.
25014 package body API is
25015 function Factorial (Val : Integer) return Integer is
25016 Fact : Integer := 1;
25018 Count := Count + 1;
25019 for K in 1 .. Val loop
25026 -- The remainder of this package body is unchanged.
25031 Note that if you do not export the Ada entities with a @code{C} or
25032 @code{Stdcall} convention you will have to provide the mangled Ada names
25033 in the definition file of the Ada DLL
25034 (@ref{206,,Creating the Definition File}).
25036 @node Ada DLLs and Elaboration,,Exporting Ada Entities,Building DLLs with gnatdll
25037 @anchor{gnat_ugn/platform_specific_information ada-dlls-and-elaboration}@anchor{202}@anchor{gnat_ugn/platform_specific_information id27}@anchor{207}
25038 @subsubsection Ada DLLs and Elaboration
25041 @geindex DLLs and elaboration
25043 The DLL that you are building contains your Ada code as well as all the
25044 routines in the Ada library that are needed by it. The first thing a
25045 user of your DLL must do is elaborate the Ada code
25046 (@ref{f,,Elaboration Order Handling in GNAT}).
25048 To achieve this you must export an initialization routine
25049 (@code{Initialize_API} in the previous example), which must be invoked
25050 before using any of the DLL services. This elaboration routine must call
25051 the Ada elaboration routine @code{adainit} generated by the GNAT binder
25052 (@ref{b4,,Binding with Non-Ada Main Programs}). See the body of
25053 @code{Initialize_Api} for an example. Note that the GNAT binder is
25054 automatically invoked during the DLL build process by the @code{gnatdll}
25055 tool (@ref{1fa,,Using gnatdll}).
25057 When a DLL is loaded, Windows systematically invokes a routine called
25058 @code{DllMain}. It would therefore be possible to call @code{adainit}
25059 directly from @code{DllMain} without having to provide an explicit
25060 initialization routine. Unfortunately, it is not possible to call
25061 @code{adainit} from the @code{DllMain} if your program has library level
25062 tasks because access to the @code{DllMain} entry point is serialized by
25063 the system (that is, only a single thread can execute 'through' it at a
25064 time), which means that the GNAT run-time will deadlock waiting for the
25065 newly created task to complete its initialization.
25067 @node Ada DLLs and Finalization,Creating a Spec for Ada DLLs,Building DLLs with gnatdll,Mixed-Language Programming on Windows
25068 @anchor{gnat_ugn/platform_specific_information id28}@anchor{208}@anchor{gnat_ugn/platform_specific_information ada-dlls-and-finalization}@anchor{203}
25069 @subsubsection Ada DLLs and Finalization
25072 @geindex DLLs and finalization
25074 When the services of an Ada DLL are no longer needed, the client code should
25075 invoke the DLL finalization routine, if available. The DLL finalization
25076 routine is in charge of releasing all resources acquired by the DLL. In the
25077 case of the Ada code contained in the DLL, this is achieved by calling
25078 routine @code{adafinal} generated by the GNAT binder
25079 (@ref{b4,,Binding with Non-Ada Main Programs}).
25080 See the body of @code{Finalize_Api} for an
25081 example. As already pointed out the GNAT binder is automatically invoked
25082 during the DLL build process by the @code{gnatdll} tool
25083 (@ref{1fa,,Using gnatdll}).
25085 @node Creating a Spec for Ada DLLs,GNAT and Windows Resources,Ada DLLs and Finalization,Mixed-Language Programming on Windows
25086 @anchor{gnat_ugn/platform_specific_information id29}@anchor{209}@anchor{gnat_ugn/platform_specific_information creating-a-spec-for-ada-dlls}@anchor{20a}
25087 @subsubsection Creating a Spec for Ada DLLs
25090 To use the services exported by the Ada DLL from another programming
25091 language (e.g., C), you have to translate the specs of the exported Ada
25092 entities in that language. For instance in the case of @code{API.dll},
25093 the corresponding C header file could look like:
25098 extern int *_imp__count;
25099 #define count (*_imp__count)
25100 int factorial (int);
25104 It is important to understand that when building an Ada DLL to be used by
25105 other Ada applications, you need two different specs for the packages
25106 contained in the DLL: one for building the DLL and the other for using
25107 the DLL. This is because the @code{DLL} calling convention is needed to
25108 use a variable defined in a DLL, but when building the DLL, the variable
25109 must have either the @code{Ada} or @code{C} calling convention. As an
25110 example consider a DLL comprising the following package @code{API}:
25116 Count : Integer := 0;
25118 -- Remainder of the package omitted.
25123 After producing a DLL containing package @code{API}, the spec that
25124 must be used to import @code{API.Count} from Ada code outside of the
25132 pragma Import (DLL, Count);
25138 * Creating the Definition File::
25143 @node Creating the Definition File,Using gnatdll,,Creating a Spec for Ada DLLs
25144 @anchor{gnat_ugn/platform_specific_information creating-the-definition-file}@anchor{206}@anchor{gnat_ugn/platform_specific_information id30}@anchor{20b}
25145 @subsubsection Creating the Definition File
25148 The definition file is the last file needed to build the DLL. It lists
25149 the exported symbols. As an example, the definition file for a DLL
25150 containing only package @code{API} (where all the entities are exported
25151 with a @code{C} calling convention) is:
25164 If the @code{C} calling convention is missing from package @code{API},
25165 then the definition file contains the mangled Ada names of the above
25166 entities, which in this case are:
25175 api__initialize_api
25179 @node Using gnatdll,,Creating the Definition File,Creating a Spec for Ada DLLs
25180 @anchor{gnat_ugn/platform_specific_information using-gnatdll}@anchor{1fa}@anchor{gnat_ugn/platform_specific_information id31}@anchor{20c}
25181 @subsubsection Using @code{gnatdll}
25186 @code{gnatdll} is a tool to automate the DLL build process once all the Ada
25187 and non-Ada sources that make up your DLL have been compiled.
25188 @code{gnatdll} is actually in charge of two distinct tasks: build the
25189 static import library for the DLL and the actual DLL. The form of the
25190 @code{gnatdll} command is
25195 $ gnatdll [ switches ] list-of-files [ -largs opts ]
25199 where @code{list-of-files} is a list of ALI and object files. The object
25200 file list must be the exact list of objects corresponding to the non-Ada
25201 sources whose services are to be included in the DLL. The ALI file list
25202 must be the exact list of ALI files for the corresponding Ada sources
25203 whose services are to be included in the DLL. If @code{list-of-files} is
25204 missing, only the static import library is generated.
25206 You may specify any of the following switches to @code{gnatdll}:
25210 @geindex -a (gnatdll)
25216 @item @code{-a[@emph{address}]}
25218 Build a non-relocatable DLL at @code{address}. If @code{address} is not
25219 specified the default address @code{0x11000000} will be used. By default,
25220 when this switch is missing, @code{gnatdll} builds relocatable DLL. We
25221 advise the reader to build relocatable DLL.
25223 @geindex -b (gnatdll)
25225 @item @code{-b @emph{address}}
25227 Set the relocatable DLL base address. By default the address is
25230 @geindex -bargs (gnatdll)
25232 @item @code{-bargs @emph{opts}}
25234 Binder options. Pass @code{opts} to the binder.
25236 @geindex -d (gnatdll)
25238 @item @code{-d @emph{dllfile}}
25240 @code{dllfile} is the name of the DLL. This switch must be present for
25241 @code{gnatdll} to do anything. The name of the generated import library is
25242 obtained algorithmically from @code{dllfile} as shown in the following
25243 example: if @code{dllfile} is @code{xyz.dll}, the import library name is
25244 @code{libxyz.dll.a}. The name of the definition file to use (if not specified
25245 by option @code{-e}) is obtained algorithmically from @code{dllfile}
25246 as shown in the following example:
25247 if @code{dllfile} is @code{xyz.dll}, the definition
25248 file used is @code{xyz.def}.
25250 @geindex -e (gnatdll)
25252 @item @code{-e @emph{deffile}}
25254 @code{deffile} is the name of the definition file.
25256 @geindex -g (gnatdll)
25260 Generate debugging information. This information is stored in the object
25261 file and copied from there to the final DLL file by the linker,
25262 where it can be read by the debugger. You must use the
25263 @code{-g} switch if you plan on using the debugger or the symbolic
25266 @geindex -h (gnatdll)
25270 Help mode. Displays @code{gnatdll} switch usage information.
25272 @geindex -I (gnatdll)
25274 @item @code{-I@emph{dir}}
25276 Direct @code{gnatdll} to search the @code{dir} directory for source and
25277 object files needed to build the DLL.
25278 (@ref{89,,Search Paths and the Run-Time Library (RTL)}).
25280 @geindex -k (gnatdll)
25284 Removes the @code{@@@emph{nn}} suffix from the import library's exported
25285 names, but keeps them for the link names. You must specify this
25286 option if you want to use a @code{Stdcall} function in a DLL for which
25287 the @code{@@@emph{nn}} suffix has been removed. This is the case for most
25288 of the Windows NT DLL for example. This option has no effect when
25289 @code{-n} option is specified.
25291 @geindex -l (gnatdll)
25293 @item @code{-l @emph{file}}
25295 The list of ALI and object files used to build the DLL are listed in
25296 @code{file}, instead of being given in the command line. Each line in
25297 @code{file} contains the name of an ALI or object file.
25299 @geindex -n (gnatdll)
25303 No Import. Do not create the import library.
25305 @geindex -q (gnatdll)
25309 Quiet mode. Do not display unnecessary messages.
25311 @geindex -v (gnatdll)
25315 Verbose mode. Display extra information.
25317 @geindex -largs (gnatdll)
25319 @item @code{-largs @emph{opts}}
25321 Linker options. Pass @code{opts} to the linker.
25324 @subsubheading @code{gnatdll} Example
25327 As an example the command to build a relocatable DLL from @code{api.adb}
25328 once @code{api.adb} has been compiled and @code{api.def} created is
25333 $ gnatdll -d api.dll api.ali
25337 The above command creates two files: @code{libapi.dll.a} (the import
25338 library) and @code{api.dll} (the actual DLL). If you want to create
25339 only the DLL, just type:
25344 $ gnatdll -d api.dll -n api.ali
25348 Alternatively if you want to create just the import library, type:
25353 $ gnatdll -d api.dll
25357 @subsubheading @code{gnatdll} behind the Scenes
25360 This section details the steps involved in creating a DLL. @code{gnatdll}
25361 does these steps for you. Unless you are interested in understanding what
25362 goes on behind the scenes, you should skip this section.
25364 We use the previous example of a DLL containing the Ada package @code{API},
25365 to illustrate the steps necessary to build a DLL. The starting point is a
25366 set of objects that will make up the DLL and the corresponding ALI
25367 files. In the case of this example this means that @code{api.o} and
25368 @code{api.ali} are available. To build a relocatable DLL, @code{gnatdll} does
25375 @code{gnatdll} builds the base file (@code{api.base}). A base file gives
25376 the information necessary to generate relocation information for the
25381 $ gnatlink api -o api.jnk -mdll -Wl,--base-file,api.base
25384 In addition to the base file, the @code{gnatlink} command generates an
25385 output file @code{api.jnk} which can be discarded. The @code{-mdll} switch
25386 asks @code{gnatlink} to generate the routines @code{DllMain} and
25387 @code{DllMainCRTStartup} that are called by the Windows loader when the DLL
25388 is loaded into memory.
25391 @code{gnatdll} uses @code{dlltool} (see @ref{20d,,Using dlltool}) to build the
25392 export table (@code{api.exp}). The export table contains the relocation
25393 information in a form which can be used during the final link to ensure
25394 that the Windows loader is able to place the DLL anywhere in memory.
25397 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25398 --output-exp api.exp
25402 @code{gnatdll} builds the base file using the new export table. Note that
25403 @code{gnatbind} must be called once again since the binder generated file
25404 has been deleted during the previous call to @code{gnatlink}.
25408 $ gnatlink api -o api.jnk api.exp -mdll
25409 -Wl,--base-file,api.base
25413 @code{gnatdll} builds the new export table using the new base file and
25414 generates the DLL import library @code{libAPI.dll.a}.
25417 $ dlltool --dllname api.dll --def api.def --base-file api.base \\
25418 --output-exp api.exp --output-lib libAPI.a
25422 Finally @code{gnatdll} builds the relocatable DLL using the final export
25427 $ gnatlink api api.exp -o api.dll -mdll
25430 @anchor{gnat_ugn/platform_specific_information using-dlltool}@anchor{20d}
25431 @subsubheading Using @code{dlltool}
25434 @code{dlltool} is the low-level tool used by @code{gnatdll} to build
25435 DLLs and static import libraries. This section summarizes the most
25436 common @code{dlltool} switches. The form of the @code{dlltool} command
25442 $ dlltool [`switches`]
25446 @code{dlltool} switches include:
25448 @geindex --base-file (dlltool)
25453 @item @code{--base-file @emph{basefile}}
25455 Read the base file @code{basefile} generated by the linker. This switch
25456 is used to create a relocatable DLL.
25459 @geindex --def (dlltool)
25464 @item @code{--def @emph{deffile}}
25466 Read the definition file.
25469 @geindex --dllname (dlltool)
25474 @item @code{--dllname @emph{name}}
25476 Gives the name of the DLL. This switch is used to embed the name of the
25477 DLL in the static import library generated by @code{dlltool} with switch
25478 @code{--output-lib}.
25481 @geindex -k (dlltool)
25488 Kill @code{@@@emph{nn}} from exported names
25489 (@ref{1e6,,Windows Calling Conventions}
25490 for a discussion about @code{Stdcall}-style symbols.
25493 @geindex --help (dlltool)
25498 @item @code{--help}
25500 Prints the @code{dlltool} switches with a concise description.
25503 @geindex --output-exp (dlltool)
25508 @item @code{--output-exp @emph{exportfile}}
25510 Generate an export file @code{exportfile}. The export file contains the
25511 export table (list of symbols in the DLL) and is used to create the DLL.
25514 @geindex --output-lib (dlltool)
25519 @item @code{--output-lib @emph{libfile}}
25521 Generate a static import library @code{libfile}.
25524 @geindex -v (dlltool)
25534 @geindex --as (dlltool)
25539 @item @code{--as @emph{assembler-name}}
25541 Use @code{assembler-name} as the assembler. The default is @code{as}.
25544 @node GNAT and Windows Resources,Using GNAT DLLs from Microsoft Visual Studio Applications,Creating a Spec for Ada DLLs,Mixed-Language Programming on Windows
25545 @anchor{gnat_ugn/platform_specific_information gnat-and-windows-resources}@anchor{20e}@anchor{gnat_ugn/platform_specific_information id32}@anchor{20f}
25546 @subsubsection GNAT and Windows Resources
25552 Resources are an easy way to add Windows specific objects to your
25553 application. The objects that can be added as resources include:
25583 version information
25586 For example, a version information resource can be defined as follow and
25587 embedded into an executable or DLL:
25589 A version information resource can be used to embed information into an
25590 executable or a DLL. These information can be viewed using the file properties
25591 from the Windows Explorer. Here is an example of a version information
25598 FILEVERSION 1,0,0,0
25599 PRODUCTVERSION 1,0,0,0
25601 BLOCK "StringFileInfo"
25605 VALUE "CompanyName", "My Company Name"
25606 VALUE "FileDescription", "My application"
25607 VALUE "FileVersion", "1.0"
25608 VALUE "InternalName", "my_app"
25609 VALUE "LegalCopyright", "My Name"
25610 VALUE "OriginalFilename", "my_app.exe"
25611 VALUE "ProductName", "My App"
25612 VALUE "ProductVersion", "1.0"
25616 BLOCK "VarFileInfo"
25618 VALUE "Translation", 0x809, 1252
25624 The value @code{0809} (langID) is for the U.K English language and
25625 @code{04E4} (charsetID), which is equal to @code{1252} decimal, for
25628 This section explains how to build, compile and use resources. Note that this
25629 section does not cover all resource objects, for a complete description see
25630 the corresponding Microsoft documentation.
25633 * Building Resources::
25634 * Compiling Resources::
25635 * Using Resources::
25639 @node Building Resources,Compiling Resources,,GNAT and Windows Resources
25640 @anchor{gnat_ugn/platform_specific_information building-resources}@anchor{210}@anchor{gnat_ugn/platform_specific_information id33}@anchor{211}
25641 @subsubsection Building Resources
25647 A resource file is an ASCII file. By convention resource files have an
25648 @code{.rc} extension.
25649 The easiest way to build a resource file is to use Microsoft tools
25650 such as @code{imagedit.exe} to build bitmaps, icons and cursors and
25651 @code{dlgedit.exe} to build dialogs.
25652 It is always possible to build an @code{.rc} file yourself by writing a
25655 It is not our objective to explain how to write a resource file. A
25656 complete description of the resource script language can be found in the
25657 Microsoft documentation.
25659 @node Compiling Resources,Using Resources,Building Resources,GNAT and Windows Resources
25660 @anchor{gnat_ugn/platform_specific_information compiling-resources}@anchor{212}@anchor{gnat_ugn/platform_specific_information id34}@anchor{213}
25661 @subsubsection Compiling Resources
25671 This section describes how to build a GNAT-compatible (COFF) object file
25672 containing the resources. This is done using the Resource Compiler
25673 @code{windres} as follows:
25678 $ windres -i myres.rc -o myres.o
25682 By default @code{windres} will run @code{gcc} to preprocess the @code{.rc}
25683 file. You can specify an alternate preprocessor (usually named
25684 @code{cpp.exe}) using the @code{windres} @code{--preprocessor}
25685 parameter. A list of all possible options may be obtained by entering
25686 the command @code{windres} @code{--help}.
25688 It is also possible to use the Microsoft resource compiler @code{rc.exe}
25689 to produce a @code{.res} file (binary resource file). See the
25690 corresponding Microsoft documentation for further details. In this case
25691 you need to use @code{windres} to translate the @code{.res} file to a
25692 GNAT-compatible object file as follows:
25697 $ windres -i myres.res -o myres.o
25701 @node Using Resources,,Compiling Resources,GNAT and Windows Resources
25702 @anchor{gnat_ugn/platform_specific_information using-resources}@anchor{214}@anchor{gnat_ugn/platform_specific_information id35}@anchor{215}
25703 @subsubsection Using Resources
25709 To include the resource file in your program just add the
25710 GNAT-compatible object file for the resource(s) to the linker
25711 arguments. With @code{gnatmake} this is done by using the @code{-largs}
25717 $ gnatmake myprog -largs myres.o
25721 @node Using GNAT DLLs from Microsoft Visual Studio Applications,Debugging a DLL,GNAT and Windows Resources,Mixed-Language Programming on Windows
25722 @anchor{gnat_ugn/platform_specific_information using-gnat-dll-from-msvs}@anchor{216}@anchor{gnat_ugn/platform_specific_information using-gnat-dlls-from-microsoft-visual-studio-applications}@anchor{217}
25723 @subsubsection Using GNAT DLLs from Microsoft Visual Studio Applications
25726 @geindex Microsoft Visual Studio
25727 @geindex use with GNAT DLLs
25729 This section describes a common case of mixed GNAT/Microsoft Visual Studio
25730 application development, where the main program is developed using MSVS, and
25731 is linked with a DLL developed using GNAT. Such a mixed application should
25732 be developed following the general guidelines outlined above; below is the
25733 cookbook-style sequence of steps to follow:
25739 First develop and build the GNAT shared library using a library project
25740 (let's assume the project is @code{mylib.gpr}, producing the library @code{libmylib.dll}):
25746 $ gprbuild -p mylib.gpr
25754 Produce a .def file for the symbols you need to interface with, either by
25755 hand or automatically with possibly some manual adjustments
25756 (see @ref{1f8,,Creating Definition File Automatically}):
25762 $ dlltool libmylib.dll -z libmylib.def --export-all-symbols
25770 Make sure that MSVS command-line tools are accessible on the path.
25773 Create the Microsoft-style import library (see @ref{1fb,,MSVS-Style Import Library}):
25779 $ lib -machine:IX86 -def:libmylib.def -out:libmylib.lib
25783 If you are using a 64-bit toolchain, the above becomes...
25788 $ lib -machine:X64 -def:libmylib.def -out:libmylib.lib
25802 $ cl /O2 /MD main.c libmylib.lib
25810 Before running the executable, make sure you have set the PATH to the DLL,
25811 or copy the DLL into into the directory containing the .exe.
