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d0a5eb32 | 1 | @c Copyright (C) 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, |
b684a3df | 2 | @c 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc. |
74291a4b MM |
3 | @c This is part of the GCC manual. |
4 | @c For copying conditions, see the file gcc.texi. | |
5 | ||
9d86bffc JM |
6 | @ignore |
7 | @c man begin COPYRIGHT | |
8 | Copyright @copyright{} 1988, 1989, 1992, 1993, 1994, 1995, 1996, 1997, | |
daef8bbd | 9 | 1998, 1999, 2000, 2001, 2002, 2003, 2004 Free Software Foundation, Inc. |
9d86bffc | 10 | |
77bd67cb | 11 | Permission is granted to copy, distribute and/or modify this document |
b3a8389d | 12 | under the terms of the GNU Free Documentation License, Version 1.2 or |
77bd67cb JM |
13 | any later version published by the Free Software Foundation; with the |
14 | Invariant Sections being ``GNU General Public License'' and ``Funding | |
15 | Free Software'', the Front-Cover texts being (a) (see below), and with | |
16 | the Back-Cover Texts being (b) (see below). A copy of the license is | |
17 | included in the gfdl(7) man page. | |
9d86bffc | 18 | |
77bd67cb | 19 | (a) The FSF's Front-Cover Text is: |
9d86bffc | 20 | |
77bd67cb JM |
21 | A GNU Manual |
22 | ||
23 | (b) The FSF's Back-Cover Text is: | |
24 | ||
25 | You have freedom to copy and modify this GNU Manual, like GNU | |
26 | software. Copies published by the Free Software Foundation raise | |
27 | funds for GNU development. | |
9d86bffc JM |
28 | @c man end |
29 | @c Set file name and title for the man page. | |
30 | @setfilename gcc | |
31 | @settitle GNU project C and C++ compiler | |
32 | @c man begin SYNOPSIS | |
630d3d5a JM |
33 | gcc [@option{-c}|@option{-S}|@option{-E}] [@option{-std=}@var{standard}] |
34 | [@option{-g}] [@option{-pg}] [@option{-O}@var{level}] | |
35 | [@option{-W}@var{warn}@dots{}] [@option{-pedantic}] | |
36 | [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}] | |
37 | [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}] | |
38 | [@option{-f}@var{option}@dots{}] [@option{-m}@var{machine-option}@dots{}] | |
39 | [@option{-o} @var{outfile}] @var{infile}@dots{} | |
9d86bffc JM |
40 | |
41 | Only the most useful options are listed here; see below for the | |
42 | remainder. @samp{g++} accepts mostly the same options as @samp{gcc}. | |
43 | @c man end | |
44 | @c man begin SEEALSO | |
77bd67cb | 45 | gpl(7), gfdl(7), fsf-funding(7), |
b4117c30 ZW |
46 | cpp(1), gcov(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1) |
47 | and the Info entries for @file{gcc}, @file{cpp}, @file{as}, | |
9d86bffc JM |
48 | @file{ld}, @file{binutils} and @file{gdb}. |
49 | @c man end | |
2642624b JM |
50 | @c man begin BUGS |
51 | For instructions on reporting bugs, see | |
bedc7537 | 52 | @w{@uref{http://gcc.gnu.org/bugs.html}}. Use of the @command{gccbug} |
2642624b JM |
53 | script to report bugs is recommended. |
54 | @c man end | |
55 | @c man begin AUTHOR | |
24dbb440 GP |
56 | See the Info entry for @command{gcc}, or |
57 | @w{@uref{http://gcc.gnu.org/onlinedocs/gcc/Contributors.html}}, | |
58 | for contributors to GCC@. | |
2642624b | 59 | @c man end |
9d86bffc JM |
60 | @end ignore |
61 | ||
74291a4b | 62 | @node Invoking GCC |
0c2d1a2a JB |
63 | @chapter GCC Command Options |
64 | @cindex GCC command options | |
74291a4b | 65 | @cindex command options |
0c2d1a2a | 66 | @cindex options, GCC command |
74291a4b | 67 | |
9d86bffc | 68 | @c man begin DESCRIPTION |
0c2d1a2a | 69 | When you invoke GCC, it normally does preprocessing, compilation, |
74291a4b | 70 | assembly and linking. The ``overall options'' allow you to stop this |
630d3d5a | 71 | process at an intermediate stage. For example, the @option{-c} option |
74291a4b MM |
72 | says not to run the linker. Then the output consists of object files |
73 | output by the assembler. | |
74 | ||
75 | Other options are passed on to one stage of processing. Some options | |
76 | control the preprocessor and others the compiler itself. Yet other | |
77 | options control the assembler and linker; most of these are not | |
78 | documented here, since you rarely need to use any of them. | |
79 | ||
80 | @cindex C compilation options | |
0c2d1a2a | 81 | Most of the command line options that you can use with GCC are useful |
74291a4b MM |
82 | for C programs; when an option is only useful with another language |
83 | (usually C++), the explanation says so explicitly. If the description | |
84 | for a particular option does not mention a source language, you can use | |
85 | that option with all supported languages. | |
86 | ||
87 | @cindex C++ compilation options | |
88 | @xref{Invoking G++,,Compiling C++ Programs}, for a summary of special | |
89 | options for compiling C++ programs. | |
90 | ||
91 | @cindex grouping options | |
92 | @cindex options, grouping | |
bedc7537 | 93 | The @command{gcc} program accepts options and file names as operands. Many |
b192711e | 94 | options have multi-letter names; therefore multiple single-letter options |
630d3d5a | 95 | may @emph{not} be grouped: @option{-dr} is very different from @w{@samp{-d |
74291a4b MM |
96 | -r}}. |
97 | ||
98 | @cindex order of options | |
99 | @cindex options, order | |
100 | You can mix options and other arguments. For the most part, the order | |
101 | you use doesn't matter. Order does matter when you use several options | |
630d3d5a | 102 | of the same kind; for example, if you specify @option{-L} more than once, |
74291a4b MM |
103 | the directories are searched in the order specified. |
104 | ||
105 | Many options have long names starting with @samp{-f} or with | |
630d3d5a JM |
106 | @samp{-W}---for example, @option{-fforce-mem}, |
107 | @option{-fstrength-reduce}, @option{-Wformat} and so on. Most of | |
74291a4b | 108 | these have both positive and negative forms; the negative form of |
630d3d5a | 109 | @option{-ffoo} would be @option{-fno-foo}. This manual documents |
74291a4b MM |
110 | only one of these two forms, whichever one is not the default. |
111 | ||
9d86bffc JM |
112 | @c man end |
113 | ||
cd3bb277 JM |
114 | @xref{Option Index}, for an index to GCC's options. |
115 | ||
74291a4b MM |
116 | @menu |
117 | * Option Summary:: Brief list of all options, without explanations. | |
118 | * Overall Options:: Controlling the kind of output: | |
119 | an executable, object files, assembler files, | |
120 | or preprocessed source. | |
121 | * Invoking G++:: Compiling C++ programs. | |
122 | * C Dialect Options:: Controlling the variant of C language compiled. | |
123 | * C++ Dialect Options:: Variations on C++. | |
60de6385 | 124 | * Objective-C Dialect Options:: Variations on Objective-C. |
764dbbf2 | 125 | * Language Independent Options:: Controlling how diagnostics should be |
02f52e19 | 126 | formatted. |
74291a4b MM |
127 | * Warning Options:: How picky should the compiler be? |
128 | * Debugging Options:: Symbol tables, measurements, and debugging dumps. | |
129 | * Optimize Options:: How much optimization? | |
130 | * Preprocessor Options:: Controlling header files and macro definitions. | |
131 | Also, getting dependency information for Make. | |
132 | * Assembler Options:: Passing options to the assembler. | |
133 | * Link Options:: Specifying libraries and so on. | |
134 | * Directory Options:: Where to find header files and libraries. | |
135 | Where to find the compiler executable files. | |
a743d340 | 136 | * Spec Files:: How to pass switches to sub-processes. |
0c2d1a2a | 137 | * Target Options:: Running a cross-compiler, or an old version of GCC. |
74291a4b MM |
138 | * Submodel Options:: Specifying minor hardware or convention variations, |
139 | such as 68010 vs 68020. | |
140 | * Code Gen Options:: Specifying conventions for function calls, data layout | |
141 | and register usage. | |
0c2d1a2a | 142 | * Environment Variables:: Env vars that affect GCC. |
17211ab5 | 143 | * Precompiled Headers:: Compiling a header once, and using it many times. |
74291a4b MM |
144 | * Running Protoize:: Automatically adding or removing function prototypes. |
145 | @end menu | |
146 | ||
4bc1997b JM |
147 | @c man begin OPTIONS |
148 | ||
74291a4b MM |
149 | @node Option Summary |
150 | @section Option Summary | |
151 | ||
152 | Here is a summary of all the options, grouped by type. Explanations are | |
153 | in the following sections. | |
154 | ||
155 | @table @emph | |
156 | @item Overall Options | |
157 | @xref{Overall Options,,Options Controlling the Kind of Output}. | |
0855eab7 | 158 | @gccoptlist{-c -S -E -o @var{file} -combine -pipe -pass-exit-codes @gol |
9a94f7f3 | 159 | -x @var{language} -v -### --help --target-help --version} |
74291a4b MM |
160 | |
161 | @item C Language Options | |
162 | @xref{C Dialect Options,,Options Controlling C Dialect}. | |
9a94f7f3 JM |
163 | @gccoptlist{-ansi -std=@var{standard} -aux-info @var{filename} @gol |
164 | -fno-asm -fno-builtin -fno-builtin-@var{function} @gol | |
750491fc | 165 | -fhosted -ffreestanding -fms-extensions @gol |
8a035a6b | 166 | -trigraphs -no-integrated-cpp -traditional -traditional-cpp @gol |
4bc1997b JM |
167 | -fallow-single-precision -fcond-mismatch @gol |
168 | -fsigned-bitfields -fsigned-char @gol | |
3521b33c | 169 | -funsigned-bitfields -funsigned-char} |
74291a4b MM |
170 | |
171 | @item C++ Language Options | |
172 | @xref{C++ Dialect Options,,Options Controlling C++ Dialect}. | |
9a94f7f3 | 173 | @gccoptlist{-fabi-version=@var{n} -fno-access-control -fcheck-new @gol |
b1822ccc | 174 | -fconserve-space -fno-const-strings @gol |
aa0cc562 | 175 | -fno-elide-constructors @gol |
7813d14c | 176 | -fno-enforce-eh-specs @gol |
1dbb6023 | 177 | -ffor-scope -fno-for-scope -fno-gnu-keywords @gol |
90ecce3e | 178 | -fno-implicit-templates @gol |
4bc1997b JM |
179 | -fno-implicit-inline-templates @gol |
180 | -fno-implement-inlines -fms-extensions @gol | |
aa0cc562 | 181 | -fno-nonansi-builtins -fno-operator-names @gol |
4bc1997b | 182 | -fno-optional-diags -fpermissive @gol |
aa0cc562 | 183 | -frepo -fno-rtti -fstats -ftemplate-depth-@var{n} @gol |
a0c8285b | 184 | -fuse-cxa-atexit -fno-weak -nostdinc++ @gol |
9a94f7f3 | 185 | -fno-default-inline -Wabi -Wctor-dtor-privacy @gol |
4bc1997b JM |
186 | -Wnon-virtual-dtor -Wreorder @gol |
187 | -Weffc++ -Wno-deprecated @gol | |
188 | -Wno-non-template-friend -Wold-style-cast @gol | |
189 | -Woverloaded-virtual -Wno-pmf-conversions @gol | |
190 | -Wsign-promo -Wsynth} | |
74291a4b | 191 | |
60de6385 SS |
192 | @item Objective-C Language Options |
193 | @xref{Objective-C Dialect Options,,Options Controlling Objective-C Dialect}. | |
264fa2db ZL |
194 | @gccoptlist{ |
195 | -fconstant-string-class=@var{class-name} @gol | |
196 | -fgnu-runtime -fnext-runtime @gol | |
197 | -fno-nil-receivers @gol | |
198 | -fobjc-exceptions @gol | |
199 | -freplace-objc-classes @gol | |
200 | -fzero-link @gol | |
201 | -gen-decls @gol | |
1f676100 | 202 | -Wno-protocol -Wselector -Wundeclared-selector} |
60de6385 | 203 | |
764dbbf2 GDR |
204 | @item Language Independent Options |
205 | @xref{Language Independent Options,,Options to Control Diagnostic Messages Formatting}. | |
9a94f7f3 | 206 | @gccoptlist{-fmessage-length=@var{n} @gol |
4bc1997b | 207 | -fdiagnostics-show-location=@r{[}once@r{|}every-line@r{]}} |
764dbbf2 | 208 | |
74291a4b MM |
209 | @item Warning Options |
210 | @xref{Warning Options,,Options to Request or Suppress Warnings}. | |
9a94f7f3 | 211 | @gccoptlist{-fsyntax-only -pedantic -pedantic-errors @gol |
65ca2d60 | 212 | -w -Wextra -Wall -Waggregate-return @gol |
4bc1997b | 213 | -Wcast-align -Wcast-qual -Wchar-subscripts -Wcomment @gol |
e23bd218 | 214 | -Wconversion -Wno-deprecated-declarations @gol |
fb0317c6 VR |
215 | -Wdisabled-optimization -Wno-div-by-zero -Wendif-labels @gol |
216 | -Werror -Werror-implicit-function-declaration @gol | |
c65a01af | 217 | -Wfatal-errors -Wfloat-equal -Wformat -Wformat=2 @gol |
fb0317c6 | 218 | -Wno-format-extra-args -Wformat-nonliteral @gol |
c76f4e8e | 219 | -Wformat-security -Wformat-y2k @gol |
fb0317c6 VR |
220 | -Wimplicit -Wimplicit-function-declaration -Wimplicit-int @gol |
221 | -Wimport -Wno-import -Winit-self -Winline @gol | |
222 | -Wno-invalid-offsetof -Winvalid-pch @gol | |
4bc1997b | 223 | -Wlarger-than-@var{len} -Wlong-long @gol |
87ec8de9 | 224 | -Wmain -Wmissing-braces @gol |
b02398bd BE |
225 | -Wmissing-format-attribute -Wmissing-include-dirs @gol |
226 | -Wmissing-noreturn @gol | |
fb0317c6 | 227 | -Wno-multichar -Wnonnull -Wpacked -Wpadded @gol |
310668e8 | 228 | -Wparentheses -Wpointer-arith -Wredundant-decls @gol |
4bc1997b | 229 | -Wreturn-type -Wsequence-point -Wshadow @gol |
5399d643 | 230 | -Wsign-compare -Wstrict-aliasing -Wstrict-aliasing=2 @gol |
9a94f7f3 JM |
231 | -Wswitch -Wswitch-default -Wswitch-enum @gol |
232 | -Wsystem-headers -Wtrigraphs -Wundef -Wuninitialized @gol | |
4bc1997b JM |
233 | -Wunknown-pragmas -Wunreachable-code @gol |
234 | -Wunused -Wunused-function -Wunused-label -Wunused-parameter @gol | |
7c4d376d RH |
235 | -Wunused-value -Wunused-variable -Wwrite-strings @gol |
236 | -Wvariadic-macros} | |
74291a4b | 237 | |
fe50c0eb | 238 | @item C-only Warning Options |
9a94f7f3 | 239 | @gccoptlist{-Wbad-function-cast -Wmissing-declarations @gol |
fb0317c6 | 240 | -Wmissing-prototypes -Wnested-externs -Wold-style-definition @gol |
85617eba HPN |
241 | -Wstrict-prototypes -Wtraditional @gol |
242 | -Wdeclaration-after-statement} | |
fe50c0eb | 243 | |
74291a4b MM |
244 | @item Debugging Options |
245 | @xref{Debugging Options,,Options for Debugging Your Program or GCC}. | |
9a94f7f3 JM |
246 | @gccoptlist{-d@var{letters} -dumpspecs -dumpmachine -dumpversion @gol |
247 | -fdump-unnumbered -fdump-translation-unit@r{[}-@var{n}@r{]} @gol | |
aee96fe9 | 248 | -fdump-class-hierarchy@r{[}-@var{n}@r{]} @gol |
6de9cd9a | 249 | -fdump-tree-all @gol |
9a94f7f3 JM |
250 | -fdump-tree-original@r{[}-@var{n}@r{]} @gol |
251 | -fdump-tree-optimized@r{[}-@var{n}@r{]} @gol | |
22367161 | 252 | -fdump-tree-inlined@r{[}-@var{n}@r{]} @gol |
6de9cd9a DN |
253 | -fdump-tree-cfg -fdump-tree-vcg -fdump-tree-alias @gol |
254 | -fdump-tree-ch @gol | |
255 | -fdump-tree-ssa@r{[}-@var{n}@r{]} -fdump-tree-pre@r{[}-@var{n}@r{]} @gol | |
256 | -fdump-tree-ccp@r{[}-@var{n}@r{]} -fdump-tree-dce@r{[}-@var{n}@r{]} @gol | |
257 | -fdump-tree-gimple@r{[}-raw@r{]} -fdump-tree-mudflap@r{[}-@var{n}@r{]} @gol | |
258 | -fdump-tree-dom@r{[}-@var{n}@r{]} @gol | |
259 | -fdump-tree-dse@r{[}-@var{n}@r{]} @gol | |
260 | -fdump-tree-phiopt@r{[}-@var{n}@r{]} @gol | |
261 | -fdump-tree-forwprop@r{[}-@var{n}@r{]} @gol | |
262 | -fdump-tree-copyrename@r{[}-@var{n}@r{]} @gol | |
263 | -fdump-tree-nrv @gol | |
264 | -fdump-tree-sra@r{[}-@var{n}@r{]} @gol | |
ff2ad0f7 | 265 | -fdump-tree-fre@r{[}-@var{n}@r{]} @gol |
a37db56b | 266 | -feliminate-dwarf2-dups -feliminate-unused-debug-types @gol |
6de9cd9a | 267 | -feliminate-unused-debug-symbols -fmem-report -fprofile-arcs -ftree-based-profiling @gol |
a37db56b | 268 | -frandom-seed=@var{string} -fsched-verbose=@var{n} @gol |
014a1138 | 269 | -ftest-coverage -ftime-report -fvar-tracking @gol |
def66b10 | 270 | -g -g@var{level} -gcoff -gdwarf-2 @gol |
5f98259a | 271 | -ggdb -gstabs -gstabs+ -gvms -gxcoff -gxcoff+ @gol |
4bc1997b | 272 | -p -pg -print-file-name=@var{library} -print-libgcc-file-name @gol |
b1018de6 | 273 | -print-multi-directory -print-multi-lib @gol |
4bc1997b JM |
274 | -print-prog-name=@var{program} -print-search-dirs -Q @gol |
275 | -save-temps -time} | |
74291a4b MM |
276 | |
277 | @item Optimization Options | |
278 | @xref{Optimize Options,,Options that Control Optimization}. | |
9a94f7f3 | 279 | @gccoptlist{-falign-functions=@var{n} -falign-jumps=@var{n} @gol |
4bc1997b | 280 | -falign-labels=@var{n} -falign-loops=@var{n} @gol |
6de9cd9a | 281 | -fbounds-check -fmudflap -fmudflapth -fmudflapir @gol |
fca9dc00 | 282 | -fbranch-probabilities -fprofile-values -fvpt -fbranch-target-load-optimize @gol |
1194fc79 R |
283 | -fbranch-target-load-optimize2 -fbtr-bb-exclusive @gol |
284 | -fcaller-saves -fcprop-registers @gol | |
62d285ff | 285 | -fcse-follow-jumps -fcse-skip-blocks -fdata-sections @gol |
4bc1997b JM |
286 | -fdelayed-branch -fdelete-null-pointer-checks @gol |
287 | -fexpensive-optimizations -ffast-math -ffloat-store @gol | |
feb48bde | 288 | -fforce-addr -fforce-mem -ffunction-sections @gol |
db643b91 SH |
289 | -fgcse -fgcse-lm -fgcse-sm -fgcse-las -fgcse-after-reload @gol |
290 | -floop-optimize -fcrossjumping -fif-conversion -fif-conversion2 @gol | |
4bc1997b | 291 | -finline-functions -finline-limit=@var{n} -fkeep-inline-functions @gol |
201556f0 | 292 | -fkeep-static-consts -fmerge-constants -fmerge-all-constants @gol |
e5626198 | 293 | -fmodulo-sched -fmove-all-movables -fnew-ra -fno-branch-count-reg @gol |
5e962776 | 294 | -fno-default-inline -fno-defer-pop -floop-optimize2 -fmove-loop-invariants @gol |
feb48bde | 295 | -fno-function-cse -fno-guess-branch-probability @gol |
6cfc0341 | 296 | -fno-inline -fno-math-errno -fno-peephole -fno-peephole2 @gol |
9a94f7f3 JM |
297 | -funsafe-math-optimizations -ffinite-math-only @gol |
298 | -fno-trapping-math -fno-zero-initialized-in-bss @gol | |
4bc1997b | 299 | -fomit-frame-pointer -foptimize-register-move @gol |
5d22c1a5 | 300 | -foptimize-sibling-calls -fprefetch-loop-arrays @gol |
a8a5f53a | 301 | -fprofile-generate -fprofile-use @gol |
9a94f7f3 | 302 | -freduce-all-givs -fregmove -frename-registers @gol |
750054a2 | 303 | -freorder-blocks -freorder-blocks-and-partition -freorder-functions @gol |
4bc1997b | 304 | -frerun-cse-after-loop -frerun-loop-opt @gol |
039c3d42 | 305 | -frounding-math -fschedule-insns -fschedule-insns2 @gol |
e03b7153 | 306 | -fno-sched-interblock -fno-sched-spec -fsched-spec-load @gol |
569fa502 DN |
307 | -fsched-spec-load-dangerous @gol |
308 | -fsched-stalled-insns=@var{n} -sched-stalled-insns-dep=@var{n} @gol | |
309 | -fsched2-use-superblocks @gol | |
b9422b69 | 310 | -fsched2-use-traces -fsignaling-nans @gol |
c132886e | 311 | -fsingle-precision-constant @gol |
9a94f7f3 JM |
312 | -fstrength-reduce -fstrict-aliasing -ftracer -fthread-jumps @gol |
313 | -funroll-all-loops -funroll-loops -fpeel-loops @gol | |
314 | -funswitch-loops -fold-unroll-loops -fold-unroll-all-loops @gol | |
c66b6c66 | 315 | -ftree-pre -ftree-ccp -ftree-dce -ftree-loop-optimize @gol |
6de9cd9a | 316 | -ftree-dominator-opts -ftree-dse -ftree-copyrename @gol |
ff2ad0f7 | 317 | -ftree-ch -ftree-sra -ftree-ter -ftree-lrs -ftree-fre @gol |
3af64fd6 | 318 | --param @var{name}=@var{value} |
4bc1997b | 319 | -O -O0 -O1 -O2 -O3 -Os} |
74291a4b MM |
320 | |
321 | @item Preprocessor Options | |
322 | @xref{Preprocessor Options,,Options Controlling the Preprocessor}. | |
c2d635bc | 323 | @gccoptlist{-A@var{question}=@var{answer} @gol |
9a94f7f3 | 324 | -A-@var{question}@r{[}=@var{answer}@r{]} @gol |
4bc1997b JM |
325 | -C -dD -dI -dM -dN @gol |
326 | -D@var{macro}@r{[}=@var{defn}@r{]} -E -H @gol | |
327 | -idirafter @var{dir} @gol | |
328 | -include @var{file} -imacros @var{file} @gol | |
329 | -iprefix @var{file} -iwithprefix @var{dir} @gol | |
bdd42dd9 | 330 | -iwithprefixbefore @var{dir} -isystem @var{dir} @gol |
b20d9f0c AO |
331 | -M -MM -MF -MG -MP -MQ -MT -nostdinc @gol |
332 | -P -fworking-directory -remap @gol | |
9a94f7f3 JM |
333 | -trigraphs -undef -U@var{macro} -Wp,@var{option} @gol |
334 | -Xpreprocessor @var{option}} | |
74291a4b MM |
335 | |
336 | @item Assembler Option | |
337 | @xref{Assembler Options,,Passing Options to the Assembler}. | |
9a94f7f3 | 338 | @gccoptlist{-Wa,@var{option} -Xassembler @var{option}} |
74291a4b MM |
339 | |
340 | @item Linker Options | |
341 | @xref{Link Options,,Options for Linking}. | |
9a94f7f3 | 342 | @gccoptlist{@var{object-file-name} -l@var{library} @gol |
24a4dd31 | 343 | -nostartfiles -nodefaultlibs -nostdlib -pie @gol |
4bc1997b | 344 | -s -static -static-libgcc -shared -shared-libgcc -symbolic @gol |
aee96fe9 | 345 | -Wl,@var{option} -Xlinker @var{option} @gol |
4bc1997b | 346 | -u @var{symbol}} |
74291a4b MM |
347 | |
348 | @item Directory Options | |
349 | @xref{Directory Options,,Options for Directory Search}. | |
4bed3787 | 350 | @gccoptlist{-B@var{prefix} -I@var{dir} -iquote@var{dir} -L@var{dir} -specs=@var{file} -I-} |
74291a4b MM |
351 | |
352 | @item Target Options | |
353 | @c I wrote this xref this way to avoid overfull hbox. -- rms | |
354 | @xref{Target Options}. | |
9a94f7f3 | 355 | @gccoptlist{-V @var{version} -b @var{machine}} |
74291a4b MM |
356 | |
357 | @item Machine Dependent Options | |
358 | @xref{Submodel Options,,Hardware Models and Configurations}. | |
39bc1876 NS |
359 | @c This list is ordered alphanumerically by subsection name. |
360 | @c Try and put the significant identifier (CPU or system) first, | |
361 | @c so users have a clue at guessing where the ones they want will be. | |
5d22c1a5 | 362 | |
39bc1876 NS |
363 | @emph{ARC Options} |
364 | @gccoptlist{-EB -EL @gol | |
365 | -mmangle-cpu -mcpu=@var{cpu} -mtext=@var{text-section} @gol | |
366 | -mdata=@var{data-section} -mrodata=@var{readonly-data-section}} | |
74291a4b | 367 | |
74291a4b | 368 | @emph{ARM Options} |
9a94f7f3 | 369 | @gccoptlist{-mapcs-frame -mno-apcs-frame @gol |
5848830f | 370 | -mabi=@var{name} @gol |
310668e8 JM |
371 | -mapcs-stack-check -mno-apcs-stack-check @gol |
372 | -mapcs-float -mno-apcs-float @gol | |
373 | -mapcs-reentrant -mno-apcs-reentrant @gol | |
374 | -msched-prolog -mno-sched-prolog @gol | |
375 | -mlittle-endian -mbig-endian -mwords-little-endian @gol | |
34a86306 | 376 | -mfloat-abi=@var{name} -msoft-float -mhard-float -mfpe @gol |
310668e8 | 377 | -mthumb-interwork -mno-thumb-interwork @gol |
9b66ebb1 | 378 | -mcpu=@var{name} -march=@var{name} -mfpu=@var{name} @gol |
247f8561 | 379 | -mstructure-size-boundary=@var{n} @gol |
4bc1997b | 380 | -mabort-on-noreturn @gol |
310668e8 JM |
381 | -mlong-calls -mno-long-calls @gol |
382 | -msingle-pic-base -mno-single-pic-base @gol | |
247f8561 PB |
383 | -mpic-register=@var{reg} @gol |
384 | -mnop-fun-dllimport @gol | |
9b6b54e2 | 385 | -mcirrus-fix-invalid-insns -mno-cirrus-fix-invalid-insns @gol |
247f8561 | 386 | -mpoke-function-name @gol |
310668e8 JM |
387 | -mthumb -marm @gol |
388 | -mtpcs-frame -mtpcs-leaf-frame @gol | |
9a94f7f3 | 389 | -mcaller-super-interworking -mcallee-super-interworking} |
74291a4b | 390 | |
39bc1876 NS |
391 | @emph{AVR Options} |
392 | @gccoptlist{-mmcu=@var{mcu} -msize -minit-stack=@var{n} -mno-interrupts @gol | |
393 | -mcall-prologues -mno-tablejump -mtiny-stack -mint8} | |
861bb6c1 | 394 | |
39bc1876 NS |
395 | @emph{CRIS Options} |
396 | @gccoptlist{-mcpu=@var{cpu} -march=@var{cpu} -mtune=@var{cpu} @gol | |
397 | -mmax-stack-frame=@var{n} -melinux-stacksize=@var{n} @gol | |
398 | -metrax4 -metrax100 -mpdebug -mcc-init -mno-side-effects @gol | |
399 | -mstack-align -mdata-align -mconst-align @gol | |
400 | -m32-bit -m16-bit -m8-bit -mno-prologue-epilogue -mno-gotplt @gol | |
401 | -melf -maout -melinux -mlinux -sim -sim2 @gol | |
402 | -mmul-bug-workaround -mno-mul-bug-workaround} | |
74291a4b | 403 | |
48aec0bc | 404 | @emph{Darwin Options} |
6d2f9dd3 JM |
405 | @gccoptlist{-all_load -allowable_client -arch -arch_errors_fatal @gol |
406 | -arch_only -bind_at_load -bundle -bundle_loader @gol | |
407 | -client_name -compatibility_version -current_version @gol | |
408 | -dependency-file -dylib_file -dylinker_install_name @gol | |
409 | -dynamic -dynamiclib -exported_symbols_list @gol | |
410 | -filelist -flat_namespace -force_cpusubtype_ALL @gol | |
411 | -force_flat_namespace -headerpad_max_install_names @gol | |
412 | -image_base -init -install_name -keep_private_externs @gol | |
413 | -multi_module -multiply_defined -multiply_defined_unused @gol | |
e62f462e | 414 | -noall_load -nofixprebinding -nomultidefs -noprebind -noseglinkedit @gol |
6d2f9dd3 JM |
415 | -pagezero_size -prebind -prebind_all_twolevel_modules @gol |
416 | -private_bundle -read_only_relocs -sectalign @gol | |
417 | -sectobjectsymbols -whyload -seg1addr @gol | |
418 | -sectcreate -sectobjectsymbols -sectorder @gol | |
419 | -seg_addr_table -seg_addr_table_filename -seglinkedit @gol | |
420 | -segprot -segs_read_only_addr -segs_read_write_addr @gol | |
421 | -single_module -static -sub_library -sub_umbrella @gol | |
422 | -twolevel_namespace -umbrella -undefined @gol | |
423 | -unexported_symbols_list -weak_reference_mismatches @gol | |
f08a3544 | 424 | -whatsloaded -F} |
48aec0bc | 425 | |
74291a4b | 426 | @emph{DEC Alpha Options} |
9a94f7f3 | 427 | @gccoptlist{-mno-fp-regs -msoft-float -malpha-as -mgas @gol |
4bc1997b JM |
428 | -mieee -mieee-with-inexact -mieee-conformant @gol |
429 | -mfp-trap-mode=@var{mode} -mfp-rounding-mode=@var{mode} @gol | |
430 | -mtrap-precision=@var{mode} -mbuild-constants @gol | |
58605ba0 RH |
431 | -mcpu=@var{cpu-type} -mtune=@var{cpu-type} @gol |
432 | -mbwx -mmax -mfix -mcix @gol | |
433 | -mfloat-vax -mfloat-ieee @gol | |
9a94f7f3 JM |
434 | -mexplicit-relocs -msmall-data -mlarge-data @gol |
435 | -msmall-text -mlarge-text @gol | |
4bc1997b | 436 | -mmemory-latency=@var{time}} |
74291a4b | 437 | |