25814 @node Debugging a DLL,Setting Stack Size from gnatlink,Using GNAT DLLs from Microsoft Visual Studio Applications,Mixed-Language Programming on Windows
25815 @anchor{gnat_ugn/platform_specific_information id36}@anchor{218}@anchor{gnat_ugn/platform_specific_information debugging-a-dll}@anchor{219}
25816 @subsubsection Debugging a DLL
25819 @geindex DLL debugging
25821 Debugging a DLL is similar to debugging a standard program. But
25822 we have to deal with two different executable parts: the DLL and the
25823 program that uses it. We have the following four possibilities:
25829 The program and the DLL are built with GCC/GNAT.
25832 The program is built with foreign tools and the DLL is built with
25836 The program is built with GCC/GNAT and the DLL is built with
25840 In this section we address only cases one and two above.
25841 There is no point in trying to debug
25842 a DLL with GNU/GDB, if there is no GDB-compatible debugging
25843 information in it. To do so you must use a debugger compatible with the
25844 tools suite used to build the DLL.
25847 * Program and DLL Both Built with GCC/GNAT::
25848 * Program Built with Foreign Tools and DLL Built with GCC/GNAT::
25852 @node Program and DLL Both Built with GCC/GNAT,Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Debugging a DLL
25853 @anchor{gnat_ugn/platform_specific_information id37}@anchor{21a}@anchor{gnat_ugn/platform_specific_information program-and-dll-both-built-with-gcc-gnat}@anchor{21b}
25854 @subsubsection Program and DLL Both Built with GCC/GNAT
25857 This is the simplest case. Both the DLL and the program have @code{GDB}
25858 compatible debugging information. It is then possible to break anywhere in
25859 the process. Let's suppose here that the main procedure is named
25860 @code{ada_main} and that in the DLL there is an entry point named
25863 The DLL (@ref{1f1,,Introduction to Dynamic Link Libraries (DLLs)}) and
25864 program must have been built with the debugging information (see GNAT -g
25865 switch). Here are the step-by-step instructions for debugging it:
25871 Launch @code{GDB} on the main program.
25878 Start the program and stop at the beginning of the main procedure
25884 This step is required to be able to set a breakpoint inside the DLL. As long
25885 as the program is not run, the DLL is not loaded. This has the
25886 consequence that the DLL debugging information is also not loaded, so it is not
25887 possible to set a breakpoint in the DLL.
25890 Set a breakpoint inside the DLL
25893 (gdb) break ada_dll
25898 At this stage a breakpoint is set inside the DLL. From there on
25899 you can use the standard approach to debug the whole program
25900 (@ref{24,,Running and Debugging Ada Programs}).
25902 @node Program Built with Foreign Tools and DLL Built with GCC/GNAT,,Program and DLL Both Built with GCC/GNAT,Debugging a DLL
25903 @anchor{gnat_ugn/platform_specific_information program-built-with-foreign-tools-and-dll-built-with-gcc-gnat}@anchor{21c}@anchor{gnat_ugn/platform_specific_information id38}@anchor{21d}
25904 @subsubsection Program Built with Foreign Tools and DLL Built with GCC/GNAT
25907 In this case things are slightly more complex because it is not possible to
25908 start the main program and then break at the beginning to load the DLL and the
25909 associated DLL debugging information. It is not possible to break at the
25910 beginning of the program because there is no @code{GDB} debugging information,
25911 and therefore there is no direct way of getting initial control. This
25912 section addresses this issue by describing some methods that can be used
25913 to break somewhere in the DLL to debug it.
25915 First suppose that the main procedure is named @code{main} (this is for
25916 example some C code built with Microsoft Visual C) and that there is a
25917 DLL named @code{test.dll} containing an Ada entry point named
25920 The DLL (see @ref{1f1,,Introduction to Dynamic Link Libraries (DLLs)}) must have
25921 been built with debugging information (see the GNAT @code{-g} option).
25923 @subsubheading Debugging the DLL Directly
25930 Find out the executable starting address
25933 $ objdump --file-header main.exe
25936 The starting address is reported on the last line. For example:
25939 main.exe: file format pei-i386
25940 architecture: i386, flags 0x0000010a:
25941 EXEC_P, HAS_DEBUG, D_PAGED
25942 start address 0x00401010
25946 Launch the debugger on the executable.
25953 Set a breakpoint at the starting address, and launch the program.
25956 $ (gdb) break *0x00401010
25960 The program will stop at the given address.
25963 Set a breakpoint on a DLL subroutine.
25966 (gdb) break ada_dll.adb:45
25969 Or if you want to break using a symbol on the DLL, you need first to
25970 select the Ada language (language used by the DLL).
25973 (gdb) set language ada
25974 (gdb) break ada_dll
25978 Continue the program.
25984 This will run the program until it reaches the breakpoint that has been
25985 set. From that point you can use the standard way to debug a program
25986 as described in (@ref{24,,Running and Debugging Ada Programs}).
25989 It is also possible to debug the DLL by attaching to a running process.
25991 @subsubheading Attaching to a Running Process
25994 @geindex DLL debugging
25995 @geindex attach to process
25997 With @code{GDB} it is always possible to debug a running process by
25998 attaching to it. It is possible to debug a DLL this way. The limitation
25999 of this approach is that the DLL must run long enough to perform the
26000 attach operation. It may be useful for instance to insert a time wasting
26001 loop in the code of the DLL to meet this criterion.
26007 Launch the main program @code{main.exe}.
26014 Use the Windows @emph{Task Manager} to find the process ID. Let's say
26015 that the process PID for @code{main.exe} is 208.
26025 Attach to the running process to be debugged.
26032 Load the process debugging information.
26035 (gdb) symbol-file main.exe
26039 Break somewhere in the DLL.
26042 (gdb) break ada_dll
26046 Continue process execution.
26053 This last step will resume the process execution, and stop at
26054 the breakpoint we have set. From there you can use the standard
26055 approach to debug a program as described in
26056 @ref{24,,Running and Debugging Ada Programs}.
26058 @node Setting Stack Size from gnatlink,Setting Heap Size from gnatlink,Debugging a DLL,Mixed-Language Programming on Windows
26059 @anchor{gnat_ugn/platform_specific_information setting-stack-size-from-gnatlink}@anchor{136}@anchor{gnat_ugn/platform_specific_information id39}@anchor{21e}
26060 @subsubsection Setting Stack Size from @code{gnatlink}
26063 It is possible to specify the program stack size at link time. On modern
26064 versions of Windows, starting with XP, this is mostly useful to set the size of
26065 the main stack (environment task). The other task stacks are set with pragma
26066 Storage_Size or with the @emph{gnatbind -d} command.
26068 Since older versions of Windows (2000, NT4, etc.) do not allow setting the
26069 reserve size of individual tasks, the link-time stack size applies to all
26070 tasks, and pragma Storage_Size has no effect.
26071 In particular, Stack Overflow checks are made against this
26072 link-time specified size.
26074 This setting can be done with @code{gnatlink} using either of the following:
26080 @code{-Xlinker} linker option
26083 $ gnatlink hello -Xlinker --stack=0x10000,0x1000
26086 This sets the stack reserve size to 0x10000 bytes and the stack commit
26087 size to 0x1000 bytes.
26090 @code{-Wl} linker option
26093 $ gnatlink hello -Wl,--stack=0x1000000
26096 This sets the stack reserve size to 0x1000000 bytes. Note that with
26097 @code{-Wl} option it is not possible to set the stack commit size
26098 because the comma is a separator for this option.
26101 @node Setting Heap Size from gnatlink,,Setting Stack Size from gnatlink,Mixed-Language Programming on Windows
26102 @anchor{gnat_ugn/platform_specific_information setting-heap-size-from-gnatlink}@anchor{137}@anchor{gnat_ugn/platform_specific_information id40}@anchor{21f}
26103 @subsubsection Setting Heap Size from @code{gnatlink}
26106 Under Windows systems, it is possible to specify the program heap size from
26107 @code{gnatlink} using either of the following:
26113 @code{-Xlinker} linker option
26116 $ gnatlink hello -Xlinker --heap=0x10000,0x1000
26119 This sets the heap reserve size to 0x10000 bytes and the heap commit
26120 size to 0x1000 bytes.
26123 @code{-Wl} linker option
26126 $ gnatlink hello -Wl,--heap=0x1000000
26129 This sets the heap reserve size to 0x1000000 bytes. Note that with
26130 @code{-Wl} option it is not possible to set the heap commit size
26131 because the comma is a separator for this option.
26134 @node Windows Specific Add-Ons,,Mixed-Language Programming on Windows,Microsoft Windows Topics
26135 @anchor{gnat_ugn/platform_specific_information windows-specific-add-ons}@anchor{220}@anchor{gnat_ugn/platform_specific_information win32-specific-addons}@anchor{221}
26136 @subsection Windows Specific Add-Ons
26139 This section describes the Windows specific add-ons.
26147 @node Win32Ada,wPOSIX,,Windows Specific Add-Ons
26148 @anchor{gnat_ugn/platform_specific_information win32ada}@anchor{222}@anchor{gnat_ugn/platform_specific_information id41}@anchor{223}
26149 @subsubsection Win32Ada
26152 Win32Ada is a binding for the Microsoft Win32 API. This binding can be
26153 easily installed from the provided installer. To use the Win32Ada
26154 binding you need to use a project file, and adding a single with_clause
26155 will give you full access to the Win32Ada binding sources and ensure
26156 that the proper libraries are passed to the linker.
26163 for Sources use ...;
26168 To build the application you just need to call gprbuild for the
26169 application's project, here p.gpr:
26178 @node wPOSIX,,Win32Ada,Windows Specific Add-Ons
26179 @anchor{gnat_ugn/platform_specific_information id42}@anchor{224}@anchor{gnat_ugn/platform_specific_information wposix}@anchor{225}
26180 @subsubsection wPOSIX
26183 wPOSIX is a minimal POSIX binding whose goal is to help with building
26184 cross-platforms applications. This binding is not complete though, as
26185 the Win32 API does not provide the necessary support for all POSIX APIs.
26187 To use the wPOSIX binding you need to use a project file, and adding
26188 a single with_clause will give you full access to the wPOSIX binding
26189 sources and ensure that the proper libraries are passed to the linker.
26196 for Sources use ...;
26201 To build the application you just need to call gprbuild for the
26202 application's project, here p.gpr:
26211 @node Mac OS Topics,,Microsoft Windows Topics,Platform-Specific Information
26212 @anchor{gnat_ugn/platform_specific_information mac-os-topics}@anchor{2d}@anchor{gnat_ugn/platform_specific_information id43}@anchor{226}
26213 @section Mac OS Topics
26218 This section describes topics that are specific to Apple's OS X
26222 * Codesigning the Debugger::
26226 @node Codesigning the Debugger,,,Mac OS Topics
26227 @anchor{gnat_ugn/platform_specific_information codesigning-the-debugger}@anchor{227}
26228 @subsection Codesigning the Debugger
26231 The Darwin Kernel requires the debugger to have special permissions
26232 before it is allowed to control other processes. These permissions
26233 are granted by codesigning the GDB executable. Without these
26234 permissions, the debugger will report error messages such as:
26237 Starting program: /x/y/foo
26238 Unable to find Mach task port for process-id 28885: (os/kern) failure (0x5).
26239 (please check gdb is codesigned - see taskgated(8))
26242 Codesigning requires a certificate. The following procedure explains
26249 Start the Keychain Access application (in
26250 /Applications/Utilities/Keychain Access.app)
26253 Select the Keychain Access -> Certificate Assistant ->
26254 Create a Certificate... menu
26263 Choose a name for the new certificate (this procedure will use
26264 "gdb-cert" as an example)
26267 Set "Identity Type" to "Self Signed Root"
26270 Set "Certificate Type" to "Code Signing"
26273 Activate the "Let me override defaults" option
26277 Click several times on "Continue" until the "Specify a Location
26278 For The Certificate" screen appears, then set "Keychain" to "System"
26281 Click on "Continue" until the certificate is created
26284 Finally, in the view, double-click on the new certificate,
26285 and set "When using this certificate" to "Always Trust"
26288 Exit the Keychain Access application and restart the computer
26289 (this is unfortunately required)
26292 Once a certificate has been created, the debugger can be codesigned
26293 as follow. In a Terminal, run the following command:
26298 $ codesign -f -s "gdb-cert" <gnat_install_prefix>/bin/gdb
26302 where "gdb-cert" should be replaced by the actual certificate
26303 name chosen above, and <gnat_install_prefix> should be replaced by
26304 the location where you installed GNAT. Also, be sure that users are
26305 in the Unix group @code{_developer}.
26307 @node Example of Binder Output File,Elaboration Order Handling in GNAT,Platform-Specific Information,Top
26308 @anchor{gnat_ugn/example_of_binder_output example-of-binder-output-file}@anchor{e}@anchor{gnat_ugn/example_of_binder_output doc}@anchor{228}@anchor{gnat_ugn/example_of_binder_output id1}@anchor{229}
26309 @chapter Example of Binder Output File
26312 @geindex Binder output (example)
26314 This Appendix displays the source code for the output file
26315 generated by @emph{gnatbind} for a simple 'Hello World' program.
26316 Comments have been added for clarification purposes.
26319 -- The package is called Ada_Main unless this name is actually used
26320 -- as a unit name in the partition, in which case some other unique
26325 package ada_main is
26326 pragma Warnings (Off);
26328 -- The main program saves the parameters (argument count,
26329 -- argument values, environment pointer) in global variables
26330 -- for later access by other units including
26331 -- Ada.Command_Line.
26333 gnat_argc : Integer;
26334 gnat_argv : System.Address;
26335 gnat_envp : System.Address;
26337 -- The actual variables are stored in a library routine. This
26338 -- is useful for some shared library situations, where there
26339 -- are problems if variables are not in the library.
26341 pragma Import (C, gnat_argc);
26342 pragma Import (C, gnat_argv);
26343 pragma Import (C, gnat_envp);
26345 -- The exit status is similarly an external location
26347 gnat_exit_status : Integer;
26348 pragma Import (C, gnat_exit_status);
26350 GNAT_Version : constant String :=
26351 "GNAT Version: Pro 7.4.0w (20141119-49)" & ASCII.NUL;
26352 pragma Export (C, GNAT_Version, "__gnat_version");
26354 Ada_Main_Program_Name : constant String := "_ada_hello" & ASCII.NUL;
26355 pragma Export (C, Ada_Main_Program_Name, "__gnat_ada_main_program_name");
26357 -- This is the generated adainit routine that performs
26358 -- initialization at the start of execution. In the case
26359 -- where Ada is the main program, this main program makes
26360 -- a call to adainit at program startup.
26363 pragma Export (C, adainit, "adainit");
26365 -- This is the generated adafinal routine that performs
26366 -- finalization at the end of execution. In the case where
26367 -- Ada is the main program, this main program makes a call
26368 -- to adafinal at program termination.
26370 procedure adafinal;
26371 pragma Export (C, adafinal, "adafinal");
26373 -- This routine is called at the start of execution. It is
26374 -- a dummy routine that is used by the debugger to breakpoint
26375 -- at the start of execution.
26377 -- This is the actual generated main program (it would be
26378 -- suppressed if the no main program switch were used). As
26379 -- required by standard system conventions, this program has
26380 -- the external name main.
26384 argv : System.Address;
26385 envp : System.Address)
26387 pragma Export (C, main, "main");
26389 -- The following set of constants give the version
26390 -- identification values for every unit in the bound
26391 -- partition. This identification is computed from all
26392 -- dependent semantic units, and corresponds to the
26393 -- string that would be returned by use of the
26394 -- Body_Version or Version attributes.
26396 -- The following Export pragmas export the version numbers
26397 -- with symbolic names ending in B (for body) or S
26398 -- (for spec) so that they can be located in a link. The
26399 -- information provided here is sufficient to track down
26400 -- the exact versions of units used in a given build.
26402 type Version_32 is mod 2 ** 32;
26403 u00001 : constant Version_32 := 16#8ad6e54a#;
26404 pragma Export (C, u00001, "helloB");
26405 u00002 : constant Version_32 := 16#fbff4c67#;
26406 pragma Export (C, u00002, "system__standard_libraryB");
26407 u00003 : constant Version_32 := 16#1ec6fd90#;
26408 pragma Export (C, u00003, "system__standard_libraryS");
26409 u00004 : constant Version_32 := 16#3ffc8e18#;
26410 pragma Export (C, u00004, "adaS");
26411 u00005 : constant Version_32 := 16#28f088c2#;
26412 pragma Export (C, u00005, "ada__text_ioB");
26413 u00006 : constant Version_32 := 16#f372c8ac#;
26414 pragma Export (C, u00006, "ada__text_ioS");
26415 u00007 : constant Version_32 := 16#2c143749#;
26416 pragma Export (C, u00007, "ada__exceptionsB");
26417 u00008 : constant Version_32 := 16#f4f0cce8#;
26418 pragma Export (C, u00008, "ada__exceptionsS");
26419 u00009 : constant Version_32 := 16#a46739c0#;
26420 pragma Export (C, u00009, "ada__exceptions__last_chance_handlerB");
26421 u00010 : constant Version_32 := 16#3aac8c92#;
26422 pragma Export (C, u00010, "ada__exceptions__last_chance_handlerS");
26423 u00011 : constant Version_32 := 16#1d274481#;
26424 pragma Export (C, u00011, "systemS");
26425 u00012 : constant Version_32 := 16#a207fefe#;
26426 pragma Export (C, u00012, "system__soft_linksB");
26427 u00013 : constant Version_32 := 16#467d9556#;
26428 pragma Export (C, u00013, "system__soft_linksS");
26429 u00014 : constant Version_32 := 16#b01dad17#;
26430 pragma Export (C, u00014, "system__parametersB");
26431 u00015 : constant Version_32 := 16#630d49fe#;
26432 pragma Export (C, u00015, "system__parametersS");
26433 u00016 : constant Version_32 := 16#b19b6653#;
26434 pragma Export (C, u00016, "system__secondary_stackB");
26435 u00017 : constant Version_32 := 16#b6468be8#;
26436 pragma Export (C, u00017, "system__secondary_stackS");
26437 u00018 : constant Version_32 := 16#39a03df9#;
26438 pragma Export (C, u00018, "system__storage_elementsB");
26439 u00019 : constant Version_32 := 16#30e40e85#;
26440 pragma Export (C, u00019, "system__storage_elementsS");
26441 u00020 : constant Version_32 := 16#41837d1e#;
26442 pragma Export (C, u00020, "system__stack_checkingB");
26443 u00021 : constant Version_32 := 16#93982f69#;
26444 pragma Export (C, u00021, "system__stack_checkingS");
26445 u00022 : constant Version_32 := 16#393398c1#;
26446 pragma Export (C, u00022, "system__exception_tableB");
26447 u00023 : constant Version_32 := 16#b33e2294#;
26448 pragma Export (C, u00023, "system__exception_tableS");
26449 u00024 : constant Version_32 := 16#ce4af020#;
26450 pragma Export (C, u00024, "system__exceptionsB");
26451 u00025 : constant Version_32 := 16#75442977#;
26452 pragma Export (C, u00025, "system__exceptionsS");
26453 u00026 : constant Version_32 := 16#37d758f1#;
26454 pragma Export (C, u00026, "system__exceptions__machineS");
26455 u00027 : constant Version_32 := 16#b895431d#;
26456 pragma Export (C, u00027, "system__exceptions_debugB");
26457 u00028 : constant Version_32 := 16#aec55d3f#;
26458 pragma Export (C, u00028, "system__exceptions_debugS");
26459 u00029 : constant Version_32 := 16#570325c8#;
26460 pragma Export (C, u00029, "system__img_intB");
26461 u00030 : constant Version_32 := 16#1ffca443#;
26462 pragma Export (C, u00030, "system__img_intS");
26463 u00031 : constant Version_32 := 16#b98c3e16#;
26464 pragma Export (C, u00031, "system__tracebackB");
26465 u00032 : constant Version_32 := 16#831a9d5a#;
26466 pragma Export (C, u00032, "system__tracebackS");
26467 u00033 : constant Version_32 := 16#9ed49525#;
26468 pragma Export (C, u00033, "system__traceback_entriesB");
26469 u00034 : constant Version_32 := 16#1d7cb2f1#;
26470 pragma Export (C, u00034, "system__traceback_entriesS");
26471 u00035 : constant Version_32 := 16#8c33a517#;
26472 pragma Export (C, u00035, "system__wch_conB");
26473 u00036 : constant Version_32 := 16#065a6653#;
26474 pragma Export (C, u00036, "system__wch_conS");
26475 u00037 : constant Version_32 := 16#9721e840#;
26476 pragma Export (C, u00037, "system__wch_stwB");
26477 u00038 : constant Version_32 := 16#2b4b4a52#;
26478 pragma Export (C, u00038, "system__wch_stwS");
26479 u00039 : constant Version_32 := 16#92b797cb#;
26480 pragma Export (C, u00039, "system__wch_cnvB");
26481 u00040 : constant Version_32 := 16#09eddca0#;
26482 pragma Export (C, u00040, "system__wch_cnvS");
26483 u00041 : constant Version_32 := 16#6033a23f#;
26484 pragma Export (C, u00041, "interfacesS");
26485 u00042 : constant Version_32 := 16#ece6fdb6#;
26486 pragma Export (C, u00042, "system__wch_jisB");
26487 u00043 : constant Version_32 := 16#899dc581#;
26488 pragma Export (C, u00043, "system__wch_jisS");
26489 u00044 : constant Version_32 := 16#10558b11#;
26490 pragma Export (C, u00044, "ada__streamsB");
26491 u00045 : constant Version_32 := 16#2e6701ab#;
26492 pragma Export (C, u00045, "ada__streamsS");
26493 u00046 : constant Version_32 := 16#db5c917c#;
26494 pragma Export (C, u00046, "ada__io_exceptionsS");
26495 u00047 : constant Version_32 := 16#12c8cd7d#;
26496 pragma Export (C, u00047, "ada__tagsB");
26497 u00048 : constant Version_32 := 16#ce72c228#;
26498 pragma Export (C, u00048, "ada__tagsS");
26499 u00049 : constant Version_32 := 16#c3335bfd#;
26500 pragma Export (C, u00049, "system__htableB");
26501 u00050 : constant Version_32 := 16#99e5f76b#;
26502 pragma Export (C, u00050, "system__htableS");
26503 u00051 : constant Version_32 := 16#089f5cd0#;
26504 pragma Export (C, u00051, "system__string_hashB");
26505 u00052 : constant Version_32 := 16#3bbb9c15#;
26506 pragma Export (C, u00052, "system__string_hashS");
26507 u00053 : constant Version_32 := 16#807fe041#;
26508 pragma Export (C, u00053, "system__unsigned_typesS");
26509 u00054 : constant Version_32 := 16#d27be59e#;
26510 pragma Export (C, u00054, "system__val_lluB");
26511 u00055 : constant Version_32 := 16#fa8db733#;
26512 pragma Export (C, u00055, "system__val_lluS");
26513 u00056 : constant Version_32 := 16#27b600b2#;
26514 pragma Export (C, u00056, "system__val_utilB");
26515 u00057 : constant Version_32 := 16#b187f27f#;
26516 pragma Export (C, u00057, "system__val_utilS");
26517 u00058 : constant Version_32 := 16#d1060688#;
26518 pragma Export (C, u00058, "system__case_utilB");
26519 u00059 : constant Version_32 := 16#392e2d56#;
26520 pragma Export (C, u00059, "system__case_utilS");
26521 u00060 : constant Version_32 := 16#84a27f0d#;
26522 pragma Export (C, u00060, "interfaces__c_streamsB");
26523 u00061 : constant Version_32 := 16#8bb5f2c0#;
26524 pragma Export (C, u00061, "interfaces__c_streamsS");
26525 u00062 : constant Version_32 := 16#6db6928f#;
26526 pragma Export (C, u00062, "system__crtlS");
26527 u00063 : constant Version_32 := 16#4e6a342b#;
26528 pragma Export (C, u00063, "system__file_ioB");
26529 u00064 : constant Version_32 := 16#ba56a5e4#;
26530 pragma Export (C, u00064, "system__file_ioS");
26531 u00065 : constant Version_32 := 16#b7ab275c#;
26532 pragma Export (C, u00065, "ada__finalizationB");
26533 u00066 : constant Version_32 := 16#19f764ca#;
26534 pragma Export (C, u00066, "ada__finalizationS");
26535 u00067 : constant Version_32 := 16#95817ed8#;
26536 pragma Export (C, u00067, "system__finalization_rootB");
26537 u00068 : constant Version_32 := 16#52d53711#;
26538 pragma Export (C, u00068, "system__finalization_rootS");
26539 u00069 : constant Version_32 := 16#769e25e6#;
26540 pragma Export (C, u00069, "interfaces__cB");
26541 u00070 : constant Version_32 := 16#4a38bedb#;
26542 pragma Export (C, u00070, "interfaces__cS");
26543 u00071 : constant Version_32 := 16#07e6ee66#;
26544 pragma Export (C, u00071, "system__os_libB");
26545 u00072 : constant Version_32 := 16#d7b69782#;
26546 pragma Export (C, u00072, "system__os_libS");
26547 u00073 : constant Version_32 := 16#1a817b8e#;
26548 pragma Export (C, u00073, "system__stringsB");
26549 u00074 : constant Version_32 := 16#639855e7#;
26550 pragma Export (C, u00074, "system__stringsS");
26551 u00075 : constant Version_32 := 16#e0b8de29#;
26552 pragma Export (C, u00075, "system__file_control_blockS");
26553 u00076 : constant Version_32 := 16#b5b2aca1#;
26554 pragma Export (C, u00076, "system__finalization_mastersB");
26555 u00077 : constant Version_32 := 16#69316dc1#;
26556 pragma Export (C, u00077, "system__finalization_mastersS");
26557 u00078 : constant Version_32 := 16#57a37a42#;
26558 pragma Export (C, u00078, "system__address_imageB");
26559 u00079 : constant Version_32 := 16#bccbd9bb#;
26560 pragma Export (C, u00079, "system__address_imageS");
26561 u00080 : constant Version_32 := 16#7268f812#;
26562 pragma Export (C, u00080, "system__img_boolB");
26563 u00081 : constant Version_32 := 16#e8fe356a#;
26564 pragma Export (C, u00081, "system__img_boolS");
26565 u00082 : constant Version_32 := 16#d7aac20c#;
26566 pragma Export (C, u00082, "system__ioB");
26567 u00083 : constant Version_32 := 16#8365b3ce#;
26568 pragma Export (C, u00083, "system__ioS");
26569 u00084 : constant Version_32 := 16#6d4d969a#;
26570 pragma Export (C, u00084, "system__storage_poolsB");
26571 u00085 : constant Version_32 := 16#e87cc305#;
26572 pragma Export (C, u00085, "system__storage_poolsS");
26573 u00086 : constant Version_32 := 16#e34550ca#;
26574 pragma Export (C, u00086, "system__pool_globalB");
26575 u00087 : constant Version_32 := 16#c88d2d16#;
26576 pragma Export (C, u00087, "system__pool_globalS");
26577 u00088 : constant Version_32 := 16#9d39c675#;
26578 pragma Export (C, u00088, "system__memoryB");
26579 u00089 : constant Version_32 := 16#445a22b5#;
26580 pragma Export (C, u00089, "system__memoryS");
26581 u00090 : constant Version_32 := 16#6a859064#;
26582 pragma Export (C, u00090, "system__storage_pools__subpoolsB");
26583 u00091 : constant Version_32 := 16#e3b008dc#;
26584 pragma Export (C, u00091, "system__storage_pools__subpoolsS");
26585 u00092 : constant Version_32 := 16#63f11652#;
26586 pragma Export (C, u00092, "system__storage_pools__subpools__finalizationB");
26587 u00093 : constant Version_32 := 16#fe2f4b3a#;
26588 pragma Export (C, u00093, "system__storage_pools__subpools__finalizationS");
26590 -- BEGIN ELABORATION ORDER
26594 -- system.case_util%s
26595 -- system.case_util%b
26597 -- system.img_bool%s
26598 -- system.img_bool%b
26599 -- system.img_int%s
26600 -- system.img_int%b
26603 -- system.parameters%s
26604 -- system.parameters%b
26606 -- interfaces.c_streams%s
26607 -- interfaces.c_streams%b
26608 -- system.standard_library%s
26609 -- system.exceptions_debug%s
26610 -- system.exceptions_debug%b
26611 -- system.storage_elements%s
26612 -- system.storage_elements%b
26613 -- system.stack_checking%s
26614 -- system.stack_checking%b
26615 -- system.string_hash%s
26616 -- system.string_hash%b
26618 -- system.strings%s
26619 -- system.strings%b
26621 -- system.traceback_entries%s
26622 -- system.traceback_entries%b
26623 -- ada.exceptions%s
26624 -- system.soft_links%s
26625 -- system.unsigned_types%s
26626 -- system.val_llu%s
26627 -- system.val_util%s
26628 -- system.val_util%b
26629 -- system.val_llu%b
26630 -- system.wch_con%s
26631 -- system.wch_con%b
26632 -- system.wch_cnv%s
26633 -- system.wch_jis%s
26634 -- system.wch_jis%b
26635 -- system.wch_cnv%b
26636 -- system.wch_stw%s
26637 -- system.wch_stw%b
26638 -- ada.exceptions.last_chance_handler%s
26639 -- ada.exceptions.last_chance_handler%b
26640 -- system.address_image%s
26641 -- system.exception_table%s
26642 -- system.exception_table%b
26643 -- ada.io_exceptions%s
26648 -- system.exceptions%s
26649 -- system.exceptions%b
26650 -- system.exceptions.machine%s
26651 -- system.finalization_root%s
26652 -- system.finalization_root%b
26653 -- ada.finalization%s
26654 -- ada.finalization%b
26655 -- system.storage_pools%s
26656 -- system.storage_pools%b
26657 -- system.finalization_masters%s
26658 -- system.storage_pools.subpools%s
26659 -- system.storage_pools.subpools.finalization%s
26660 -- system.storage_pools.subpools.finalization%b
26663 -- system.standard_library%b
26664 -- system.pool_global%s
26665 -- system.pool_global%b
26666 -- system.file_control_block%s
26667 -- system.file_io%s
26668 -- system.secondary_stack%s
26669 -- system.file_io%b
26670 -- system.storage_pools.subpools%b
26671 -- system.finalization_masters%b
26674 -- system.soft_links%b
26676 -- system.secondary_stack%b
26677 -- system.address_image%b
26678 -- system.traceback%s
26679 -- ada.exceptions%b
26680 -- system.traceback%b
26684 -- END ELABORATION ORDER
26691 -- The following source file name pragmas allow the generated file
26692 -- names to be unique for different main programs. They are needed
26693 -- since the package name will always be Ada_Main.
26695 pragma Source_File_Name (ada_main, Spec_File_Name => "b~hello.ads");
26696 pragma Source_File_Name (ada_main, Body_File_Name => "b~hello.adb");
26698 pragma Suppress (Overflow_Check);
26699 with Ada.Exceptions;
26701 -- Generated package body for Ada_Main starts here
26703 package body ada_main is
26704 pragma Warnings (Off);
26706 -- These values are reference counter associated to units which have
26707 -- been elaborated. It is also used to avoid elaborating the
26708 -- same unit twice.
26710 E72 : Short_Integer; pragma Import (Ada, E72, "system__os_lib_E");
26711 E13 : Short_Integer; pragma Import (Ada, E13, "system__soft_links_E");
26712 E23 : Short_Integer; pragma Import (Ada, E23, "system__exception_table_E");
26713 E46 : Short_Integer; pragma Import (Ada, E46, "ada__io_exceptions_E");
26714 E48 : Short_Integer; pragma Import (Ada, E48, "ada__tags_E");
26715 E45 : Short_Integer; pragma Import (Ada, E45, "ada__streams_E");
26716 E70 : Short_Integer; pragma Import (Ada, E70, "interfaces__c_E");
26717 E25 : Short_Integer; pragma Import (Ada, E25, "system__exceptions_E");
26718 E68 : Short_Integer; pragma Import (Ada, E68, "system__finalization_root_E");
26719 E66 : Short_Integer; pragma Import (Ada, E66, "ada__finalization_E");
26720 E85 : Short_Integer; pragma Import (Ada, E85, "system__storage_pools_E");
26721 E77 : Short_Integer; pragma Import (Ada, E77, "system__finalization_masters_E");
26722 E91 : Short_Integer; pragma Import (Ada, E91, "system__storage_pools__subpools_E");
26723 E87 : Short_Integer; pragma Import (Ada, E87, "system__pool_global_E");
26724 E75 : Short_Integer; pragma Import (Ada, E75, "system__file_control_block_E");
26725 E64 : Short_Integer; pragma Import (Ada, E64, "system__file_io_E");
26726 E17 : Short_Integer; pragma Import (Ada, E17, "system__secondary_stack_E");
26727 E06 : Short_Integer; pragma Import (Ada, E06, "ada__text_io_E");
26729 Local_Priority_Specific_Dispatching : constant String := "";
26730 Local_Interrupt_States : constant String := "";
26732 Is_Elaborated : Boolean := False;
26734 procedure finalize_library is
26739 pragma Import (Ada, F1, "ada__text_io__finalize_spec");
26747 pragma Import (Ada, F2, "system__file_io__finalize_body");
26754 pragma Import (Ada, F3, "system__file_control_block__finalize_spec");
26762 pragma Import (Ada, F4, "system__pool_global__finalize_spec");
26768 pragma Import (Ada, F5, "system__storage_pools__subpools__finalize_spec");
26774 pragma Import (Ada, F6, "system__finalization_masters__finalize_spec");
26779 procedure Reraise_Library_Exception_If_Any;
26780 pragma Import (Ada, Reraise_Library_Exception_If_Any, "__gnat_reraise_library_exception_if_any");
26782 Reraise_Library_Exception_If_Any;
26784 end finalize_library;
26790 procedure adainit is
26792 Main_Priority : Integer;
26793 pragma Import (C, Main_Priority, "__gl_main_priority");
26794 Time_Slice_Value : Integer;
26795 pragma Import (C, Time_Slice_Value, "__gl_time_slice_val");
26796 WC_Encoding : Character;
26797 pragma Import (C, WC_Encoding, "__gl_wc_encoding");
26798 Locking_Policy : Character;
26799 pragma Import (C, Locking_Policy, "__gl_locking_policy");
26800 Queuing_Policy : Character;
26801 pragma Import (C, Queuing_Policy, "__gl_queuing_policy");
26802 Task_Dispatching_Policy : Character;
26803 pragma Import (C, Task_Dispatching_Policy, "__gl_task_dispatching_policy");
26804 Priority_Specific_Dispatching : System.Address;
26805 pragma Import (C, Priority_Specific_Dispatching, "__gl_priority_specific_dispatching");
26806 Num_Specific_Dispatching : Integer;
26807 pragma Import (C, Num_Specific_Dispatching, "__gl_num_specific_dispatching");
26808 Main_CPU : Integer;
26809 pragma Import (C, Main_CPU, "__gl_main_cpu");
26810 Interrupt_States : System.Address;
26811 pragma Import (C, Interrupt_States, "__gl_interrupt_states");
26812 Num_Interrupt_States : Integer;
26813 pragma Import (C, Num_Interrupt_States, "__gl_num_interrupt_states");
26814 Unreserve_All_Interrupts : Integer;
26815 pragma Import (C, Unreserve_All_Interrupts, "__gl_unreserve_all_interrupts");
26816 Detect_Blocking : Integer;
26817 pragma Import (C, Detect_Blocking, "__gl_detect_blocking");
26818 Default_Stack_Size : Integer;
26819 pragma Import (C, Default_Stack_Size, "__gl_default_stack_size");
26820 Leap_Seconds_Support : Integer;
26821 pragma Import (C, Leap_Seconds_Support, "__gl_leap_seconds_support");
26823 procedure Runtime_Initialize;
26824 pragma Import (C, Runtime_Initialize, "__gnat_runtime_initialize");
26826 Finalize_Library_Objects : No_Param_Proc;
26827 pragma Import (C, Finalize_Library_Objects, "__gnat_finalize_library_objects");
26829 -- Start of processing for adainit
26833 -- Record various information for this partition. The values
26834 -- are derived by the binder from information stored in the ali
26835 -- files by the compiler.
26837 if Is_Elaborated then
26840 Is_Elaborated := True;
26841 Main_Priority := -1;
26842 Time_Slice_Value := -1;
26843 WC_Encoding := 'b';
26844 Locking_Policy := ' ';
26845 Queuing_Policy := ' ';
26846 Task_Dispatching_Policy := ' ';
26847 Priority_Specific_Dispatching :=
26848 Local_Priority_Specific_Dispatching'Address;
26849 Num_Specific_Dispatching := 0;
26851 Interrupt_States := Local_Interrupt_States'Address;
26852 Num_Interrupt_States := 0;
26853 Unreserve_All_Interrupts := 0;
26854 Detect_Blocking := 0;
26855 Default_Stack_Size := -1;
26856 Leap_Seconds_Support := 0;
26858 Runtime_Initialize;
26860 Finalize_Library_Objects := finalize_library'access;
26862 -- Now we have the elaboration calls for all units in the partition.
26863 -- The Elab_Spec and Elab_Body attributes generate references to the
26864 -- implicit elaboration procedures generated by the compiler for
26865 -- each unit that requires elaboration. Increment a counter of
26866 -- reference for each unit.
26868 System.Soft_Links'Elab_Spec;
26869 System.Exception_Table'Elab_Body;
26871 Ada.Io_Exceptions'Elab_Spec;
26873 Ada.Tags'Elab_Spec;
26874 Ada.Streams'Elab_Spec;
26876 Interfaces.C'Elab_Spec;
26877 System.Exceptions'Elab_Spec;
26879 System.Finalization_Root'Elab_Spec;
26881 Ada.Finalization'Elab_Spec;
26883 System.Storage_Pools'Elab_Spec;
26885 System.Finalization_Masters'Elab_Spec;
26886 System.Storage_Pools.Subpools'Elab_Spec;
26887 System.Pool_Global'Elab_Spec;
26889 System.File_Control_Block'Elab_Spec;
26891 System.File_Io'Elab_Body;
26894 System.Finalization_Masters'Elab_Body;
26897 Ada.Tags'Elab_Body;
26899 System.Soft_Links'Elab_Body;
26901 System.Os_Lib'Elab_Body;
26903 System.Secondary_Stack'Elab_Body;
26905 Ada.Text_Io'Elab_Spec;
26906 Ada.Text_Io'Elab_Body;
26914 procedure adafinal is
26915 procedure s_stalib_adafinal;
26916 pragma Import (C, s_stalib_adafinal, "system__standard_library__adafinal");
26918 procedure Runtime_Finalize;
26919 pragma Import (C, Runtime_Finalize, "__gnat_runtime_finalize");
26922 if not Is_Elaborated then
26925 Is_Elaborated := False;
26930 -- We get to the main program of the partition by using
26931 -- pragma Import because if we try to with the unit and
26932 -- call it Ada style, then not only do we waste time
26933 -- recompiling it, but also, we don't really know the right
26934 -- switches (e.g.@@: identifier character set) to be used
26937 procedure Ada_Main_Program;
26938 pragma Import (Ada, Ada_Main_Program, "_ada_hello");
26944 -- main is actually a function, as in the ANSI C standard,
26945 -- defined to return the exit status. The three parameters
26946 -- are the argument count, argument values and environment
26951 argv : System.Address;
26952 envp : System.Address)
26955 -- The initialize routine performs low level system
26956 -- initialization using a standard library routine which
26957 -- sets up signal handling and performs any other
26958 -- required setup. The routine can be found in file
26961 procedure initialize;
26962 pragma Import (C, initialize, "__gnat_initialize");
26964 -- The finalize routine performs low level system
26965 -- finalization using a standard library routine. The
26966 -- routine is found in file a-final.c and in the standard
26967 -- distribution is a dummy routine that does nothing, so
26968 -- really this is a hook for special user finalization.