d7c23cdc | 438 | @emph{DEC Alpha/VMS Options} |
9a94f7f3 | 439 | @gccoptlist{-mvms-return-codes} |
d7c23cdc | 440 | |
39bc1876 NS |
441 | @emph{FRV Options} |
442 | @gccoptlist{-mgpr-32 -mgpr-64 -mfpr-32 -mfpr-64 @gol | |
443 | -mhard-float -msoft-float @gol | |
444 | -malloc-cc -mfixed-cc -mdword -mno-dword @gol | |
445 | -mdouble -mno-double @gol | |
446 | -mmedia -mno-media -mmuladd -mno-muladd @gol | |
447 | -mfdpic -minline-plt -mgprel-ro -multilib-library-pic -mlinked-fp @gol | |
448 | -mlibrary-pic -macc-4 -macc-8 @gol | |
449 | -mpack -mno-pack -mno-eflags -mcond-move -mno-cond-move @gol | |
450 | -mscc -mno-scc -mcond-exec -mno-cond-exec @gol | |
451 | -mvliw-branch -mno-vliw-branch @gol | |
452 | -mmulti-cond-exec -mno-multi-cond-exec -mnested-cond-exec @gol | |
453 | -mno-nested-cond-exec -mtomcat-stats @gol | |
454 | -mcpu=@var{cpu}} | |
455 | ||
74291a4b | 456 | @emph{H8/300 Options} |
9a94f7f3 | 457 | @gccoptlist{-mrelax -mh -ms -mn -mint32 -malign-300} |
74291a4b | 458 | |
39bc1876 NS |
459 | @emph{HPPA Options} |
460 | @gccoptlist{-march=@var{architecture-type} @gol | |
461 | -mbig-switch -mdisable-fpregs -mdisable-indexing @gol | |
462 | -mfast-indirect-calls -mgas -mgnu-ld -mhp-ld @gol | |
463 | -mjump-in-delay -mlinker-opt -mlong-calls @gol | |
464 | -mlong-load-store -mno-big-switch -mno-disable-fpregs @gol | |
465 | -mno-disable-indexing -mno-fast-indirect-calls -mno-gas @gol | |
466 | -mno-jump-in-delay -mno-long-load-store @gol | |
467 | -mno-portable-runtime -mno-soft-float @gol | |
468 | -mno-space-regs -msoft-float -mpa-risc-1-0 @gol | |
469 | -mpa-risc-1-1 -mpa-risc-2-0 -mportable-runtime @gol | |
470 | -mschedule=@var{cpu-type} -mspace-regs -msio -mwsio @gol | |
471 | -nolibdld -static -threads} | |
74291a4b | 472 | |
39bc1876 NS |
473 | @emph{i386 and x86-64 Options} |
474 | @gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol | |
475 | -mfpmath=@var{unit} @gol | |
476 | -masm=@var{dialect} -mno-fancy-math-387 @gol | |
477 | -mno-fp-ret-in-387 -msoft-float -msvr3-shlib @gol | |
478 | -mno-wide-multiply -mrtd -malign-double @gol | |
479 | -mpreferred-stack-boundary=@var{num} @gol | |
480 | -mmmx -msse -msse2 -msse3 -m3dnow @gol | |
481 | -mthreads -mno-align-stringops -minline-all-stringops @gol | |
482 | -mpush-args -maccumulate-outgoing-args -m128bit-long-double @gol | |
483 | -m96bit-long-double -mregparm=@var{num} -momit-leaf-frame-pointer @gol | |
484 | -mno-red-zone -mno-tls-direct-seg-refs @gol | |
485 | -mcmodel=@var{code-model} @gol | |
486 | -m32 -m64} | |
56b2d7a7 | 487 | |
39bc1876 NS |
488 | @emph{IA-64 Options} |
489 | @gccoptlist{-mbig-endian -mlittle-endian -mgnu-as -mgnu-ld -mno-pic @gol | |
490 | -mvolatile-asm-stop -mb-step -mregister-names -mno-sdata @gol | |
491 | -mconstant-gp -mauto-pic -minline-float-divide-min-latency @gol | |
492 | -minline-float-divide-max-throughput @gol | |
493 | -minline-int-divide-min-latency @gol | |
494 | -minline-int-divide-max-throughput -mno-dwarf2-asm @gol | |
495 | -mfixed-range=@var{register-range}} | |
282a61e6 | 496 | |
39bc1876 NS |
497 | @emph{M32R/D Options} |
498 | @gccoptlist{-m32r2 -m32rx -m32r @gol | |
499 | -mdebug @gol | |
500 | -malign-loops -mno-align-loops @gol | |
501 | -missue-rate=@var{number} @gol | |
502 | -mbranch-cost=@var{number} @gol | |
503 | -mmodel=@var{code-size-model-type} @gol | |
504 | -msdata=@var{sdata-type} @gol | |
505 | -mno-flush-func -mflush-func=@var{name} @gol | |
506 | -mno-flush-trap -mflush-trap=@var{number} @gol | |
507 | -G @var{num}} | |
83575957 | 508 | |
39bc1876 NS |
509 | @emph{M680x0 Options} |
510 | @gccoptlist{-m68000 -m68020 -m68020-40 -m68020-60 -m68030 -m68040 @gol | |
511 | -m68060 -mcpu32 -m5200 -m68881 -mbitfield -mc68000 -mc68020 @gol | |
512 | -mnobitfield -mrtd -mshort -msoft-float -mpcrel @gol | |
513 | -malign-int -mstrict-align -msep-data -mno-sep-data @gol | |
514 | -mshared-library-id=n -mid-shared-library -mno-id-shared-library} | |
789a3090 | 515 | |
39bc1876 NS |
516 | @emph{M68hc1x Options} |
517 | @gccoptlist{-m6811 -m6812 -m68hc11 -m68hc12 -m68hcs12 @gol | |
518 | -mauto-incdec -minmax -mlong-calls -mshort @gol | |
519 | -msoft-reg-count=@var{count}} | |
052a4b28 | 520 | |
789a3090 | 521 | @emph{MCore Options} |
9a94f7f3 | 522 | @gccoptlist{-mhardlit -mno-hardlit -mdiv -mno-div -mrelax-immediates @gol |
310668e8 JM |
523 | -mno-relax-immediates -mwide-bitfields -mno-wide-bitfields @gol |
524 | -m4byte-functions -mno-4byte-functions -mcallgraph-data @gol | |
525 | -mno-callgraph-data -mslow-bytes -mno-slow-bytes -mno-lsim @gol | |
526 | -mlittle-endian -mbig-endian -m210 -m340 -mstack-increment} | |
f84271d9 | 527 | |
39bc1876 NS |
528 | @emph{MIPS Options} |
529 | @gccoptlist{-EL -EB -march=@var{arch} -mtune=@var{arch} @gol | |
530 | -mips1 -mips2 -mips3 -mips4 -mips32 -mips32r2 -mips64 @gol | |
531 | -mips16 -mno-mips16 -mabi=@var{abi} -mabicalls -mno-abicalls @gol | |
532 | -mxgot -mno-xgot -mgp32 -mgp64 -mfp32 -mfp64 @gol | |
533 | -mhard-float -msoft-float -msingle-float -mdouble-float @gol | |
534 | -mint64 -mlong64 -mlong32 @gol | |
535 | -G@var{num} -membedded-data -mno-embedded-data @gol | |
536 | -muninit-const-in-rodata -mno-uninit-const-in-rodata @gol | |
537 | -msplit-addresses -mno-split-addresses @gol | |
538 | -mexplicit-relocs -mno-explicit-relocs @gol | |
539 | -mrnames -mno-rnames @gol | |
540 | -mcheck-zero-division -mno-check-zero-division @gol | |
541 | -mmemcpy -mno-memcpy -mlong-calls -mno-long-calls @gol | |
542 | -mmad -mno-mad -mfused-madd -mno-fused-madd -nocpp @gol | |
543 | -mfix-r4000 -mno-fix-r4000 -mfix-r4400 -mno-fix-r4400 @gol | |
544 | -mfix-vr4120 -mno-fix-vr4120 -mfix-sb1 -mno-fix-sb1 @gol | |
545 | -mflush-func=@var{func} -mno-flush-func @gol | |
546 | -mbranch-likely -mno-branch-likely @gol | |
547 | -mfp-exceptions -mno-fp-exceptions @gol | |
548 | -mvr4130-align -mno-vr4130-align} | |
bcf684c7 | 549 | |
39bc1876 NS |
550 | @emph{MMIX Options} |
551 | @gccoptlist{-mlibfuncs -mno-libfuncs -mepsilon -mno-epsilon -mabi=gnu @gol | |
552 | -mabi=mmixware -mzero-extend -mknuthdiv -mtoplevel-symbols @gol | |
553 | -melf -mbranch-predict -mno-branch-predict -mbase-addresses @gol | |
554 | -mno-base-addresses -msingle-exit -mno-single-exit} | |
df6194d4 | 555 | |
39bc1876 NS |
556 | @emph{MN10300 Options} |
557 | @gccoptlist{-mmult-bug -mno-mult-bug @gol | |
558 | -mam33 -mno-am33 @gol | |
559 | -mam33-2 -mno-am33-2 @gol | |
560 | -mno-crt0 -mrelax} | |
91abf72d | 561 | |
39bc1876 NS |
562 | @emph{NS32K Options} |
563 | @gccoptlist{-m32032 -m32332 -m32532 -m32081 -m32381 @gol | |
564 | -mmult-add -mnomult-add -msoft-float -mrtd -mnortd @gol | |
565 | -mregparam -mnoregparam -msb -mnosb @gol | |
566 | -mbitfield -mnobitfield -mhimem -mnohimem} | |
0b85d816 | 567 | |
9f85bca7 | 568 | @emph{PDP-11 Options} |
9a94f7f3 | 569 | @gccoptlist{-mfpu -msoft-float -mac0 -mno-ac0 -m40 -m45 -m10 @gol |
9f85bca7 JM |
570 | -mbcopy -mbcopy-builtin -mint32 -mno-int16 @gol |
571 | -mint16 -mno-int32 -mfloat32 -mno-float64 @gol | |
572 | -mfloat64 -mno-float32 -mabshi -mno-abshi @gol | |
573 | -mbranch-expensive -mbranch-cheap @gol | |
574 | -msplit -mno-split -munix-asm -mdec-asm} | |
575 | ||
39bc1876 NS |
576 | @emph{PowerPC Options} |
577 | See RS/6000 and PowerPC Options. | |
578 | ||
579 | @emph{RS/6000 and PowerPC Options} | |
580 | @gccoptlist{-mcpu=@var{cpu-type} @gol | |
581 | -mtune=@var{cpu-type} @gol | |
582 | -mpower -mno-power -mpower2 -mno-power2 @gol | |
583 | -mpowerpc -mpowerpc64 -mno-powerpc @gol | |
584 | -maltivec -mno-altivec @gol | |
585 | -mpowerpc-gpopt -mno-powerpc-gpopt @gol | |
586 | -mpowerpc-gfxopt -mno-powerpc-gfxopt @gol | |
587 | -mnew-mnemonics -mold-mnemonics @gol | |
588 | -mfull-toc -mminimal-toc -mno-fp-in-toc -mno-sum-in-toc @gol | |
589 | -m64 -m32 -mxl-call -mno-xl-call -mpe @gol | |
590 | -malign-power -malign-natural @gol | |
591 | -msoft-float -mhard-float -mmultiple -mno-multiple @gol | |
592 | -mstring -mno-string -mupdate -mno-update @gol | |
593 | -mfused-madd -mno-fused-madd -mbit-align -mno-bit-align @gol | |
594 | -mstrict-align -mno-strict-align -mrelocatable @gol | |
595 | -mno-relocatable -mrelocatable-lib -mno-relocatable-lib @gol | |
596 | -mtoc -mno-toc -mlittle -mlittle-endian -mbig -mbig-endian @gol | |
597 | -mdynamic-no-pic @gol | |
598 | -mprioritize-restricted-insns=@var{priority} @gol | |
599 | -msched-costly-dep=@var{dependence_type} @gol | |
600 | -minsert-sched-nops=@var{scheme} @gol | |
601 | -mcall-sysv -mcall-netbsd @gol | |
602 | -maix-struct-return -msvr4-struct-return @gol | |
603 | -mabi=altivec -mabi=no-altivec @gol | |
604 | -mabi=spe -mabi=no-spe @gol | |
605 | -misel=yes -misel=no @gol | |
606 | -mspe=yes -mspe=no @gol | |
607 | -mfloat-gprs=yes -mfloat-gprs=no @gol | |
608 | -mprototype -mno-prototype @gol | |
609 | -msim -mmvme -mads -myellowknife -memb -msdata @gol | |
610 | -msdata=@var{opt} -mvxworks -mwindiss -G @var{num} -pthread} | |
611 | ||
612 | @emph{S/390 and zSeries Options} | |
613 | @gccoptlist{-mtune=@var{cpu-type} -march=@var{cpu-type} @gol | |
614 | -mhard-float -msoft-float -mbackchain -mno-backchain @gol | |
615 | -msmall-exec -mno-small-exec -mmvcle -mno-mvcle @gol | |
616 | -m64 -m31 -mdebug -mno-debug -mesa -mzarch @gol | |
617 | -mtpf-trace -mno-tpf-trace -mfused-madd -mno-fused-madd} | |
618 | ||
619 | @emph{SH Options} | |
620 | @gccoptlist{-m1 -m2 -m2e -m3 -m3e @gol | |
621 | -m4-nofpu -m4-single-only -m4-single -m4 @gol | |
622 | -m5-64media -m5-64media-nofpu @gol | |
623 | -m5-32media -m5-32media-nofpu @gol | |
624 | -m5-compact -m5-compact-nofpu @gol | |
625 | -mb -ml -mdalign -mrelax @gol | |
626 | -mbigtable -mfmovd -mhitachi -mnomacsave @gol | |
627 | -mieee -misize -mpadstruct -mspace @gol | |
628 | -mprefergot -musermode} | |
629 | ||
630 | @emph{SPARC Options} | |
631 | @gccoptlist{-mcpu=@var{cpu-type} @gol | |
632 | -mtune=@var{cpu-type} @gol | |
633 | -mcmodel=@var{code-model} @gol | |
634 | -m32 -m64 -mapp-regs -mno-app-regs @gol | |
635 | -mfaster-structs -mno-faster-structs @gol | |
636 | -mfpu -mno-fpu -mhard-float -msoft-float @gol | |
637 | -mhard-quad-float -msoft-quad-float @gol | |
638 | -mimpure-text -mno-impure-text -mlittle-endian @gol | |
639 | -mstack-bias -mno-stack-bias @gol | |
640 | -munaligned-doubles -mno-unaligned-doubles @gol | |
641 | -mv8plus -mno-v8plus -mvis -mno-vis} | |
642 | ||
643 | @emph{System V Options} | |
644 | @gccoptlist{-Qy -Qn -YP,@var{paths} -Ym,@var{dir}} | |
645 | ||
646 | @emph{TMS320C3x/C4x Options} | |
647 | @gccoptlist{-mcpu=@var{cpu} -mbig -msmall -mregparm -mmemparm @gol | |
648 | -mfast-fix -mmpyi -mbk -mti -mdp-isr-reload @gol | |
649 | -mrpts=@var{count} -mrptb -mdb -mloop-unsigned @gol | |
650 | -mparallel-insns -mparallel-mpy -mpreserve-float} | |
651 | ||
652 | @emph{V850 Options} | |
653 | @gccoptlist{-mlong-calls -mno-long-calls -mep -mno-ep @gol | |
654 | -mprolog-function -mno-prolog-function -mspace @gol | |
655 | -mtda=@var{n} -msda=@var{n} -mzda=@var{n} @gol | |
656 | -mapp-regs -mno-app-regs @gol | |
657 | -mdisable-callt -mno-disable-callt @gol | |
658 | -mv850e1 @gol | |
659 | -mv850e @gol | |
660 | -mv850 -mbig-switch} | |
661 | ||
662 | @emph{VAX Options} | |
663 | @gccoptlist{-mg -mgnu -munix} | |
664 | ||
665 | @emph{x86-64 Options} | |
666 | See i386 and x86-64 Options. | |
667 | ||
69a0611f | 668 | @emph{Xstormy16 Options} |
9a94f7f3 | 669 | @gccoptlist{-msim} |
69a0611f | 670 | |
03984308 | 671 | @emph{Xtensa Options} |
6cedbe44 | 672 | @gccoptlist{-mconst16 -mno-const16 @gol |
9a94f7f3 | 673 | -mfused-madd -mno-fused-madd @gol |
9a94f7f3 JM |
674 | -mtext-section-literals -mno-text-section-literals @gol |
675 | -mtarget-align -mno-target-align @gol | |
676 | -mlongcalls -mno-longcalls} | |
03984308 | 677 | |
39bc1876 NS |
678 | @emph{zSeries Options} |
679 | See S/390 and zSeries Options. | |
70899148 | 680 | |
74291a4b MM |
681 | @item Code Generation Options |
682 | @xref{Code Gen Options,,Options for Code Generation Conventions}. | |
9a94f7f3 JM |
683 | @gccoptlist{-fcall-saved-@var{reg} -fcall-used-@var{reg} @gol |
684 | -ffixed-@var{reg} -fexceptions @gol | |
5d22c1a5 | 685 | -fnon-call-exceptions -funwind-tables @gol |
a944ceb9 | 686 | -fasynchronous-unwind-tables @gol |
4bc1997b | 687 | -finhibit-size-directive -finstrument-functions @gol |
dc170a87 | 688 | -fno-common -fno-ident @gol |
24a4dd31 | 689 | -fpcc-struct-return -fpic -fPIC -fpie -fPIE @gol |
4bc1997b | 690 | -freg-struct-return -fshared-data -fshort-enums @gol |
271bd540 | 691 | -fshort-double -fshort-wchar @gol |
4bc1997b JM |
692 | -fverbose-asm -fpack-struct -fstack-check @gol |
693 | -fstack-limit-register=@var{reg} -fstack-limit-symbol=@var{sym} @gol | |
694 | -fargument-alias -fargument-noalias @gol | |
478c9e72 | 695 | -fargument-noalias-global -fleading-underscore @gol |
d4463dfc | 696 | -ftls-model=@var{model} @gol |
4fa26a60 | 697 | -ftrapv -fwrapv -fbounds-check} |
74291a4b MM |
698 | @end table |
699 | ||
700 | @menu | |
701 | * Overall Options:: Controlling the kind of output: | |
702 | an executable, object files, assembler files, | |
703 | or preprocessed source. | |
704 | * C Dialect Options:: Controlling the variant of C language compiled. | |
705 | * C++ Dialect Options:: Variations on C++. | |
60de6385 | 706 | * Objective-C Dialect Options:: Variations on Objective-C. |
764dbbf2 | 707 | * Language Independent Options:: Controlling how diagnostics should be |
02f52e19 | 708 | formatted. |
74291a4b MM |
709 | * Warning Options:: How picky should the compiler be? |
710 | * Debugging Options:: Symbol tables, measurements, and debugging dumps. | |
711 | * Optimize Options:: How much optimization? | |
712 | * Preprocessor Options:: Controlling header files and macro definitions. | |
713 | Also, getting dependency information for Make. | |
714 | * Assembler Options:: Passing options to the assembler. | |
715 | * Link Options:: Specifying libraries and so on. | |
716 | * Directory Options:: Where to find header files and libraries. | |
717 | Where to find the compiler executable files. | |
a743d340 | 718 | * Spec Files:: How to pass switches to sub-processes. |
0c2d1a2a | 719 | * Target Options:: Running a cross-compiler, or an old version of GCC. |
74291a4b MM |
720 | @end menu |
721 | ||
722 | @node Overall Options | |
723 | @section Options Controlling the Kind of Output | |
724 | ||
725 | Compilation can involve up to four stages: preprocessing, compilation | |
d1bd0ded GK |
726 | proper, assembly and linking, always in that order. GCC is capable of |
727 | preprocessing and compiling several files either into several | |
728 | assembler input files, or into one assembler input file; then each | |
729 | assembler input file produces an object file, and linking combines all | |
730 | the object files (those newly compiled, and those specified as input) | |
731 | into an executable file. | |
74291a4b MM |
732 | |
733 | @cindex file name suffix | |
734 | For any given input file, the file name suffix determines what kind of | |
735 | compilation is done: | |
736 | ||
2642624b | 737 | @table @gcctabopt |
74291a4b MM |
738 | @item @var{file}.c |
739 | C source code which must be preprocessed. | |
740 | ||
741 | @item @var{file}.i | |
742 | C source code which should not be preprocessed. | |
743 | ||
744 | @item @var{file}.ii | |
745 | C++ source code which should not be preprocessed. | |
746 | ||
747 | @item @var{file}.m | |
748 | Objective-C source code. Note that you must link with the library | |
749 | @file{libobjc.a} to make an Objective-C program work. | |
750 | ||
b9265ec1 JM |
751 | @item @var{file}.mi |
752 | Objective-C source code which should not be preprocessed. | |
753 | ||
74291a4b | 754 | @item @var{file}.h |
17211ab5 | 755 | C or C++ header file to be turned into a precompiled header. |
74291a4b MM |
756 | |
757 | @item @var{file}.cc | |
b9265ec1 | 758 | @itemx @var{file}.cp |
74291a4b MM |
759 | @itemx @var{file}.cxx |
760 | @itemx @var{file}.cpp | |
ee8acf89 | 761 | @itemx @var{file}.CPP |
b9265ec1 | 762 | @itemx @var{file}.c++ |
74291a4b MM |
763 | @itemx @var{file}.C |
764 | C++ source code which must be preprocessed. Note that in @samp{.cxx}, | |
765 | the last two letters must both be literally @samp{x}. Likewise, | |
161d7b59 | 766 | @samp{.C} refers to a literal capital C@. |
74291a4b | 767 | |
17211ab5 GK |
768 | @item @var{file}.hh |
769 | @itemx @var{file}.H | |
770 | C++ header file to be turned into a precompiled header. | |
771 | ||
b9265ec1 JM |
772 | @item @var{file}.f |
773 | @itemx @var{file}.for | |
774 | @itemx @var{file}.FOR | |
775 | Fortran source code which should not be preprocessed. | |
776 | ||
777 | @item @var{file}.F | |
778 | @itemx @var{file}.fpp | |
779 | @itemx @var{file}.FPP | |
780 | Fortran source code which must be preprocessed (with the traditional | |
781 | preprocessor). | |
782 | ||
783 | @item @var{file}.r | |
784 | Fortran source code which must be preprocessed with a RATFOR | |
161d7b59 | 785 | preprocessor (not included with GCC)@. |
b9265ec1 | 786 | |
6de9cd9a DN |
787 | @item @var{file}.f90 |
788 | @itemx @var{file}.f95 | |
789 | Fortran 90/95 source code which should not be preprocessed. | |
790 | ||
b9265ec1 JM |
791 | @c FIXME: Descriptions of Java file types. |
792 | @c @var{file}.java | |
793 | @c @var{file}.class | |
794 | @c @var{file}.zip | |
795 | @c @var{file}.jar | |
796 | ||
e23381df GB |
797 | @item @var{file}.ads |
798 | Ada source code file which contains a library unit declaration (a | |
799 | declaration of a package, subprogram, or generic, or a generic | |
800 | instantiation), or a library unit renaming declaration (a package, | |
801 | generic, or subprogram renaming declaration). Such files are also | |
802 | called @dfn{specs}. | |
803 | ||
804 | @itemx @var{file}.adb | |
805 | Ada source code file containing a library unit body (a subprogram or | |
806 | package body). Such files are also called @dfn{bodies}. | |
807 | ||
b9265ec1 | 808 | @c GCC also knows about some suffixes for languages not yet included: |
b9265ec1 JM |
809 | @c Pascal: |
810 | @c @var{file}.p | |
811 | @c @var{file}.pas | |
812 | ||
74291a4b MM |
813 | @item @var{file}.s |
814 | Assembler code. | |
815 | ||
816 | @item @var{file}.S | |
817 | Assembler code which must be preprocessed. | |
818 | ||
819 | @item @var{other} | |
820 | An object file to be fed straight into linking. | |
821 | Any file name with no recognized suffix is treated this way. | |
822 | @end table | |
823 | ||
cd3bb277 | 824 | @opindex x |
630d3d5a | 825 | You can specify the input language explicitly with the @option{-x} option: |
74291a4b | 826 | |
2642624b | 827 | @table @gcctabopt |
74291a4b MM |
828 | @item -x @var{language} |
829 | Specify explicitly the @var{language} for the following input files | |
830 | (rather than letting the compiler choose a default based on the file | |
831 | name suffix). This option applies to all following input files until | |
630d3d5a | 832 | the next @option{-x} option. Possible values for @var{language} are: |
3ab51846 | 833 | @smallexample |
b9265ec1 | 834 | c c-header cpp-output |
17211ab5 | 835 | c++ c++-header c++-cpp-output |
f4ddb75b | 836 | objective-c objective-c-header objc-cpp-output |
74291a4b | 837 | assembler assembler-with-cpp |
e23381df | 838 | ada |
b9265ec1 | 839 | f77 f77-cpp-input ratfor |
6de9cd9a | 840 | f95 |
e23381df | 841 | java |
b38b97c4 | 842 | treelang |
3ab51846 | 843 | @end smallexample |
74291a4b MM |
844 | |
845 | @item -x none | |
846 | Turn off any specification of a language, so that subsequent files are | |
630d3d5a | 847 | handled according to their file name suffixes (as they are if @option{-x} |
74291a4b | 848 | has not been used at all). |
14a774a9 RK |
849 | |
850 | @item -pass-exit-codes | |
cd3bb277 | 851 | @opindex pass-exit-codes |
bedc7537 | 852 | Normally the @command{gcc} program will exit with the code of 1 if any |
14a774a9 | 853 | phase of the compiler returns a non-success return code. If you specify |
630d3d5a | 854 | @option{-pass-exit-codes}, the @command{gcc} program will instead return with |
14a774a9 RK |
855 | numerically highest error produced by any phase that returned an error |
856 | indication. | |
74291a4b MM |
857 | @end table |
858 | ||
859 | If you only want some of the stages of compilation, you can use | |
630d3d5a JM |
860 | @option{-x} (or filename suffixes) to tell @command{gcc} where to start, and |
861 | one of the options @option{-c}, @option{-S}, or @option{-E} to say where | |
bedc7537 NC |
862 | @command{gcc} is to stop. Note that some combinations (for example, |
863 | @samp{-x cpp-output -E}) instruct @command{gcc} to do nothing at all. | |
74291a4b | 864 | |
2642624b | 865 | @table @gcctabopt |
74291a4b | 866 | @item -c |
cd3bb277 | 867 | @opindex c |
74291a4b MM |
868 | Compile or assemble the source files, but do not link. The linking |
869 | stage simply is not done. The ultimate output is in the form of an | |
870 | object file for each source file. | |
871 | ||
872 | By default, the object file name for a source file is made by replacing | |
873 | the suffix @samp{.c}, @samp{.i}, @samp{.s}, etc., with @samp{.o}. | |
874 | ||
875 | Unrecognized input files, not requiring compilation or assembly, are | |
876 | ignored. | |
877 | ||
878 | @item -S | |
cd3bb277 | 879 | @opindex S |
74291a4b MM |
880 | Stop after the stage of compilation proper; do not assemble. The output |
881 | is in the form of an assembler code file for each non-assembler input | |
882 | file specified. | |
883 | ||
884 | By default, the assembler file name for a source file is made by | |
885 | replacing the suffix @samp{.c}, @samp{.i}, etc., with @samp{.s}. | |
886 | ||
887 | Input files that don't require compilation are ignored. | |
888 | ||
889 | @item -E | |
cd3bb277 | 890 | @opindex E |
74291a4b MM |
891 | Stop after the preprocessing stage; do not run the compiler proper. The |
892 | output is in the form of preprocessed source code, which is sent to the | |
893 | standard output. | |
894 | ||
895 | Input files which don't require preprocessing are ignored. | |
896 | ||
897 | @cindex output file option | |
898 | @item -o @var{file} | |
cd3bb277 | 899 | @opindex o |
74291a4b MM |
900 | Place output in file @var{file}. This applies regardless to whatever |
901 | sort of output is being produced, whether it be an executable file, | |
902 | an object file, an assembler file or preprocessed C code. | |
903 | ||
488061c8 GK |
904 | If @option{-o} is not specified, the default is to put an executable |
905 | file in @file{a.out}, the object file for | |
906 | @file{@var{source}.@var{suffix}} in @file{@var{source}.o}, its | |
907 | assembler file in @file{@var{source}.s}, a precompiled header file in | |
908 | @file{@var{source}.@var{suffix}.gch}, and all preprocessed C source on | |
909 | standard output. | |
74291a4b MM |
910 | |
911 | @item -v | |
cd3bb277 | 912 | @opindex v |
74291a4b MM |
913 | Print (on standard error output) the commands executed to run the stages |
914 | of compilation. Also print the version number of the compiler driver | |
915 | program and of the preprocessor and the compiler proper. | |
916 | ||
e8b3c8ac IR |
917 | @item -### |
918 | @opindex ### | |
919 | Like @option{-v} except the commands are not executed and all command | |
920 | arguments are quoted. This is useful for shell scripts to capture the | |
921 | driver-generated command lines. | |
922 | ||
74291a4b | 923 | @item -pipe |
cd3bb277 | 924 | @opindex pipe |
74291a4b MM |
925 | Use pipes rather than temporary files for communication between the |
926 | various stages of compilation. This fails to work on some systems where | |
927 | the assembler is unable to read from a pipe; but the GNU assembler has | |
928 | no trouble. | |
844642e6 | 929 | |
0855eab7 CT |
930 | @item -combine |
931 | @opindex combine | |
932 | If you are compiling multiple source files, this option tells the driver | |
f26c1794 | 933 | to pass all the source files to the compiler at once (for those |
0855eab7 CT |
934 | languages for which the compiler can handle this). This will allow |
935 | intermodule analysis (IMA) to be performed by the compiler. Currently the only | |
936 | language for which this is supported is C. If you pass source files for | |
937 | multiple languages to the driver, using this option, the driver will invoke | |
938 | the compiler(s) that support IMA once each, passing each compiler all the | |
939 | source files appropriate for it. For those languages that do not support | |
940 | IMA this option will be ignored, and the compiler will be invoked once for | |
941 | each source file in that language. If you use this option in conjunction | |
942 | with -save-temps, the compiler will generate multiple pre-processed files | |
f26c1794 | 943 | (one for each source file), but only one (combined) .o or .s file. |
0855eab7 | 944 | |
844642e6 | 945 | @item --help |
cd3bb277 | 946 | @opindex help |
844642e6 | 947 | Print (on the standard output) a description of the command line options |
bedc7537 NC |
948 | understood by @command{gcc}. If the @option{-v} option is also specified |