26970 procedure finalize;
26971 pragma Import (C, finalize, "__gnat_finalize");
26973 -- The following is to initialize the SEH exceptions
26975 SEH : aliased array (1 .. 2) of Integer;
26977 Ensure_Reference : aliased System.Address := Ada_Main_Program_Name'Address;
26978 pragma Volatile (Ensure_Reference);
26980 -- Start of processing for main
26983 -- Save global variables
26989 -- Call low level system initialization
26991 Initialize (SEH'Address);
26993 -- Call our generated Ada initialization routine
26997 -- Now we call the main program of the partition
27001 -- Perform Ada finalization
27005 -- Perform low level system finalization
27009 -- Return the proper exit status
27010 return (gnat_exit_status);
27013 -- This section is entirely comments, so it has no effect on the
27014 -- compilation of the Ada_Main package. It provides the list of
27015 -- object files and linker options, as well as some standard
27016 -- libraries needed for the link. The gnatlink utility parses
27017 -- this b~hello.adb file to read these comment lines to generate
27018 -- the appropriate command line arguments for the call to the
27019 -- system linker. The BEGIN/END lines are used for sentinels for
27020 -- this parsing operation.
27022 -- The exact file names will of course depend on the environment,
27023 -- host/target and location of files on the host system.
27025 -- BEGIN Object file/option list
27028 -- -L/usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/
27029 -- /usr/local/gnat/lib/gcc-lib/i686-pc-linux-gnu/2.8.1/adalib/libgnat.a
27030 -- END Object file/option list
27035 The Ada code in the above example is exactly what is generated by the
27036 binder. We have added comments to more clearly indicate the function
27037 of each part of the generated @code{Ada_Main} package.
27039 The code is standard Ada in all respects, and can be processed by any
27040 tools that handle Ada. In particular, it is possible to use the debugger
27041 in Ada mode to debug the generated @code{Ada_Main} package. For example,
27042 suppose that for reasons that you do not understand, your program is crashing
27043 during elaboration of the body of @code{Ada.Text_IO}. To locate this bug,
27044 you can place a breakpoint on the call:
27049 Ada.Text_Io'Elab_Body;
27053 and trace the elaboration routine for this package to find out where
27054 the problem might be (more usually of course you would be debugging
27055 elaboration code in your own application).
27057 @c -- Example: A |withing| unit has a |with| clause, it |withs| a |withed| unit
27059 @node Elaboration Order Handling in GNAT,Inline Assembler,Example of Binder Output File,Top
27060 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order-handling-in-gnat}@anchor{f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat doc}@anchor{22a}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id1}@anchor{22b}
27061 @chapter Elaboration Order Handling in GNAT
27064 @geindex Order of elaboration
27066 @geindex Elaboration control
27068 This appendix describes the handling of elaboration code in Ada and GNAT, and
27069 discusses how the order of elaboration of program units can be controlled in
27070 GNAT, either automatically or with explicit programming features.
27073 * Elaboration Code::
27074 * Elaboration Order::
27075 * Checking the Elaboration Order::
27076 * Controlling the Elaboration Order in Ada::
27077 * Controlling the Elaboration Order in GNAT::
27078 * Common Elaboration-model Traits::
27079 * Dynamic Elaboration Model in GNAT::
27080 * Static Elaboration Model in GNAT::
27081 * SPARK Elaboration Model in GNAT::
27082 * Legacy Elaboration Model in GNAT::
27083 * Mixing Elaboration Models::
27084 * Elaboration Circularities::
27085 * Resolving Elaboration Circularities::
27086 * Resolving Task Issues::
27087 * Elaboration-related Compiler Switches::
27088 * Summary of Procedures for Elaboration Control::
27089 * Inspecting the Chosen Elaboration Order::
27093 @node Elaboration Code,Elaboration Order,,Elaboration Order Handling in GNAT
27094 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-code}@anchor{22c}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id2}@anchor{22d}
27095 @section Elaboration Code
27098 Ada defines the term @emph{execution} as the process by which a construct achieves
27099 its run-time effect. This process is also referred to as @strong{elaboration} for
27100 declarations and @emph{evaluation} for expressions.
27102 The execution model in Ada allows for certain sections of an Ada program to be
27103 executed prior to execution of the program itself, primarily with the intent of
27104 initializing data. These sections are referred to as @strong{elaboration code}.
27105 Elaboration code is executed as follows:
27111 All partitions of an Ada program are executed in parallel with one another,
27112 possibly in a separate address space, and possibly on a separate computer.
27115 The execution of a partition involves running the environment task for that
27119 The environment task executes all elaboration code (if available) for all
27120 units within that partition. This code is said to be executed at
27121 @strong{elaboration time}.
27124 The environment task executes the Ada program (if available) for that
27128 In addition to the Ada terminology, this appendix defines the following terms:
27136 A construct that is elaborated or executed by elaboration code is referred to
27137 as an @emph{elaboration scenario} or simply a @strong{scenario}. GNAT recognizes the
27138 following scenarios:
27144 @code{'Access} of entries, operators, and subprograms
27147 Activation of tasks
27150 Calls to entries, operators, and subprograms
27153 Instantiations of generic templates
27159 A construct elaborated by a scenario is referred to as @emph{elaboration target}
27160 or simply @strong{target}. GNAT recognizes the following targets:
27166 For @code{'Access} of entries, operators, and subprograms, the target is the
27167 entry, operator, or subprogram being aliased.
27170 For activation of tasks, the target is the task body
27173 For calls to entries, operators, and subprograms, the target is the entry,
27174 operator, or subprogram being invoked.
27177 For instantiations of generic templates, the target is the generic template
27178 being instantiated.
27182 Elaboration code may appear in two distinct contexts:
27188 @emph{Library level}
27190 A scenario appears at the library level when it is encapsulated by a package
27191 [body] compilation unit, ignoring any other package [body] declarations in
27200 Val : ... := Server.Func;
27205 In the example above, the call to @code{Server.Func} is an elaboration scenario
27206 because it appears at the library level of package @code{Client}. Note that the
27207 declaration of package @code{Nested} is ignored according to the definition
27208 given above. As a result, the call to @code{Server.Func} will be executed when
27209 the spec of unit @code{Client} is elaborated.
27212 @emph{Package body statements}
27214 A scenario appears within the statement sequence of a package body when it is
27215 bounded by the region starting from the @code{begin} keyword of the package body
27216 and ending at the @code{end} keyword of the package body.
27219 package body Client is
27229 In the example above, the call to @code{Proc} is an elaboration scenario because
27230 it appears within the statement sequence of package body @code{Client}. As a
27231 result, the call to @code{Proc} will be executed when the body of @code{Client} is
27235 @node Elaboration Order,Checking the Elaboration Order,Elaboration Code,Elaboration Order Handling in GNAT
27236 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-order}@anchor{22e}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id3}@anchor{22f}
27237 @section Elaboration Order
27240 The sequence by which the elaboration code of all units within a partition is
27241 executed is referred to as @strong{elaboration order}.
27243 Within a single unit, elaboration code is executed in sequential order.
27246 package body Client is
27247 Result : ... := Server.Func;
27250 package Inst is new Server.Gen;
27252 Inst.Eval (Result);
27259 In the example above, the elaboration order within package body @code{Client} is
27266 The object declaration of @code{Result} is elaborated.
27272 Function @code{Server.Func} is invoked.
27276 The subprogram body of @code{Proc} is elaborated.
27279 Procedure @code{Proc} is invoked.
27285 Generic unit @code{Server.Gen} is instantiated as @code{Inst}.
27288 Instance @code{Inst} is elaborated.
27291 Procedure @code{Inst.Eval} is invoked.
27295 The elaboration order of all units within a partition depends on the following
27302 @emph{with}ed units
27308 preelaborability of units
27311 presence of elaboration control pragmas
27314 A program may have several elaboration orders depending on its structure.
27318 function Func (Index : Integer) return Integer;
27323 package body Server is
27324 Results : array (1 .. 5) of Integer := (1, 2, 3, 4, 5);
27326 function Func (Index : Integer) return Integer is
27328 return Results (Index);
27336 Val : constant Integer := Server.Func (3);
27342 procedure Main is begin null; end Main;
27345 The following elaboration order exhibits a fundamental problem referred to as
27346 @emph{access-before-elaboration} or simply @strong{ABE}.
27355 The elaboration of @code{Server}'s spec materializes function @code{Func}, making it
27356 callable. The elaboration of @code{Client}'s spec elaborates the declaration of
27357 @code{Val}. This invokes function @code{Server.Func}, however the body of
27358 @code{Server.Func} has not been elaborated yet because @code{Server}'s body comes
27359 after @code{Client}'s spec in the elaboration order. As a result, the value of
27360 constant @code{Val} is now undefined.
27362 Without any guarantees from the language, an undetected ABE problem may hinder
27363 proper initialization of data, which in turn may lead to undefined behavior at
27364 run time. To prevent such ABE problems, Ada employs dynamic checks in the same
27365 vein as index or null exclusion checks. A failed ABE check raises exception
27366 @code{Program_Error}.
27368 The following elaboration order avoids the ABE problem and the program can be
27369 successfully elaborated.
27378 Ada states that a total elaboration order must exist, but it does not define
27379 what this order is. A compiler is thus tasked with choosing a suitable
27380 elaboration order which satisfies the dependencies imposed by @emph{with} clauses,
27381 unit categorization, and elaboration control pragmas. Ideally an order which
27382 avoids ABE problems should be chosen, however a compiler may not always find
27383 such an order due to complications with respect to control and data flow.
27385 @node Checking the Elaboration Order,Controlling the Elaboration Order in Ada,Elaboration Order,Elaboration Order Handling in GNAT
27386 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id4}@anchor{230}@anchor{gnat_ugn/elaboration_order_handling_in_gnat checking-the-elaboration-order}@anchor{231}
27387 @section Checking the Elaboration Order
27390 To avoid placing the entire elaboration order burden on the programmer, Ada
27391 provides three lines of defense:
27397 @emph{Static semantics}
27399 Static semantic rules restrict the possible choice of elaboration order. For
27400 instance, if unit Client @emph{with}s unit Server, then the spec of Server is
27401 always elaborated prior to Client. The same principle applies to child units
27402 - the spec of a parent unit is always elaborated prior to the child unit.
27405 @emph{Dynamic semantics}
27407 Dynamic checks are performed at run time, to ensure that a target is
27408 elaborated prior to a scenario that executes it, thus avoiding ABE problems.
27409 A failed run-time check raises exception @code{Program_Error}. The following
27410 restrictions apply:
27416 @emph{Restrictions on calls}
27418 An entry, operator, or subprogram can be called from elaboration code only
27419 when the corresponding body has been elaborated.
27422 @emph{Restrictions on instantiations}
27424 A generic unit can be instantiated by elaboration code only when the
27425 corresponding body has been elaborated.
27428 @emph{Restrictions on task activation}
27430 A task can be activated by elaboration code only when the body of the
27431 associated task type has been elaborated.
27434 The restrictions above can be summarized by the following rule:
27436 @emph{If a target has a body, then this body must be elaborated prior to the
27437 execution of the scenario that invokes, instantiates, or activates the
27441 @emph{Elaboration control}
27443 Pragmas are provided for the programmer to specify the desired elaboration
27447 @node Controlling the Elaboration Order in Ada,Controlling the Elaboration Order in GNAT,Checking the Elaboration Order,Elaboration Order Handling in GNAT
27448 @anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-the-elaboration-order-in-ada}@anchor{232}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id5}@anchor{233}
27449 @section Controlling the Elaboration Order in Ada
27452 Ada provides several idioms and pragmas to aid the programmer with specifying
27453 the desired elaboration order and avoiding ABE problems altogether.
27459 @emph{Packages without a body}
27461 A library package which does not require a completing body does not suffer
27467 type Element is private;
27468 package Containers is
27469 type Element_Array is array (1 .. 10) of Element;
27474 In the example above, package @code{Pack} does not require a body because it
27475 does not contain any constructs which require completion in a body. As a
27476 result, generic @code{Pack.Containers} can be instantiated without encountering
27480 @geindex pragma Pure
27488 Pragma @code{Pure} places sufficient restrictions on a unit to guarantee that no
27489 scenario within the unit can result in an ABE problem.
27492 @geindex pragma Preelaborate
27498 @emph{pragma Preelaborate}
27500 Pragma @code{Preelaborate} is slightly less restrictive than pragma @code{Pure},
27501 but still strong enough to prevent ABE problems within a unit.
27504 @geindex pragma Elaborate_Body
27510 @emph{pragma Elaborate_Body}
27512 Pragma @code{Elaborate_Body} requires that the body of a unit is elaborated
27513 immediately after its spec. This restriction guarantees that no client
27514 scenario can execute a server target before the target body has been
27515 elaborated because the spec and body are effectively "glued" together.
27519 pragma Elaborate_Body;
27521 function Func return Integer;
27526 package body Server is
27527 function Func return Integer is
27537 Val : constant Integer := Server.Func;
27541 In the example above, pragma @code{Elaborate_Body} guarantees the following
27550 because the spec of @code{Server} must be elaborated prior to @code{Client} by
27551 virtue of the @emph{with} clause, and in addition the body of @code{Server} must be
27552 elaborated immediately after the spec of @code{Server}.
27554 Removing pragma @code{Elaborate_Body} could result in the following incorrect
27563 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func} has
27564 not been elaborated yet.
27567 The pragmas outlined above allow a server unit to guarantee safe elaboration
27568 use by client units. Thus it is a good rule to mark units as @code{Pure} or
27569 @code{Preelaborate}, and if this is not possible, mark them as @code{Elaborate_Body}.
27571 There are however situations where @code{Pure}, @code{Preelaborate}, and
27572 @code{Elaborate_Body} are not applicable. Ada provides another set of pragmas for
27573 use by client units to help ensure the elaboration safety of server units they
27576 @geindex pragma Elaborate (Unit)
27582 @emph{pragma Elaborate (Unit)}
27584 Pragma @code{Elaborate} can be placed in the context clauses of a unit, after a
27585 @emph{with} clause. It guarantees that both the spec and body of its argument will
27586 be elaborated prior to the unit with the pragma. Note that other unrelated
27587 units may be elaborated in between the spec and the body.
27591 function Func return Integer;
27596 package body Server is
27597 function Func return Integer is
27606 pragma Elaborate (Server);
27608 Val : constant Integer := Server.Func;
27612 In the example above, pragma @code{Elaborate} guarantees the following
27621 Removing pragma @code{Elaborate} could result in the following incorrect
27630 where @code{Client} invokes @code{Server.Func}, but the body of @code{Server.Func}
27631 has not been elaborated yet.
27634 @geindex pragma Elaborate_All (Unit)
27640 @emph{pragma Elaborate_All (Unit)}
27642 Pragma @code{Elaborate_All} is placed in the context clauses of a unit, after
27643 a @emph{with} clause. It guarantees that both the spec and body of its argument
27644 will be elaborated prior to the unit with the pragma, as well as all units
27645 @emph{with}ed by the spec and body of the argument, recursively. Note that other
27646 unrelated units may be elaborated in between the spec and the body.
27650 function Factorial (Val : Natural) return Natural;
27655 package body Math is
27656 function Factorial (Val : Natural) return Natural is
27664 package Computer is
27665 type Operation_Kind is (None, Op_Factorial);
27669 Op : Operation_Kind) return Natural;
27675 package body Computer is
27678 Op : Operation_Kind) return Natural
27680 if Op = Op_Factorial then
27681 return Math.Factorial (Val);
27691 pragma Elaborate_All (Computer);
27693 Val : constant Natural :=
27694 Computer.Compute (123, Computer.Op_Factorial);
27698 In the example above, pragma @code{Elaborate_All} can result in the following
27709 Note that there are several allowable suborders for the specs and bodies of
27710 @code{Math} and @code{Computer}, but the point is that these specs and bodies will
27711 be elaborated prior to @code{Client}.
27713 Removing pragma @code{Elaborate_All} could result in the following incorrect
27724 where @code{Client} invokes @code{Computer.Compute}, which in turn invokes
27725 @code{Math.Factorial}, but the body of @code{Math.Factorial} has not been
27729 All pragmas shown above can be summarized by the following rule:
27731 @emph{If a client unit elaborates a server target directly or indirectly, then if
27732 the server unit requires a body and does not have pragma Pure, Preelaborate,
27733 or Elaborate_Body, then the client unit should have pragma Elaborate or
27734 Elaborate_All for the server unit.}
27736 If the rule outlined above is not followed, then a program may fall in one of
27737 the following states:
27743 @emph{No elaboration order exists}
27745 In this case a compiler must diagnose the situation, and refuse to build an
27746 executable program.
27749 @emph{One or more incorrect elaboration orders exist}
27751 In this case a compiler can build an executable program, but
27752 @code{Program_Error} will be raised when the program is run.
27755 @emph{Several elaboration orders exist, some correct, some incorrect}
27757 In this case the programmer has not controlled the elaboration order. As a
27758 result, a compiler may or may not pick one of the correct orders, and the
27759 program may or may not raise @code{Program_Error} when it is run. This is the
27760 worst possible state because the program may fail on another compiler, or
27761 even another version of the same compiler.
27764 @emph{One or more correct orders exist}
27766 In this case a compiler can build an executable program, and the program is
27767 run successfully. This state may be guaranteed by following the outlined
27768 rules, or may be the result of good program architecture.
27771 Note that one additional advantage of using @code{Elaborate} and @code{Elaborate_All}
27772 is that the program continues to stay in the last state (one or more correct
27773 orders exist) even if maintenance changes the bodies of targets.
27775 @node Controlling the Elaboration Order in GNAT,Common Elaboration-model Traits,Controlling the Elaboration Order in Ada,Elaboration Order Handling in GNAT
27776 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id6}@anchor{234}@anchor{gnat_ugn/elaboration_order_handling_in_gnat controlling-the-elaboration-order-in-gnat}@anchor{235}
27777 @section Controlling the Elaboration Order in GNAT
27780 In addition to Ada semantics and rules synthesized from them, GNAT offers
27781 three elaboration models to aid the programmer with specifying the correct
27782 elaboration order and to diagnose elaboration problems.
27784 @geindex Dynamic elaboration model
27790 @emph{Dynamic elaboration model}
27792 This is the most permissive of the three elaboration models. When the
27793 dynamic model is in effect, GNAT assumes that all code within all units in
27794 a partition is elaboration code. GNAT performs very few diagnostics and
27795 generates run-time checks to verify the elaboration order of a program. This
27796 behavior is identical to that specified by the Ada Reference Manual. The
27797 dynamic model is enabled with compiler switch @code{-gnatE}.
27800 @geindex Static elaboration model
27806 @emph{Static elaboration model}
27808 This is the middle ground of the three models. When the static model is in
27809 effect, GNAT performs extensive diagnostics on a unit-by-unit basis for all
27810 scenarios that elaborate or execute internal targets. GNAT also generates
27811 run-time checks for all external targets and for all scenarios that may
27812 exhibit ABE problems. Finally, GNAT installs implicit @code{Elaborate} and
27813 @code{Elaborate_All} pragmas for server units based on the dependencies of
27814 client units. The static model is the default model in GNAT.
27817 @geindex SPARK elaboration model
27823 @emph{SPARK elaboration model}
27825 This is the most conservative of the three models and enforces the SPARK
27826 rules of elaboration as defined in the SPARK Reference Manual, section 7.7.
27827 The SPARK model is in effect only when a scenario and a target reside in a
27828 region subject to SPARK_Mode On, otherwise the dynamic or static model is in
27832 @geindex Legacy elaboration model
27838 @emph{Legacy elaboration model}
27840 In addition to the three elaboration models outlined above, GNAT provides the
27841 elaboration model of pre-18.x versions referred to as @cite{legacy elaboration model}. The legacy elaboration model is enabled with compiler switch
27845 @geindex Relaxed elaboration mode
27847 The dynamic, legacy, and static models can be relaxed using compiler switch
27848 @code{-gnatJ}, making them more permissive. Note that in this mode, GNAT
27849 may not diagnose certain elaboration issues or install run-time checks.
27851 @node Common Elaboration-model Traits,Dynamic Elaboration Model in GNAT,Controlling the Elaboration Order in GNAT,Elaboration Order Handling in GNAT
27852 @anchor{gnat_ugn/elaboration_order_handling_in_gnat common-elaboration-model-traits}@anchor{236}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id7}@anchor{237}
27853 @section Common Elaboration-model Traits
27856 All three GNAT models are able to detect elaboration problems related to
27857 dispatching calls and a particular kind of ABE referred to as @emph{guaranteed ABE}.
27863 @emph{Dispatching calls}
27865 GNAT installs run-time checks for each primitive subprogram of each tagged
27866 type defined in a partition on the assumption that a dispatching call
27867 invoked at elaboration time will execute one of these primitives. As a
27868 result, a dispatching call that executes a primitive whose body has not
27869 been elaborated yet will raise exception @code{Program_Error} at run time. The
27870 checks can be suppressed using pragma @code{Suppress (Elaboration_Check)}.
27873 @emph{Guaranteed ABE}
27875 A guaranteed ABE arises when the body of a target is not elaborated early
27876 enough, and causes all scenarios that directly execute the target to fail.
27879 package body Guaranteed_ABE is
27880 function ABE return Integer;
27882 Val : constant Integer := ABE;
27884 function ABE return Integer is
27888 end Guaranteed_ABE;
27891 In the example above, the elaboration of @code{Guaranteed_ABE}'s body elaborates
27892 the declaration of @code{Val}. This invokes function @code{ABE}, however the body
27893 of @code{ABE} has not been elaborated yet. GNAT emits similar diagnostics in all
27897 1. package body Guaranteed_ABE is
27898 2. function ABE return Integer;
27900 4. Val : constant Integer := ABE;
27902 >>> warning: cannot call "ABE" before body seen
27903 >>> warning: Program_Error will be raised at run time
27906 6. function ABE return Integer is
27910 10. end Guaranteed_ABE;
27914 Note that GNAT emits warnings rather than hard errors whenever it encounters an
27915 elaboration problem. This is because the elaboration model in effect may be too
27916 conservative, or a particular scenario may not be elaborated or executed due to
27917 data and control flow. The warnings can be suppressed selectively with @code{pragma
27918 Warnigns (Off)} or globally with compiler switch @code{-gnatwL}.
27920 @node Dynamic Elaboration Model in GNAT,Static Elaboration Model in GNAT,Common Elaboration-model Traits,Elaboration Order Handling in GNAT
27921 @anchor{gnat_ugn/elaboration_order_handling_in_gnat dynamic-elaboration-model-in-gnat}@anchor{238}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id8}@anchor{239}
27922 @section Dynamic Elaboration Model in GNAT
27925 The dynamic model assumes that all code within all units in a partition is
27926 elaboration code. As a result, run-time checks are installed for each scenario
27927 regardless of whether the target is internal or external. The checks can be
27928 suppressed using pragma @code{Suppress (Elaboration_Check)}. This behavior is
27929 identical to that specified by the Ada Reference Manual. The following example
27930 showcases run-time checks installed by GNAT to verify the elaboration state of
27931 package @code{Dynamic_Model}.
27935 package body Dynamic_Model is
27941 <check that the body of Server.Gen is elaborated>
27942 package Inst is new Server.Gen;
27944 T : Server.Task_Type;
27947 <check that the body of Server.Task_Type is elaborated>
27949 <check that the body of Server.Proc is elaborated>
27954 The checks verify that the body of a target has been successfully elaborated
27955 before a scenario activates, calls, or instantiates a target.
27957 Note that no scenario within package @code{Dynamic_Model} calls procedure @code{API}.
27958 In fact, procedure @code{API} may not be invoked by elaboration code within the
27959 partition, however the dynamic model assumes that this can happen.
27961 The dynamic model emits very few diagnostics, but can make suggestions on
27962 missing @code{Elaborate} and @code{Elaborate_All} pragmas for library-level
27963 scenarios. This information is available when compiler switch @code{-gnatel}
27968 2. package body Dynamic_Model is
27969 3. Val : constant Integer := Server.Func;
27971 >>> info: call to "Func" during elaboration
27972 >>> info: missing pragma "Elaborate_All" for unit "Server"
27974 4. end Dynamic_Model;
27977 @node Static Elaboration Model in GNAT,SPARK Elaboration Model in GNAT,Dynamic Elaboration Model in GNAT,Elaboration Order Handling in GNAT
27978 @anchor{gnat_ugn/elaboration_order_handling_in_gnat static-elaboration-model-in-gnat}@anchor{23a}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id9}@anchor{23b}
27979 @section Static Elaboration Model in GNAT
27982 In contrast to the dynamic model, the static model is more precise in its
27983 analysis of elaboration code. The model makes a clear distinction between
27984 internal and external targets, and resorts to different diagnostics and
27985 run-time checks based on the nature of the target.
27991 @emph{Internal targets}
27993 The static model performs extensive diagnostics on scenarios which elaborate
27994 or execute internal targets. The warnings resulting from these diagnostics
27995 are enabled by default, but can be suppressed selectively with @code{pragma
27996 Warnings (Off)} or globally with compiler switch @code{-gnatwL}.
27999 1. package body Static_Model is
28001 3. with function Func return Integer;
28003 5. Val : constant Integer := Func;
28006 8. function ABE return Integer;
28008 10. function Cause_ABE return Boolean is
28009 11. package Inst is new Gen (ABE);
28011 >>> warning: in instantiation at line 5
28012 >>> warning: cannot call "ABE" before body seen
28013 >>> warning: Program_Error may be raised at run time
28014 >>> warning: body of unit "Static_Model" elaborated
28015 >>> warning: function "Cause_ABE" called at line 16
28016 >>> warning: function "ABE" called at line 5, instance at line 11
28022 16. Val : constant Boolean := Cause_ABE;
28024 18. function ABE return Integer is
28028 22. end Static_Model;
28031 The example above illustrates an ABE problem within package @code{Static_Model},
28032 which is hidden by several layers of indirection. The elaboration of package
28033 body @code{Static_Model} elaborates the declaration of @code{Val}. This invokes
28034 function @code{Cause_ABE}, which instantiates generic unit @code{Gen} as @code{Inst}.
28035 The elaboration of @code{Inst} invokes function @code{ABE}, however the body of
28036 @code{ABE} has not been elaborated yet.
28039 @emph{External targets}
28041 The static model installs run-time checks to verify the elaboration status
28042 of server targets only when the scenario that elaborates or executes that
28043 target is part of the elaboration code of the client unit. The checks can be
28044 suppressed using pragma @code{Suppress (Elaboration_Check)}.
28048 package body Static_Model is
28050 with function Func return Integer;
28052 Val : constant Integer := Func;
28055 function Call_Func return Boolean is
28056 <check that the body of Server.Func is elaborated>
28057 package Inst is new Gen (Server.Func);
28062 Val : constant Boolean := Call_Func;
28066 In the example above, the elaboration of package body @code{Static_Model}
28067 elaborates the declaration of @code{Val}. This invokes function @code{Call_Func},
28068 which instantiates generic unit @code{Gen} as @code{Inst}. The elaboration of
28069 @code{Inst} invokes function @code{Server.Func}. Since @code{Server.Func} is an
28070 external target, GNAT installs a run-time check to verify that its body has
28073 In addition to checks, the static model installs implicit @code{Elaborate} and
28074 @code{Elaborate_All} pragmas to guarantee safe elaboration use of server units.
28075 This information is available when compiler switch @code{-gnatel} is in
28080 2. package body Static_Model is
28082 4. with function Func return Integer;
28084 6. Val : constant Integer := Func;
28087 9. function Call_Func return Boolean is
28088 10. package Inst is new Gen (Server.Func);
28090 >>> info: instantiation of "Gen" during elaboration
28091 >>> info: in instantiation at line 6
28092 >>> info: call to "Func" during elaboration
28093 >>> info: in instantiation at line 6
28094 >>> info: implicit pragma "Elaborate_All" generated for unit "Server"
28095 >>> info: body of unit "Static_Model" elaborated
28096 >>> info: function "Call_Func" called at line 15
28097 >>> info: function "Func" called at line 6, instance at line 10
28103 15. Val : constant Boolean := Call_Func;
28105 >>> info: call to "Call_Func" during elaboration
28107 16. end Static_Model;
28110 In the example above, the elaboration of package body @code{Static_Model}
28111 elaborates the declaration of @code{Val}. This invokes function @code{Call_Func},
28112 which instantiates generic unit @code{Gen} as @code{Inst}. The elaboration of
28113 @code{Inst} invokes function @code{Server.Func}. Since @code{Server.Func} is an
28114 external target, GNAT installs an implicit @code{Elaborate_All} pragma for unit
28115 @code{Server}. The pragma guarantees that both the spec and body of @code{Server},
28116 along with any additional dependencies that @code{Server} may require, are
28117 elaborated prior to the body of @code{Static_Model}.
28120 @node SPARK Elaboration Model in GNAT,Legacy Elaboration Model in GNAT,Static Elaboration Model in GNAT,Elaboration Order Handling in GNAT
28121 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id10}@anchor{23c}@anchor{gnat_ugn/elaboration_order_handling_in_gnat spark-elaboration-model-in-gnat}@anchor{23d}
28122 @section SPARK Elaboration Model in GNAT
28125 The SPARK model is identical to the static model in its handling of internal
28126 targets. The SPARK model, however, requires explicit @code{Elaborate} or
28127 @code{Elaborate_All} pragmas to be present in the program when a target is
28128 external, and compiler switch @code{-gnatd.v} is in effect.
28132 2. package body SPARK_Model with SPARK_Mode is
28133 3. Val : constant Integer := Server.Func;
28135 >>> call to "Func" during elaboration in SPARK
28136 >>> unit "SPARK_Model" requires pragma "Elaborate_All" for "Server"
28137 >>> body of unit "SPARK_Model" elaborated
28138 >>> function "Func" called at line 3
28140 4. end SPARK_Model;
28143 @node Legacy Elaboration Model in GNAT,Mixing Elaboration Models,SPARK Elaboration Model in GNAT,Elaboration Order Handling in GNAT
28144 @anchor{gnat_ugn/elaboration_order_handling_in_gnat legacy-elaboration-model-in-gnat}@anchor{23e}
28145 @section Legacy Elaboration Model in GNAT
28148 The legacy elaboration model is provided for compatibility with code bases
28149 developed with pre-18.x versions of GNAT. It is similar in functionality to
28150 the dynamic and static models of post-18.x version of GNAT, but may differ
28151 in terms of diagnostics and run-time checks. The legacy elaboration model is
28152 enabled with compiler switch @code{-gnatH}.
28154 @node Mixing Elaboration Models,Elaboration Circularities,Legacy Elaboration Model in GNAT,Elaboration Order Handling in GNAT
28155 @anchor{gnat_ugn/elaboration_order_handling_in_gnat mixing-elaboration-models}@anchor{23f}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id11}@anchor{240}
28156 @section Mixing Elaboration Models
28159 It is possible to mix units compiled with a different elaboration model,
28160 however the following rules must be observed:
28166 A client unit compiled with the dynamic model can only @emph{with} a server unit
28167 that meets at least one of the following criteria:
28173 The server unit is compiled with the dynamic model.
28176 The server unit is a GNAT implementation unit from the Ada, GNAT,
28177 Interfaces, or System hierarchies.
28180 The server unit has pragma @code{Pure} or @code{Preelaborate}.
28183 The client unit has an explicit @code{Elaborate_All} pragma for the server
28188 These rules ensure that elaboration checks are not omitted. If the rules are
28189 violated, the binder emits a warning:
28192 warning: "x.ads" has dynamic elaboration checks and with's
28193 warning: "y.ads" which has static elaboration checks
28196 The warnings can be suppressed by binder switch @code{-ws}.
28198 @node Elaboration Circularities,Resolving Elaboration Circularities,Mixing Elaboration Models,Elaboration Order Handling in GNAT
28199 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id12}@anchor{241}@anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-circularities}@anchor{242}
28200 @section Elaboration Circularities
28203 If the binder cannot find an acceptable elaboration order, it outputs detailed
28204 diagnostics describing an @strong{elaboration circularity}.
28208 function Func return Integer;
28214 package body Server is
28215 function Func return Integer is
28225 Val : constant Integer := Server.Func;
28231 procedure Main is begin null; end Main;
28235 error: elaboration circularity detected
28236 info: "server (body)" must be elaborated before "client (spec)"
28237 info: reason: implicit Elaborate_All in unit "client (spec)"
28238 info: recompile "client (spec)" with -gnatel for full details
28239 info: "server (body)"
28240 info: must be elaborated along with its spec:
28241 info: "server (spec)"
28242 info: which is withed by:
28243 info: "client (spec)"
28244 info: "client (spec)" must be elaborated before "server (body)"
28245 info: reason: with clause
28248 In the example above, @code{Client} must be elaborated prior to @code{Main} by virtue
28249 of a @emph{with} clause. The elaboration of @code{Client} invokes @code{Server.Func}, and
28250 static model generates an implicit @code{Elaborate_All} pragma for @code{Server}. The
28251 pragma implies that both the spec and body of @code{Server}, along with any units
28252 they @emph{with}, must be elaborated prior to @code{Client}. However, @code{Server}'s body
28253 @emph{with}s @code{Client}, implying that @code{Client} must be elaborated prior to
28254 @code{Server}. The end result is that @code{Client} must be elaborated prior to
28255 @code{Client}, and this leads to a circularity.
28257 @node Resolving Elaboration Circularities,Resolving Task Issues,Elaboration Circularities,Elaboration Order Handling in GNAT
28258 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id13}@anchor{243}@anchor{gnat_ugn/elaboration_order_handling_in_gnat resolving-elaboration-circularities}@anchor{244}
28259 @section Resolving Elaboration Circularities
28262 When faced with an elaboration circularity, a programmer has several options
28269 @emph{Fix the program}
28271 The most desirable option from the point of view of long-term maintenance
28272 is to rearrange the program so that the elaboration problems are avoided.
28273 One useful technique is to place the elaboration code into separate child
28274 packages. Another is to move some of the initialization code to explicitly
28275 invoked subprograms, where the program controls the order of initialization
28276 explicitly. Although this is the most desirable option, it may be impractical
28277 and involve too much modification, especially in the case of complex legacy
28281 @emph{Switch to more permissive elaboration model}
28283 If the compilation was performed using the static model, enable the dynamic
28284 model with compiler switch @code{-gnatE}. GNAT will no longer generate
28285 implicit @code{Elaborate} and @code{Elaborate_All} pragmas, resulting in a behavior
28286 identical to that specified by the Ada Reference Manual. The binder will
28287 generate an executable program that may or may not raise @code{Program_Error},
28288 and it is the programmer's responsibility to ensure that it does not raise
28289 @code{Program_Error}.
28291 If the compilation was performed using a post-18.x version of GNAT, consider
28292 using the legacy elaboration model, in the following order:
28298 Use the legacy static elaboration model, with compiler switch
28302 Use the legacy dynamic elaboration model, with compiler switches
28303 @code{-gnatH} @code{-gnatE}.
28306 Use the relaxed legacy static elaboration model, with compiler switches
28307 @code{-gnatH} @code{-gnatJ}.
28310 Use the relaxed legacy dynamic elaboration model, with compiler switches
28311 @code{-gnatH} @code{-gnatJ} @code{-gnatE}.
28315 @emph{Suppress all elaboration checks}
28317 The drawback of run-time checks is that they generate overhead at run time,
28318 both in space and time. If the programmer is absolutely sure that a program
28319 will not raise an elaboration-related @code{Program_Error}, then using the
28320 pragma @code{Suppress (Elaboration_Check)} globally (as a configuration pragma)
28321 will eliminate all run-time checks.
28324 @emph{Suppress elaboration checks selectively}
28326 If a scenario cannot possibly lead to an elaboration @code{Program_Error},
28327 and the binder nevertheless complains about implicit @code{Elaborate} and
28328 @code{Elaborate_All} pragmas that lead to elaboration circularities, it
28329 is possible to suppress the generation of implicit @code{Elaborate} and
28330 @code{Elaborate_All} pragmas, as well as run-time checks. Clearly this can
28331 be unsafe, and it is the responsibility of the programmer to make sure
28332 that the resulting program has no elaboration anomalies. Pragma
28333 @code{Suppress (Elaboration_Check)} can be used with different levels of
28334 granularity to achieve these effects.
28340 @emph{Target suppression}
28342 When the pragma is placed in a declarative part, without a second argument
28343 naming an entity, it will suppress implicit @code{Elaborate} and
28344 @code{Elaborate_All} pragma generation, as well as run-time checks, on all
28345 targets within the region.
28348 package Range_Suppress is
28349 pragma Suppress (Elaboration_Check);
28351 function Func return Integer;
28356 pragma Unsuppress (Elaboration_Check);
28359 end Range_Suppress;
28362 In the example above, a pair of Suppress/Unsuppress pragmas define a region
28363 of suppression within package @code{Range_Suppress}. As a result, no implicit
28364 @code{Elaborate} and @code{Elaborate_All} pragmas, nor any run-time checks, will
28365 be generated by callers of @code{Func} and instantiators of @code{Gen}. Note that
28366 task type @code{Tsk} is not within this region.
28368 An alternative to the region-based suppression is to use multiple
28369 @code{Suppress} pragmas with arguments naming specific entities for which
28370 elaboration checks should be suppressed:
28373 package Range_Suppress is
28374 function Func return Integer;
28375 pragma Suppress (Elaboration_Check, Func);
28379 pragma Suppress (Elaboration_Check, Gen);
28382 end Range_Suppress;
28386 @emph{Scenario suppression}
28388 When the pragma @code{Suppress} is placed in a declarative or statement
28389 part, without an entity argument, it will suppress implicit @code{Elaborate}
28390 and @code{Elaborate_All} pragma generation, as well as run-time checks, on
28391 all scenarios within the region.
28395 package body Range_Suppress is
28396 pragma Suppress (Elaboration_Check);
28398 function Func return Integer is
28400 return Server.Func;
28408 pragma Unsuppress (Elaboration_Check);
28414 end Range_Suppress;
28417 In the example above, a pair of Suppress/Unsuppress pragmas define a region
28418 of suppression within package body @code{Range_Suppress}. As a result, the
28419 calls to @code{Server.Func} in @code{Func} and @code{Server.Proc} in @code{Gen} will
28420 not generate any implicit @code{Elaborate} and @code{Elaborate_All} pragmas or
28425 @node Resolving Task Issues,Elaboration-related Compiler Switches,Resolving Elaboration Circularities,Elaboration Order Handling in GNAT
28426 @anchor{gnat_ugn/elaboration_order_handling_in_gnat id14}@anchor{245}@anchor{gnat_ugn/elaboration_order_handling_in_gnat resolving-task-issues}@anchor{246}
28427 @section Resolving Task Issues
28430 The model of execution in Ada dictates that elaboration must first take place,
28431 and only then can the main program be started. Tasks which are activated during
28432 elaboration violate this model and may lead to serious concurrent problems at
28435 A task can be activated in two different ways:
28441 The task is created by an allocator in which case it is activated immediately
28442 after the allocator is evaluated.