949 | then @option{--help} will also be passed on to the various processes | |
950 | invoked by @command{gcc}, so that they can display the command line options | |
65ca2d60 | 951 | they accept. If the @option{-Wextra} option is also specified then command |
844642e6 NC |
952 | line options which have no documentation associated with them will also |
953 | be displayed. | |
10501d8f CC |
954 | |
955 | @item --target-help | |
cd3bb277 | 956 | @opindex target-help |
10501d8f CC |
957 | Print (on the standard output) a description of target specific command |
958 | line options for each tool. | |
e03b7153 RS |
959 | |
960 | @item --version | |
961 | @opindex version | |
962 | Display the version number and copyrights of the invoked GCC. | |
74291a4b MM |
963 | @end table |
964 | ||
965 | @node Invoking G++ | |
966 | @section Compiling C++ Programs | |
967 | ||
968 | @cindex suffixes for C++ source | |
969 | @cindex C++ source file suffixes | |
970 | C++ source files conventionally use one of the suffixes @samp{.C}, | |
17211ab5 GK |
971 | @samp{.cc}, @samp{.cpp}, @samp{.CPP}, @samp{.c++}, @samp{.cp}, or |
972 | @samp{.cxx}; C++ header files often use @samp{.hh} or @samp{.H}; and | |
0c2d1a2a | 973 | preprocessed C++ files use the suffix @samp{.ii}. GCC recognizes |
bba975d4 | 974 | files with these names and compiles them as C++ programs even if you |
17211ab5 GK |
975 | call the compiler the same way as for compiling C programs (usually |
976 | with the name @command{gcc}). | |
74291a4b MM |
977 | |
978 | @findex g++ | |
979 | @findex c++ | |
980 | However, C++ programs often require class libraries as well as a | |
981 | compiler that understands the C++ language---and under some | |
17211ab5 GK |
982 | circumstances, you might want to compile programs or header files from |
983 | standard input, or otherwise without a suffix that flags them as C++ | |
984 | programs. You might also like to precompile a C header file with a | |
985 | @samp{.h} extension to be used in C++ compilations. @command{g++} is a | |
986 | program that calls GCC with the default language set to C++, and | |
987 | automatically specifies linking against the C++ library. On many | |
988 | systems, @command{g++} is also installed with the name @command{c++}. | |
74291a4b | 989 | |
bedc7537 | 990 | @cindex invoking @command{g++} |
74291a4b MM |
991 | When you compile C++ programs, you may specify many of the same |
992 | command-line options that you use for compiling programs in any | |
993 | language; or command-line options meaningful for C and related | |
994 | languages; or options that are meaningful only for C++ programs. | |
995 | @xref{C Dialect Options,,Options Controlling C Dialect}, for | |
161d7b59 | 996 | explanations of options for languages related to C@. |
74291a4b MM |
997 | @xref{C++ Dialect Options,,Options Controlling C++ Dialect}, for |
998 | explanations of options that are meaningful only for C++ programs. | |
999 | ||
1000 | @node C Dialect Options | |
1001 | @section Options Controlling C Dialect | |
1002 | @cindex dialect options | |
1003 | @cindex language dialect options | |
1004 | @cindex options, dialect | |
1005 | ||
1006 | The following options control the dialect of C (or languages derived | |
2147b154 | 1007 | from C, such as C++ and Objective-C) that the compiler accepts: |
74291a4b | 1008 | |
2642624b | 1009 | @table @gcctabopt |
74291a4b | 1010 | @cindex ANSI support |
c1030c7c | 1011 | @cindex ISO support |
74291a4b | 1012 | @item -ansi |
cd3bb277 | 1013 | @opindex ansi |
3764f879 | 1014 | In C mode, support all ISO C90 programs. In C++ mode, |
775afb25 | 1015 | remove GNU extensions that conflict with ISO C++. |
74291a4b | 1016 | |
c1030c7c | 1017 | This turns off certain features of GCC that are incompatible with ISO |
3764f879 | 1018 | C90 (when compiling C code), or of standard C++ (when compiling C++ code), |
0c2d1a2a | 1019 | such as the @code{asm} and @code{typeof} keywords, and |
74291a4b MM |
1020 | predefined macros such as @code{unix} and @code{vax} that identify the |
1021 | type of system you are using. It also enables the undesirable and | |
02f52e19 | 1022 | rarely used ISO trigraph feature. For the C compiler, |
0c2d1a2a | 1023 | it disables recognition of C++ style @samp{//} comments as well as |
775afb25 | 1024 | the @code{inline} keyword. |
74291a4b MM |
1025 | |
1026 | The alternate keywords @code{__asm__}, @code{__extension__}, | |
1027 | @code{__inline__} and @code{__typeof__} continue to work despite | |
630d3d5a | 1028 | @option{-ansi}. You would not want to use them in an ISO C program, of |
74291a4b | 1029 | course, but it is useful to put them in header files that might be included |
630d3d5a | 1030 | in compilations done with @option{-ansi}. Alternate predefined macros |
74291a4b | 1031 | such as @code{__unix__} and @code{__vax__} are also available, with or |
630d3d5a | 1032 | without @option{-ansi}. |
74291a4b | 1033 | |
630d3d5a JM |
1034 | The @option{-ansi} option does not cause non-ISO programs to be |
1035 | rejected gratuitously. For that, @option{-pedantic} is required in | |
1036 | addition to @option{-ansi}. @xref{Warning Options}. | |
74291a4b | 1037 | |
630d3d5a | 1038 | The macro @code{__STRICT_ANSI__} is predefined when the @option{-ansi} |
74291a4b MM |
1039 | option is used. Some header files may notice this macro and refrain |
1040 | from declaring certain functions or defining certain macros that the | |
c1030c7c | 1041 | ISO standard doesn't call for; this is to avoid interfering with any |
74291a4b MM |
1042 | programs that might use these names for other things. |
1043 | ||
c771326b JM |
1044 | Functions which would normally be built in but do not have semantics |
1045 | defined by ISO C (such as @code{alloca} and @code{ffs}) are not built-in | |
630d3d5a | 1046 | functions with @option{-ansi} is used. @xref{Other Builtins,,Other |
f0523f02 | 1047 | built-in functions provided by GCC}, for details of the functions |
01702459 | 1048 | affected. |
74291a4b | 1049 | |
49419c8f | 1050 | @item -std= |
cd3bb277 | 1051 | @opindex std |
aee96fe9 | 1052 | Determine the language standard. This option is currently only |
f749a36b NB |
1053 | supported when compiling C or C++. A value for this option must be |
1054 | provided; possible values are | |
3932261a | 1055 | |
ee457005 | 1056 | @table @samp |
aee96fe9 JM |
1057 | @item c89 |
1058 | @itemx iso9899:1990 | |
3764f879 | 1059 | ISO C90 (same as @option{-ansi}). |
3043b30e ML |
1060 | |
1061 | @item iso9899:199409 | |
3764f879 | 1062 | ISO C90 as modified in amendment 1. |
3043b30e | 1063 | |
49419c8f | 1064 | @item c99 |
aee96fe9 JM |
1065 | @itemx c9x |
1066 | @itemx iso9899:1999 | |
1067 | @itemx iso9899:199x | |
1068 | ISO C99. Note that this standard is not yet fully supported; see | |
1069 | @w{@uref{http://gcc.gnu.org/c99status.html}} for more information. The | |
1070 | names @samp{c9x} and @samp{iso9899:199x} are deprecated. | |
3043b30e ML |
1071 | |
1072 | @item gnu89 | |
3764f879 | 1073 | Default, ISO C90 plus GNU extensions (including some C99 features). |
3043b30e | 1074 | |
49419c8f | 1075 | @item gnu99 |
31775d31 | 1076 | @itemx gnu9x |
d15a05b3 EC |
1077 | ISO C99 plus GNU extensions. When ISO C99 is fully implemented in GCC, |
1078 | this will become the default. The name @samp{gnu9x} is deprecated. | |
49419c8f | 1079 | |
f749a36b NB |
1080 | @item c++98 |
1081 | The 1998 ISO C++ standard plus amendments. | |
1082 | ||
1083 | @item gnu++98 | |
1084 | The same as @option{-std=c++98} plus GNU extensions. This is the | |
1085 | default for C++ code. | |
ee457005 | 1086 | @end table |
3043b30e ML |
1087 | |
1088 | Even when this option is not specified, you can still use some of the | |
1089 | features of newer standards in so far as they do not conflict with | |
1090 | previous C standards. For example, you may use @code{__restrict__} even | |
bedc7537 | 1091 | when @option{-std=c99} is not specified. |
3932261a | 1092 | |
5490d604 | 1093 | The @option{-std} options specifying some version of ISO C have the same |
3764f879 | 1094 | effects as @option{-ansi}, except that features that were not in ISO C90 |
5490d604 JM |
1095 | but are in the specified version (for example, @samp{//} comments and |
1096 | the @code{inline} keyword in ISO C99) are not disabled. | |
1097 | ||
c1030c7c JM |
1098 | @xref{Standards,,Language Standards Supported by GCC}, for details of |
1099 | these standard versions. | |
1100 | ||
b1018de6 AO |
1101 | @item -aux-info @var{filename} |
1102 | @opindex aux-info | |
1103 | Output to the given filename prototyped declarations for all functions | |
1104 | declared and/or defined in a translation unit, including those in header | |
161d7b59 | 1105 | files. This option is silently ignored in any language other than C@. |
b1018de6 AO |
1106 | |
1107 | Besides declarations, the file indicates, in comments, the origin of | |
1108 | each declaration (source file and line), whether the declaration was | |
1109 | implicit, prototyped or unprototyped (@samp{I}, @samp{N} for new or | |
1110 | @samp{O} for old, respectively, in the first character after the line | |
1111 | number and the colon), and whether it came from a declaration or a | |
1112 | definition (@samp{C} or @samp{F}, respectively, in the following | |
1113 | character). In the case of function definitions, a K&R-style list of | |
1114 | arguments followed by their declarations is also provided, inside | |
1115 | comments, after the declaration. | |
1116 | ||
74291a4b | 1117 | @item -fno-asm |
cd3bb277 | 1118 | @opindex fno-asm |
74291a4b MM |
1119 | Do not recognize @code{asm}, @code{inline} or @code{typeof} as a |
1120 | keyword, so that code can use these words as identifiers. You can use | |
1121 | the keywords @code{__asm__}, @code{__inline__} and @code{__typeof__} | |
630d3d5a | 1122 | instead. @option{-ansi} implies @option{-fno-asm}. |
74291a4b MM |
1123 | |
1124 | In C++, this switch only affects the @code{typeof} keyword, since | |
1125 | @code{asm} and @code{inline} are standard keywords. You may want to | |
630d3d5a | 1126 | use the @option{-fno-gnu-keywords} flag instead, which has the same |
5490d604 JM |
1127 | effect. In C99 mode (@option{-std=c99} or @option{-std=gnu99}), this |
1128 | switch only affects the @code{asm} and @code{typeof} keywords, since | |
1129 | @code{inline} is a standard keyword in ISO C99. | |
74291a4b MM |
1130 | |
1131 | @item -fno-builtin | |
a3926fe1 | 1132 | @itemx -fno-builtin-@var{function} |
cd3bb277 | 1133 | @opindex fno-builtin |
c771326b JM |
1134 | @cindex built-in functions |
1135 | Don't recognize built-in functions that do not begin with | |
01702459 | 1136 | @samp{__builtin_} as prefix. @xref{Other Builtins,,Other built-in |
f0523f02 | 1137 | functions provided by GCC}, for details of the functions affected, |
c771326b | 1138 | including those which are not built-in functions when @option{-ansi} or |
5490d604 JM |
1139 | @option{-std} options for strict ISO C conformance are used because they |
1140 | do not have an ISO standard meaning. | |
74291a4b | 1141 | |
c771326b | 1142 | GCC normally generates special code to handle certain built-in functions |
74291a4b MM |
1143 | more efficiently; for instance, calls to @code{alloca} may become single |
1144 | instructions that adjust the stack directly, and calls to @code{memcpy} | |
1145 | may become inline copy loops. The resulting code is often both smaller | |
1146 | and faster, but since the function calls no longer appear as such, you | |
1147 | cannot set a breakpoint on those calls, nor can you change the behavior | |
1148 | of the functions by linking with a different library. | |
1149 | ||
a3926fe1 RS |
1150 | With the @option{-fno-builtin-@var{function}} option |
1151 | only the built-in function @var{function} is | |
7d14c755 JM |
1152 | disabled. @var{function} must not begin with @samp{__builtin_}. If a |
1153 | function is named this is not built-in in this version of GCC, this | |
1154 | option is ignored. There is no corresponding | |
1155 | @option{-fbuiltin-@var{function}} option; if you wish to enable | |
1156 | built-in functions selectively when using @option{-fno-builtin} or | |
1157 | @option{-ffreestanding}, you may define macros such as: | |
1158 | ||
1159 | @smallexample | |
1160 | #define abs(n) __builtin_abs ((n)) | |
1161 | #define strcpy(d, s) __builtin_strcpy ((d), (s)) | |
1162 | @end smallexample | |
1163 | ||
861bb6c1 | 1164 | @item -fhosted |
cd3bb277 | 1165 | @opindex fhosted |
861bb6c1 JL |
1166 | @cindex hosted environment |
1167 | ||
1168 | Assert that compilation takes place in a hosted environment. This implies | |
630d3d5a | 1169 | @option{-fbuiltin}. A hosted environment is one in which the |
861bb6c1 JL |
1170 | entire standard library is available, and in which @code{main} has a return |
1171 | type of @code{int}. Examples are nearly everything except a kernel. | |
630d3d5a | 1172 | This is equivalent to @option{-fno-freestanding}. |
861bb6c1 JL |
1173 | |
1174 | @item -ffreestanding | |
cd3bb277 | 1175 | @opindex ffreestanding |
861bb6c1 JL |
1176 | @cindex hosted environment |
1177 | ||
1178 | Assert that compilation takes place in a freestanding environment. This | |
630d3d5a | 1179 | implies @option{-fno-builtin}. A freestanding environment |
861bb6c1 JL |
1180 | is one in which the standard library may not exist, and program startup may |
1181 | not necessarily be at @code{main}. The most obvious example is an OS kernel. | |
630d3d5a | 1182 | This is equivalent to @option{-fno-hosted}. |
861bb6c1 | 1183 | |
c1030c7c JM |
1184 | @xref{Standards,,Language Standards Supported by GCC}, for details of |
1185 | freestanding and hosted environments. | |
1186 | ||
750491fc RH |
1187 | @item -fms-extensions |
1188 | @opindex fms-extensions | |
1189 | Accept some non-standard constructs used in Microsoft header files. | |
1190 | ||
74291a4b | 1191 | @item -trigraphs |
cd3bb277 | 1192 | @opindex trigraphs |
3bce8a01 NB |
1193 | Support ISO C trigraphs. The @option{-ansi} option (and @option{-std} |
1194 | options for strict ISO C conformance) implies @option{-trigraphs}. | |
74291a4b | 1195 | |
8a035a6b AH |
1196 | @item -no-integrated-cpp |
1197 | @opindex no-integrated-cpp | |
1198 | Performs a compilation in two passes: preprocessing and compiling. This | |
1199 | option allows a user supplied "cc1", "cc1plus", or "cc1obj" via the | |
1200 | @option{-B} option. The user supplied compilation step can then add in | |
1201 | an additional preprocessing step after normal preprocessing but before | |
1202 | compiling. The default is to use the integrated cpp (internal cpp) | |
1203 | ||
1204 | The semantics of this option will change if "cc1", "cc1plus", and | |
1205 | "cc1obj" are merged. | |
1206 | ||
74291a4b MM |
1207 | @cindex traditional C language |
1208 | @cindex C language, traditional | |
1209 | @item -traditional | |
f458d1d5 | 1210 | @itemx -traditional-cpp |
cd3bb277 | 1211 | @opindex traditional-cpp |
f458d1d5 ZW |
1212 | @opindex traditional |
1213 | Formerly, these options caused GCC to attempt to emulate a pre-standard | |
1214 | C compiler. They are now only supported with the @option{-E} switch. | |
1215 | The preprocessor continues to support a pre-standard mode. See the GNU | |
1216 | CPP manual for details. | |
74291a4b MM |
1217 | |
1218 | @item -fcond-mismatch | |
cd3bb277 | 1219 | @opindex fcond-mismatch |
74291a4b | 1220 | Allow conditional expressions with mismatched types in the second and |
a7537031 JM |
1221 | third arguments. The value of such an expression is void. This option |
1222 | is not supported for C++. | |
74291a4b MM |
1223 | |
1224 | @item -funsigned-char | |
cd3bb277 | 1225 | @opindex funsigned-char |
74291a4b MM |
1226 | Let the type @code{char} be unsigned, like @code{unsigned char}. |
1227 | ||
1228 | Each kind of machine has a default for what @code{char} should | |
1229 | be. It is either like @code{unsigned char} by default or like | |
1230 | @code{signed char} by default. | |
1231 | ||
1232 | Ideally, a portable program should always use @code{signed char} or | |
1233 | @code{unsigned char} when it depends on the signedness of an object. | |
1234 | But many programs have been written to use plain @code{char} and | |
1235 | expect it to be signed, or expect it to be unsigned, depending on the | |
1236 | machines they were written for. This option, and its inverse, let you | |
1237 | make such a program work with the opposite default. | |
1238 | ||
1239 | The type @code{char} is always a distinct type from each of | |
1240 | @code{signed char} or @code{unsigned char}, even though its behavior | |
1241 | is always just like one of those two. | |
1242 | ||
1243 | @item -fsigned-char | |
cd3bb277 | 1244 | @opindex fsigned-char |
74291a4b MM |
1245 | Let the type @code{char} be signed, like @code{signed char}. |
1246 | ||
630d3d5a JM |
1247 | Note that this is equivalent to @option{-fno-unsigned-char}, which is |
1248 | the negative form of @option{-funsigned-char}. Likewise, the option | |
1249 | @option{-fno-signed-char} is equivalent to @option{-funsigned-char}. | |
74291a4b | 1250 | |
74291a4b MM |
1251 | @item -fsigned-bitfields |
1252 | @itemx -funsigned-bitfields | |
1253 | @itemx -fno-signed-bitfields | |
1254 | @itemx -fno-unsigned-bitfields | |
cd3bb277 JM |
1255 | @opindex fsigned-bitfields |
1256 | @opindex funsigned-bitfields | |
1257 | @opindex fno-signed-bitfields | |
1258 | @opindex fno-unsigned-bitfields | |
c771326b | 1259 | These options control whether a bit-field is signed or unsigned, when the |
74291a4b | 1260 | declaration does not use either @code{signed} or @code{unsigned}. By |
c771326b | 1261 | default, such a bit-field is signed, because this is consistent: the |
74291a4b | 1262 | basic integer types such as @code{int} are signed types. |
74291a4b MM |
1263 | @end table |
1264 | ||
1265 | @node C++ Dialect Options | |
1266 | @section Options Controlling C++ Dialect | |
1267 | ||
1268 | @cindex compiler options, C++ | |
1269 | @cindex C++ options, command line | |
1270 | @cindex options, C++ | |
1271 | This section describes the command-line options that are only meaningful | |
1272 | for C++ programs; but you can also use most of the GNU compiler options | |
1273 | regardless of what language your program is in. For example, you | |
1274 | might compile a file @code{firstClass.C} like this: | |
1275 | ||
3ab51846 | 1276 | @smallexample |
1dc5fc4b | 1277 | g++ -g -frepo -O -c firstClass.C |
3ab51846 | 1278 | @end smallexample |
74291a4b MM |
1279 | |
1280 | @noindent | |
630d3d5a | 1281 | In this example, only @option{-frepo} is an option meant |
74291a4b | 1282 | only for C++ programs; you can use the other options with any |
161d7b59 | 1283 | language supported by GCC@. |
74291a4b MM |
1284 | |
1285 | Here is a list of options that are @emph{only} for compiling C++ programs: | |
1286 | ||
2642624b | 1287 | @table @gcctabopt |
2d3e278d MM |
1288 | |
1289 | @item -fabi-version=@var{n} | |
1290 | @opindex fabi-version | |
57702a80 MM |
1291 | Use version @var{n} of the C++ ABI. Version 2 is the version of the |
1292 | C++ ABI that first appeared in G++ 3.4. Version 1 is the version of | |
1293 | the C++ ABI that first appeared in G++ 3.2. Version 0 will always be | |
1294 | the version that conforms most closely to the C++ ABI specification. | |
1295 | Therefore, the ABI obtained using version 0 will change as ABI bugs | |
1296 | are fixed. | |
2d3e278d | 1297 | |
d150ccef | 1298 | The default is version 2. |
46c83bce | 1299 | |
74291a4b | 1300 | @item -fno-access-control |
cd3bb277 | 1301 | @opindex fno-access-control |
74291a4b MM |
1302 | Turn off all access checking. This switch is mainly useful for working |
1303 | around bugs in the access control code. | |
1304 | ||
74291a4b | 1305 | @item -fcheck-new |
cd3bb277 | 1306 | @opindex fcheck-new |
74291a4b | 1307 | Check that the pointer returned by @code{operator new} is non-null |
6d9c4c83 JW |
1308 | before attempting to modify the storage allocated. This check is |
1309 | normally unnecessary because the C++ standard specifies that | |
1310 | @code{operator new} will only return @code{0} if it is declared | |
1311 | @samp{throw()}, in which case the compiler will always check the | |
1312 | return value even without this option. In all other cases, when | |
1313 | @code{operator new} has a non-empty exception specification, memory | |
1314 | exhaustion is signalled by throwing @code{std::bad_alloc}. See also | |
1315 | @samp{new (nothrow)}. | |
1dc5fc4b | 1316 | |
74291a4b | 1317 | @item -fconserve-space |
cd3bb277 | 1318 | @opindex fconserve-space |
74291a4b MM |
1319 | Put uninitialized or runtime-initialized global variables into the |
1320 | common segment, as C does. This saves space in the executable at the | |
1321 | cost of not diagnosing duplicate definitions. If you compile with this | |
1322 | flag and your program mysteriously crashes after @code{main()} has | |
1323 | completed, you may have an object that is being destroyed twice because | |
1324 | two definitions were merged. | |
1325 | ||
1dc5fc4b JM |
1326 | This option is no longer useful on most targets, now that support has |
1327 | been added for putting variables into BSS without making them common. | |
1328 | ||
02f52e19 | 1329 | @item -fno-const-strings |
cd3bb277 | 1330 | @opindex fno-const-strings |
fcca588c MM |
1331 | Give string constants type @code{char *} instead of type @code{const |
1332 | char *}. By default, G++ uses type @code{const char *} as required by | |
630d3d5a | 1333 | the standard. Even if you use @option{-fno-const-strings}, you cannot |
3521b33c | 1334 | actually modify the value of a string constant. |
fcca588c MM |
1335 | |
1336 | This option might be removed in a future release of G++. For maximum | |
1337 | portability, you should structure your code so that it works with | |
1338 | string constants that have type @code{const char *}. | |
1339 | ||
1dc5fc4b | 1340 | @item -fno-elide-constructors |
cd3bb277 | 1341 | @opindex fno-elide-constructors |
1dc5fc4b JM |
1342 | The C++ standard allows an implementation to omit creating a temporary |
1343 | which is only used to initialize another object of the same type. | |
aee96fe9 | 1344 | Specifying this option disables that optimization, and forces G++ to |
1dc5fc4b | 1345 | call the copy constructor in all cases. |
74291a4b | 1346 | |
dd1ba632 | 1347 | @item -fno-enforce-eh-specs |
cd3bb277 | 1348 | @opindex fno-enforce-eh-specs |
dd1ba632 JM |
1349 | Don't check for violation of exception specifications at runtime. This |
1350 | option violates the C++ standard, but may be useful for reducing code | |
1351 | size in production builds, much like defining @samp{NDEBUG}. The compiler | |
1352 | will still optimize based on the exception specifications. | |
1353 | ||
74291a4b | 1354 | @item -ffor-scope |
8c81598d | 1355 | @itemx -fno-for-scope |
cd3bb277 JM |
1356 | @opindex ffor-scope |
1357 | @opindex fno-for-scope | |
695ac33f | 1358 | If @option{-ffor-scope} is specified, the scope of variables declared in |
74291a4b | 1359 | a @i{for-init-statement} is limited to the @samp{for} loop itself, |
34527c47 | 1360 | as specified by the C++ standard. |
695ac33f | 1361 | If @option{-fno-for-scope} is specified, the scope of variables declared in |
74291a4b | 1362 | a @i{for-init-statement} extends to the end of the enclosing scope, |
aee96fe9 | 1363 | as was the case in old versions of G++, and other (traditional) |
74291a4b MM |
1364 | implementations of C++. |
1365 | ||
1366 | The default if neither flag is given to follow the standard, | |
1367 | but to allow and give a warning for old-style code that would | |
1368 | otherwise be invalid, or have different behavior. | |
1369 | ||
1370 | @item -fno-gnu-keywords | |
cd3bb277 | 1371 | @opindex fno-gnu-keywords |
9762e8a4 | 1372 | Do not recognize @code{typeof} as a keyword, so that code can use this |
767094dd | 1373 | word as an identifier. You can use the keyword @code{__typeof__} instead. |
630d3d5a | 1374 | @option{-ansi} implies @option{-fno-gnu-keywords}. |
74291a4b | 1375 | |
1dc5fc4b | 1376 | @item -fno-implicit-templates |
cd3bb277 | 1377 | @opindex fno-implicit-templates |
bba975d4 | 1378 | Never emit code for non-inline templates which are instantiated |
e979f9e8 | 1379 | implicitly (i.e.@: by use); only emit code for explicit instantiations. |
bba975d4 JM |
1380 | @xref{Template Instantiation}, for more information. |
1381 | ||
1382 | @item -fno-implicit-inline-templates | |
cd3bb277 | 1383 | @opindex fno-implicit-inline-templates |
bba975d4 JM |
1384 | Don't emit code for implicit instantiations of inline templates, either. |
1385 | The default is to handle inlines differently so that compiles with and | |
1386 | without optimization will need the same set of explicit instantiations. | |
1dc5fc4b | 1387 | |
74291a4b | 1388 | @item -fno-implement-inlines |
cd3bb277 | 1389 | @opindex fno-implement-inlines |
74291a4b MM |
1390 | To save space, do not emit out-of-line copies of inline functions |