28445 The task is declared at the library level or within some nested master in
28446 which case it is activated before starting execution of the statement
28447 sequence of the master defining the task.
28450 Since the elaboration of a partition is performed by the environment task
28451 servicing that partition, any tasks activated during elaboration may be in
28452 a race with the environment task, and lead to unpredictable state and behavior.
28453 The static model seeks to avoid such interactions by assuming that all code in
28454 the task body is executed at elaboration time, if the task was activated by
28463 type My_Int is new Integer;
28465 function Ident (M : My_Int) return My_Int;
28471 package body Decls is
28472 task body Lib_Task is
28478 function Ident (M : My_Int) return My_Int is
28488 procedure Put_Val (Arg : Decls.My_Int);
28493 with Ada.Text_IO; use Ada.Text_IO;
28494 package body Utils is
28495 procedure Put_Val (Arg : Decls.My_Int) is
28497 Put_Line (Arg'Img);
28506 Decls.Lib_Task.Start;
28510 When the above example is compiled with the static model, an elaboration
28511 circularity arises:
28514 error: elaboration circularity detected
28515 info: "decls (body)" must be elaborated before "decls (body)"
28516 info: reason: implicit Elaborate_All in unit "decls (body)"
28517 info: recompile "decls (body)" with -gnatel for full details
28518 info: "decls (body)"
28519 info: must be elaborated along with its spec:
28520 info: "decls (spec)"
28521 info: which is withed by:
28522 info: "utils (spec)"
28523 info: which is withed by:
28524 info: "decls (body)"
28527 In the above example, @code{Decls} must be elaborated prior to @code{Main} by virtue
28528 of a with clause. The elaboration of @code{Decls} activates task @code{Lib_Task}. The
28529 static model conservatibely assumes that all code within the body of
28530 @code{Lib_Task} is executed, and generates an implicit @code{Elaborate_All} pragma
28531 for @code{Units} due to the call to @code{Utils.Put_Val}. The pragma implies that
28532 both the spec and body of @code{Utils}, along with any units they @emph{with},
28533 must be elaborated prior to @code{Decls}. However, @code{Utils}'s spec @emph{with}s
28534 @code{Decls}, implying that @code{Decls} must be elaborated before @code{Utils}. The end
28535 result is that @code{Utils} must be elaborated prior to @code{Utils}, and this
28536 leads to a circularity.
28538 In reality, the example above will not exhibit an ABE problem at run time.
28539 When the body of task @code{Lib_Task} is activated, execution will wait for entry
28540 @code{Start} to be accepted, and the call to @code{Utils.Put_Val} will not take place
28541 at elaboration time. Task @code{Lib_Task} will resume its execution after the main
28542 program is executed because @code{Main} performs a rendezvous with
28543 @code{Lib_Task.Start}, and at that point all units have already been elaborated.
28544 As a result, the static model may seem overly conservative, partly because it
28545 does not take control and data flow into account.
28547 When faced with a task elaboration circularity, a programmer has several
28554 @emph{Use the dynamic model}
28556 The dynamic model does not generate implicit @code{Elaborate} and
28557 @code{Elaborate_All} pragmas. Instead, it will install checks prior to every
28558 call in the example above, thus verifying the successful elaboration of
28559 @code{Utils.Put_Val} in case the call to it takes place at elaboration time.
28560 The dynamic model is enabled with compiler switch @code{-gnatE}.
28563 @emph{Isolate the tasks}
28565 Relocating tasks in their own separate package could decouple them from
28566 dependencies that would otherwise cause an elaboration circularity. The
28567 example above can be rewritten as follows:
28570 package Decls1 is -- new
28579 package body Decls1 is -- new
28580 task body Lib_Task is
28589 package Decls2 is -- new
28590 type My_Int is new Integer;
28591 function Ident (M : My_Int) return My_Int;
28597 package body Decls2 is -- new
28598 function Ident (M : My_Int) return My_Int is
28608 procedure Put_Val (Arg : Decls2.My_Int);
28613 with Ada.Text_IO; use Ada.Text_IO;
28614 package body Utils is
28615 procedure Put_Val (Arg : Decls2.My_Int) is
28617 Put_Line (Arg'Img);
28626 Decls1.Lib_Task.Start;
28631 @emph{Declare the tasks}
28633 The original example uses a single task declaration for @code{Lib_Task}. An
28634 explicit task type declaration and a properly placed task object could avoid
28635 the dependencies that would otherwise cause an elaboration circularity. The
28636 example can be rewritten as follows:
28640 task type Lib_Task is -- new
28644 type My_Int is new Integer;
28646 function Ident (M : My_Int) return My_Int;
28652 package body Decls is
28653 task body Lib_Task is
28659 function Ident (M : My_Int) return My_Int is
28669 procedure Put_Val (Arg : Decls.My_Int);
28674 with Ada.Text_IO; use Ada.Text_IO;
28675 package body Utils is
28676 procedure Put_Val (Arg : Decls.My_Int) is
28678 Put_Line (Arg'Img);
28685 package Obj_Decls is -- new
28686 Task_Obj : Decls.Lib_Task;
28694 Obj_Decls.Task_Obj.Start; -- new
28699 @emph{Use restriction No_Entry_Calls_In_Elaboration_Code}
28701 The issue exhibited in the original example under this section revolves
28702 around the body of @code{Lib_Task} blocking on an accept statement. There is
28703 no rule to prevent elaboration code from performing entry calls, however in
28704 practice this is highly unusual. In addition, the pattern of starting tasks
28705 at elaboration time and then immediately blocking on accept or select
28706 statements is quite common.
28708 If a programmer knows that elaboration code will not perform any entry
28709 calls, then the programmer can indicate that the static model should not
28710 process the remainder of a task body once an accept or select statement has
28711 been encountered. This behavior can be specified by a configuration pragma:
28714 pragma Restrictions (No_Entry_Calls_In_Elaboration_Code);
28717 In addition to the change in behavior with respect to task bodies, the
28718 static model will verify that no entry calls take place at elaboration time.
28721 @node Elaboration-related Compiler Switches,Summary of Procedures for Elaboration Control,Resolving Task Issues,Elaboration Order Handling in GNAT
28722 @anchor{gnat_ugn/elaboration_order_handling_in_gnat elaboration-related-compiler-switches}@anchor{247}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id15}@anchor{248}
28723 @section Elaboration-related Compiler Switches
28726 GNAT has several switches that affect the elaboration model and consequently
28727 the elaboration order chosen by the binder.
28729 @geindex -gnatE (gnat)
28734 @item @code{-gnatE}
28736 Dynamic elaboration checking mode enabled
28738 When this switch is in effect, GNAT activates the dynamic elaboration model.
28741 @geindex -gnatel (gnat)
28746 @item @code{-gnatel}
28748 Turn on info messages on generated Elaborate[_All] pragmas
28750 When this switch is in effect, GNAT will emit the following supplementary
28751 information depending on the elaboration model in effect.
28757 @emph{Dynamic model}
28759 GNAT will indicate missing @code{Elaborate} and @code{Elaborate_All} pragmas for
28760 all library-level scenarios within the partition.
28763 @emph{Static model}
28765 GNAT will indicate all scenarios executed during elaboration. In addition,
28766 it will provide detailed traceback when an implicit @code{Elaborate} or
28767 @code{Elaborate_All} pragma is generated.
28772 GNAT will indicate how an elaboration requirement is met by the context of
28773 a unit. This diagnostic requires compiler switch @code{-gnatd.v}.
28776 1. with Server; pragma Elaborate_All (Server);
28777 2. package Client with SPARK_Mode is
28778 3. Val : constant Integer := Server.Func;
28780 >>> info: call to "Func" during elaboration in SPARK
28781 >>> info: "Elaborate_All" requirement for unit "Server" met by pragma at line 1
28788 @geindex -gnatH (gnat)
28793 @item @code{-gnatH}
28795 Legacy elaboration checking mode enabled
28797 When this switch is in effect, GNAT will utilize the pre-18.x elaboration
28801 @geindex -gnatJ (gnat)
28806 @item @code{-gnatJ}
28808 Relaxed elaboration checking mode enabled
28810 When this switch is in effect, GNAT will not process certain scenarios,
28811 resulting in a more permissive elaboration model. Note that this may
28812 eliminate some diagnostics and run-time checks.
28815 @geindex -gnatw.f (gnat)
28820 @item @code{-gnatw.f}
28822 Turn on warnings for suspicious Subp'Access
28824 When this switch is in effect, GNAT will treat @code{'Access} of an entry,
28825 operator, or subprogram as a potential call to the target and issue warnings:
28828 1. package body Attribute_Call is
28829 2. function Func return Integer;
28830 3. type Func_Ptr is access function return Integer;
28832 5. Ptr : constant Func_Ptr := Func'Access;
28834 >>> warning: "Access" attribute of "Func" before body seen
28835 >>> warning: possible Program_Error on later references
28836 >>> warning: body of unit "Attribute_Call" elaborated
28837 >>> warning: "Access" of "Func" taken at line 5
28840 7. function Func return Integer is
28844 11. end Attribute_Call;
28847 In the example above, the elaboration of declaration @code{Ptr} is assigned
28848 @code{Func'Access} before the body of @code{Func} has been elaborated.
28851 @geindex -gnatwl (gnat)
28856 @item @code{-gnatwl}
28858 Turn on warnings for elaboration problems
28860 When this switch is in effect, GNAT emits diagnostics in the form of warnings
28861 concerning various elaboration problems. The warnings are enabled by default.
28862 The switch is provided in case all warnings are suppressed, but elaboration
28863 warnings are still desired.
28865 @item @code{-gnatwL}
28867 Turn off warnings for elaboration problems
28869 When this switch is in effect, GNAT no longer emits any diagnostics in the
28870 form of warnings. Selective suppression of elaboration problems is possible
28871 using @code{pragma Warnings (Off)}.
28874 1. package body Selective_Suppression is
28875 2. function ABE return Integer;
28877 4. Val_1 : constant Integer := ABE;
28879 >>> warning: cannot call "ABE" before body seen
28880 >>> warning: Program_Error will be raised at run time
28883 6. pragma Warnings (Off);
28884 7. Val_2 : constant Integer := ABE;
28885 8. pragma Warnings (On);
28887 10. function ABE return Integer is
28891 14. end Selective_Suppression;
28894 Note that suppressing elaboration warnings does not eliminate run-time
28895 checks. The example above will still fail at run time with an ABE.
28898 @node Summary of Procedures for Elaboration Control,Inspecting the Chosen Elaboration Order,Elaboration-related Compiler Switches,Elaboration Order Handling in GNAT
28899 @anchor{gnat_ugn/elaboration_order_handling_in_gnat summary-of-procedures-for-elaboration-control}@anchor{249}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id16}@anchor{24a}
28900 @section Summary of Procedures for Elaboration Control
28903 A programmer should first compile the program with the default options, using
28904 none of the binder or compiler switches. If the binder succeeds in finding an
28905 elaboration order, then apart from possible cases involing dispatching calls
28906 and access-to-subprogram types, the program is free of elaboration errors.
28908 If it is important for the program to be portable to compilers other than GNAT,
28909 then the programmer should use compiler switch @code{-gnatel} and consider
28910 the messages about missing or implicitly created @code{Elaborate} and
28911 @code{Elaborate_All} pragmas.
28913 If the binder reports an elaboration circularity, the programmer has several
28920 Ensure that elaboration warnings are enabled. This will allow the static
28921 model to output trace information of elaboration issues. The trace
28922 information could shed light on previously unforeseen dependencies, as well
28923 as their origins. Elaboration warnings are enabled with compiler switch
28927 Use switch @code{-gnatel} to obtain messages on generated implicit
28928 @code{Elaborate} and @code{Elaborate_All} pragmas. The trace information could
28929 indicate why a server unit must be elaborated prior to a client unit.
28932 If the warnings produced by the static model indicate that a task is
28933 involved, consider the options in section @ref{245,,Resolving Task Issues}.
28936 If none of the steps outlined above resolve the circularity, use a more
28937 permissive elaboration model, in the following order:
28943 Use the dynamic elaboration model, with compiler switch @code{-gnatE}.
28946 Use the legacy static elaboration model, with compiler switch
28950 Use the legacy dynamic elaboration model, with compiler switches
28951 @code{-gnatH} @code{-gnatE}.
28954 Use the relaxed legacy static elaboration model, with compiler switches
28955 @code{-gnatH} @code{-gnatJ}.
28958 Use the relaxed legacy dynamic elaboration model, with compiler switches
28959 @code{-gnatH} @code{-gnatJ} @code{-gnatE}.
28963 @node Inspecting the Chosen Elaboration Order,,Summary of Procedures for Elaboration Control,Elaboration Order Handling in GNAT
28964 @anchor{gnat_ugn/elaboration_order_handling_in_gnat inspecting-the-chosen-elaboration-order}@anchor{24b}@anchor{gnat_ugn/elaboration_order_handling_in_gnat id17}@anchor{24c}
28965 @section Inspecting the Chosen Elaboration Order
28968 To see the elaboration order chosen by the binder, inspect the contents of file
28969 @cite{b~xxx.adb}. On certain targets, this file appears as @cite{b_xxx.adb}. The
28970 elaboration order appears as a sequence of calls to @code{Elab_Body} and
28971 @code{Elab_Spec}, interspersed with assignments to @cite{Exxx} which indicates that a
28972 particular unit is elaborated. For example:
28975 System.Soft_Links'Elab_Body;
28977 System.Secondary_Stack'Elab_Body;
28979 System.Exception_Table'Elab_Body;
28981 Ada.Io_Exceptions'Elab_Spec;
28983 Ada.Tags'Elab_Spec;
28984 Ada.Streams'Elab_Spec;
28986 Interfaces.C'Elab_Spec;
28988 System.Finalization_Root'Elab_Spec;
28990 System.Os_Lib'Elab_Body;
28992 System.Finalization_Implementation'Elab_Spec;
28993 System.Finalization_Implementation'Elab_Body;
28995 Ada.Finalization'Elab_Spec;
28997 Ada.Finalization.List_Controller'Elab_Spec;
28999 System.File_Control_Block'Elab_Spec;
29001 System.File_Io'Elab_Body;
29003 Ada.Tags'Elab_Body;
29005 Ada.Text_Io'Elab_Spec;
29006 Ada.Text_Io'Elab_Body;
29010 Note also binder switch @code{-l}, which outputs the chosen elaboration
29011 order and provides a more readable form of the above:
29017 system.case_util (spec)
29018 system.case_util (body)
29019 system.concat_2 (spec)
29020 system.concat_2 (body)
29021 system.concat_3 (spec)
29022 system.concat_3 (body)
29023 system.htable (spec)
29024 system.parameters (spec)
29025 system.parameters (body)
29027 interfaces.c_streams (spec)
29028 interfaces.c_streams (body)
29029 system.restrictions (spec)
29030 system.restrictions (body)
29031 system.standard_library (spec)
29032 system.exceptions (spec)
29033 system.exceptions (body)
29034 system.storage_elements (spec)
29035 system.storage_elements (body)
29036 system.secondary_stack (spec)
29037 system.stack_checking (spec)
29038 system.stack_checking (body)
29039 system.string_hash (spec)
29040 system.string_hash (body)
29041 system.htable (body)
29042 system.strings (spec)
29043 system.strings (body)
29044 system.traceback (spec)
29045 system.traceback (body)
29046 system.traceback_entries (spec)
29047 system.traceback_entries (body)
29048 ada.exceptions (spec)
29049 ada.exceptions.last_chance_handler (spec)
29050 system.soft_links (spec)
29051 system.soft_links (body)
29052 ada.exceptions.last_chance_handler (body)
29053 system.secondary_stack (body)
29054 system.exception_table (spec)
29055 system.exception_table (body)
29056 ada.io_exceptions (spec)
29059 interfaces.c (spec)
29060 interfaces.c (body)
29061 system.finalization_root (spec)
29062 system.finalization_root (body)
29063 system.memory (spec)
29064 system.memory (body)
29065 system.standard_library (body)
29066 system.os_lib (spec)
29067 system.os_lib (body)
29068 system.unsigned_types (spec)
29069 system.stream_attributes (spec)
29070 system.stream_attributes (body)
29071 system.finalization_implementation (spec)
29072 system.finalization_implementation (body)
29073 ada.finalization (spec)
29074 ada.finalization (body)
29075 ada.finalization.list_controller (spec)
29076 ada.finalization.list_controller (body)
29077 system.file_control_block (spec)
29078 system.file_io (spec)
29079 system.file_io (body)
29080 system.val_uns (spec)
29081 system.val_util (spec)
29082 system.val_util (body)
29083 system.val_uns (body)
29084 system.wch_con (spec)
29085 system.wch_con (body)
29086 system.wch_cnv (spec)
29087 system.wch_jis (spec)
29088 system.wch_jis (body)
29089 system.wch_cnv (body)
29090 system.wch_stw (spec)
29091 system.wch_stw (body)
29093 ada.exceptions (body)
29100 @node Inline Assembler,GNU Free Documentation License,Elaboration Order Handling in GNAT,Top
29101 @anchor{gnat_ugn/inline_assembler inline-assembler}@anchor{10}@anchor{gnat_ugn/inline_assembler doc}@anchor{24d}@anchor{gnat_ugn/inline_assembler id1}@anchor{24e}
29102 @chapter Inline Assembler
29105 @geindex Inline Assembler
29107 If you need to write low-level software that interacts directly
29108 with the hardware, Ada provides two ways to incorporate assembly
29109 language code into your program. First, you can import and invoke
29110 external routines written in assembly language, an Ada feature fully
29111 supported by GNAT. However, for small sections of code it may be simpler
29112 or more efficient to include assembly language statements directly
29113 in your Ada source program, using the facilities of the implementation-defined
29114 package @code{System.Machine_Code}, which incorporates the gcc
29115 Inline Assembler. The Inline Assembler approach offers a number of advantages,
29116 including the following:
29122 No need to use non-Ada tools
29125 Consistent interface over different targets
29128 Automatic usage of the proper calling conventions
29131 Access to Ada constants and variables
29134 Definition of intrinsic routines
29137 Possibility of inlining a subprogram comprising assembler code
29140 Code optimizer can take Inline Assembler code into account
29143 This appendix presents a series of examples to show you how to use
29144 the Inline Assembler. Although it focuses on the Intel x86,
29145 the general approach applies also to other processors.
29146 It is assumed that you are familiar with Ada
29147 and with assembly language programming.
29150 * Basic Assembler Syntax::
29151 * A Simple Example of Inline Assembler::
29152 * Output Variables in Inline Assembler::
29153 * Input Variables in Inline Assembler::
29154 * Inlining Inline Assembler Code::
29155 * Other Asm Functionality::
29159 @node Basic Assembler Syntax,A Simple Example of Inline Assembler,,Inline Assembler
29160 @anchor{gnat_ugn/inline_assembler id2}@anchor{24f}@anchor{gnat_ugn/inline_assembler basic-assembler-syntax}@anchor{250}
29161 @section Basic Assembler Syntax
29164 The assembler used by GNAT and gcc is based not on the Intel assembly
29165 language, but rather on a language that descends from the AT&T Unix
29166 assembler @code{as} (and which is often referred to as 'AT&T syntax').
29167 The following table summarizes the main features of @code{as} syntax
29168 and points out the differences from the Intel conventions.