1391 | controlled by @samp{#pragma implementation}. This will cause linker | |
1392 | errors if these functions are not inlined everywhere they are called. | |
1393 | ||
631cf95d | 1394 | @item -fms-extensions |
cd3bb277 | 1395 | @opindex fms-extensions |
32fb1fb2 PE |
1396 | Disable pedantic warnings about constructs used in MFC, such as implicit |
1397 | int and getting a pointer to member function via non-standard syntax. | |
631cf95d | 1398 | |
fcca588c | 1399 | @item -fno-nonansi-builtins |
cd3bb277 | 1400 | @opindex fno-nonansi-builtins |
c771326b | 1401 | Disable built-in declarations of functions that are not mandated by |
161d7b59 | 1402 | ANSI/ISO C@. These include @code{ffs}, @code{alloca}, @code{_exit}, |
fcca588c MM |
1403 | @code{index}, @code{bzero}, @code{conjf}, and other related functions. |
1404 | ||
775afb25 | 1405 | @item -fno-operator-names |
cd3bb277 | 1406 | @opindex fno-operator-names |
775afb25 | 1407 | Do not treat the operator name keywords @code{and}, @code{bitand}, |
74291a4b | 1408 | @code{bitor}, @code{compl}, @code{not}, @code{or} and @code{xor} as |
775afb25 | 1409 | synonyms as keywords. |
74291a4b | 1410 | |
4f8b4fd9 | 1411 | @item -fno-optional-diags |
cd3bb277 | 1412 | @opindex fno-optional-diags |
4f8b4fd9 | 1413 | Disable diagnostics that the standard says a compiler does not need to |
aee96fe9 | 1414 | issue. Currently, the only such diagnostic issued by G++ is the one for |
bba975d4 | 1415 | a name having multiple meanings within a class. |
4f8b4fd9 | 1416 | |
8c7707b0 | 1417 | @item -fpermissive |
cd3bb277 | 1418 | @opindex fpermissive |
4a386498 MM |
1419 | Downgrade some diagnostics about nonconformant code from errors to |
1420 | warnings. Thus, using @option{-fpermissive} will allow some | |
1421 | nonconforming code to compile. | |
8c7707b0 | 1422 | |
8c81598d | 1423 | @item -frepo |
cd3bb277 | 1424 | @opindex frepo |
9c34dbbf ZW |
1425 | Enable automatic template instantiation at link time. This option also |
1426 | implies @option{-fno-implicit-templates}. @xref{Template | |
1427 | Instantiation}, for more information. | |
8c81598d | 1428 | |
8c7707b0 | 1429 | @item -fno-rtti |
cd3bb277 | 1430 | @opindex fno-rtti |
a7fbfcf9 JM |
1431 | Disable generation of information about every class with virtual |
1432 | functions for use by the C++ runtime type identification features | |
1433 | (@samp{dynamic_cast} and @samp{typeid}). If you don't use those parts | |
1434 | of the language, you can save some space by using this flag. Note that | |
1435 | exception handling uses the same information, but it will generate it as | |
1436 | needed. | |
8c7707b0 | 1437 | |
fcca588c | 1438 | @item -fstats |
cd3bb277 | 1439 | @opindex fstats |
fcca588c MM |
1440 | Emit statistics about front-end processing at the end of the compilation. |
1441 | This information is generally only useful to the G++ development team. | |
1442 | ||
1dc5fc4b | 1443 | @item -ftemplate-depth-@var{n} |
cd3bb277 | 1444 | @opindex ftemplate-depth |
1dc5fc4b JM |
1445 | Set the maximum instantiation depth for template classes to @var{n}. |
1446 | A limit on the template instantiation depth is needed to detect | |
767094dd | 1447 | endless recursions during template class instantiation. ANSI/ISO C++ |
1dc5fc4b JM |
1448 | conforming programs must not rely on a maximum depth greater than 17. |
1449 | ||
fc693822 | 1450 | @item -fuse-cxa-atexit |
cd3bb277 | 1451 | @opindex fuse-cxa-atexit |
fc693822 MM |
1452 | Register destructors for objects with static storage duration with the |
1453 | @code{__cxa_atexit} function rather than the @code{atexit} function. | |
1454 | This option is required for fully standards-compliant handling of static | |
1455 | destructors, but will only work if your C library supports | |
1456 | @code{__cxa_atexit}. | |
1457 | ||
02f52e19 | 1458 | @item -fno-weak |
cd3bb277 | 1459 | @opindex fno-weak |
90ecce3e | 1460 | Do not use weak symbol support, even if it is provided by the linker. |
fcca588c MM |
1461 | By default, G++ will use weak symbols if they are available. This |
1462 | option exists only for testing, and should not be used by end-users; | |
1463 | it will result in inferior code and has no benefits. This option may | |
1464 | be removed in a future release of G++. | |
1465 | ||
74291a4b | 1466 | @item -nostdinc++ |
cd3bb277 | 1467 | @opindex nostdinc++ |
74291a4b MM |
1468 | Do not search for header files in the standard directories specific to |
1469 | C++, but do still search the other standard directories. (This option | |
e5e809f4 | 1470 | is used when building the C++ library.) |
74291a4b MM |
1471 | @end table |
1472 | ||
1473 | In addition, these optimization, warning, and code generation options | |
1474 | have meanings only for C++ programs: | |
1475 | ||
2642624b | 1476 | @table @gcctabopt |
74291a4b | 1477 | @item -fno-default-inline |
cd3bb277 | 1478 | @opindex fno-default-inline |
74291a4b | 1479 | Do not assume @samp{inline} for functions defined inside a class scope. |
1dc5fc4b JM |
1480 | @xref{Optimize Options,,Options That Control Optimization}. Note that these |
1481 | functions will have linkage like inline functions; they just won't be | |
1482 | inlined by default. | |
74291a4b | 1483 | |
eca7f13c MM |
1484 | @item -Wabi @r{(C++ only)} |
1485 | @opindex Wabi | |
1486 | Warn when G++ generates code that is probably not compatible with the | |
1487 | vendor-neutral C++ ABI. Although an effort has been made to warn about | |
daf2f129 | 1488 | all such cases, there are probably some cases that are not warned about, |
eca7f13c MM |
1489 | even though G++ is generating incompatible code. There may also be |
1490 | cases where warnings are emitted even though the code that is generated | |
1491 | will be compatible. | |
1492 | ||
1493 | You should rewrite your code to avoid these warnings if you are | |
1494 | concerned about the fact that code generated by G++ may not be binary | |
1495 | compatible with code generated by other compilers. | |
1496 | ||
3364c33b | 1497 | The known incompatibilities at this point include: |
eca7f13c MM |
1498 | |
1499 | @itemize @bullet | |
1500 | ||
1501 | @item | |
1502 | Incorrect handling of tail-padding for bit-fields. G++ may attempt to | |
1503 | pack data into the same byte as a base class. For example: | |
1504 | ||
1505 | @smallexample | |
1506 | struct A @{ virtual void f(); int f1 : 1; @}; | |
1507 | struct B : public A @{ int f2 : 1; @}; | |
1508 | @end smallexample | |
1509 | ||
1510 | @noindent | |
1511 | In this case, G++ will place @code{B::f2} into the same byte | |
daf2f129 | 1512 | as@code{A::f1}; other compilers will not. You can avoid this problem |
eca7f13c MM |
1513 | by explicitly padding @code{A} so that its size is a multiple of the |
1514 | byte size on your platform; that will cause G++ and other compilers to | |
1515 | layout @code{B} identically. | |
1516 | ||
1517 | @item | |
1518 | Incorrect handling of tail-padding for virtual bases. G++ does not use | |
1519 | tail padding when laying out virtual bases. For example: | |
1520 | ||
1521 | @smallexample | |
1522 | struct A @{ virtual void f(); char c1; @}; | |
1523 | struct B @{ B(); char c2; @}; | |
1524 | struct C : public A, public virtual B @{@}; | |
1525 | @end smallexample | |
1526 | ||
1527 | @noindent | |
1528 | In this case, G++ will not place @code{B} into the tail-padding for | |
1529 | @code{A}; other compilers will. You can avoid this problem by | |
1530 | explicitly padding @code{A} so that its size is a multiple of its | |
1531 | alignment (ignoring virtual base classes); that will cause G++ and other | |
1532 | compilers to layout @code{C} identically. | |
1533 | ||
2d3e278d MM |
1534 | @item |
1535 | Incorrect handling of bit-fields with declared widths greater than that | |
1536 | of their underlying types, when the bit-fields appear in a union. For | |
1537 | example: | |
1538 | ||
1539 | @smallexample | |
1540 | union U @{ int i : 4096; @}; | |
1541 | @end smallexample | |
1542 | ||
1543 | @noindent | |
1544 | Assuming that an @code{int} does not have 4096 bits, G++ will make the | |
1545 | union too small by the number of bits in an @code{int}. | |
1546 | ||
956d9305 MM |
1547 | @item |
1548 | Empty classes can be placed at incorrect offsets. For example: | |
daf2f129 | 1549 | |
956d9305 MM |
1550 | @smallexample |
1551 | struct A @{@}; | |
1552 | ||
1553 | struct B @{ | |
1554 | A a; | |
1555 | virtual void f (); | |
1556 | @}; | |
1557 | ||
1558 | struct C : public B, public A @{@}; | |
1559 | @end smallexample | |
1560 | ||
1561 | @noindent | |
c0478a66 | 1562 | G++ will place the @code{A} base class of @code{C} at a nonzero offset; |
956d9305 MM |
1563 | it should be placed at offset zero. G++ mistakenly believes that the |
1564 | @code{A} data member of @code{B} is already at offset zero. | |
1565 | ||
6397d80b MM |
1566 | @item |
1567 | Names of template functions whose types involve @code{typename} or | |
1568 | template template parameters can be mangled incorrectly. | |
1569 | ||
1570 | @smallexample | |
1571 | template <typename Q> | |
1572 | void f(typename Q::X) @{@} | |
1573 | ||
1574 | template <template <typename> class Q> | |
1575 | void f(typename Q<int>::X) @{@} | |
1576 | @end smallexample | |
1577 | ||
1578 | @noindent | |
3364c33b | 1579 | Instantiations of these templates may be mangled incorrectly. |
6397d80b | 1580 | |
eca7f13c MM |
1581 | @end itemize |
1582 | ||
aee96fe9 | 1583 | @item -Wctor-dtor-privacy @r{(C++ only)} |
cd3bb277 | 1584 | @opindex Wctor-dtor-privacy |
9eff22bc LG |
1585 | Warn when a class seems unusable because all the constructors or |
1586 | destructors in that class are private, and it has neither friends nor | |
78d0a54d | 1587 | public static member functions. |
bba975d4 | 1588 | |
aee96fe9 | 1589 | @item -Wnon-virtual-dtor @r{(C++ only)} |
cd3bb277 | 1590 | @opindex Wnon-virtual-dtor |
9eff22bc LG |
1591 | Warn when a class appears to be polymorphic, thereby requiring a virtual |
1592 | destructor, yet it declares a non-virtual one. | |
bd8f9aec | 1593 | This warning is enabled by @option{-Wall}. |
bba975d4 | 1594 | |
aee96fe9 | 1595 | @item -Wreorder @r{(C++ only)} |
cd3bb277 | 1596 | @opindex Wreorder |
bba975d4 JM |
1597 | @cindex reordering, warning |
1598 | @cindex warning for reordering of member initializers | |
1599 | Warn when the order of member initializers given in the code does not | |
1600 | match the order in which they must be executed. For instance: | |
1601 | ||
1602 | @smallexample | |
1603 | struct A @{ | |
1604 | int i; | |
1605 | int j; | |
1606 | A(): j (0), i (1) @{ @} | |
1607 | @}; | |
1608 | @end smallexample | |
1609 | ||
9eff22bc LG |
1610 | The compiler will rearrange the member initializers for @samp{i} |
1611 | and @samp{j} to match the declaration order of the members, emitting | |
1612 | a warning to that effect. This warning is enabled by @option{-Wall}. | |
bba975d4 JM |
1613 | @end table |
1614 | ||
630d3d5a | 1615 | The following @option{-W@dots{}} options are not affected by @option{-Wall}. |
bba975d4 | 1616 | |
2642624b | 1617 | @table @gcctabopt |
aee96fe9 | 1618 | @item -Weffc++ @r{(C++ only)} |
cd3bb277 | 1619 | @opindex Weffc++ |
77f6c1eb RS |
1620 | Warn about violations of the following style guidelines from Scott Meyers' |
1621 | @cite{Effective C++} book: | |
1622 | ||
1623 | @itemize @bullet | |
1624 | @item | |
1625 | Item 11: Define a copy constructor and an assignment operator for classes | |
1626 | with dynamically allocated memory. | |
1627 | ||
1628 | @item | |
1629 | Item 12: Prefer initialization to assignment in constructors. | |
1630 | ||
1631 | @item | |
1632 | Item 14: Make destructors virtual in base classes. | |
1633 | ||
1634 | @item | |
1635 | Item 15: Have @code{operator=} return a reference to @code{*this}. | |
1636 | ||
1637 | @item | |
1638 | Item 23: Don't try to return a reference when you must return an object. | |
1639 | ||
1640 | @end itemize | |
1641 | ||
daf2f129 | 1642 | Also warn about violations of the following style guidelines from |
9eff22bc | 1643 | Scott Meyers' @cite{More Effective C++} book: |
77f6c1eb RS |
1644 | |
1645 | @itemize @bullet | |
1646 | @item | |
1647 | Item 6: Distinguish between prefix and postfix forms of increment and | |
1648 | decrement operators. | |
1649 | ||
1650 | @item | |
1651 | Item 7: Never overload @code{&&}, @code{||}, or @code{,}. | |
1652 | ||
1653 | @end itemize | |
1654 | ||
9eff22bc LG |
1655 | When selecting this option, be aware that the standard library |
1656 | headers do not obey all of these guidelines; use @samp{grep -v} | |
77f6c1eb | 1657 | to filter out those warnings. |
bba975d4 | 1658 | |
aee96fe9 | 1659 | @item -Wno-deprecated @r{(C++ only)} |
cd3bb277 | 1660 | @opindex Wno-deprecated |
767094dd | 1661 | Do not warn about usage of deprecated features. @xref{Deprecated Features}. |
2de45c06 | 1662 | |
aee96fe9 | 1663 | @item -Wno-non-template-friend @r{(C++ only)} |
cd3bb277 | 1664 | @opindex Wno-non-template-friend |
bba975d4 | 1665 | Disable warnings when non-templatized friend functions are declared |
9eff22bc | 1666 | within a template. Since the advent of explicit template specification |
aee96fe9 | 1667 | support in G++, if the name of the friend is an unqualified-id (i.e., |
bba975d4 | 1668 | @samp{friend foo(int)}), the C++ language specification demands that the |
767094dd | 1669 | friend declare or define an ordinary, nontemplate function. (Section |
aee96fe9 | 1670 | 14.5.3). Before G++ implemented explicit specification, unqualified-ids |
bba975d4 | 1671 | could be interpreted as a particular specialization of a templatized |
767094dd | 1672 | function. Because this non-conforming behavior is no longer the default |
aee96fe9 | 1673 | behavior for G++, @option{-Wnon-template-friend} allows the compiler to |
9eff22bc | 1674 | check existing code for potential trouble spots and is on by default. |
2228d450 | 1675 | This new compiler behavior can be turned off with |
630d3d5a | 1676 | @option{-Wno-non-template-friend} which keeps the conformant compiler code |
2228d450 | 1677 | but disables the helpful warning. |
bba975d4 | 1678 | |
aee96fe9 | 1679 | @item -Wold-style-cast @r{(C++ only)} |
cd3bb277 | 1680 | @opindex Wold-style-cast |
323728aa NS |
1681 | Warn if an old-style (C-style) cast to a non-void type is used within |
1682 | a C++ program. The new-style casts (@samp{static_cast}, | |
1683 | @samp{reinterpret_cast}, and @samp{const_cast}) are less vulnerable to | |
9eff22bc | 1684 | unintended effects and much easier to search for. |
bba975d4 | 1685 | |
aee96fe9 | 1686 | @item -Woverloaded-virtual @r{(C++ only)} |
cd3bb277 | 1687 | @opindex Woverloaded-virtual |
bba975d4 JM |
1688 | @cindex overloaded virtual fn, warning |
1689 | @cindex warning for overloaded virtual fn | |
3747f3dc MM |
1690 | Warn when a function declaration hides virtual functions from a |
1691 | base class. For example, in: | |
1692 | ||
1693 | @smallexample | |
1694 | struct A @{ | |
1695 | virtual void f(); | |
1696 | @}; | |
1697 | ||
1698 | struct B: public A @{ | |
1699 | void f(int); | |
1700 | @}; | |
1701 | @end smallexample | |
1702 | ||
1703 | the @code{A} class version of @code{f} is hidden in @code{B}, and code | |
9eff22bc | 1704 | like: |
3747f3dc MM |
1705 | |
1706 | @smallexample | |
1707 | B* b; | |
1708 | b->f(); | |
1709 | @end smallexample | |
1710 | ||
1711 | will fail to compile. | |
bba975d4 | 1712 | |
aee96fe9 | 1713 | @item -Wno-pmf-conversions @r{(C++ only)} |
cd3bb277 | 1714 | @opindex Wno-pmf-conversions |
bba975d4 JM |
1715 | Disable the diagnostic for converting a bound pointer to member function |
1716 | to a plain pointer. | |
1717 | ||
aee96fe9 | 1718 | @item -Wsign-promo @r{(C++ only)} |
cd3bb277 | 1719 | @opindex Wsign-promo |
bba975d4 | 1720 | Warn when overload resolution chooses a promotion from unsigned or |
2eac577f | 1721 | enumerated type to a signed type, over a conversion to an unsigned type of |
aee96fe9 | 1722 | the same size. Previous versions of G++ would try to preserve |
bba975d4 JM |
1723 | unsignedness, but the standard mandates the current behavior. |
1724 | ||
aee96fe9 | 1725 | @item -Wsynth @r{(C++ only)} |
cd3bb277 | 1726 | @opindex Wsynth |
bba975d4 JM |
1727 | @cindex warning for synthesized methods |
1728 | @cindex synthesized methods, warning | |
aee96fe9 | 1729 | Warn when G++'s synthesis behavior does not match that of cfront. For |
bba975d4 JM |
1730 | instance: |
1731 | ||
1732 | @smallexample | |
1733 | struct A @{ | |
1734 | operator int (); | |
1735 | A& operator = (int); | |
1736 | @}; | |
1737 | ||
1738 | main () | |
1739 | @{ | |
1740 | A a,b; | |
1741 | a = b; | |
1742 | @} | |
1743 | @end smallexample | |
74291a4b | 1744 | |
aee96fe9 | 1745 | In this example, G++ will synthesize a default @samp{A& operator = |
bba975d4 | 1746 | (const A&);}, while cfront will use the user-defined @samp{operator =}. |
74291a4b MM |
1747 | @end table |
1748 | ||
60de6385 SS |
1749 | @node Objective-C Dialect Options |
1750 | @section Options Controlling Objective-C Dialect | |
1751 | ||
1752 | @cindex compiler options, Objective-C | |
1753 | @cindex Objective-C options, command line | |
1754 | @cindex options, Objective-C | |
264fa2db ZL |
1755 | (NOTE: This manual does not describe the Objective-C language itself. See |
1756 | @w{@uref{http://gcc.gnu.org/readings.html}} for references.) | |
1757 | ||
60de6385 | 1758 | This section describes the command-line options that are only meaningful |
9eff22bc | 1759 | for Objective-C programs, but you can also use most of the GNU compiler |
60de6385 SS |
1760 | options regardless of what language your program is in. For example, |
1761 | you might compile a file @code{some_class.m} like this: | |
1762 | ||
3ab51846 | 1763 | @smallexample |
60de6385 | 1764 | gcc -g -fgnu-runtime -O -c some_class.m |
3ab51846 | 1765 | @end smallexample |
60de6385 SS |
1766 | |
1767 | @noindent | |
9eff22bc | 1768 | In this example, @option{-fgnu-runtime} is an option meant only for |
60de6385 | 1769 | Objective-C programs; you can use the other options with any language |
161d7b59 | 1770 | supported by GCC@. |
60de6385 SS |
1771 | |
1772 | Here is a list of options that are @emph{only} for compiling Objective-C | |
1773 | programs: | |
1774 | ||
1775 | @table @gcctabopt | |
630d3d5a | 1776 | @item -fconstant-string-class=@var{class-name} |
cd3bb277 | 1777 | @opindex fconstant-string-class |
630d3d5a | 1778 | Use @var{class-name} as the name of the class to instantiate for each |
695ac33f | 1779 | literal string specified with the syntax @code{@@"@dots{}"}. The default |
264fa2db ZL |
1780 | class name is @code{NXConstantString} if the GNU runtime is being used, and |
1781 | @code{NSConstantString} if the NeXT runtime is being used (see below). The | |
1782 | @option{-fconstant-cfstrings} option, if also present, will override the | |
1783 | @option{-fconstant-string-class} setting and cause @code{@@"@dots{}"} literals | |
1784 | to be laid out as constant CoreFoundation strings. | |
60de6385 SS |
1785 | |
1786 | @item -fgnu-runtime | |
cd3bb277 | 1787 | @opindex fgnu-runtime |
60de6385 SS |
1788 | Generate object code compatible with the standard GNU Objective-C |
1789 | runtime. This is the default for most types of systems. | |
1790 | ||
1791 | @item -fnext-runtime | |
cd3bb277 | 1792 | @opindex fnext-runtime |
60de6385 | 1793 | Generate output compatible with the NeXT runtime. This is the default |
1f676100 NP |
1794 | for NeXT-based systems, including Darwin and Mac OS X@. The macro |
1795 | @code{__NEXT_RUNTIME__} is predefined if (and only if) this option is | |
1796 | used. | |
60de6385 | 1797 | |
264fa2db | 1798 | @item -fno-nil-receivers |
5ad7ae7f | 1799 | @opindex fno-nil-receivers |
daf2f129 JM |
1800 | Assume that all Objective-C message dispatches (e.g., |
1801 | @code{[receiver message:arg]}) in this translation unit ensure that the receiver | |
1802 | is not @code{nil}. This allows for more efficient entry points in the runtime to be | |
1803 | used. Currently, this option is only available in conjunction with | |
264fa2db ZL |
1804 | the NeXT runtime on Mac OS X 10.3 and later. |
1805 | ||
1806 | @item -fobjc-exceptions | |
5ad7ae7f | 1807 | @opindex fobjc-exceptions |
daf2f129 JM |
1808 | Enable syntactic support for structured exception handling in Objective-C, |
1809 | similar to what is offered by C++ and Java. Currently, this option is only | |
1810 | available in conjunction with the NeXT runtime on Mac OS X 10.3 and later. | |
264fa2db ZL |
1811 | |
1812 | @smallexample | |
1813 | @@try @{ | |
1814 | @dots{} | |
1815 | @@throw expr; | |
1816 | @dots{} | |
1817 | @} | |
1818 | @@catch (AnObjCClass *exc) @{ | |
1819 | @dots{} | |
1820 | @@throw expr; | |
1821 | @dots{} | |
1822 | @@throw; | |
1823 | @dots{} | |
1824 | @} | |
1825 | @@catch (AnotherClass *exc) @{ | |
1826 | @dots{} | |
1827 | @} | |
1828 | @@catch (id allOthers) @{ | |
1829 | @dots{} | |
1830 | @} | |
1831 | @@finally @{ | |
1832 | @dots{} | |
1833 | @@throw expr; | |
1834 | @dots{} | |
1835 | @} | |
1836 | @end smallexample | |
1837 | ||
1838 | The @code{@@throw} statement may appear anywhere in an Objective-C or | |
daf2f129 JM |
1839 | Objective-C++ program; when used inside of a @code{@@catch} block, the |
1840 | @code{@@throw} may appear without an argument (as shown above), in which case | |
264fa2db ZL |
1841 | the object caught by the @code{@@catch} will be rethrown. |
1842 | ||
1843 | Note that only (pointers to) Objective-C objects may be thrown and | |
1844 | caught using this scheme. When an object is thrown, it will be caught | |
1845 | by the nearest @code{@@catch} clause capable of handling objects of that type, | |
daf2f129 JM |
1846 | analogously to how @code{catch} blocks work in C++ and Java. A |
1847 | @code{@@catch(id @dots{})} clause (as shown above) may also be provided to catch | |
264fa2db ZL |
1848 | any and all Objective-C exceptions not caught by previous @code{@@catch} |
1849 | clauses (if any). | |
1850 | ||
1851 | The @code{@@finally} clause, if present, will be executed upon exit from the | |
1852 | immediately preceding @code{@@try @dots{} @@catch} section. This will happen | |
1853 | regardless of whether any exceptions are thrown, caught or rethrown | |
1854 | inside the @code{@@try @dots{} @@catch} section, analogously to the behavior | |
1855 | of the @code{finally} clause in Java. | |
1856 | ||
1857 | There are several caveats to using the new exception mechanism: | |
1858 | ||
1859 | @itemize @bullet | |
1860 | @item | |
daf2f129 | 1861 | Although currently designed to be binary compatible with @code{NS_HANDLER}-style |
264fa2db ZL |
1862 | idioms provided by the @code{NSException} class, the new |
1863 | exceptions can only be used on Mac OS X 10.3 (Panther) and later | |
1864 | systems, due to additional functionality needed in the (NeXT) Objective-C | |
1865 | runtime. | |
1866 | ||
1867 | @item | |
1868 | As mentioned above, the new exceptions do not support handling | |
daf2f129 | 1869 | types other than Objective-C objects. Furthermore, when used from |
264fa2db ZL |
1870 | Objective-C++, the Objective-C exception model does not interoperate with C++ |
1871 | exceptions at this time. This means you cannot @code{@@throw} an exception | |
daf2f129 | 1872 | from Objective-C and @code{catch} it in C++, or vice versa |
264fa2db ZL |
1873 | (i.e., @code{throw @dots{} @@catch}). |
1874 | @end itemize | |
daf2f129 | 1875 | |
264fa2db ZL |
1876 | The @option{-fobjc-exceptions} switch also enables the use of synchronization |
1877 | blocks for thread-safe execution: | |
1878 | ||
1879 | @smallexample | |
1880 | @@synchronized (ObjCClass *guard) @{ | |
1881 | @dots{} | |
1882 | @} | |
1883 | @end smallexample | |
1884 | ||
1885 | Upon entering the @code{@@synchronized} block, a thread of execution shall | |
1886 | first check whether a lock has been placed on the corresponding @code{guard} | |
1887 | object by another thread. If it has, the current thread shall wait until | |
daf2f129 | 1888 | the other thread relinquishes its lock. Once @code{guard} becomes available, |
264fa2db ZL |
1889 | the current thread will place its own lock on it, execute the code contained in |
1890 | the @code{@@synchronized} block, and finally relinquish the lock (thereby | |
1891 | making @code{guard} available to other threads). | |
1892 | ||
1893 | Unlike Java, Objective-C does not allow for entire methods to be marked | |
1894 | @code{@@synchronized}. Note that throwing exceptions out of | |
1895 | @code{@@synchronized} blocks is allowed, and will cause the guarding object | |
1896 | to be unlocked properly. | |
1897 | ||
1898 | @item -freplace-objc-classes | |
5ad7ae7f | 1899 | @opindex freplace-objc-classes |
264fa2db ZL |
1900 | Emit a special marker instructing @command{ld(1)} not to statically link in |
1901 | the resulting object file, and allow @command{dyld(1)} to load it in at | |
1902 | run time instead. This is used in conjunction with the Fix-and-Continue | |
daf2f129 | 1903 | debugging mode, where the object file in question may be recompiled and |
264fa2db ZL |