29169 See the gcc @code{as} and @code{gas} (an @code{as} macro
29170 pre-processor) documentation for further information.
29174 @emph{Register names}@w{ }
29176 gcc / @code{as}: Prefix with '%'; for example @code{%eax}@w{ }
29177 Intel: No extra punctuation; for example @code{eax}@w{ }
29185 @emph{Immediate operand}@w{ }
29187 gcc / @code{as}: Prefix with '$'; for example @code{$4}@w{ }
29188 Intel: No extra punctuation; for example @code{4}@w{ }
29196 @emph{Address}@w{ }
29198 gcc / @code{as}: Prefix with '$'; for example @code{$loc}@w{ }
29199 Intel: No extra punctuation; for example @code{loc}@w{ }
29207 @emph{Memory contents}@w{ }
29209 gcc / @code{as}: No extra punctuation; for example @code{loc}@w{ }
29210 Intel: Square brackets; for example @code{[loc]}@w{ }
29218 @emph{Register contents}@w{ }
29220 gcc / @code{as}: Parentheses; for example @code{(%eax)}@w{ }
29221 Intel: Square brackets; for example @code{[eax]}@w{ }
29229 @emph{Hexadecimal numbers}@w{ }
29231 gcc / @code{as}: Leading '0x' (C language syntax); for example @code{0xA0}@w{ }
29232 Intel: Trailing 'h'; for example @code{A0h}@w{ }
29240 @emph{Operand size}@w{ }
29242 gcc / @code{as}: Explicit in op code; for example @code{movw} to move a 16-bit word@w{ }
29243 Intel: Implicit, deduced by assembler; for example @code{mov}@w{ }
29251 @emph{Instruction repetition}@w{ }
29253 gcc / @code{as}: Split into two lines; for example@w{ }
29258 Intel: Keep on one line; for example @code{rep stosl}@w{ }
29266 @emph{Order of operands}@w{ }
29268 gcc / @code{as}: Source first; for example @code{movw $4, %eax}@w{ }
29269 Intel: Destination first; for example @code{mov eax, 4}@w{ }
29275 @node A Simple Example of Inline Assembler,Output Variables in Inline Assembler,Basic Assembler Syntax,Inline Assembler
29276 @anchor{gnat_ugn/inline_assembler a-simple-example-of-inline-assembler}@anchor{251}@anchor{gnat_ugn/inline_assembler id3}@anchor{252}
29277 @section A Simple Example of Inline Assembler
29280 The following example will generate a single assembly language statement,
29281 @code{nop}, which does nothing. Despite its lack of run-time effect,
29282 the example will be useful in illustrating the basics of
29283 the Inline Assembler facility.
29288 with System.Machine_Code; use System.Machine_Code;
29289 procedure Nothing is
29296 @code{Asm} is a procedure declared in package @code{System.Machine_Code};
29297 here it takes one parameter, a @emph{template string} that must be a static
29298 expression and that will form the generated instruction.
29299 @code{Asm} may be regarded as a compile-time procedure that parses
29300 the template string and additional parameters (none here),
29301 from which it generates a sequence of assembly language instructions.
29303 The examples in this chapter will illustrate several of the forms
29304 for invoking @code{Asm}; a complete specification of the syntax
29305 is found in the @code{Machine_Code_Insertions} section of the
29306 @cite{GNAT Reference Manual}.
29308 Under the standard GNAT conventions, the @code{Nothing} procedure
29309 should be in a file named @code{nothing.adb}.
29310 You can build the executable in the usual way:
29319 However, the interesting aspect of this example is not its run-time behavior
29320 but rather the generated assembly code.
29321 To see this output, invoke the compiler as follows:
29326 $ gcc -c -S -fomit-frame-pointer -gnatp nothing.adb
29330 where the options are:
29341 compile only (no bind or link)
29350 generate assembler listing
29357 @item @code{-fomit-frame-pointer}
29359 do not set up separate stack frames
29366 @item @code{-gnatp}
29368 do not add runtime checks
29372 This gives a human-readable assembler version of the code. The resulting
29373 file will have the same name as the Ada source file, but with a @code{.s}
29374 extension. In our example, the file @code{nothing.s} has the following
29380 .file "nothing.adb"
29382 ___gnu_compiled_ada:
29385 .globl __ada_nothing
29397 The assembly code you included is clearly indicated by
29398 the compiler, between the @code{#APP} and @code{#NO_APP}
29399 delimiters. The character before the 'APP' and 'NOAPP'
29400 can differ on different targets. For example, GNU/Linux uses '#APP' while
29401 on NT you will see '/APP'.
29403 If you make a mistake in your assembler code (such as using the
29404 wrong size modifier, or using a wrong operand for the instruction) GNAT
29405 will report this error in a temporary file, which will be deleted when
29406 the compilation is finished. Generating an assembler file will help
29407 in such cases, since you can assemble this file separately using the
29408 @code{as} assembler that comes with gcc.
29410 Assembling the file using the command
29419 will give you error messages whose lines correspond to the assembler
29420 input file, so you can easily find and correct any mistakes you made.
29421 If there are no errors, @code{as} will generate an object file
29422 @code{nothing.out}.
29424 @node Output Variables in Inline Assembler,Input Variables in Inline Assembler,A Simple Example of Inline Assembler,Inline Assembler
29425 @anchor{gnat_ugn/inline_assembler id4}@anchor{253}@anchor{gnat_ugn/inline_assembler output-variables-in-inline-assembler}@anchor{254}
29426 @section Output Variables in Inline Assembler
29429 The examples in this section, showing how to access the processor flags,
29430 illustrate how to specify the destination operands for assembly language
29436 with Interfaces; use Interfaces;
29437 with Ada.Text_IO; use Ada.Text_IO;
29438 with System.Machine_Code; use System.Machine_Code;
29439 procedure Get_Flags is
29440 Flags : Unsigned_32;
29443 Asm ("pushfl" & LF & HT & -- push flags on stack
29444 "popl %%eax" & LF & HT & -- load eax with flags
29445 "movl %%eax, %0", -- store flags in variable
29446 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29447 Put_Line ("Flags register:" & Flags'Img);
29452 In order to have a nicely aligned assembly listing, we have separated
29453 multiple assembler statements in the Asm template string with linefeed
29454 (ASCII.LF) and horizontal tab (ASCII.HT) characters.
29455 The resulting section of the assembly output file is:
29463 movl %eax, -40(%ebp)
29468 It would have been legal to write the Asm invocation as:
29473 Asm ("pushfl popl %%eax movl %%eax, %0")
29477 but in the generated assembler file, this would come out as:
29483 pushfl popl %eax movl %eax, -40(%ebp)
29488 which is not so convenient for the human reader.
29490 We use Ada comments
29491 at the end of each line to explain what the assembler instructions
29492 actually do. This is a useful convention.
29494 When writing Inline Assembler instructions, you need to precede each register
29495 and variable name with a percent sign. Since the assembler already requires
29496 a percent sign at the beginning of a register name, you need two consecutive
29497 percent signs for such names in the Asm template string, thus @code{%%eax}.
29498 In the generated assembly code, one of the percent signs will be stripped off.
29500 Names such as @code{%0}, @code{%1}, @code{%2}, etc., denote input or output
29501 variables: operands you later define using @code{Input} or @code{Output}
29502 parameters to @code{Asm}.
29503 An output variable is illustrated in
29504 the third statement in the Asm template string:
29513 The intent is to store the contents of the eax register in a variable that can
29514 be accessed in Ada. Simply writing @code{movl %%eax, Flags} would not
29515 necessarily work, since the compiler might optimize by using a register
29516 to hold Flags, and the expansion of the @code{movl} instruction would not be
29517 aware of this optimization. The solution is not to store the result directly
29518 but rather to advise the compiler to choose the correct operand form;
29519 that is the purpose of the @code{%0} output variable.
29521 Information about the output variable is supplied in the @code{Outputs}
29522 parameter to @code{Asm}:
29527 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29531 The output is defined by the @code{Asm_Output} attribute of the target type;
29532 the general format is
29537 Type'Asm_Output (constraint_string, variable_name)
29541 The constraint string directs the compiler how
29542 to store/access the associated variable. In the example
29547 Unsigned_32'Asm_Output ("=m", Flags);
29551 the @code{"m"} (memory) constraint tells the compiler that the variable
29552 @code{Flags} should be stored in a memory variable, thus preventing
29553 the optimizer from keeping it in a register. In contrast,
29558 Unsigned_32'Asm_Output ("=r", Flags);
29562 uses the @code{"r"} (register) constraint, telling the compiler to
29563 store the variable in a register.
29565 If the constraint is preceded by the equal character '=', it tells
29566 the compiler that the variable will be used to store data into it.
29568 In the @code{Get_Flags} example, we used the @code{"g"} (global) constraint,
29569 allowing the optimizer to choose whatever it deems best.
29571 There are a fairly large number of constraints, but the ones that are
29572 most useful (for the Intel x86 processor) are the following:
29577 @multitable {xxxxxxxx} {xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx}
29592 global (i.e., can be stored anywhere)
29664 use one of eax, ebx, ecx or edx
29672 use one of eax, ebx, ecx, edx, esi or edi
29678 The full set of constraints is described in the gcc and @code{as}
29679 documentation; note that it is possible to combine certain constraints
29680 in one constraint string.
29682 You specify the association of an output variable with an assembler operand
29683 through the @code{%@emph{n}} notation, where @emph{n} is a non-negative
29689 Asm ("pushfl" & LF & HT & -- push flags on stack
29690 "popl %%eax" & LF & HT & -- load eax with flags
29691 "movl %%eax, %0", -- store flags in variable
29692 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29696 @code{%0} will be replaced in the expanded code by the appropriate operand,
29698 the compiler decided for the @code{Flags} variable.
29700 In general, you may have any number of output variables:
29706 Count the operands starting at 0; thus @code{%0}, @code{%1}, etc.
29709 Specify the @code{Outputs} parameter as a parenthesized comma-separated list
29710 of @code{Asm_Output} attributes
29718 Asm ("movl %%eax, %0" & LF & HT &
29719 "movl %%ebx, %1" & LF & HT &
29721 Outputs => (Unsigned_32'Asm_Output ("=g", Var_A), -- %0 = Var_A
29722 Unsigned_32'Asm_Output ("=g", Var_B), -- %1 = Var_B
29723 Unsigned_32'Asm_Output ("=g", Var_C))); -- %2 = Var_C
29727 where @code{Var_A}, @code{Var_B}, and @code{Var_C} are variables
29728 in the Ada program.
29730 As a variation on the @code{Get_Flags} example, we can use the constraints
29731 string to direct the compiler to store the eax register into the @code{Flags}
29732 variable, instead of including the store instruction explicitly in the
29733 @code{Asm} template string:
29738 with Interfaces; use Interfaces;
29739 with Ada.Text_IO; use Ada.Text_IO;
29740 with System.Machine_Code; use System.Machine_Code;
29741 procedure Get_Flags_2 is
29742 Flags : Unsigned_32;
29745 Asm ("pushfl" & LF & HT & -- push flags on stack
29746 "popl %%eax", -- save flags in eax
29747 Outputs => Unsigned_32'Asm_Output ("=a", Flags));
29748 Put_Line ("Flags register:" & Flags'Img);
29753 The @code{"a"} constraint tells the compiler that the @code{Flags}
29754 variable will come from the eax register. Here is the resulting code:
29763 movl %eax,-40(%ebp)
29767 The compiler generated the store of eax into Flags after
29768 expanding the assembler code.
29770 Actually, there was no need to pop the flags into the eax register;
29771 more simply, we could just pop the flags directly into the program variable:
29776 with Interfaces; use Interfaces;
29777 with Ada.Text_IO; use Ada.Text_IO;
29778 with System.Machine_Code; use System.Machine_Code;
29779 procedure Get_Flags_3 is
29780 Flags : Unsigned_32;
29783 Asm ("pushfl" & LF & HT & -- push flags on stack
29784 "pop %0", -- save flags in Flags
29785 Outputs => Unsigned_32'Asm_Output ("=g", Flags));
29786 Put_Line ("Flags register:" & Flags'Img);
29791 @node Input Variables in Inline Assembler,Inlining Inline Assembler Code,Output Variables in Inline Assembler,Inline Assembler
29792 @anchor{gnat_ugn/inline_assembler id5}@anchor{255}@anchor{gnat_ugn/inline_assembler input-variables-in-inline-assembler}@anchor{256}
29793 @section Input Variables in Inline Assembler
29796 The example in this section illustrates how to specify the source operands
29797 for assembly language statements.
29798 The program simply increments its input value by 1:
29803 with Interfaces; use Interfaces;
29804 with Ada.Text_IO; use Ada.Text_IO;
29805 with System.Machine_Code; use System.Machine_Code;
29806 procedure Increment is
29808 function Incr (Value : Unsigned_32) return Unsigned_32 is
29809 Result : Unsigned_32;
29812 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29813 Inputs => Unsigned_32'Asm_Input ("a", Value));
29817 Value : Unsigned_32;
29821 Put_Line ("Value before is" & Value'Img);
29822 Value := Incr (Value);
29823 Put_Line ("Value after is" & Value'Img);
29828 The @code{Outputs} parameter to @code{Asm} specifies
29829 that the result will be in the eax register and that it is to be stored
29830 in the @code{Result} variable.
29832 The @code{Inputs} parameter looks much like the @code{Outputs} parameter,
29833 but with an @code{Asm_Input} attribute.
29834 The @code{"="} constraint, indicating an output value, is not present.
29836 You can have multiple input variables, in the same way that you can have more
29837 than one output variable.
29839 The parameter count (%0, %1) etc, still starts at the first output statement,
29840 and continues with the input statements.
29842 Just as the @code{Outputs} parameter causes the register to be stored into the
29843 target variable after execution of the assembler statements, so does the
29844 @code{Inputs} parameter cause its variable to be loaded into the register
29845 before execution of the assembler statements.
29847 Thus the effect of the @code{Asm} invocation is:
29853 load the 32-bit value of @code{Value} into eax
29856 execute the @code{incl %eax} instruction
29859 store the contents of eax into the @code{Result} variable
29862 The resulting assembler file (with @code{-O2} optimization) contains:
29867 _increment__incr.1:
29880 @node Inlining Inline Assembler Code,Other Asm Functionality,Input Variables in Inline Assembler,Inline Assembler
29881 @anchor{gnat_ugn/inline_assembler id6}@anchor{257}@anchor{gnat_ugn/inline_assembler inlining-inline-assembler-code}@anchor{258}
29882 @section Inlining Inline Assembler Code
29885 For a short subprogram such as the @code{Incr} function in the previous
29886 section, the overhead of the call and return (creating / deleting the stack
29887 frame) can be significant, compared to the amount of code in the subprogram
29888 body. A solution is to apply Ada's @code{Inline} pragma to the subprogram,
29889 which directs the compiler to expand invocations of the subprogram at the
29890 point(s) of call, instead of setting up a stack frame for out-of-line calls.
29891 Here is the resulting program:
29896 with Interfaces; use Interfaces;
29897 with Ada.Text_IO; use Ada.Text_IO;
29898 with System.Machine_Code; use System.Machine_Code;
29899 procedure Increment_2 is
29901 function Incr (Value : Unsigned_32) return Unsigned_32 is
29902 Result : Unsigned_32;
29905 Outputs => Unsigned_32'Asm_Output ("=a", Result),
29906 Inputs => Unsigned_32'Asm_Input ("a", Value));
29909 pragma Inline (Increment);
29911 Value : Unsigned_32;
29915 Put_Line ("Value before is" & Value'Img);
29916 Value := Increment (Value);
29917 Put_Line ("Value after is" & Value'Img);
29922 Compile the program with both optimization (@code{-O2}) and inlining
29923 (@code{-gnatn}) enabled.
29925 The @code{Incr} function is still compiled as usual, but at the
29926 point in @code{Increment} where our function used to be called:
29932 call _increment__incr.1
29936 the code for the function body directly appears:
29949 thus saving the overhead of stack frame setup and an out-of-line call.
29951 @node Other Asm Functionality,,Inlining Inline Assembler Code,Inline Assembler
29952 @anchor{gnat_ugn/inline_assembler other-asm-functionality}@anchor{259}@anchor{gnat_ugn/inline_assembler id7}@anchor{25a}
29953 @section Other @code{Asm} Functionality
29956 This section describes two important parameters to the @code{Asm}
29957 procedure: @code{Clobber}, which identifies register usage;
29958 and @code{Volatile}, which inhibits unwanted optimizations.
29961 * The Clobber Parameter::
29962 * The Volatile Parameter::
29966 @node The Clobber Parameter,The Volatile Parameter,,Other Asm Functionality
29967 @anchor{gnat_ugn/inline_assembler the-clobber-parameter}@anchor{25b}@anchor{gnat_ugn/inline_assembler id8}@anchor{25c}
29968 @subsection The @code{Clobber} Parameter
29971 One of the dangers of intermixing assembly language and a compiled language
29972 such as Ada is that the compiler needs to be aware of which registers are
29973 being used by the assembly code. In some cases, such as the earlier examples,
29974 the constraint string is sufficient to indicate register usage (e.g.,
29976 the eax register). But more generally, the compiler needs an explicit
29977 identification of the registers that are used by the Inline Assembly
29980 Using a register that the compiler doesn't know about
29981 could be a side effect of an instruction (like @code{mull}
29982 storing its result in both eax and edx).
29983 It can also arise from explicit register usage in your
29984 assembly code; for example:
29989 Asm ("movl %0, %%ebx" & LF & HT &
29991 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
29992 Inputs => Unsigned_32'Asm_Input ("g", Var_In));
29996 where the compiler (since it does not analyze the @code{Asm} template string)
29997 does not know you are using the ebx register.
29999 In such cases you need to supply the @code{Clobber} parameter to @code{Asm},
30000 to identify the registers that will be used by your assembly code:
30005 Asm ("movl %0, %%ebx" & LF & HT &
30007 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30008 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30013 The Clobber parameter is a static string expression specifying the
30014 register(s) you are using. Note that register names are @emph{not} prefixed
30015 by a percent sign. Also, if more than one register is used then their names
30016 are separated by commas; e.g., @code{"eax, ebx"}
30018 The @code{Clobber} parameter has several additional uses:
30024 Use 'register' name @code{cc} to indicate that flags might have changed
30027 Use 'register' name @code{memory} if you changed a memory location
30030 @node The Volatile Parameter,,The Clobber Parameter,Other Asm Functionality
30031 @anchor{gnat_ugn/inline_assembler the-volatile-parameter}@anchor{25d}@anchor{gnat_ugn/inline_assembler id9}@anchor{25e}
30032 @subsection The @code{Volatile} Parameter
30035 @geindex Volatile parameter
30037 Compiler optimizations in the presence of Inline Assembler may sometimes have
30038 unwanted effects. For example, when an @code{Asm} invocation with an input
30039 variable is inside a loop, the compiler might move the loading of the input
30040 variable outside the loop, regarding it as a one-time initialization.
30042 If this effect is not desired, you can disable such optimizations by setting
30043 the @code{Volatile} parameter to @code{True}; for example:
30048 Asm ("movl %0, %%ebx" & LF & HT &
30050 Outputs => Unsigned_32'Asm_Output ("=g", Var_Out),
30051 Inputs => Unsigned_32'Asm_Input ("g", Var_In),
30057 By default, @code{Volatile} is set to @code{False} unless there is no
30058 @code{Outputs} parameter.