1904 | dynamically reloaded in the course of program execution, without the need |
1905 | to restart the program itself. Currently, Fix-and-Continue functionality | |
daf2f129 | 1906 | is only available in conjunction with the NeXT runtime on Mac OS X 10.3 |
264fa2db ZL |
1907 | and later. |
1908 | ||
1909 | @item -fzero-link | |
5ad7ae7f | 1910 | @opindex fzero-link |
264fa2db ZL |
1911 | When compiling for the NeXT runtime, the compiler ordinarily replaces calls |
1912 | to @code{objc_getClass("@dots{}")} (when the name of the class is known at | |
1913 | compile time) with static class references that get initialized at load time, | |
1914 | which improves run-time performance. Specifying the @option{-fzero-link} flag | |
1915 | suppresses this behavior and causes calls to @code{objc_getClass("@dots{}")} | |
daf2f129 | 1916 | to be retained. This is useful in Zero-Link debugging mode, since it allows |
264fa2db ZL |
1917 | for individual class implementations to be modified during program execution. |
1918 | ||
60de6385 | 1919 | @item -gen-decls |
cd3bb277 | 1920 | @opindex gen-decls |
60de6385 SS |
1921 | Dump interface declarations for all classes seen in the source file to a |
1922 | file named @file{@var{sourcename}.decl}. | |
1923 | ||
1924 | @item -Wno-protocol | |
cd3bb277 | 1925 | @opindex Wno-protocol |
1f676100 NP |
1926 | If a class is declared to implement a protocol, a warning is issued for |
1927 | every method in the protocol that is not implemented by the class. The | |
6335b0aa | 1928 | default behavior is to issue a warning for every method not explicitly |
1f676100 NP |
1929 | implemented in the class, even if a method implementation is inherited |
1930 | from the superclass. If you use the @code{-Wno-protocol} option, then | |
1931 | methods inherited from the superclass are considered to be implemented, | |
1932 | and no warning is issued for them. | |
60de6385 SS |
1933 | |
1934 | @item -Wselector | |
cd3bb277 | 1935 | @opindex Wselector |
1f676100 NP |
1936 | Warn if multiple methods of different types for the same selector are |
1937 | found during compilation. The check is performed on the list of methods | |
1938 | in the final stage of compilation. Additionally, a check is performed | |
9eff22bc LG |
1939 | for each selector appearing in a @code{@@selector(@dots{})} |
1940 | expression, and a corresponding method for that selector has been found | |
1f676100 NP |
1941 | during compilation. Because these checks scan the method table only at |
1942 | the end of compilation, these warnings are not produced if the final | |
1943 | stage of compilation is not reached, for example because an error is | |
1944 | found during compilation, or because the @code{-fsyntax-only} option is | |
1945 | being used. | |
1946 | ||
1947 | @item -Wundeclared-selector | |
1948 | @opindex Wundeclared-selector | |
1949 | Warn if a @code{@@selector(@dots{})} expression referring to an | |
1950 | undeclared selector is found. A selector is considered undeclared if no | |
daf2f129 | 1951 | method with that name has been declared before the |
9eff22bc LG |
1952 | @code{@@selector(@dots{})} expression, either explicitly in an |
1953 | @code{@@interface} or @code{@@protocol} declaration, or implicitly in | |
1954 | an @code{@@implementation} section. This option always performs its | |
1955 | checks as soon as a @code{@@selector(@dots{})} expression is found, | |
1956 | while @code{-Wselector} only performs its checks in the final stage of | |
1957 | compilation. This also enforces the coding style convention | |
1f676100 | 1958 | that methods and selectors must be declared before being used. |
60de6385 | 1959 | |
7989e4dc | 1960 | @item -print-objc-runtime-info |
5ad7ae7f | 1961 | @opindex print-objc-runtime-info |
7989e4dc RO |
1962 | Generate C header describing the largest structure that is passed by |
1963 | value, if any. | |
60de6385 SS |
1964 | |
1965 | @end table | |
1966 | ||
764dbbf2 GDR |
1967 | @node Language Independent Options |
1968 | @section Options to Control Diagnostic Messages Formatting | |
1969 | @cindex options to control diagnostics formatting | |
1970 | @cindex diagnostic messages | |
1971 | @cindex message formatting | |
1972 | ||
b192711e | 1973 | Traditionally, diagnostic messages have been formatted irrespective of |
e979f9e8 | 1974 | the output device's aspect (e.g.@: its width, @dots{}). The options described |
764dbbf2 | 1975 | below can be used to control the diagnostic messages formatting |
e979f9e8 | 1976 | algorithm, e.g.@: how many characters per line, how often source location |
6c0a4eab | 1977 | information should be reported. Right now, only the C++ front end can |
764dbbf2 | 1978 | honor these options. However it is expected, in the near future, that |
6c0a4eab | 1979 | the remaining front ends would be able to digest them correctly. |
764dbbf2 | 1980 | |
2642624b | 1981 | @table @gcctabopt |
764dbbf2 | 1982 | @item -fmessage-length=@var{n} |
cd3bb277 | 1983 | @opindex fmessage-length |
764dbbf2 | 1984 | Try to format error messages so that they fit on lines of about @var{n} |
aee96fe9 | 1985 | characters. The default is 72 characters for @command{g++} and 0 for the rest of |
161d7b59 | 1986 | the front ends supported by GCC@. If @var{n} is zero, then no |
02f52e19 | 1987 | line-wrapping will be done; each error message will appear on a single |
764dbbf2 GDR |
1988 | line. |
1989 | ||
cd3bb277 | 1990 | @opindex fdiagnostics-show-location |
764dbbf2 | 1991 | @item -fdiagnostics-show-location=once |
b192711e | 1992 | Only meaningful in line-wrapping mode. Instructs the diagnostic messages |
764dbbf2 GDR |
1993 | reporter to emit @emph{once} source location information; that is, in |
1994 | case the message is too long to fit on a single physical line and has to | |
1995 | be wrapped, the source location won't be emitted (as prefix) again, | |
1996 | over and over, in subsequent continuation lines. This is the default | |
c21cd8b1 | 1997 | behavior. |
764dbbf2 GDR |
1998 | |
1999 | @item -fdiagnostics-show-location=every-line | |
2000 | Only meaningful in line-wrapping mode. Instructs the diagnostic | |
2001 | messages reporter to emit the same source location information (as | |
4fe9b91c | 2002 | prefix) for physical lines that result from the process of breaking |
b192711e | 2003 | a message which is too long to fit on a single line. |
764dbbf2 GDR |
2004 | |
2005 | @end table | |
2006 | ||
74291a4b MM |
2007 | @node Warning Options |
2008 | @section Options to Request or Suppress Warnings | |
2009 | @cindex options to control warnings | |
2010 | @cindex warning messages | |
2011 | @cindex messages, warning | |
2012 | @cindex suppressing warnings | |
2013 | ||
2014 | Warnings are diagnostic messages that report constructions which | |
2015 | are not inherently erroneous but which are risky or suggest there | |
2016 | may have been an error. | |
2017 | ||
2018 | You can request many specific warnings with options beginning @samp{-W}, | |
630d3d5a | 2019 | for example @option{-Wimplicit} to request warnings on implicit |
74291a4b MM |
2020 | declarations. Each of these specific warning options also has a |
2021 | negative form beginning @samp{-Wno-} to turn off warnings; | |
630d3d5a | 2022 | for example, @option{-Wno-implicit}. This manual lists only one of the |
74291a4b MM |
2023 | two forms, whichever is not the default. |
2024 | ||
62aaa62c GP |
2025 | The following options control the amount and kinds of warnings produced |
2026 | by GCC; for further, language-specific options also refer to | |
2027 | @ref{C++ Dialect Options} and @ref{Objective-C Dialect Options}. | |
74291a4b | 2028 | |
2642624b | 2029 | @table @gcctabopt |
74291a4b MM |
2030 | @cindex syntax checking |
2031 | @item -fsyntax-only | |
cd3bb277 | 2032 | @opindex fsyntax-only |
74291a4b MM |
2033 | Check the code for syntax errors, but don't do anything beyond that. |
2034 | ||
2035 | @item -pedantic | |
cd3bb277 | 2036 | @opindex pedantic |
074e95e3 JM |
2037 | Issue all the warnings demanded by strict ISO C and ISO C++; |
2038 | reject all programs that use forbidden extensions, and some other | |
2039 | programs that do not follow ISO C and ISO C++. For ISO C, follows the | |
630d3d5a | 2040 | version of the ISO C standard specified by any @option{-std} option used. |
74291a4b | 2041 | |
074e95e3 | 2042 | Valid ISO C and ISO C++ programs should compile properly with or without |
5490d604 | 2043 | this option (though a rare few will require @option{-ansi} or a |
161d7b59 | 2044 | @option{-std} option specifying the required version of ISO C)@. However, |
b1d16193 JL |
2045 | without this option, certain GNU extensions and traditional C and C++ |
2046 | features are supported as well. With this option, they are rejected. | |
74291a4b | 2047 | |
630d3d5a | 2048 | @option{-pedantic} does not cause warning messages for use of the |
74291a4b MM |
2049 | alternate keywords whose names begin and end with @samp{__}. Pedantic |
2050 | warnings are also disabled in the expression that follows | |
2051 | @code{__extension__}. However, only system header files should use | |
2052 | these escape routes; application programs should avoid them. | |
2053 | @xref{Alternate Keywords}. | |
2054 | ||
630d3d5a | 2055 | Some users try to use @option{-pedantic} to check programs for strict ISO |
74291a4b | 2056 | C conformance. They soon find that it does not do quite what they want: |
c1030c7c | 2057 | it finds some non-ISO practices, but not all---only those for which |
074e95e3 JM |
2058 | ISO C @emph{requires} a diagnostic, and some others for which |
2059 | diagnostics have been added. | |
74291a4b | 2060 | |
074e95e3 | 2061 | A feature to report any failure to conform to ISO C might be useful in |
74291a4b | 2062 | some instances, but would require considerable additional work and would |
630d3d5a | 2063 | be quite different from @option{-pedantic}. We don't have plans to |
892d0a6d | 2064 | support such a feature in the near future. |
74291a4b | 2065 | |
91ea548a JM |
2066 | Where the standard specified with @option{-std} represents a GNU |
2067 | extended dialect of C, such as @samp{gnu89} or @samp{gnu99}, there is a | |
2068 | corresponding @dfn{base standard}, the version of ISO C on which the GNU | |
2069 | extended dialect is based. Warnings from @option{-pedantic} are given | |
2070 | where they are required by the base standard. (It would not make sense | |
2071 | for such warnings to be given only for features not in the specified GNU | |
2072 | C dialect, since by definition the GNU dialects of C include all | |
2073 | features the compiler supports with the given option, and there would be | |
2074 | nothing to warn about.) | |
2075 | ||
74291a4b | 2076 | @item -pedantic-errors |
cd3bb277 | 2077 | @opindex pedantic-errors |
630d3d5a | 2078 | Like @option{-pedantic}, except that errors are produced rather than |
74291a4b MM |
2079 | warnings. |
2080 | ||
2081 | @item -w | |
cd3bb277 | 2082 | @opindex w |
74291a4b MM |
2083 | Inhibit all warning messages. |
2084 | ||
2085 | @item -Wno-import | |
cd3bb277 | 2086 | @opindex Wno-import |
74291a4b MM |
2087 | Inhibit warning messages about the use of @samp{#import}. |
2088 | ||
2089 | @item -Wchar-subscripts | |
cd3bb277 | 2090 | @opindex Wchar-subscripts |
74291a4b MM |
2091 | Warn if an array subscript has type @code{char}. This is a common cause |
2092 | of error, as programmers often forget that this type is signed on some | |
2093 | machines. | |
2094 | ||
2095 | @item -Wcomment | |
cd3bb277 | 2096 | @opindex Wcomment |
74291a4b MM |
2097 | Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*} |
2098 | comment, or whenever a Backslash-Newline appears in a @samp{//} comment. | |
2099 | ||
c65a01af RG |
2100 | @item -Wfatal-errors |
2101 | @opindex Wfatal-errors | |
2102 | This option causes the compiler to abort compilation on the first error | |
2103 | occurred rather than trying to keep going and printing further error | |
2104 | messages. | |
2105 | ||
74291a4b | 2106 | @item -Wformat |
cd3bb277 | 2107 | @opindex Wformat |
74291a4b MM |
2108 | Check calls to @code{printf} and @code{scanf}, etc., to make sure that |
2109 | the arguments supplied have types appropriate to the format string | |
26f6672d JM |
2110 | specified, and that the conversions specified in the format string make |
2111 | sense. This includes standard functions, and others specified by format | |
2112 | attributes (@pxref{Function Attributes}), in the @code{printf}, | |
2113 | @code{scanf}, @code{strftime} and @code{strfmon} (an X/Open extension, | |
2114 | not in the C standard) families. | |
74291a4b | 2115 | |
8308e0b7 | 2116 | The formats are checked against the format features supported by GNU |
3764f879 | 2117 | libc version 2.2. These include all ISO C90 and C99 features, as well |
8308e0b7 JM |
2118 | as features from the Single Unix Specification and some BSD and GNU |
2119 | extensions. Other library implementations may not support all these | |
2120 | features; GCC does not support warning about features that go beyond a | |
630d3d5a JM |
2121 | particular library's limitations. However, if @option{-pedantic} is used |
2122 | with @option{-Wformat}, warnings will be given about format features not | |
26f6672d JM |
2123 | in the selected standard version (but not for @code{strfmon} formats, |
2124 | since those are not in any version of the C standard). @xref{C Dialect | |
2125 | Options,,Options Controlling C Dialect}. | |
8308e0b7 | 2126 | |
b34c7881 JT |
2127 | Since @option{-Wformat} also checks for null format arguments for |
2128 | several functions, @option{-Wformat} also implies @option{-Wnonnull}. | |
2129 | ||
630d3d5a | 2130 | @option{-Wformat} is included in @option{-Wall}. For more control over some |
c76f4e8e | 2131 | aspects of format checking, the options @option{-Wformat-y2k}, |
e964a556 JT |
2132 | @option{-Wno-format-extra-args}, @option{-Wno-format-zero-length}, |
2133 | @option{-Wformat-nonliteral}, @option{-Wformat-security}, and | |
2134 | @option{-Wformat=2} are available, but are not included in @option{-Wall}. | |
4d808927 | 2135 | |
c76f4e8e JM |
2136 | @item -Wformat-y2k |
2137 | @opindex Wformat-y2k | |
2138 | If @option{-Wformat} is specified, also warn about @code{strftime} | |
4d808927 JM |
2139 | formats which may yield only a two-digit year. |
2140 | ||
2141 | @item -Wno-format-extra-args | |
cd3bb277 | 2142 | @opindex Wno-format-extra-args |
630d3d5a | 2143 | If @option{-Wformat} is specified, do not warn about excess arguments to a |
4d808927 JM |
2144 | @code{printf} or @code{scanf} format function. The C standard specifies |
2145 | that such arguments are ignored. | |
2146 | ||
7e5fb12f JM |
2147 | Where the unused arguments lie between used arguments that are |
2148 | specified with @samp{$} operand number specifications, normally | |
2149 | warnings are still given, since the implementation could not know what | |
2150 | type to pass to @code{va_arg} to skip the unused arguments. However, | |
2151 | in the case of @code{scanf} formats, this option will suppress the | |
2152 | warning if the unused arguments are all pointers, since the Single | |
2153 | Unix Specification says that such unused arguments are allowed. | |
2154 | ||
e964a556 JT |
2155 | @item -Wno-format-zero-length |
2156 | @opindex Wno-format-zero-length | |
2157 | If @option{-Wformat} is specified, do not warn about zero-length formats. | |
2158 | The C standard specifies that zero-length formats are allowed. | |
2159 | ||
4d808927 | 2160 | @item -Wformat-nonliteral |
cd3bb277 | 2161 | @opindex Wformat-nonliteral |
630d3d5a | 2162 | If @option{-Wformat} is specified, also warn if the format string is not a |
4d808927 JM |
2163 | string literal and so cannot be checked, unless the format function |
2164 | takes its format arguments as a @code{va_list}. | |
2165 | ||
c907e684 | 2166 | @item -Wformat-security |
cd3bb277 | 2167 | @opindex Wformat-security |
630d3d5a | 2168 | If @option{-Wformat} is specified, also warn about uses of format |
c907e684 JM |
2169 | functions that represent possible security problems. At present, this |
2170 | warns about calls to @code{printf} and @code{scanf} functions where the | |
2171 | format string is not a string literal and there are no format arguments, | |
2172 | as in @code{printf (foo);}. This may be a security hole if the format | |
2173 | string came from untrusted input and contains @samp{%n}. (This is | |
630d3d5a JM |
2174 | currently a subset of what @option{-Wformat-nonliteral} warns about, but |
2175 | in future warnings may be added to @option{-Wformat-security} that are not | |
2176 | included in @option{-Wformat-nonliteral}.) | |
c907e684 | 2177 | |
4d808927 | 2178 | @item -Wformat=2 |
cd3bb277 | 2179 | @opindex Wformat=2 |
630d3d5a JM |
2180 | Enable @option{-Wformat} plus format checks not included in |
2181 | @option{-Wformat}. Currently equivalent to @samp{-Wformat | |
c76f4e8e | 2182 | -Wformat-nonliteral -Wformat-security -Wformat-y2k}. |
4d808927 | 2183 | |
b34c7881 JT |
2184 | @item -Wnonnull |
2185 | @opindex Wnonnull | |
f6d9224f | 2186 | Warn about passing a null pointer for arguments marked as |
b34c7881 JT |
2187 | requiring a non-null value by the @code{nonnull} function attribute. |
2188 | ||
2189 | @option{-Wnonnull} is included in @option{-Wall} and @option{-Wformat}. It | |
2190 | can be disabled with the @option{-Wno-nonnull} option. | |
2191 | ||
daf2f129 | 2192 | @item -Winit-self @r{(C, C++, and Objective-C only)} |
3390f9c9 | 2193 | @opindex Winit-self |
f6d9224f GP |
2194 | Warn about uninitialized variables which are initialized with themselves. |
2195 | Note this option can only be used with the @option{-Wuninitialized} option, | |
2196 | which in turn only works with @option{-O1} and above. | |
3390f9c9 | 2197 | |
f6d9224f GP |
2198 | For example, GCC will warn about @code{i} being uninitialized in the |
2199 | following snippet only when @option{-Winit-self} has been specified: | |
3390f9c9 AP |
2200 | @smallexample |
2201 | @group | |
2202 | int f() | |
2203 | @{ | |
2204 | int i = i; | |
2205 | return i; | |
2206 | @} | |
2207 | @end group | |
2208 | @end smallexample | |
2209 | ||
e9a25f70 | 2210 | @item -Wimplicit-int |
cd3bb277 | 2211 | @opindex Wimplicit-int |
e9a25f70 JL |
2212 | Warn when a declaration does not specify a type. |
2213 | ||
f5963e61 JL |
2214 | @item -Wimplicit-function-declaration |
2215 | @itemx -Werror-implicit-function-declaration | |
cd3bb277 JM |
2216 | @opindex Wimplicit-function-declaration |
2217 | @opindex Werror-implicit-function-declaration | |
f5963e61 JL |
2218 | Give a warning (or error) whenever a function is used before being |
2219 | declared. | |
e9a25f70 | 2220 | |
74291a4b | 2221 | @item -Wimplicit |
cd3bb277 | 2222 | @opindex Wimplicit |
630d3d5a | 2223 | Same as @option{-Wimplicit-int} and @option{-Wimplicit-function-declaration}. |
861bb6c1 JL |
2224 | |
2225 | @item -Wmain | |
cd3bb277 | 2226 | @opindex Wmain |
861bb6c1 JL |
2227 | Warn if the type of @samp{main} is suspicious. @samp{main} should be a |
2228 | function with external linkage, returning int, taking either zero | |
2229 | arguments, two, or three arguments of appropriate types. | |
4a870dba | 2230 | |
1f0c3120 | 2231 | @item -Wmissing-braces |
cd3bb277 | 2232 | @opindex Wmissing-braces |
1f0c3120 JM |
2233 | Warn if an aggregate or union initializer is not fully bracketed. In |
2234 | the following example, the initializer for @samp{a} is not fully | |
2235 | bracketed, but that for @samp{b} is fully bracketed. | |
2236 | ||
2237 | @smallexample | |
2238 | int a[2][2] = @{ 0, 1, 2, 3 @}; | |
2239 | int b[2][2] = @{ @{ 0, 1 @}, @{ 2, 3 @} @}; | |
2240 | @end smallexample | |
2241 | ||
b02398bd BE |
2242 | @item -Wmissing-include-dirs @r{(C, C++, and Objective-C only)} |
2243 | @opindex Wmissing-include-dirs | |
2244 | Warn if a user-supplied include directory does not exist. | |
2245 | ||
74291a4b | 2246 | @item -Wparentheses |
cd3bb277 | 2247 | @opindex Wparentheses |
74291a4b MM |
2248 | Warn if parentheses are omitted in certain contexts, such |
2249 | as when there is an assignment in a context where a truth value | |
2250 | is expected, or when operators are nested whose precedence people | |
2251 | often get confused about. | |
2252 | ||
e9a25f70 JL |
2253 | Also warn about constructions where there may be confusion to which |
2254 | @code{if} statement an @code{else} branch belongs. Here is an example of | |
2255 | such a case: | |
2256 | ||
2257 | @smallexample | |
aee96fe9 | 2258 | @group |
e9a25f70 JL |
2259 | @{ |
2260 | if (a) | |
2261 | if (b) | |
2262 | foo (); | |
2263 | else | |
2264 | bar (); | |
2265 | @} | |
aee96fe9 | 2266 | @end group |
e9a25f70 JL |
2267 | @end smallexample |
2268 | ||
2269 | In C, every @code{else} branch belongs to the innermost possible @code{if} | |
2270 | statement, which in this example is @code{if (b)}. This is often not | |
2271 | what the programmer expected, as illustrated in the above example by | |
2272 | indentation the programmer chose. When there is the potential for this | |
f0523f02 | 2273 | confusion, GCC will issue a warning when this flag is specified. |
e9a25f70 JL |
2274 | To eliminate the warning, add explicit braces around the innermost |
2275 | @code{if} statement so there is no way the @code{else} could belong to | |
2276 | the enclosing @code{if}. The resulting code would look like this: | |
2277 | ||
2278 | @smallexample | |
aee96fe9 | 2279 | @group |
e9a25f70 JL |
2280 | @{ |
2281 | if (a) | |
2282 | @{ | |
2283 | if (b) | |
2284 | foo (); | |
2285 | else | |
2286 | bar (); | |
2287 | @} | |
2288 | @} | |
aee96fe9 | 2289 | @end group |
e9a25f70 JL |
2290 | @end smallexample |
2291 | ||
bb58bec5 | 2292 | @item -Wsequence-point |
cd3bb277 | 2293 | @opindex Wsequence-point |
bb58bec5 JM |
2294 | Warn about code that may have undefined semantics because of violations |
2295 | of sequence point rules in the C standard. | |
2296 | ||
2297 | The C standard defines the order in which expressions in a C program are | |
2298 | evaluated in terms of @dfn{sequence points}, which represent a partial | |
2299 | ordering between the execution of parts of the program: those executed | |
2300 | before the sequence point, and those executed after it. These occur | |
2301 | after the evaluation of a full expression (one which is not part of a | |
2302 | larger expression), after the evaluation of the first operand of a | |
2303 | @code{&&}, @code{||}, @code{? :} or @code{,} (comma) operator, before a | |
2304 | function is called (but after the evaluation of its arguments and the | |
2305 | expression denoting the called function), and in certain other places. | |
2306 | Other than as expressed by the sequence point rules, the order of | |
2307 | evaluation of subexpressions of an expression is not specified. All | |
2308 | these rules describe only a partial order rather than a total order, | |
2309 | since, for example, if two functions are called within one expression | |
2310 | with no sequence point between them, the order in which the functions | |
2311 | are called is not specified. However, the standards committee have | |
2312 | ruled that function calls do not overlap. | |
2313 | ||
2314 | It is not specified when between sequence points modifications to the | |
2315 | values of objects take effect. Programs whose behavior depends on this | |
2316 | have undefined behavior; the C standard specifies that ``Between the | |
2317 | previous and next sequence point an object shall have its stored value | |
2318 | modified at most once by the evaluation of an expression. Furthermore, | |
2319 | the prior value shall be read only to determine the value to be | |
2320 | stored.''. If a program breaks these rules, the results on any | |
2321 | particular implementation are entirely unpredictable. | |
2322 | ||
2323 | Examples of code with undefined behavior are @code{a = a++;}, @code{a[n] | |
2324 | = b[n++]} and @code{a[i++] = i;}. Some more complicated cases are not | |
2325 | diagnosed by this option, and it may give an occasional false positive | |
2326 | result, but in general it has been found fairly effective at detecting | |
2327 | this sort of problem in programs. | |
2328 | ||
2329 | The present implementation of this option only works for C programs. A | |
2330 | future implementation may also work for C++ programs. | |
2331 | ||
9c34dbbf ZW |
2332 | The C standard is worded confusingly, therefore there is some debate |
2333 | over the precise meaning of the sequence point rules in subtle cases. | |
2334 | Links to discussions of the problem, including proposed formal | |
962e6e00 | 2335 | definitions, may be found on the GCC readings page, at |
c5122d75 | 2336 | @w{@uref{http://gcc.gnu.org/readings.html}}. |
bb58bec5 | 2337 | |
74291a4b | 2338 | @item -Wreturn-type |
cd3bb277 | 2339 | @opindex Wreturn-type |
32c4c36c ML |
2340 | Warn whenever a function is defined with a return-type that defaults to |
2341 | @code{int}. Also warn about any @code{return} statement with no | |
02f52e19 | 2342 | return-value in a function whose return-type is not @code{void}. |
32c4c36c ML |
2343 | |
2344 | For C++, a function without return type always produces a diagnostic | |
767094dd | 2345 | message, even when @option{-Wno-return-type} is specified. The only |
32c4c36c | 2346 | exceptions are @samp{main} and functions defined in system headers. |
74291a4b MM |
2347 | |
2348 | @item -Wswitch | |
cd3bb277 | 2349 | @opindex Wswitch |
2eac577f | 2350 | Warn whenever a @code{switch} statement has an index of enumerated type |
74291a4b MM |
2351 | and lacks a @code{case} for one or more of the named codes of that |
2352 | enumeration. (The presence of a @code{default} label prevents this | |
2353 | warning.) @code{case} labels outside the enumeration range also | |
2354 | provoke warnings when this option is used. | |
2355 | ||
d6961341 AC |
2356 | @item -Wswitch-default |
2357 | @opindex Wswitch-switch | |
2358 | Warn whenever a @code{switch} statement does not have a @code{default} | |
2359 | case. | |
2360 | ||
173028e5 AC |
2361 | @item -Wswitch-enum |
2362 | @opindex Wswitch-enum | |
2eac577f | 2363 | Warn whenever a @code{switch} statement has an index of enumerated type |
173028e5 AC |
2364 | and lacks a @code{case} for one or more of the named codes of that |
2365 | enumeration. @code{case} labels outside the enumeration range also | |
2366 | provoke warnings when this option is used. | |
2367 | ||
74291a4b | 2368 | @item -Wtrigraphs |
cd3bb277 | 2369 | @opindex Wtrigraphs |
f2ecb02d JM |
2370 | Warn if any trigraphs are encountered that might change the meaning of |
2371 | the program (trigraphs within comments are not warned about). | |
74291a4b | 2372 | |
078721e1 | 2373 | @item -Wunused-function |
cd3bb277 | 2374 | @opindex Wunused-function |
078721e1 AC |
2375 | Warn whenever a static function is declared but not defined or a |
2376 | non\-inline static function is unused. | |
74291a4b | 2377 | |
078721e1 | 2378 | @item -Wunused-label |
cd3bb277 | 2379 | @opindex Wunused-label |
078721e1 AC |
2380 | Warn whenever a label is declared but not used. |
2381 | ||
2382 | To suppress this warning use the @samp{unused} attribute | |
2383 | (@pxref{Variable Attributes}). | |
2384 | ||
2385 | @item -Wunused-parameter | |
cd3bb277 | 2386 | @opindex Wunused-parameter |
078721e1 AC |
2387 | Warn whenever a function parameter is unused aside from its declaration. |
2388 | ||
2389 | To suppress this warning use the @samp{unused} attribute | |
2390 | (@pxref{Variable Attributes}). | |
956d6950 | 2391 | |
078721e1 | 2392 | @item -Wunused-variable |
cd3bb277 | 2393 | @opindex Wunused-variable |
078721e1 AC |
2394 | Warn whenever a local variable or non-constant static variable is unused |
2395 | aside from its declaration | |
2396 | ||
2397 | To suppress this warning use the @samp{unused} attribute | |
74291a4b MM |
2398 | (@pxref{Variable Attributes}). |
2399 | ||
078721e1 | 2400 | @item -Wunused-value |
cd3bb277 | 2401 | @opindex Wunused-value |
078721e1 AC |
2402 | Warn whenever a statement computes a result that is explicitly not used. |
2403 | ||
2404 | To suppress this warning cast the expression to @samp{void}. | |
2405 | ||
2406 | @item -Wunused | |
cd3bb277 | 2407 | @opindex Wunused |
d3075b6c | 2408 | All the above @option{-Wunused} options combined. |
078721e1 AC |
2409 | |
2410 | In order to get a warning about an unused function parameter, you must | |
65ca2d60 PE |
2411 | either specify @samp{-Wextra -Wunused} (note that @samp{-Wall} implies |
2412 | @samp{-Wunused}), or separately specify @option{-Wunused-parameter}. | |
078721e1 | 2413 | |
74291a4b | 2414 | @item -Wuninitialized |
cd3bb277 | 2415 | @opindex Wuninitialized |
c5c76735 JL |
2416 | Warn if an automatic variable is used without first being initialized or |
2417 | if a variable may be clobbered by a @code{setjmp} call. | |
74291a4b MM |
2418 | |
2419 | These warnings are possible only in optimizing compilation, | |
2420 | because they require data flow information that is computed only | |
630d3d5a | 2421 | when optimizing. If you don't specify @option{-O}, you simply won't |
74291a4b MM |
2422 | get these warnings. |
2423 | ||
3390f9c9 AP |
2424 | If you want to warn about code which uses the uninitialized value of the |
2425 | variable in its own initializer, use the @option{-Winit-self} option. | |
2426 | ||
74291a4b MM |
2427 | These warnings occur only for variables that are candidates for |
2428 | register allocation. Therefore, they do not occur for a variable that | |
2429 | is declared @code{volatile}, or whose address is taken, or whose size | |
2430 | is other than 1, 2, 4 or 8 bytes. Also, they do not occur for | |
2431 | structures, unions or arrays, even when they are in registers. | |
2432 | ||
2433 | Note that there may be no warning about a variable that is used only | |
2434 | to compute a value that itself is never used, because such | |
2435 | computations may be deleted by data flow analysis before the warnings | |
2436 | are printed. | |
2437 | ||
0c2d1a2a | 2438 | These warnings are made optional because GCC is not smart |
74291a4b MM |
2439 | enough to see all the reasons why the code might be correct |
2440 | despite appearing to have an error. Here is one example of how | |
2441 | this can happen: | |
2442 | ||
2443 | @smallexample | |
aee96fe9 | 2444 | @group |
74291a4b MM |
2445 | @{ |
2446 | int x; | |
2447 | switch (y) | |
2448 | @{ | |
2449 | case 1: x = 1; | |
2450 | break; | |
2451 | case 2: x = 4; | |
2452 | break; | |
2453 | case 3: x = 5; | |
2454 | @} | |
2455 | foo (x); | |
2456 | @} | |
aee96fe9 | 2457 | @end group |
74291a4b MM |
2458 | @end smallexample |
2459 | ||
2460 | @noindent | |
2461 | If the value of @code{y} is always 1, 2 or 3, then @code{x} is | |
0c2d1a2a | 2462 | always initialized, but GCC doesn't know this. Here is |
74291a4b MM |
2463 | another common case: |
2464 | ||
2465 | @smallexample | |
2466 | @{ | |
2467 | int save_y; | |
2468 | if (change_y) save_y = y, y = new_y; | |
2469 | @dots{} | |
2470 | if (change_y) y = save_y; | |
2471 | @} | |
2472 | @end smallexample | |
2473 | ||
2474 | @noindent | |
2475 | This has no bug because @code{save_y} is used only if it is set. | |
2476 | ||
20300b05 | 2477 | @cindex @code{longjmp} warnings |
b192711e | 2478 | This option also warns when a non-volatile automatic variable might be |
c5c76735 JL |
2479 | changed by a call to @code{longjmp}. These warnings as well are possible |
2480 | only in optimizing compilation. | |
20300b05 GK |
2481 | |
2482 | The compiler sees only the calls to @code{setjmp}. It cannot know | |
2483 | where @code{longjmp} will be called; in fact, a signal handler could | |
2484 | call it at any point in the code. As a result, you may get a warning | |
2485 | even when there is in fact no problem because @code{longjmp} cannot | |
2486 | in fact be called at the place which would cause a problem. | |
2487 | ||
74291a4b MM |
2488 | Some spurious warnings can be avoided if you declare all the functions |
2489 | you use that never return as @code{noreturn}. @xref{Function | |
2490 | Attributes}. | |
2491 | ||
d300e551 | 2492 | @item -Wunknown-pragmas |
cd3bb277 | 2493 | @opindex Wunknown-pragmas |
d300e551 NC |
2494 | @cindex warning for unknown pragmas |
2495 | @cindex unknown pragmas, warning | |
2496 | @cindex pragmas, warning of unknown | |
2497 | Warn when a #pragma directive is encountered which is not understood by | |
161d7b59 | 2498 | GCC@. If this command line option is used, warnings will even be issued |
d300e551 | 2499 | for unknown pragmas in system header files. This is not the case if |
630d3d5a | 2500 | the warnings were only enabled by the @option{-Wall} command line option. |
d300e551 | 2501 | |
bf52f899 NS |
2502 | @item -Wstrict-aliasing |
2503 | @opindex Wstrict-aliasing | |
2504 | This option is only active when @option{-fstrict-aliasing} is active. | |
2505 | It warns about code which might break the strict aliasing rules that the | |
2506 | compiler is using for optimization. The warning does not catch all | |
2507 | cases, but does attempt to catch the more common pitfalls. It is | |
2508 | included in @option{-Wall}. | |
2509 | ||
5399d643 JW |
2510 | @item -Wstrict-aliasing=2 |
2511 | @opindex Wstrict-aliasing=2 | |
2512 | This option is only active when @option{-fstrict-aliasing} is active. | |
2513 | It warns about all code which might break the strict aliasing rules that the | |
2514 | compiler is using for optimization. This warning catches all cases, but | |
2515 | it will also give a warning for some ambiguous cases that are safe. | |
2516 | ||
74291a4b | 2517 | @item -Wall |
cd3bb277 | 2518 | @opindex Wall |
74291a4b MM |
2519 | All of the above @samp{-W} options combined. This enables all the |
2520 | warnings about constructions that some users consider questionable, and | |
2521 | that are easy to avoid (or modify to prevent the warning), even in | |
bd8f9aec SP |
2522 | conjunction with macros. This also enables some language-specific |
2523 | warnings described in @ref{C++ Dialect Options} and | |
2524 | @ref{Objective-C Dialect Options}. | |
74291a4b MM |
2525 | @end table |
2526 | ||
630d3d5a | 2527 | The following @option{-W@dots{}} options are not implied by @option{-Wall}. |
74291a4b MM |
2528 | Some of them warn about constructions that users generally do not |
2529 | consider questionable, but which occasionally you might wish to check | |
2530 | for; others warn about constructions that are necessary or hard to avoid | |
2531 | in some cases, and there is no simple way to modify the code to suppress | |
2532 | the warning. | |
2533 | ||
2642624b | 2534 | @table @gcctabopt |
65ca2d60 | 2535 | @item -Wextra |
cd3bb277 | 2536 | @opindex W |
65ca2d60 PE |
2537 | @opindex Wextra |
2538 | (This option used to be called @option{-W}. The older name is still | |
2539 | supported, but the newer name is more descriptive.) Print extra warning | |
2540 | messages for these events: | |
74291a4b MM |
2541 | |
2542 | @itemize @bullet | |
74291a4b MM |
2543 | @item |
2544 | A function can return either with or without a value. (Falling | |
2545 | off the end of the function body is considered returning without | |
2546 | a value.) For example, this function would evoke such a | |
2547 | warning: | |
2548 | ||
2549 | @smallexample | |
2550 | @group | |
2551 | foo (a) | |
2552 | @{ | |
2553 | if (a > 0) | |
2554 | return a; | |
2555 | @} | |
2556 | @end group | |
2557 | @end smallexample | |
2558 | ||
2559 | @item | |
2560 | An expression-statement or the left-hand side of a comma expression | |
2561 | contains no side effects. | |
2562 | To suppress the warning, cast the unused expression to void. | |
2563 | For example, an expression such as @samp{x[i,j]} will cause a warning, | |
2564 | but @samp{x[(void)i,j]} will not. | |
2565 | ||
2566 | @item | |
65ca2d60 | 2567 | An unsigned value is compared against zero with @samp{<} or @samp{>=}. |
74291a4b MM |
2568 | |
2569 | @item | |
2570 | A comparison like @samp{x<=y<=z} appears; this is equivalent to | |
2571 | @samp{(x<=y ? 1 : 0) <= z}, which is a different interpretation from | |
2572 | that of ordinary mathematical notation. | |
2573 | ||
2574 | @item | |
2575 | Storage-class specifiers like @code{static} are not the first things in | |
2576 | a declaration. According to the C Standard, this usage is obsolescent. | |
2577 | ||
e0c9fbb7 JM |
2578 | @item |
2579 | The return type of a function has a type qualifier such as @code{const}. | |
2580 | Such a type qualifier has no effect, since the value returned by a | |
2581 | function is not an lvalue. (But don't warn about the GNU extension of | |
2582 | @code{volatile void} return types. That extension will be warned about | |
630d3d5a | 2583 | if @option{-pedantic} is specified.) |
e0c9fbb7 | 2584 | |
74291a4b | 2585 | @item |
630d3d5a | 2586 | If @option{-Wall} or @option{-Wunused} is also specified, warn about unused |
74291a4b MM |
2587 | arguments. |
2588 | ||
e9a25f70 JL |
2589 | @item |
2590 | A comparison between signed and unsigned values could produce an | |
2591 | incorrect result when the signed value is converted to unsigned. | |
630d3d5a | 2592 | (But don't warn if @option{-Wno-sign-compare} is also specified.) |
e9a25f70 | 2593 | |
dbde0d5d BH |
2594 | @item |
2595 | An aggregate has an initializer which does not initialize all members. | |
2596 | For example, the following code would cause such a warning, because | |
2597 | @code{x.h} would be implicitly initialized to zero: | |
2598 | ||
2599 | @smallexample | |
2600 | struct s @{ int f, g, h; @}; | |
2601 | struct s x = @{ 3, 4 @}; | |
2602 | @end smallexample | |
65ca2d60 PE |
2603 | |
2604 | @item | |
2605 | A function parameter is declared without a type specifier in K&R-style | |
2606 | functions: | |
2607 | ||
2608 | @smallexample | |
2609 | void foo(bar) @{ @} | |
2610 | @end smallexample | |
2611 | ||
2612 | @item | |
2613 | An empty body occurs in an @samp{if} or @samp{else} statement. | |
2614 | ||
2615 | @item | |
2616 | A pointer is compared against integer zero with @samp{<}, @samp{<=}, | |
2617 | @samp{>}, or @samp{>=}. | |
2618 | ||
2619 | @item | |
2620 | A variable might be changed by @samp{longjmp} or @samp{vfork}. | |
2621 | ||
2622 | @item | |
2623 | Any of several floating-point events that often indicate errors, such as | |
2624 | overflow, underflow, loss of precision, etc. | |
2625 | ||
2626 | @item @r{(C++ only)} | |
2627 | An enumerator and a non-enumerator both appear in a conditional expression. | |
2628 | ||
2629 | @item @r{(C++ only)} | |
2630 | A non-static reference or non-static @samp{const} member appears in a | |
2631 | class without constructors. | |
2632 | ||
2633 | @item @r{(C++ only)} | |
2634 | Ambiguous virtual bases. | |
2635 | ||
2636 | @item @r{(C++ only)} | |
2637 | Subscripting an array which has been declared @samp{register}. | |
2638 | ||
2639 | @item @r{(C++ only)} | |
2640 | Taking the address of a variable which has been declared @samp{register}. | |
2641 | ||
2642 | @item @r{(C++ only)} | |
62b9c42c | 2643 | A base class is not initialized in a derived class' copy constructor. |
74291a4b MM |
2644 | @end itemize |
2645 | ||
75227a33 GK |
2646 | @item -Wno-div-by-zero |
2647 | @opindex Wno-div-by-zero | |
2648 | @opindex Wdiv-by-zero | |
2649 | Do not warn about compile-time integer division by zero. Floating point | |
2650 | division by zero is not warned about, as it can be a legitimate way of | |
2651 | obtaining infinities and NaNs. | |
2652 | ||
2653 | @item -Wsystem-headers | |
2654 | @opindex Wsystem-headers | |
2655 | @cindex warnings from system headers | |
2656 | @cindex system headers, warnings from | |
2657 | Print warning messages for constructs found in system header files. | |
2658 | Warnings from system headers are normally suppressed, on the assumption | |
2659 | that they usually do not indicate real problems and would only make the | |
2660 | compiler output harder to read. Using this command line option tells | |
2661 | GCC to emit warnings from system headers as if they occurred in user | |
2662 | code. However, note that using @option{-Wall} in conjunction with this | |
2663 | option will @emph{not} warn about unknown pragmas in system | |
2664 | headers---for that, @option{-Wunknown-pragmas} must also be used. | |
2665 | ||
f793a95e | 2666 | @item -Wfloat-equal |
cd3bb277 | 2667 | @opindex Wfloat-equal |
f793a95e JL |
2668 | Warn if floating point values are used in equality comparisons. |
2669 | ||
488d3985 GK |
2670 | The idea behind this is that sometimes it is convenient (for the |
2671 | programmer) to consider floating-point values as approximations to | |
2672 | infinitely precise real numbers. If you are doing this, then you need | |
c0478a66 | 2673 | to compute (by analyzing the code, or in some other way) the maximum or |
488d3985 GK |
2674 | likely maximum error that the computation introduces, and allow for it |
2675 | when performing comparisons (and when producing output, but that's a | |
2676 | different problem). In particular, instead of testing for equality, you | |
2677 | would check to see whether the two values have ranges that overlap; and | |
2678 | this is done with the relational operators, so equality comparisons are | |
2679 | probably mistaken. | |
2680 | ||
aee96fe9 | 2681 | @item -Wtraditional @r{(C only)} |
cd3bb277 | 2682 | @opindex Wtraditional |
74291a4b | 2683 | Warn about certain constructs that behave differently in traditional and |
161d7b59 | 2684 | ISO C@. Also warn about ISO C constructs that have no traditional C |
c8abc684 | 2685 | equivalent, and/or problematic constructs which should be avoided. |
74291a4b MM |
2686 | |
2687 | @itemize @bullet | |
2688 | @item | |
da312b55 NB |
2689 | Macro parameters that appear within string literals in the macro body. |
2690 | In traditional C macro replacement takes place within string literals, | |
161d7b59 | 2691 | but does not in ISO C@. |
da312b55 NB |
2692 | |
2693 | @item | |
2694 | In traditional C, some preprocessor directives did not exist. | |
2695 | Traditional preprocessors would only consider a line to be a directive | |
2696 | if the @samp{#} appeared in column 1 on the line. Therefore | |
630d3d5a | 2697 | @option{-Wtraditional} warns about directives that traditional C |
da312b55 NB |
2698 | understands but would ignore because the @samp{#} does not appear as the |
2699 | first character on the line. It also suggests you hide directives like | |
2700 | @samp{#pragma} not understood by traditional C by indenting them. Some | |
c21cd8b1 | 2701 | traditional implementations would not recognize @samp{#elif}, so it |
da312b55 NB |
2702 | suggests avoiding it altogether. |
2703 | ||
2704 | @item | |
2705 | A function-like macro that appears without arguments. | |
2706 | ||
2707 | @item | |
2708 | The unary plus operator. | |
2709 | ||
2710 | @item | |
c771326b JM |
2711 | The @samp{U} integer constant suffix, or the @samp{F} or @samp{L} floating point |
2712 | constant suffixes. (Traditional C does support the @samp{L} suffix on integer | |
da312b55 | 2713 | constants.) Note, these suffixes appear in macros defined in the system |
e979f9e8 | 2714 | headers of most modern systems, e.g.@: the @samp{_MIN}/@samp{_MAX} macros in @code{<limits.h>}. |
c8abc684 | 2715 | Use of these macros in user code might normally lead to spurious |
2dd76960 | 2716 | warnings, however GCC's integrated preprocessor has enough context to |
c8abc684 | 2717 | avoid warning in these cases. |
74291a4b MM |
2718 | |
2719 | @item | |
2720 | A function declared external in one block and then used after the end of | |
2721 | the block. | |
2722 | ||
2723 | @item | |
2724 | A @code{switch} statement has an operand of type @code{long}. | |
db838bb8 KG |
2725 | |
2726 | @item | |
2727 | A non-@code{static} function declaration follows a @code{static} one. | |
2728 | This construct is not accepted by some traditional C compilers. | |
48776cde KG |
2729 | |
2730 | @item | |
c1030c7c | 2731 | The ISO type of an integer constant has a different width or |
48776cde | 2732 | signedness from its traditional type. This warning is only issued if |
e979f9e8 | 2733 | the base of the constant is ten. I.e.@: hexadecimal or octal values, which |
48776cde | 2734 | typically represent bit patterns, are not warned about. |
bb66adca KG |
2735 | |
2736 | @item | |
c1030c7c | 2737 | Usage of ISO string concatenation is detected. |
7f094a94 | 2738 | |
895ea614 KG |
2739 | @item |
2740 | Initialization of automatic aggregates. | |
2741 | ||
2742 | @item | |
2743 | Identifier conflicts with labels. Traditional C lacks a separate | |
2744 | namespace for labels. | |
253b6b82 KG |
2745 | |
2746 | @item | |
2747 | Initialization of unions. If the initializer is zero, the warning is | |
2748 | omitted. This is done under the assumption that the zero initializer in | |
e979f9e8 | 2749 | user code appears conditioned on e.g.@: @code{__STDC__} to avoid missing |
253b6b82 KG |
2750 | initializer warnings and relies on default initialization to zero in the |
2751 | traditional C case. | |
03829ad2 KG |
2752 | |
2753 | @item | |
3ed56f8a KG |
2754 | Conversions by prototypes between fixed/floating point values and vice |
2755 | versa. The absence of these prototypes when compiling with traditional | |
2756 | C would cause serious problems. This is a subset of the possible | |
630d3d5a | 2757 | conversion warnings, for the full set use @option{-Wconversion}. |
622d3731 KG |
2758 | |
2759 | @item | |
2760 | Use of ISO C style function definitions. This warning intentionally is | |
2761 | @emph{not} issued for prototype declarations or variadic functions | |
2762 | because these ISO C features will appear in your code when using | |
2763 | libiberty's traditional C compatibility macros, @code{PARAMS} and | |
2764 | @code{VPARAMS}. This warning is also bypassed for nested functions | |
2dd76960 | 2765 | because that feature is already a GCC extension and thus not relevant to |
622d3731 | 2766 | traditional C compatibility. |
74291a4b MM |
2767 | @end itemize |
2768 | ||
85617eba HPN |
2769 | @item -Wdeclaration-after-statement @r{(C only)} |
2770 | @opindex Wdeclaration-after-statement | |
2771 | Warn when a declaration is found after a statement in a block. This | |
2772 | construct, known from C++, was introduced with ISO C99 and is by default | |
2773 | allowed in GCC@. It is not supported by ISO C90 and was not supported by | |
2774 | GCC versions before GCC 3.0. @xref{Mixed Declarations}. | |
2775 | ||
861bb6c1 | 2776 | @item -Wundef |
cd3bb277 | 2777 | @opindex Wundef |
861bb6c1 JL |
2778 | Warn if an undefined identifier is evaluated in an @samp{#if} directive. |
2779 | ||
909de5da PE |
2780 | @item -Wendif-labels |
2781 | @opindex Wendif-labels | |
2782 | Warn whenever an @samp{#else} or an @samp{#endif} are followed by text. | |
2783 | ||
74291a4b | 2784 | @item -Wshadow |
cd3bb277 | 2785 | @opindex Wshadow |
d773df5a DB |
2786 | Warn whenever a local variable shadows another local variable, parameter or |
2787 | global variable or whenever a built-in function is shadowed. | |
74291a4b | 2788 | |
74291a4b | 2789 | @item -Wlarger-than-@var{len} |
cd3bb277 | 2790 | @opindex Wlarger-than |
74291a4b MM |
2791 | Warn whenever an object of larger than @var{len} bytes is defined. |
2792 | ||
2793 | @item -Wpointer-arith | |
cd3bb277 | 2794 | @opindex Wpointer-arith |
74291a4b MM |
2795 | Warn about anything that depends on the ``size of'' a function type or |
2796 | of @code{void}. GNU C assigns these types a size of 1, for | |
2797 | convenience in calculations with @code{void *} pointers and pointers | |
2798 | to functions. | |
2799 | ||
aee96fe9 | 2800 | @item -Wbad-function-cast @r{(C only)} |
cd3bb277 | 2801 | @opindex Wbad-function-cast |
74291a4b MM |
2802 | Warn whenever a function call is cast to a non-matching type. |
2803 | For example, warn if @code{int malloc()} is cast to @code{anything *}. | |
2804 | ||
2805 | @item -Wcast-qual | |
cd3bb277 | 2806 | @opindex Wcast-qual |
74291a4b MM |
2807 | Warn whenever a pointer is cast so as to remove a type qualifier from |
2808 | the target type. For example, warn if a @code{const char *} is cast | |
2809 | to an ordinary @code{char *}. | |
2810 | ||
2811 | @item -Wcast-align | |
cd3bb277 | 2812 | @opindex Wcast-align |
74291a4b MM |
2813 | Warn whenever a pointer is cast such that the required alignment of the |
2814 | target is increased. For example, warn if a @code{char *} is cast to | |
2815 | an @code{int *} on machines where integers can only be accessed at | |
2816 | two- or four-byte boundaries. | |
2817 | ||
2818 | @item -Wwrite-strings | |
cd3bb277 | 2819 | @opindex Wwrite-strings |
aee96fe9 JM |
2820 | When compiling C, give string constants the type @code{const |
2821 | char[@var{length}]} so that | |
74291a4b | 2822 | copying the address of one into a non-@code{const} @code{char *} |
aee96fe9 JM |
2823 | pointer will get a warning; when compiling C++, warn about the |
2824 | deprecated conversion from string constants to @code{char *}. | |
2825 | These warnings will help you find at | |
74291a4b MM |
2826 | compile time code that can try to write into a string constant, but |
2827 | only if you have been very careful about using @code{const} in | |
2828 | declarations and prototypes. Otherwise, it will just be a nuisance; | |
630d3d5a | 2829 | this is why we did not make @option{-Wall} request these warnings. |
74291a4b MM |
2830 | |
2831 | @item -Wconversion | |
cd3bb277 | 2832 | @opindex Wconversion |
74291a4b MM |
2833 | Warn if a prototype causes a type conversion that is different from what |
2834 | would happen to the same argument in the absence of a prototype. This | |
2835 | includes conversions of fixed point to floating and vice versa, and | |
2836 | conversions changing the width or signedness of a fixed point argument | |
2837 | except when the same as the default promotion. | |
2838 | ||
2839 | Also, warn if a negative integer constant expression is implicitly | |
2840 | converted to an unsigned type. For example, warn about the assignment | |