30060 Although setting @code{Volatile} to @code{True} prevents unwanted
30061 optimizations, it will also disable other optimizations that might be
30062 important for efficiency. In general, you should set @code{Volatile}
30063 to @code{True} only if the compiler's optimizations have created
30066 @node GNU Free Documentation License,Index,Inline Assembler,Top
30067 @anchor{share/gnu_free_documentation_license gnu-fdl}@anchor{1}@anchor{share/gnu_free_documentation_license doc}@anchor{25f}@anchor{share/gnu_free_documentation_license gnu-free-documentation-license}@anchor{260}
30068 @chapter GNU Free Documentation License
30071 Version 1.3, 3 November 2008
30073 Copyright 2000, 2001, 2002, 2007, 2008 Free Software Foundation, Inc
30074 @indicateurl{http://fsf.org/}
30076 Everyone is permitted to copy and distribute verbatim copies of this
30077 license document, but changing it is not allowed.
30081 The purpose of this License is to make a manual, textbook, or other
30082 functional and useful document "free" in the sense of freedom: to
30083 assure everyone the effective freedom to copy and redistribute it,
30084 with or without modifying it, either commercially or noncommercially.
30085 Secondarily, this License preserves for the author and publisher a way
30086 to get credit for their work, while not being considered responsible
30087 for modifications made by others.
30089 This License is a kind of "copyleft", which means that derivative
30090 works of the document must themselves be free in the same sense. It
30091 complements the GNU General Public License, which is a copyleft
30092 license designed for free software.
30094 We have designed this License in order to use it for manuals for free
30095 software, because free software needs free documentation: a free
30096 program should come with manuals providing the same freedoms that the
30097 software does. But this License is not limited to software manuals;
30098 it can be used for any textual work, regardless of subject matter or
30099 whether it is published as a printed book. We recommend this License
30100 principally for works whose purpose is instruction or reference.
30102 @strong{1. APPLICABILITY AND DEFINITIONS}
30104 This License applies to any manual or other work, in any medium, that
30105 contains a notice placed by the copyright holder saying it can be
30106 distributed under the terms of this License. Such a notice grants a
30107 world-wide, royalty-free license, unlimited in duration, to use that
30108 work under the conditions stated herein. The @strong{Document}, below,
30109 refers to any such manual or work. Any member of the public is a
30110 licensee, and is addressed as "@strong{you}". You accept the license if you
30111 copy, modify or distribute the work in a way requiring permission
30112 under copyright law.
30114 A "@strong{Modified Version}" of the Document means any work containing the
30115 Document or a portion of it, either copied verbatim, or with
30116 modifications and/or translated into another language.
30118 A "@strong{Secondary Section}" is a named appendix or a front-matter section of
30119 the Document that deals exclusively with the relationship of the
30120 publishers or authors of the Document to the Document's overall subject
30121 (or to related matters) and contains nothing that could fall directly
30122 within that overall subject. (Thus, if the Document is in part a
30123 textbook of mathematics, a Secondary Section may not explain any
30124 mathematics.) The relationship could be a matter of historical
30125 connection with the subject or with related matters, or of legal,
30126 commercial, philosophical, ethical or political position regarding
30129 The "@strong{Invariant Sections}" are certain Secondary Sections whose titles
30130 are designated, as being those of Invariant Sections, in the notice
30131 that says that the Document is released under this License. If a
30132 section does not fit the above definition of Secondary then it is not
30133 allowed to be designated as Invariant. The Document may contain zero
30134 Invariant Sections. If the Document does not identify any Invariant
30135 Sections then there are none.
30137 The "@strong{Cover Texts}" are certain short passages of text that are listed,
30138 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
30139 the Document is released under this License. A Front-Cover Text may
30140 be at most 5 words, and a Back-Cover Text may be at most 25 words.
30142 A "@strong{Transparent}" copy of the Document means a machine-readable copy,
30143 represented in a format whose specification is available to the
30144 general public, that is suitable for revising the document
30145 straightforwardly with generic text editors or (for images composed of
30146 pixels) generic paint programs or (for drawings) some widely available
30147 drawing editor, and that is suitable for input to text formatters or
30148 for automatic translation to a variety of formats suitable for input
30149 to text formatters. A copy made in an otherwise Transparent file
30150 format whose markup, or absence of markup, has been arranged to thwart
30151 or discourage subsequent modification by readers is not Transparent.
30152 An image format is not Transparent if used for any substantial amount
30153 of text. A copy that is not "Transparent" is called @strong{Opaque}.
30155 Examples of suitable formats for Transparent copies include plain
30156 ASCII without markup, Texinfo input format, LaTeX input format, SGML
30157 or XML using a publicly available DTD, and standard-conforming simple
30158 HTML, PostScript or PDF designed for human modification. Examples of
30159 transparent image formats include PNG, XCF and JPG. Opaque formats
30160 include proprietary formats that can be read and edited only by
30161 proprietary word processors, SGML or XML for which the DTD and/or
30162 processing tools are not generally available, and the
30163 machine-generated HTML, PostScript or PDF produced by some word
30164 processors for output purposes only.
30166 The "@strong{Title Page}" means, for a printed book, the title page itself,
30167 plus such following pages as are needed to hold, legibly, the material
30168 this License requires to appear in the title page. For works in
30169 formats which do not have any title page as such, "Title Page" means
30170 the text near the most prominent appearance of the work's title,
30171 preceding the beginning of the body of the text.
30173 The "@strong{publisher}" means any person or entity that distributes
30174 copies of the Document to the public.
30176 A section "@strong{Entitled XYZ}" means a named subunit of the Document whose
30177 title either is precisely XYZ or contains XYZ in parentheses following
30178 text that translates XYZ in another language. (Here XYZ stands for a
30179 specific section name mentioned below, such as "@strong{Acknowledgements}",
30180 "@strong{Dedications}", "@strong{Endorsements}", or "@strong{History}".)
30181 To "@strong{Preserve the Title}"
30182 of such a section when you modify the Document means that it remains a
30183 section "Entitled XYZ" according to this definition.
30185 The Document may include Warranty Disclaimers next to the notice which
30186 states that this License applies to the Document. These Warranty
30187 Disclaimers are considered to be included by reference in this
30188 License, but only as regards disclaiming warranties: any other
30189 implication that these Warranty Disclaimers may have is void and has
30190 no effect on the meaning of this License.
30192 @strong{2. VERBATIM COPYING}
30194 You may copy and distribute the Document in any medium, either
30195 commercially or noncommercially, provided that this License, the
30196 copyright notices, and the license notice saying this License applies
30197 to the Document are reproduced in all copies, and that you add no other
30198 conditions whatsoever to those of this License. You may not use
30199 technical measures to obstruct or control the reading or further
30200 copying of the copies you make or distribute. However, you may accept
30201 compensation in exchange for copies. If you distribute a large enough
30202 number of copies you must also follow the conditions in section 3.
30204 You may also lend copies, under the same conditions stated above, and
30205 you may publicly display copies.
30207 @strong{3. COPYING IN QUANTITY}
30209 If you publish printed copies (or copies in media that commonly have
30210 printed covers) of the Document, numbering more than 100, and the
30211 Document's license notice requires Cover Texts, you must enclose the
30212 copies in covers that carry, clearly and legibly, all these Cover
30213 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
30214 the back cover. Both covers must also clearly and legibly identify
30215 you as the publisher of these copies. The front cover must present
30216 the full title with all words of the title equally prominent and
30217 visible. You may add other material on the covers in addition.
30218 Copying with changes limited to the covers, as long as they preserve
30219 the title of the Document and satisfy these conditions, can be treated
30220 as verbatim copying in other respects.
30222 If the required texts for either cover are too voluminous to fit
30223 legibly, you should put the first ones listed (as many as fit
30224 reasonably) on the actual cover, and continue the rest onto adjacent
30227 If you publish or distribute Opaque copies of the Document numbering
30228 more than 100, you must either include a machine-readable Transparent
30229 copy along with each Opaque copy, or state in or with each Opaque copy
30230 a computer-network location from which the general network-using
30231 public has access to download using public-standard network protocols
30232 a complete Transparent copy of the Document, free of added material.
30233 If you use the latter option, you must take reasonably prudent steps,
30234 when you begin distribution of Opaque copies in quantity, to ensure
30235 that this Transparent copy will remain thus accessible at the stated
30236 location until at least one year after the last time you distribute an
30237 Opaque copy (directly or through your agents or retailers) of that
30238 edition to the public.
30240 It is requested, but not required, that you contact the authors of the
30241 Document well before redistributing any large number of copies, to give
30242 them a chance to provide you with an updated version of the Document.
30244 @strong{4. MODIFICATIONS}
30246 You may copy and distribute a Modified Version of the Document under
30247 the conditions of sections 2 and 3 above, provided that you release
30248 the Modified Version under precisely this License, with the Modified
30249 Version filling the role of the Document, thus licensing distribution
30250 and modification of the Modified Version to whoever possesses a copy
30251 of it. In addition, you must do these things in the Modified Version:
30257 Use in the Title Page (and on the covers, if any) a title distinct
30258 from that of the Document, and from those of previous versions
30259 (which should, if there were any, be listed in the History section
30260 of the Document). You may use the same title as a previous version
30261 if the original publisher of that version gives permission.
30264 List on the Title Page, as authors, one or more persons or entities
30265 responsible for authorship of the modifications in the Modified
30266 Version, together with at least five of the principal authors of the
30267 Document (all of its principal authors, if it has fewer than five),
30268 unless they release you from this requirement.
30271 State on the Title page the name of the publisher of the
30272 Modified Version, as the publisher.
30275 Preserve all the copyright notices of the Document.
30278 Add an appropriate copyright notice for your modifications
30279 adjacent to the other copyright notices.
30282 Include, immediately after the copyright notices, a license notice
30283 giving the public permission to use the Modified Version under the
30284 terms of this License, in the form shown in the Addendum below.
30287 Preserve in that license notice the full lists of Invariant Sections
30288 and required Cover Texts given in the Document's license notice.
30291 Include an unaltered copy of this License.
30294 Preserve the section Entitled "History", Preserve its Title, and add
30295 to it an item stating at least the title, year, new authors, and
30296 publisher of the Modified Version as given on the Title Page. If
30297 there is no section Entitled "History" in the Document, create one
30298 stating the title, year, authors, and publisher of the Document as
30299 given on its Title Page, then add an item describing the Modified
30300 Version as stated in the previous sentence.
30303 Preserve the network location, if any, given in the Document for
30304 public access to a Transparent copy of the Document, and likewise
30305 the network locations given in the Document for previous versions
30306 it was based on. These may be placed in the "History" section.
30307 You may omit a network location for a work that was published at
30308 least four years before the Document itself, or if the original
30309 publisher of the version it refers to gives permission.
30312 For any section Entitled "Acknowledgements" or "Dedications",
30313 Preserve the Title of the section, and preserve in the section all
30314 the substance and tone of each of the contributor acknowledgements
30315 and/or dedications given therein.
30318 Preserve all the Invariant Sections of the Document,
30319 unaltered in their text and in their titles. Section numbers
30320 or the equivalent are not considered part of the section titles.
30323 Delete any section Entitled "Endorsements". Such a section
30324 may not be included in the Modified Version.
30327 Do not retitle any existing section to be Entitled "Endorsements"
30328 or to conflict in title with any Invariant Section.
30331 Preserve any Warranty Disclaimers.
30334 If the Modified Version includes new front-matter sections or
30335 appendices that qualify as Secondary Sections and contain no material
30336 copied from the Document, you may at your option designate some or all
30337 of these sections as invariant. To do this, add their titles to the
30338 list of Invariant Sections in the Modified Version's license notice.
30339 These titles must be distinct from any other section titles.
30341 You may add a section Entitled "Endorsements", provided it contains
30342 nothing but endorsements of your Modified Version by various
30343 parties---for example, statements of peer review or that the text has
30344 been approved by an organization as the authoritative definition of a
30347 You may add a passage of up to five words as a Front-Cover Text, and a
30348 passage of up to 25 words as a Back-Cover Text, to the end of the list
30349 of Cover Texts in the Modified Version. Only one passage of
30350 Front-Cover Text and one of Back-Cover Text may be added by (or
30351 through arrangements made by) any one entity. If the Document already
30352 includes a cover text for the same cover, previously added by you or
30353 by arrangement made by the same entity you are acting on behalf of,
30354 you may not add another; but you may replace the old one, on explicit
30355 permission from the previous publisher that added the old one.
30357 The author(s) and publisher(s) of the Document do not by this License
30358 give permission to use their names for publicity for or to assert or
30359 imply endorsement of any Modified Version.
30361 @strong{5. COMBINING DOCUMENTS}
30363 You may combine the Document with other documents released under this
30364 License, under the terms defined in section 4 above for modified
30365 versions, provided that you include in the combination all of the
30366 Invariant Sections of all of the original documents, unmodified, and
30367 list them all as Invariant Sections of your combined work in its
30368 license notice, and that you preserve all their Warranty Disclaimers.
30370 The combined work need only contain one copy of this License, and
30371 multiple identical Invariant Sections may be replaced with a single
30372 copy. If there are multiple Invariant Sections with the same name but
30373 different contents, make the title of each such section unique by
30374 adding at the end of it, in parentheses, the name of the original
30375 author or publisher of that section if known, or else a unique number.
30376 Make the same adjustment to the section titles in the list of
30377 Invariant Sections in the license notice of the combined work.
30379 In the combination, you must combine any sections Entitled "History"
30380 in the various original documents, forming one section Entitled
30381 "History"; likewise combine any sections Entitled "Acknowledgements",
30382 and any sections Entitled "Dedications". You must delete all sections
30383 Entitled "Endorsements".
30385 @strong{6. COLLECTIONS OF DOCUMENTS}
30387 You may make a collection consisting of the Document and other documents
30388 released under this License, and replace the individual copies of this
30389 License in the various documents with a single copy that is included in
30390 the collection, provided that you follow the rules of this License for
30391 verbatim copying of each of the documents in all other respects.
30393 You may extract a single document from such a collection, and distribute
30394 it individually under this License, provided you insert a copy of this
30395 License into the extracted document, and follow this License in all
30396 other respects regarding verbatim copying of that document.
30398 @strong{7. AGGREGATION WITH INDEPENDENT WORKS}
30400 A compilation of the Document or its derivatives with other separate
30401 and independent documents or works, in or on a volume of a storage or
30402 distribution medium, is called an "aggregate" if the copyright
30403 resulting from the compilation is not used to limit the legal rights
30404 of the compilation's users beyond what the individual works permit.
30405 When the Document is included in an aggregate, this License does not
30406 apply to the other works in the aggregate which are not themselves
30407 derivative works of the Document.
30409 If the Cover Text requirement of section 3 is applicable to these
30410 copies of the Document, then if the Document is less than one half of
30411 the entire aggregate, the Document's Cover Texts may be placed on
30412 covers that bracket the Document within the aggregate, or the
30413 electronic equivalent of covers if the Document is in electronic form.
30414 Otherwise they must appear on printed covers that bracket the whole
30417 @strong{8. TRANSLATION}
30419 Translation is considered a kind of modification, so you may
30420 distribute translations of the Document under the terms of section 4.
30421 Replacing Invariant Sections with translations requires special
30422 permission from their copyright holders, but you may include
30423 translations of some or all Invariant Sections in addition to the
30424 original versions of these Invariant Sections. You may include a
30425 translation of this License, and all the license notices in the
30426 Document, and any Warranty Disclaimers, provided that you also include
30427 the original English version of this License and the original versions
30428 of those notices and disclaimers. In case of a disagreement between
30429 the translation and the original version of this License or a notice
30430 or disclaimer, the original version will prevail.
30432 If a section in the Document is Entitled "Acknowledgements",
30433 "Dedications", or "History", the requirement (section 4) to Preserve
30434 its Title (section 1) will typically require changing the actual
30437 @strong{9. TERMINATION}
30439 You may not copy, modify, sublicense, or distribute the Document
30440 except as expressly provided under this License. Any attempt
30441 otherwise to copy, modify, sublicense, or distribute it is void, and
30442 will automatically terminate your rights under this License.
30444 However, if you cease all violation of this License, then your license
30445 from a particular copyright holder is reinstated (a) provisionally,
30446 unless and until the copyright holder explicitly and finally
30447 terminates your license, and (b) permanently, if the copyright holder
30448 fails to notify you of the violation by some reasonable means prior to
30449 60 days after the cessation.
30451 Moreover, your license from a particular copyright holder is
30452 reinstated permanently if the copyright holder notifies you of the
30453 violation by some reasonable means, this is the first time you have
30454 received notice of violation of this License (for any work) from that
30455 copyright holder, and you cure the violation prior to 30 days after
30456 your receipt of the notice.
30458 Termination of your rights under this section does not terminate the
30459 licenses of parties who have received copies or rights from you under
30460 this License. If your rights have been terminated and not permanently
30461 reinstated, receipt of a copy of some or all of the same material does
30462 not give you any rights to use it.
30464 @strong{10. FUTURE REVISIONS OF THIS LICENSE}
30466 The Free Software Foundation may publish new, revised versions
30467 of the GNU Free Documentation License from time to time. Such new
30468 versions will be similar in spirit to the present version, but may
30469 differ in detail to address new problems or concerns. See
30470 @indicateurl{http://www.gnu.org/copyleft/}.
30472 Each version of the License is given a distinguishing version number.
30473 If the Document specifies that a particular numbered version of this
30474 License "or any later version" applies to it, you have the option of
30475 following the terms and conditions either of that specified version or
30476 of any later version that has been published (not as a draft) by the
30477 Free Software Foundation. If the Document does not specify a version
30478 number of this License, you may choose any version ever published (not
30479 as a draft) by the Free Software Foundation. If the Document
30480 specifies that a proxy can decide which future versions of this
30481 License can be used, that proxy's public statement of acceptance of a
30482 version permanently authorizes you to choose that version for the
30485 @strong{11. RELICENSING}
30487 "Massive Multiauthor Collaboration Site" (or "MMC Site") means any
30488 World Wide Web server that publishes copyrightable works and also
30489 provides prominent facilities for anybody to edit those works. A
30490 public wiki that anybody can edit is an example of such a server. A
30491 "Massive Multiauthor Collaboration" (or "MMC") contained in the
30492 site means any set of copyrightable works thus published on the MMC
30495 "CC-BY-SA" means the Creative Commons Attribution-Share Alike 3.0
30496 license published by Creative Commons Corporation, a not-for-profit
30497 corporation with a principal place of business in San Francisco,
30498 California, as well as future copyleft versions of that license
30499 published by that same organization.
30501 "Incorporate" means to publish or republish a Document, in whole or
30502 in part, as part of another Document.
30504 An MMC is "eligible for relicensing" if it is licensed under this
30505 License, and if all works that were first published under this License
30506 somewhere other than this MMC, and subsequently incorporated in whole
30507 or in part into the MMC, (1) had no cover texts or invariant sections,
30508 and (2) were thus incorporated prior to November 1, 2008.
30510 The operator of an MMC Site may republish an MMC contained in the site
30511 under CC-BY-SA on the same site at any time before August 1, 2009,
30512 provided the MMC is eligible for relicensing.
30514 @strong{ADDENDUM: How to use this License for your documents}
30516 To use this License in a document you have written, include a copy of
30517 the License in the document and put the following copyright and
30518 license notices just after the title page:
30522 Copyright © YEAR YOUR NAME.
30523 Permission is granted to copy, distribute and/or modify this document
30524 under the terms of the GNU Free Documentation License, Version 1.3
30525 or any later version published by the Free Software Foundation;
30526 with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
30527 A copy of the license is included in the section entitled "GNU
30528 Free Documentation License".
30531 If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
30532 replace the "with ... Texts." line with this:
30536 with the Invariant Sections being LIST THEIR TITLES, with the
30537 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
30540 If you have Invariant Sections without Cover Texts, or some other
30541 combination of the three, merge those two alternatives to suit the
30544 If your document contains nontrivial examples of program code, we
30545 recommend releasing these examples in parallel under your choice of
30546 free software license, such as the GNU General Public License,
30547 to permit their use in free software.
30549 @node Index,,GNU Free Documentation License,Top
30556 @anchor{gnat_ugn/gnat_utility_programs switches-related-to-project-files}@w{ }