2841 | @code{x = -1} if @code{x} is unsigned. But do not warn about explicit | |
2842 | casts like @code{(unsigned) -1}. | |
2843 | ||
e9a25f70 | 2844 | @item -Wsign-compare |
cd3bb277 | 2845 | @opindex Wsign-compare |
e9a25f70 JL |
2846 | @cindex warning for comparison of signed and unsigned values |
2847 | @cindex comparison of signed and unsigned values, warning | |
2848 | @cindex signed and unsigned values, comparison warning | |
2849 | Warn when a comparison between signed and unsigned values could produce | |
2850 | an incorrect result when the signed value is converted to unsigned. | |
65ca2d60 PE |
2851 | This warning is also enabled by @option{-Wextra}; to get the other warnings |
2852 | of @option{-Wextra} without this warning, use @samp{-Wextra -Wno-sign-compare}. | |
e9a25f70 | 2853 | |
74291a4b | 2854 | @item -Waggregate-return |
cd3bb277 | 2855 | @opindex Waggregate-return |
74291a4b MM |
2856 | Warn if any functions that return structures or unions are defined or |
2857 | called. (In languages where you can return an array, this also elicits | |
2858 | a warning.) | |
2859 | ||
aee96fe9 | 2860 | @item -Wstrict-prototypes @r{(C only)} |
cd3bb277 | 2861 | @opindex Wstrict-prototypes |
74291a4b MM |
2862 | Warn if a function is declared or defined without specifying the |
2863 | argument types. (An old-style function definition is permitted without | |
2864 | a warning if preceded by a declaration which specifies the argument | |
2865 | types.) | |
2866 | ||
c034f121 AJ |
2867 | @item -Wold-style-definition @r{(C only)} |
2868 | @opindex Wold-style-definition | |
2869 | Warn if an old-style function definition is used. A warning is given | |
2870 | even if there is a previous prototype. | |
2871 | ||
aee96fe9 | 2872 | @item -Wmissing-prototypes @r{(C only)} |
cd3bb277 | 2873 | @opindex Wmissing-prototypes |
74291a4b MM |
2874 | Warn if a global function is defined without a previous prototype |
2875 | declaration. This warning is issued even if the definition itself | |
2876 | provides a prototype. The aim is to detect global functions that fail | |
2877 | to be declared in header files. | |
2878 | ||
da635858 | 2879 | @item -Wmissing-declarations @r{(C only)} |
cd3bb277 | 2880 | @opindex Wmissing-declarations |
74291a4b MM |
2881 | Warn if a global function is defined without a previous declaration. |
2882 | Do so even if the definition itself provides a prototype. | |
2883 | Use this option to detect global functions that are not declared in | |
2884 | header files. | |
2885 | ||
0ca3fb0a | 2886 | @item -Wmissing-noreturn |
cd3bb277 | 2887 | @opindex Wmissing-noreturn |
0ca3fb0a KG |
2888 | Warn about functions which might be candidates for attribute @code{noreturn}. |
2889 | Note these are only possible candidates, not absolute ones. Care should | |
2890 | be taken to manually verify functions actually do not ever return before | |
2891 | adding the @code{noreturn} attribute, otherwise subtle code generation | |
21c7361e AJ |
2892 | bugs could be introduced. You will not get a warning for @code{main} in |
2893 | hosted C environments. | |
0ca3fb0a | 2894 | |
74ff4629 | 2895 | @item -Wmissing-format-attribute |
cd3bb277 JM |
2896 | @opindex Wmissing-format-attribute |
2897 | @opindex Wformat | |
630d3d5a | 2898 | If @option{-Wformat} is enabled, also warn about functions which might be |
74ff4629 JM |
2899 | candidates for @code{format} attributes. Note these are only possible |
2900 | candidates, not absolute ones. GCC will guess that @code{format} | |
2901 | attributes might be appropriate for any function that calls a function | |
2902 | like @code{vprintf} or @code{vscanf}, but this might not always be the | |
2903 | case, and some functions for which @code{format} attributes are | |
2904 | appropriate may not be detected. This option has no effect unless | |
630d3d5a | 2905 | @option{-Wformat} is enabled (possibly by @option{-Wall}). |
74ff4629 | 2906 | |
75227a33 GK |
2907 | @item -Wno-multichar |
2908 | @opindex Wno-multichar | |
2909 | @opindex Wmultichar | |
2910 | Do not warn if a multicharacter constant (@samp{'FOOF'}) is used. | |
2911 | Usually they indicate a typo in the user's code, as they have | |
2912 | implementation-defined values, and should not be used in portable code. | |
2913 | ||
e23bd218 IR |
2914 | @item -Wno-deprecated-declarations |
2915 | @opindex Wno-deprecated-declarations | |
2916 | Do not warn about uses of functions, variables, and types marked as | |
f282ffb3 | 2917 | deprecated by using the @code{deprecated} attribute. |
e23bd218 IR |
2918 | (@pxref{Function Attributes}, @pxref{Variable Attributes}, |
2919 | @pxref{Type Attributes}.) | |
2920 | ||
3c12fcc2 | 2921 | @item -Wpacked |
cd3bb277 | 2922 | @opindex Wpacked |
3c12fcc2 | 2923 | Warn if a structure is given the packed attribute, but the packed |
02f52e19 | 2924 | attribute has no effect on the layout or size of the structure. |
3c12fcc2 GM |
2925 | Such structures may be mis-aligned for little benefit. For |
2926 | instance, in this code, the variable @code{f.x} in @code{struct bar} | |
2927 | will be misaligned even though @code{struct bar} does not itself | |
2928 | have the packed attribute: | |
2929 | ||
2930 | @smallexample | |
2931 | @group | |
2932 | struct foo @{ | |
2933 | int x; | |
2934 | char a, b, c, d; | |
2935 | @} __attribute__((packed)); | |
2936 | struct bar @{ | |
2937 | char z; | |
2938 | struct foo f; | |
2939 | @}; | |
2940 | @end group | |
2941 | @end smallexample | |
2942 | ||
2943 | @item -Wpadded | |
cd3bb277 | 2944 | @opindex Wpadded |
3c12fcc2 GM |
2945 | Warn if padding is included in a structure, either to align an element |
2946 | of the structure or to align the whole structure. Sometimes when this | |
2947 | happens it is possible to rearrange the fields of the structure to | |
2948 | reduce the padding and so make the structure smaller. | |
2949 | ||
74291a4b | 2950 | @item -Wredundant-decls |
cd3bb277 | 2951 | @opindex Wredundant-decls |
74291a4b MM |
2952 | Warn if anything is declared more than once in the same scope, even in |
2953 | cases where multiple declaration is valid and changes nothing. | |
2954 | ||
aee96fe9 | 2955 | @item -Wnested-externs @r{(C only)} |
cd3bb277 | 2956 | @opindex Wnested-externs |
252215a7 | 2957 | Warn if an @code{extern} declaration is encountered within a function. |
74291a4b | 2958 | |
312f6255 | 2959 | @item -Wunreachable-code |
cd3bb277 | 2960 | @opindex Wunreachable-code |
312f6255 GK |
2961 | Warn if the compiler detects that code will never be executed. |
2962 | ||
2963 | This option is intended to warn when the compiler detects that at | |
2964 | least a whole line of source code will never be executed, because | |
2965 | some condition is never satisfied or because it is after a | |
2966 | procedure that never returns. | |
2967 | ||
2968 | It is possible for this option to produce a warning even though there | |
2969 | are circumstances under which part of the affected line can be executed, | |
2970 | so care should be taken when removing apparently-unreachable code. | |
2971 | ||
2972 | For instance, when a function is inlined, a warning may mean that the | |
02f52e19 | 2973 | line is unreachable in only one inlined copy of the function. |
312f6255 | 2974 | |
630d3d5a | 2975 | This option is not made part of @option{-Wall} because in a debugging |
312f6255 GK |
2976 | version of a program there is often substantial code which checks |
2977 | correct functioning of the program and is, hopefully, unreachable | |
2978 | because the program does work. Another common use of unreachable | |
c21cd8b1 | 2979 | code is to provide behavior which is selectable at compile-time. |
312f6255 | 2980 | |
74291a4b | 2981 | @item -Winline |
cd3bb277 | 2982 | @opindex Winline |
c5c76735 | 2983 | Warn if a function can not be inlined and it was declared as inline. |
ae4a7155 | 2984 | Even with this option, the compiler will not warn about failures to |
daf2f129 | 2985 | inline functions declared in system headers. |
ae4a7155 MM |
2986 | |
2987 | The compiler uses a variety of heuristics to determine whether or not | |
2988 | to inline a function. For example, the compiler takes into account | |
2989 | the size of the function being inlined and the the amount of inlining | |
2990 | that has already been done in the current function. Therefore, | |
2991 | seemingly insignificant changes in the source program can cause the | |
2992 | warnings produced by @option{-Winline} to appear or disappear. | |
74291a4b | 2993 | |
a01fff59 MA |
2994 | @item -Wno-invalid-offsetof @r{(C++ only)} |
2995 | @opindex Wno-invalid-offsetof | |
2996 | Suppress warnings from applying the @samp{offsetof} macro to a non-POD | |
2997 | type. According to the 1998 ISO C++ standard, applying @samp{offsetof} | |
2998 | to a non-POD type is undefined. In existing C++ implementations, | |
2999 | however, @samp{offsetof} typically gives meaningful results even when | |
3000 | applied to certain kinds of non-POD types. (Such as a simple | |
3001 | @samp{struct} that fails to be a POD type only by virtue of having a | |
3002 | constructor.) This flag is for users who are aware that they are | |
3003 | writing nonportable code and who have deliberately chosen to ignore the | |
3004 | warning about it. | |
3005 | ||
3006 | The restrictions on @samp{offsetof} may be relaxed in a future version | |
3007 | of the C++ standard. | |
3008 | ||
17211ab5 GK |
3009 | @item -Winvalid-pch |
3010 | @opindex Winvalid-pch | |
3011 | Warn if a precompiled header (@pxref{Precompiled Headers}) is found in | |
3012 | the search path but can't be used. | |
3013 | ||
795add94 | 3014 | @item -Wlong-long |
cd3bb277 JM |
3015 | @opindex Wlong-long |
3016 | @opindex Wno-long-long | |
795add94 | 3017 | Warn if @samp{long long} type is used. This is default. To inhibit |
630d3d5a JM |
3018 | the warning messages, use @option{-Wno-long-long}. Flags |
3019 | @option{-Wlong-long} and @option{-Wno-long-long} are taken into account | |
3020 | only when @option{-pedantic} flag is used. | |
795add94 | 3021 | |
7c4d376d RH |
3022 | @item -Wvariadic-macros |
3023 | @opindex Wvariadic-macros | |
3024 | @opindex Wno-variadic-macros | |
3025 | Warn if variadic macros are used in pedantic ISO C90 mode, or the GNU | |
3026 | alternate syntax when in pedantic ISO C99 mode. This is default. | |
3027 | To inhibit the warning messages, use @option{-Wno-variadic-macros}. | |
3028 | ||
18424ae1 | 3029 | @item -Wdisabled-optimization |
cd3bb277 | 3030 | @opindex Wdisabled-optimization |
18424ae1 BL |
3031 | Warn if a requested optimization pass is disabled. This warning does |
3032 | not generally indicate that there is anything wrong with your code; it | |
3033 | merely indicates that GCC's optimizers were unable to handle the code | |
3034 | effectively. Often, the problem is that your code is too big or too | |
3035 | complex; GCC will refuse to optimize programs when the optimization | |
3036 | itself is likely to take inordinate amounts of time. | |
3037 | ||
74291a4b | 3038 | @item -Werror |
cd3bb277 | 3039 | @opindex Werror |
74291a4b MM |
3040 | Make all warnings into errors. |
3041 | @end table | |
3042 | ||
3043 | @node Debugging Options | |
0c2d1a2a | 3044 | @section Options for Debugging Your Program or GCC |
74291a4b MM |
3045 | @cindex options, debugging |
3046 | @cindex debugging information options | |
3047 | ||
0c2d1a2a | 3048 | GCC has various special options that are used for debugging |
74291a4b MM |
3049 | either your program or GCC: |
3050 | ||
2642624b | 3051 | @table @gcctabopt |
74291a4b | 3052 | @item -g |
cd3bb277 | 3053 | @opindex g |
74291a4b | 3054 | Produce debugging information in the operating system's native format |
161d7b59 | 3055 | (stabs, COFF, XCOFF, or DWARF)@. GDB can work with this debugging |
74291a4b MM |
3056 | information. |
3057 | ||
630d3d5a | 3058 | On most systems that use stabs format, @option{-g} enables use of extra |
74291a4b MM |
3059 | debugging information that only GDB can use; this extra information |
3060 | makes debugging work better in GDB but will probably make other debuggers | |
3061 | crash or | |
3062 | refuse to read the program. If you want to control for certain whether | |
630d3d5a | 3063 | to generate the extra information, use @option{-gstabs+}, @option{-gstabs}, |
def66b10 | 3064 | @option{-gxcoff+}, @option{-gxcoff}, or @option{-gvms} (see below). |
74291a4b | 3065 | |
630d3d5a JM |
3066 | Unlike most other C compilers, GCC allows you to use @option{-g} with |
3067 | @option{-O}. The shortcuts taken by optimized code may occasionally | |
74291a4b MM |
3068 | produce surprising results: some variables you declared may not exist |
3069 | at all; flow of control may briefly move where you did not expect it; | |
3070 | some statements may not be executed because they compute constant | |
3071 | results or their values were already at hand; some statements may | |
3072 | execute in different places because they were moved out of loops. | |
3073 | ||
3074 | Nevertheless it proves possible to debug optimized output. This makes | |
3075 | it reasonable to use the optimizer for programs that might have bugs. | |
3076 | ||
0c2d1a2a | 3077 | The following options are useful when GCC is generated with the |
74291a4b MM |
3078 | capability for more than one debugging format. |
3079 | ||
3080 | @item -ggdb | |
cd3bb277 | 3081 | @opindex ggdb |
161d7b59 | 3082 | Produce debugging information for use by GDB@. This means to use the |
861bb6c1 JL |
3083 | most expressive format available (DWARF 2, stabs, or the native format |
3084 | if neither of those are supported), including GDB extensions if at all | |
3085 | possible. | |
74291a4b MM |
3086 | |
3087 | @item -gstabs | |
cd3bb277 | 3088 | @opindex gstabs |
74291a4b MM |
3089 | Produce debugging information in stabs format (if that is supported), |
3090 | without GDB extensions. This is the format used by DBX on most BSD | |
3091 | systems. On MIPS, Alpha and System V Release 4 systems this option | |
161d7b59 | 3092 | produces stabs debugging output which is not understood by DBX or SDB@. |
74291a4b MM |
3093 | On System V Release 4 systems this option requires the GNU assembler. |
3094 | ||
6a08f7b3 DP |
3095 | @item -feliminate-unused-debug-symbols |
3096 | @opindex feliminate-unused-debug-symbols | |
3097 | Produce debugging information in stabs format (if that is supported), | |
c0cbdbd9 | 3098 | for only symbols that are actually used. |
6a08f7b3 | 3099 | |
74291a4b | 3100 | @item -gstabs+ |
cd3bb277 | 3101 | @opindex gstabs+ |
74291a4b | 3102 | Produce debugging information in stabs format (if that is supported), |
161d7b59 | 3103 | using GNU extensions understood only by the GNU debugger (GDB)@. The |
74291a4b MM |
3104 | use of these extensions is likely to make other debuggers crash or |
3105 | refuse to read the program. | |
3106 | ||
3107 | @item -gcoff | |
cd3bb277 | 3108 | @opindex gcoff |
74291a4b MM |
3109 | Produce debugging information in COFF format (if that is supported). |
3110 | This is the format used by SDB on most System V systems prior to | |
3111 | System V Release 4. | |
3112 | ||
3113 | @item -gxcoff | |
cd3bb277 | 3114 | @opindex gxcoff |
74291a4b MM |
3115 | Produce debugging information in XCOFF format (if that is supported). |
3116 | This is the format used by the DBX debugger on IBM RS/6000 systems. | |
3117 | ||
3118 | @item -gxcoff+ | |
cd3bb277 | 3119 | @opindex gxcoff+ |
74291a4b | 3120 | Produce debugging information in XCOFF format (if that is supported), |
161d7b59 | 3121 | using GNU extensions understood only by the GNU debugger (GDB)@. The |
74291a4b MM |
3122 | use of these extensions is likely to make other debuggers crash or |
3123 | refuse to read the program, and may cause assemblers other than the GNU | |
3124 | assembler (GAS) to fail with an error. | |
3125 | ||
861bb6c1 | 3126 | @item -gdwarf-2 |
cd3bb277 | 3127 | @opindex gdwarf-2 |
861bb6c1 JL |
3128 | Produce debugging information in DWARF version 2 format (if that is |
3129 | supported). This is the format used by DBX on IRIX 6. | |
74291a4b | 3130 | |
5f98259a RK |
3131 | @item -gvms |
3132 | @opindex gvms | |
3133 | Produce debugging information in VMS debug format (if that is | |
3134 | supported). This is the format used by DEBUG on VMS systems. | |
3135 | ||
74291a4b MM |
3136 | @item -g@var{level} |
3137 | @itemx -ggdb@var{level} | |
3138 | @itemx -gstabs@var{level} | |
3139 | @itemx -gcoff@var{level} | |
3140 | @itemx -gxcoff@var{level} | |
5f98259a | 3141 | @itemx -gvms@var{level} |
74291a4b MM |
3142 | Request debugging information and also use @var{level} to specify how |
3143 | much information. The default level is 2. | |
3144 | ||
3145 | Level 1 produces minimal information, enough for making backtraces in | |
3146 | parts of the program that you don't plan to debug. This includes | |
3147 | descriptions of functions and external variables, but no information | |
3148 | about local variables and no line numbers. | |
3149 | ||
3150 | Level 3 includes extra information, such as all the macro definitions | |
3151 | present in the program. Some debuggers support macro expansion when | |
630d3d5a | 3152 | you use @option{-g3}. |
74291a4b | 3153 | |
eb7715a4 | 3154 | Note that in order to avoid confusion between DWARF1 debug level 2, |
def66b10 MM |
3155 | and DWARF2 @option{-gdwarf-2} does not accept a concatenated debug |
3156 | level. Instead use an additional @option{-g@var{level}} option to | |
3157 | change the debug level for DWARF2. | |
eb7715a4 | 3158 | |
e03b7153 RS |
3159 | @item -feliminate-dwarf2-dups |
3160 | @opindex feliminate-dwarf2-dups | |
3161 | Compress DWARF2 debugging information by eliminating duplicated | |
3162 | information about each symbol. This option only makes sense when | |
3163 | generating DWARF2 debugging information with @option{-gdwarf-2}. | |
3164 | ||
05739753 | 3165 | @cindex @command{prof} |
74291a4b | 3166 | @item -p |
cd3bb277 | 3167 | @opindex p |
74291a4b | 3168 | Generate extra code to write profile information suitable for the |
05739753 | 3169 | analysis program @command{prof}. You must use this option when compiling |
74291a4b MM |
3170 | the source files you want data about, and you must also use it when |
3171 | linking. | |
3172 | ||
05739753 | 3173 | @cindex @command{gprof} |
74291a4b | 3174 | @item -pg |
cd3bb277 | 3175 | @opindex pg |
74291a4b | 3176 | Generate extra code to write profile information suitable for the |
05739753 | 3177 | analysis program @command{gprof}. You must use this option when compiling |
74291a4b MM |
3178 | the source files you want data about, and you must also use it when |
3179 | linking. | |
3180 | ||
898f531b | 3181 | @item -Q |
cd3bb277 | 3182 | @opindex Q |
898f531b JL |
3183 | Makes the compiler print out each function name as it is compiled, and |
3184 | print some statistics about each pass when it finishes. | |
3185 | ||
1f0c3120 | 3186 | @item -ftime-report |
cd3bb277 | 3187 | @opindex ftime-report |
1f0c3120 JM |
3188 | Makes the compiler print some statistics about the time consumed by each |
3189 | pass when it finishes. | |
3190 | ||
3191 | @item -fmem-report | |
cd3bb277 | 3192 | @opindex fmem-report |
1f0c3120 JM |
3193 | Makes the compiler print some statistics about permanent memory |
3194 | allocation when it finishes. | |
3195 | ||
861bb6c1 | 3196 | @item -fprofile-arcs |
cd3bb277 | 3197 | @opindex fprofile-arcs |
23af32e6 NS |
3198 | Add code so that program flow @dfn{arcs} are instrumented. During |
3199 | execution the program records how many times each branch and call is | |
3200 | executed and how many times it is taken or returns. When the compiled | |
3201 | program exits it saves this data to a file called | |
a4878735 | 3202 | @file{@var{auxname}.gcda} for each source file. The data may be used for |
23af32e6 NS |
3203 | profile-directed optimizations (@option{-fbranch-probabilities}), or for |
3204 | test coverage analysis (@option{-ftest-coverage}). Each object file's | |
3205 | @var{auxname} is generated from the name of the output file, if | |
3206 | explicitly specified and it is not the final executable, otherwise it is | |
3207 | the basename of the source file. In both cases any suffix is removed | |
a4878735 NS |
3208 | (e.g. @file{foo.gcda} for input file @file{dir/foo.c}, or |
3209 | @file{dir/foo.gcda} for output file specified as @option{-o dir/foo.o}). | |
23af32e6 NS |
3210 | |
3211 | @itemize | |
3212 | ||
3213 | @item | |
3214 | Compile the source files with @option{-fprofile-arcs} plus optimization | |
3215 | and code generation options. For test coverage analysis, use the | |
3216 | additional @option{-ftest-coverage} option. You do not need to profile | |
3217 | every source file in a program. | |
3218 | ||
3219 | @item | |
8555daff NS |
3220 | Link your object files with @option{-lgcov} or @option{-fprofile-arcs} |
3221 | (the latter implies the former). | |
23af32e6 NS |
3222 | |
3223 | @item | |
3224 | Run the program on a representative workload to generate the arc profile | |
8555daff NS |
3225 | information. This may be repeated any number of times. You can run |
3226 | concurrent instances of your program, and provided that the file system | |
3227 | supports locking, the data files will be correctly updated. Also | |
3228 | @code{fork} calls are detected and correctly handled (double counting | |
3229 | will not happen). | |
23af32e6 NS |
3230 | |
3231 | @item | |
3232 | For profile-directed optimizations, compile the source files again with | |
3233 | the same optimization and code generation options plus | |
630d3d5a | 3234 | @option{-fbranch-probabilities} (@pxref{Optimize Options,,Options that |
3de87bf2 JJ |
3235 | Control Optimization}). |
3236 | ||
23af32e6 NS |
3237 | @item |
3238 | For test coverage analysis, use @command{gcov} to produce human readable | |
a4878735 | 3239 | information from the @file{.gcno} and @file{.gcda} files. Refer to the |
23af32e6 NS |
3240 | @command{gcov} documentation for further information. |
3241 | ||
3242 | @end itemize | |
3de87bf2 JJ |
3243 | |
3244 | With @option{-fprofile-arcs}, for each function of your program GCC | |
3245 | creates a program flow graph, then finds a spanning tree for the graph. | |
3246 | Only arcs that are not on the spanning tree have to be instrumented: the | |
3247 | compiler adds code to count the number of times that these arcs are | |
3248 | executed. When an arc is the only exit or only entrance to a block, the | |
3249 | instrumentation code can be added to the block; otherwise, a new basic | |
3250 | block must be created to hold the instrumentation code. | |
3251 | ||
6de9cd9a DN |
3252 | @item -ftree-based-profiling |
3253 | @opindex ftree-based-profiling | |
3254 | This option is used in addition to @option{-fprofile-arcs} or | |
3255 | @option{-fbranch-probabilities} to control whether those optimizations | |
3256 | are performed on a tree-based or rtl-based internal representation. | |
3257 | If you use this option when compiling with @option{-fprofile-arcs}, | |
3258 | you must also use it when compiling later with @option{-fbranch-probabilities}. | |
3259 | Currently the tree-based optimization is in an early stage of | |
3260 | development, and this option is recommended only for those people | |
3261 | working on improving it. | |
3262 | ||
861bb6c1 JL |
3263 | @need 2000 |
3264 | @item -ftest-coverage | |
cd3bb277 | 3265 | @opindex ftest-coverage |
a4878735 | 3266 | Produce a notes file that the @command{gcov} code-coverage utility |
23af32e6 | 3267 | (@pxref{Gcov,, @command{gcov}---a Test Coverage Program}) can use to |
a4878735 NS |
3268 | show program coverage. Each source file's note file is called |
3269 | @file{@var{auxname}.gcno}. Refer to the @option{-fprofile-arcs} option | |
23af32e6 NS |
3270 | above for a description of @var{auxname} and instructions on how to |
3271 | generate test coverage data. Coverage data will match the source files | |
3272 | more closely, if you do not optimize. | |
3de87bf2 | 3273 | |
74291a4b | 3274 | @item -d@var{letters} |
cd3bb277 | 3275 | @opindex d |
74291a4b MM |
3276 | Says to make debugging dumps during compilation at times specified by |
3277 | @var{letters}. This is used for debugging the compiler. The file names | |
375e2d5c | 3278 | for most of the dumps are made by appending a pass number and a word to |
ea67fe71 NS |
3279 | the @var{dumpname}. @var{dumpname} is generated from the name of the |
3280 | output file, if explicitly specified and it is not an executable, | |
3281 | otherwise it is the basename of the source file. In both cases any | |
98edbb7a | 3282 | suffix is removed (e.g. @file{foo.01.rtl} or @file{foo.02.sibling}). |
ea67fe71 NS |
3283 | Here are the possible letters for use in @var{letters}, and their |
3284 | meanings: | |
74291a4b MM |
3285 | |
3286 | @table @samp | |
375e2d5c | 3287 | @item A |
cd3bb277 | 3288 | @opindex dA |
375e2d5c | 3289 | Annotate the assembler output with miscellaneous debugging information. |
956d6950 | 3290 | @item b |
cd3bb277 | 3291 | @opindex db |
98edbb7a | 3292 | Dump after computing branch probabilities, to @file{@var{file}.12.bp}. |
48d9ade5 | 3293 | @item B |
cd3bb277 | 3294 | @opindex dB |
e5626198 | 3295 | Dump after block reordering, to @file{@var{file}.32.bbro}. |
032713aa | 3296 | @item c |
cd3bb277 | 3297 | @opindex dc |
98edbb7a | 3298 | Dump after instruction combination, to the file @file{@var{file}.20.combine}. |
470fc13d | 3299 | @item C |
cd3bb277 | 3300 | @opindex dC |
98edbb7a KH |
3301 | Dump after the first if conversion, to the file @file{@var{file}.14.ce1}. |
3302 | Also dump after the second if conversion, to the file @file{@var{file}.21.ce2}. | |
032713aa | 3303 | @item d |
cd3bb277 | 3304 | @opindex dd |
e5626198 AZ |
3305 | Dump after branch target load optimization, to to @file{@var{file}.33.btl}. |
3306 | Also dump after delayed branch scheduling, to @file{@var{file}.37.dbr}. | |
032713aa | 3307 | @item D |
cd3bb277 | 3308 | @opindex dD |
f5963e61 JL |
3309 | Dump all macro definitions, at the end of preprocessing, in addition to |
3310 | normal output. | |
470fc13d | 3311 | @item E |
cd3bb277 | 3312 | @opindex dE |
e5626198 | 3313 | Dump after the third if conversion, to @file{@var{file}.31.ce3}. |
74291a4b | 3314 | @item f |
cd3bb277 | 3315 | @opindex df |
98edbb7a KH |
3316 | Dump after control and data flow analysis, to @file{@var{file}.11.cfg}. |
3317 | Also dump after life analysis, to @file{@var{file}.19.life}. | |
74291a4b | 3318 | @item g |
cd3bb277 | 3319 | @opindex dg |
e5626198 | 3320 | Dump after global register allocation, to @file{@var{file}.26.greg}. |
02f52e19 | 3321 | @item G |
cd3bb277 | 3322 | @opindex dG |
98edbb7a | 3323 | Dump after GCSE, to @file{@var{file}.08.gcse}. |
34695841 | 3324 | Also dump after jump bypassing and control flow optimizations, to |
98edbb7a | 3325 | @file{@var{file}.10.bypass}. |
7fedea11 KH |
3326 | @item h |
3327 | @opindex dh | |
a194aa56 | 3328 | Dump after finalization of EH handling code, to @file{@var{file}.03.eh}. |
48d9ade5 | 3329 | @item i |
cd3bb277 | 3330 | @opindex di |
a194aa56 | 3331 | Dump after sibling call optimizations, to @file{@var{file}.02.sibling}. |
032713aa | 3332 | @item j |
cd3bb277 | 3333 | @opindex dj |
a194aa56 | 3334 | Dump after the first jump optimization, to @file{@var{file}.04.jump}. |
74291a4b | 3335 | @item k |
cd3bb277 | 3336 | @opindex dk |
e5626198 | 3337 | Dump after conversion from registers to stack, to @file{@var{file}.35.stack}. |
032713aa | 3338 | @item l |
cd3bb277 | 3339 | @opindex dl |
e5626198 | 3340 | Dump after local register allocation, to @file{@var{file}.25.lreg}. |
032713aa | 3341 | @item L |
cd3bb277 | 3342 | @opindex dL |
98edbb7a KH |
3343 | Dump after loop optimization passes, to @file{@var{file}.09.loop} and |
3344 | @file{@var{file}.16.loop2}. | |
e5626198 AZ |
3345 | @item m |
3346 | @opindex dm | |
f26c1794 | 3347 | Dump after modulo scheduling, to @file{@var{file}.23.sms}. |
032713aa | 3348 | @item M |
cd3bb277 | 3349 | @opindex dM |
c0478a66 | 3350 | Dump after performing the machine dependent reorganization pass, to |
e5626198 | 3351 | @file{@var{file}.36.mach}. |
48d9ade5 | 3352 | @item n |
cd3bb277 | 3353 | @opindex dn |
e5626198 | 3354 | Dump after register renumbering, to @file{@var{file}.30.rnreg}. |
032713aa | 3355 | @item N |
cd3bb277 | 3356 | @opindex dN |
98edbb7a | 3357 | Dump after the register move pass, to @file{@var{file}.22.regmove}. |
7fedea11 KH |
3358 | @item o |
3359 | @opindex do | |
e5626198 | 3360 | Dump after post-reload optimizations, to @file{@var{file}.27.postreload}. |
032713aa | 3361 | @item r |
cd3bb277 | 3362 | @opindex dr |
a194aa56 | 3363 | Dump after RTL generation, to @file{@var{file}.01.rtl}. |
032713aa | 3364 | @item R |
cd3bb277 | 3365 | @opindex dR |
e5626198 | 3366 | Dump after the second scheduling pass, to @file{@var{file}.34.sched2}. |
032713aa | 3367 | @item s |
cd3bb277 | 3368 | @opindex ds |
032713aa | 3369 | Dump after CSE (including the jump optimization that sometimes follows |
98edbb7a | 3370 | CSE), to @file{@var{file}.06.cse}. |
032713aa | 3371 | @item S |
cd3bb277 | 3372 | @opindex dS |
e5626198 | 3373 | Dump after the first scheduling pass, to @file{@var{file}.24.sched}. |
032713aa | 3374 | @item t |
cd3bb277 | 3375 | @opindex dt |
032713aa | 3376 | Dump after the second CSE pass (including the jump optimization that |
98edbb7a | 3377 | sometimes follows CSE), to @file{@var{file}.18.cse2}. |
4319ef2a KH |
3378 | @item T |
3379 | @opindex dT | |
98edbb7a | 3380 | Dump after running tracer, to @file{@var{file}.15.tracer}. |
38c1593d JH |
3381 | @item u |
3382 | @opindex du | |
98edbb7a | 3383 | Dump after null pointer elimination pass to @file{@var{file}.05.null}. |
a194aa56 JH |
3384 | @item U |
3385 | @opindex dU | |
3386 | Dump callgraph and unit-at-a-time optimization @file{@var{file}.00.unit}. | |
9313cfdd KH |
3387 | @item V |
3388 | @opindex dV | |
3389 | Dump after the value profile transformations, to @file{@var{file}.13.vpt}. | |
014a1138 | 3390 | Also dump after variable tracking, to @file{@var{file}.35.vartrack}. |
c80e4c17 | 3391 | @item w |
cd3bb277 | 3392 | @opindex dw |
e5626198 | 3393 | Dump after the second flow pass, to @file{@var{file}.28.flow2}. |
48d9ade5 | 3394 | @item z |
cd3bb277 | 3395 | @opindex dz |
e5626198 | 3396 | Dump after the peephole pass, to @file{@var{file}.29.peephole2}. |
9313cfdd KH |
3397 | @item Z |
3398 | @opindex dZ | |
3399 | Dump after constructing the web, to @file{@var{file}.17.web}. | |
74291a4b | 3400 | @item a |
cd3bb277 | 3401 | @opindex da |
74291a4b | 3402 | Produce all the dumps listed above. |
886e0865 GK |
3403 | @item H |
3404 | @opindex dH | |
3405 | Produce a core dump whenever an error occurs. | |
74291a4b | 3406 | @item m |
cd3bb277 | 3407 | @opindex dm |
74291a4b MM |
3408 | Print statistics on memory usage, at the end of the run, to |
3409 | standard error. | |
3410 | @item p | |
cd3bb277 | 3411 | @opindex dp |
74291a4b | 3412 | Annotate the assembler output with a comment indicating which |
f20b5577 MM |
3413 | pattern and alternative was used. The length of each instruction is |
3414 | also printed. | |
2856c3e3 | 3415 | @item P |
cd3bb277 | 3416 | @opindex dP |
2856c3e3 | 3417 | Dump the RTL in the assembler output as a comment before each instruction. |
630d3d5a | 3418 | Also turns on @option{-dp} annotation. |
375e2d5c | 3419 | @item v |
cd3bb277 | 3420 | @opindex dv |
375e2d5c | 3421 | For each of the other indicated dump files (except for |
a194aa56 | 3422 | @file{@var{file}.01.rtl}), dump a representation of the control flow graph |
b192711e | 3423 | suitable for viewing with VCG to @file{@var{file}.@var{pass}.vcg}. |
62a1403d | 3424 | @item x |
cd3bb277 | 3425 | @opindex dx |
62a1403d AS |
3426 | Just generate RTL for a function instead of compiling it. Usually used |
3427 | with @samp{r}. | |
032713aa | 3428 | @item y |
cd3bb277 | 3429 | @opindex dy |
032713aa | 3430 | Dump debugging information during parsing, to standard error. |
74291a4b MM |
3431 | @end table |
3432 | ||
b707b450 | 3433 | @item -fdump-unnumbered |
cd3bb277 | 3434 | @opindex fdump-unnumbered |
695ac33f | 3435 | When doing debugging dumps (see @option{-d} option above), suppress instruction |
b707b450 | 3436 | numbers and line number note output. This makes it more feasible to |
b192711e | 3437 | use diff on debugging dumps for compiler invocations with different |
695ac33f | 3438 | options, in particular with and without @option{-g}. |
b707b450 | 3439 | |
f70a54cb CR |
3440 | @item -fdump-translation-unit @r{(C and C++ only)} |
3441 | @itemx -fdump-translation-unit-@var{options} @r{(C and C++ only)} | |
3442 | @opindex fdump-translation-unit | |
3443 | Dump a representation of the tree structure for the entire translation | |
3444 | unit to a file. The file name is made by appending @file{.tu} to the | |
3445 | source file name. If the @samp{-@var{options}} form is used, @var{options} | |
3446 | controls the details of the dump as described for the | |
3447 | @option{-fdump-tree} options. | |
3448 | ||
aee96fe9 | 3449 | @item -fdump-class-hierarchy @r{(C++ only)} |
22367161 | 3450 | @itemx -fdump-class-hierarchy-@var{options} @r{(C++ only)} |
cd3bb277 | 3451 | @opindex fdump-class-hierarchy |
e76b4820 | 3452 | Dump a representation of each class's hierarchy and virtual function |
767094dd | 3453 | table layout to a file. The file name is made by appending @file{.class} |
22367161 NS |
3454 | to the source file name. If the @samp{-@var{options}} form is used, |
3455 | @var{options} controls the details of the dump as described for the | |
3456 | @option{-fdump-tree} options. | |
3457 | ||
6de9cd9a DN |
3458 | @item -fdump-tree-@var{switch} @r{(C and C++ only)} |
3459 | @itemx -fdump-tree-@var{switch}-@var{options} @r{(C and C++ only)} | |
22367161 NS |
3460 | @opindex fdump-tree |
3461 | Control the dumping at various stages of processing the intermediate | |
3462 | language tree to a file. The file name is generated by appending a switch | |
3463 | specific suffix to the source file name. If the @samp{-@var{options}} | |
3464 | form is used, @var{options} is a list of @samp{-} separated options that | |
3465 | control the details of the dump. Not all options are applicable to all | |
3466 | dumps, those which are not meaningful will be ignored. The following | |
3467 | options are available | |
f71f87f9 | 3468 | |
e76b4820 | 3469 | @table @samp |
22367161 | 3470 | @item address |
767094dd | 3471 | Print the address of each node. Usually this is not meaningful as it |
22367161 NS |
3472 | changes according to the environment and source file. Its primary use |
3473 | is for tying up a dump file with a debug environment. | |
3474 | @item slim | |
3475 | Inhibit dumping of members of a scope or body of a function merely | |
6de9cd9a DN |
3476 | because that scope has been reached. Only dump such items when they |
3477 | are directly reachable by some other path. When dumping pretty-printed | |
3478 | trees, this option inhibits dumping the bodies of control structures. | |
3479 | @item raw | |
3480 | Print a raw representation of the tree. By default, trees are | |
3481 | pretty-printed into a C-like representation. | |
3482 | @item details | |
3483 | Enable more detailed dumps (not honored by every dump option). | |
3484 | @item stats | |
3485 | Enable dumping various statistics about the pass (not honored by every dump | |
3486 | option). | |
3487 | @item blocks | |
3488 | Enable showing basic block boundaries (disabled in raw dumps). | |
3489 | @item vops | |
3490 | Enable showing virtual operands for every statement. | |
3491 | @item lineno | |
3492 | Enable showing line numbers for statements. | |
3493 | @item uid | |
3494 | Enable showing the unique ID (@code{DECL_UID}) for each variable. | |
22367161 | 3495 | @item all |
6de9cd9a | 3496 | Turn on all options, except @option{raw}, @option{slim} and @option{lineno}. |
e76b4820 NS |
3497 | @end table |
3498 | ||
3499 | The following tree dumps are possible: | |
3500 | @table @samp | |
6de9cd9a | 3501 | |
e76b4820 NS |
3502 | @item original |
3503 | Dump before any tree based optimization, to @file{@var{file}.original}. | |
6de9cd9a | 3504 | |
e76b4820 NS |
3505 | @item optimized |
3506 | Dump after all tree based optimization, to @file{@var{file}.optimized}. | |
6de9cd9a | 3507 | |
6be77748 | 3508 | @item inlined |
9c34dbbf | 3509 | Dump after function inlining, to @file{@var{file}.inlined}. |
6de9cd9a DN |
3510 | |
3511 | @item gimple | |
3512 | @opindex fdump-tree-gimple | |
3513 | Dump each function before and after the gimplification pass to a file. The | |
3514 | file name is made by appending @file{.gimple} to the source file name. | |
3515 | ||
3516 | @item cfg | |
3517 | @opindex fdump-tree-cfg | |
3518 | Dump the control flow graph of each function to a file. The file name is | |
3519 | made by appending @file{.cfg} to the source file name. | |
3520 | ||
3521 | @item vcg | |
3522 | @opindex fdump-tree-vcg | |
3523 | Dump the control flow graph of each function to a file in VCG format. The | |
3524 | file name is made by appending @file{.vcg} to the source file name. Note | |
3525 | that if the file contains more than one function, the generated file cannot | |
3526 | be used directly by VCG. You will need to cut and paste each function's | |
3527 | graph into its own separate file first. | |
3528 | ||
3529 | @item ch | |
3530 | @opindex fdump-tree-ch | |
3531 | Dump each function after copying loop headers. The file name is made by | |
3532 | appending @file{.ch} to the source file name. | |
3533 | ||
3534 | @item ssa | |
3535 | @opindex fdump-tree-ssa | |
3536 | Dump SSA related information to a file. The file name is made by appending | |
3537 | @file{.ssa} to the source file name. | |
3538 | ||
3539 | @item alias | |
3540 | @opindex fdump-tree-alias | |
3541 | Dump aliasing information for each function. The file name is made by | |
3542 | appending @file{.alias} to the source file name. | |
3543 | ||
3544 | @item ccp | |
3545 | @opindex fdump-tree-ccp | |
3546 | Dump each function after CCP. The file name is made by appending | |
3547 | @file{.ccp} to the source file name. | |
3548 | ||
3549 | @item pre | |
3550 | @opindex fdump-tree-pre | |
3551 | Dump trees after partial redundancy elimination. The file name is made | |
3552 | by appending @file{.pre} to the source file name. | |
3553 | ||
ff2ad0f7 DN |
3554 | @item fre |
3555 | @opindex fdump-tree-fre | |
3556 | Dump trees after full redundancy elimination. The file name is made | |
3557 | by appending @file{.fre} to the source file name. | |
3558 | ||
6de9cd9a DN |
3559 | @item dce |
3560 | @opindex fdump-tree-dce | |
3561 | Dump each function after dead code elimination. The file name is made by | |
3562 | appending @file{.dce} to the source file name. | |
3563 | ||
3564 | @item mudflap | |
3565 | @opindex fdump-tree-mudflap | |
3566 | Dump each function after adding mudflap instrumentation. The file name is | |
3567 | made by appending @file{.mudflap} to the source file name. | |
3568 | ||
3569 | @item sra | |
3570 | @opindex fdump-tree-sra | |
3571 | Dump each function after performing scalar replacement of aggregates. The | |
3572 | file name is made by appending @file{.sra} to the source file name. | |
3573 | ||
3574 | @item dom | |
3575 | @opindex fdump-tree-dom | |
3576 | Dump each function after applying dominator tree optimizations. The file | |
3577 | name is made by appending @file{.dom} to the source file name. | |
3578 | ||
3579 | @item dse | |
3580 | @opindex fdump-tree-dse | |
3581 | Dump each function after applying dead store elimination. The file | |
3582 | name is made by appending @file{.dse} to the source file name. | |
3583 | ||
3584 | @item phiopt | |
3585 | @opindex fdump-tree-phiopt | |
3586 | Dump each function after optimizing PHI nodes into straightline code. The file | |
3587 | name is made by appending @file{.phiopt} to the source file name. | |
3588 | ||
3589 | @item forwprop | |
3590 | @opindex fdump-tree-forwprop | |
3591 | Dump each function after forward propagating single use variables. The file | |
3592 | name is made by appending @file{.forwprop} to the source file name. | |
3593 | ||
3594 | @item copyrename | |
3595 | @opindex fdump-tree-copyrename | |
3596 | Dump each function after applying the copy rename optimization. The file | |
3597 | name is made by appending @file{.copyrename} to the source file name. | |
3598 | ||
3599 | @item nrv | |
3600 | @opindex fdump-tree-nrv | |
3601 | Dump each function after applying the named return value optimization on | |
3602 | generic trees. The file name is made by appending @file{.nrv} to the source | |
3603 | file name. | |
3604 | ||
3605 | @item all | |
3606 | @opindex fdump-tree-all | |
3607 | Enable all the available tree dumps with the flags provided in this option. | |
e76b4820 | 3608 | @end table |
9965d119 | 3609 | |
a37db56b GK |
3610 | @item -frandom-seed=@var{string} |
3611 | @opindex frandom-string | |
3612 | This option provides a seed that GCC uses when it would otherwise use | |
e61a2eb7 NS |
3613 | random numbers. It is used to generate certain symbol names |
3614 | that have to be different in every compiled file. It is also used to | |
3615 | place unique stamps in coverage data files and the object files that | |
3616 | produce them. You can use the @option{-frandom-seed} option to produce | |
3617 | reproducibly identical object files. | |
a37db56b GK |
3618 | |
3619 | The @var{string} should be different for every file you compile. | |
3620 | ||
e03b7153 RS |
3621 | @item -fsched-verbose=@var{n} |
3622 | @opindex fsched-verbose | |
3623 | On targets that use instruction scheduling, this option controls the | |
3624 | amount of debugging output the scheduler prints. This information is | |
3625 | written to standard error, unless @option{-dS} or @option{-dR} is | |
3626 | specified, in which case it is output to the usual dump | |
3627 | listing file, @file{.sched} or @file{.sched2} respectively. However | |
3628 | for @var{n} greater than nine, the output is always printed to standard | |
3629 | error. | |
3630 | ||
3631 | For @var{n} greater than zero, @option{-fsched-verbose} outputs the | |
3632 | same information as @option{-dRS}. For @var{n} greater than one, it | |
3633 | also output basic block probabilities, detailed ready list information | |
3634 | and unit/insn info. For @var{n} greater than two, it includes RTL | |
3635 | at abort point, control-flow and regions info. And for @var{n} over | |
3636 | four, @option{-fsched-verbose} also includes dependence info. | |
3637 | ||
74291a4b | 3638 | @item -save-temps |
cd3bb277 | 3639 | @opindex save-temps |
74291a4b MM |
3640 | Store the usual ``temporary'' intermediate files permanently; place them |
3641 | in the current directory and name them based on the source file. Thus, | |
3642 | compiling @file{foo.c} with @samp{-c -save-temps} would produce files | |
f2ecb02d JM |
3643 | @file{foo.i} and @file{foo.s}, as well as @file{foo.o}. This creates a |
3644 | preprocessed @file{foo.i} output file even though the compiler now | |
3645 | normally uses an integrated preprocessor. | |
74291a4b | 3646 | |
03c41c05 | 3647 | @item -time |
cd3bb277 | 3648 | @opindex time |
03c41c05 | 3649 | Report the CPU time taken by each subprocess in the compilation |
f2ecb02d JM |
3650 | sequence. For C source files, this is the compiler proper and assembler |
3651 | (plus the linker if linking is done). The output looks like this: | |
03c41c05 ZW |
3652 | |
3653 | @smallexample | |
03c41c05 ZW |
3654 | # cc1 0.12 0.01 |
3655 | # as 0.00 0.01 | |
3656 | @end smallexample | |
3657 | ||
3658 | The first number on each line is the ``user time,'' that is time spent | |
3659 | executing the program itself. The second number is ``system time,'' | |
3660 | time spent executing operating system routines on behalf of the program. | |
3661 | Both numbers are in seconds. | |
3662 | ||
014a1138 JZ |
3663 | @item -fvar-tracking |
3664 | @opindex fvar-tracking | |
3665 | Run variable tracking pass. It computes where variables are stored at each | |
3666 | position in code. Better debugging information is then generated | |
3667 | (if the debugging information format supports this information). | |
3668 | ||
3669 | It is enabled by default when compiling with optimization (@option{-Os}, | |
3670 | @option{-O}, @option{-O2}, ...), debugging information (@option{-g}) and | |
3671 | the debug info format supports it. | |
3672 | ||
74291a4b | 3673 | @item -print-file-name=@var{library} |
cd3bb277 | 3674 | @opindex print-file-name |
74291a4b MM |
3675 | Print the full absolute name of the library file @var{library} that |
3676 | would be used when linking---and don't do anything else. With this | |
0c2d1a2a | 3677 | option, GCC does not compile or link anything; it just prints the |
74291a4b MM |
3678 | file name. |
3679 | ||
b1018de6 AO |
3680 | @item -print-multi-directory |
3681 | @opindex print-multi-directory | |
3682 | Print the directory name corresponding to the multilib selected by any | |
3683 | other switches present in the command line. This directory is supposed | |
3684 | to exist in @env{GCC_EXEC_PREFIX}. | |
3685 | ||
3686 | @item -print-multi-lib | |
3687 | @opindex print-multi-lib | |
3688 | Print the mapping from multilib directory names to compiler switches | |
3689 | that enable them. The directory name is separated from the switches by | |
3690 | @samp{;}, and each switch starts with an @samp{@@} instead of the | |
3691 | @samp{-}, without spaces between multiple switches. This is supposed to | |
3692 | ease shell-processing. | |
3693 | ||
74291a4b | 3694 | @item -print-prog-name=@var{program} |
cd3bb277 | 3695 | @opindex print-prog-name |
630d3d5a | 3696 | Like @option{-print-file-name}, but searches for a program such as @samp{cpp}. |
74291a4b MM |
3697 | |
3698 | @item -print-libgcc-file-name | |
cd3bb277 | 3699 | @opindex print-libgcc-file-name |
630d3d5a | 3700 | Same as @option{-print-file-name=libgcc.a}. |
74291a4b | 3701 | |
630d3d5a | 3702 | This is useful when you use @option{-nostdlib} or @option{-nodefaultlibs} |
74291a4b MM |
3703 | but you do want to link with @file{libgcc.a}. You can do |
3704 | ||
3ab51846 | 3705 | @smallexample |
74291a4b | 3706 | gcc -nostdlib @var{files}@dots{} `gcc -print-libgcc-file-name` |
3ab51846 | 3707 | @end smallexample |
74291a4b MM |
3708 | |
3709 | @item -print-search-dirs | |
cd3bb277 | 3710 | @opindex print-search-dirs |
74291a4b | 3711 | Print the name of the configured installation directory and a list of |
2dd76960 | 3712 | program and library directories @command{gcc} will search---and don't do anything else. |
74291a4b | 3713 | |
2dd76960 | 3714 | This is useful when @command{gcc} prints the error message |
3c0b7970 JM |
3715 | @samp{installation problem, cannot exec cpp0: No such file or directory}. |
3716 | To resolve this you either need to put @file{cpp0} and the other compiler | |
2dd76960 | 3717 | components where @command{gcc} expects to find them, or you can set the environment |
bedc7537 | 3718 | variable @env{GCC_EXEC_PREFIX} to the directory where you installed them. |
74291a4b MM |
3719 | Don't forget the trailing '/'. |
3720 | @xref{Environment Variables}. | |
1f0c3120 JM |
3721 | |
3722 | @item -dumpmachine | |
cd3bb277 | 3723 | @opindex dumpmachine |
1f0c3120 JM |
3724 | Print the compiler's target machine (for example, |
3725 | @samp{i686-pc-linux-gnu})---and don't do anything else. | |
3726 | ||
3727 | @item -dumpversion | |
cd3bb277 | 3728 | @opindex dumpversion |
1f0c3120 JM |
3729 | Print the compiler version (for example, @samp{3.0})---and don't do |
3730 | anything else. | |
3731 | ||
3732 | @item -dumpspecs | |
cd3bb277 | 3733 | @opindex dumpspecs |
1f0c3120 JM |
3734 | Print the compiler's built-in specs---and don't do anything else. (This |
3735 | is used when GCC itself is being built.) @xref{Spec Files}. | |
73c68f61 SS |
3736 | |
3737 | @item -feliminate-unused-debug-types | |
3738 | @opindex feliminate-unused-debug-types | |
3739 | Normally, when producing DWARF2 output, GCC will emit debugging | |
3740 | information for all types declared in a compilation | |
3741 | unit, regardless of whether or not they are actually used | |
3742 | in that compilation unit. Sometimes this is useful, such as | |
3743 | if, in the debugger, you want to cast a value to a type that is | |
3744 | not actually used in your program (but is declared). More often, | |
3745 | however, this results in a significant amount of wasted space. | |
3746 | With this option, GCC will avoid producing debug symbol output | |
3747 | for types that are nowhere used in the source file being compiled. | |
74291a4b MM |
3748 | @end table |
3749 | ||
3750 | @node Optimize Options | |
3751 | @section Options That Control Optimization | |
3752 | @cindex optimize options | |
3753 | @cindex options, optimization | |
3754 | ||
147d1cd3 JQ |
3755 | These options control various sorts of optimizations. |
3756 | ||
3757 | Without any optimization option, the compiler's goal is to reduce the | |
3758 | cost of compilation and to make debugging produce the expected | |
3759 | results. Statements are independent: if you stop the program with a | |
3760 | breakpoint between statements, you can then assign a new value to any | |
3761 | variable or change the program counter to any other statement in the | |
3762 | function and get exactly the results you would expect from the source | |
3763 | code. | |
3764 | ||
3765 | Turning on optimization flags makes the compiler attempt to improve | |
3766 | the performance and/or code size at the expense of compilation time | |
3767 | and possibly the ability to debug the program. | |
3768 | ||
a451b0bd | 3769 | The compiler performs optimization based on the knowledge it has of |
7797ff53 PB |
3770 | the program. Optimization levels @option{-O2} and above, in |
3771 | particular, enable @emph{unit-at-a-time} mode, which allows the | |
3772 | compiler to consider information gained from later functions in | |
3773 | the file when compiling a function. Compiling multiple files at | |
3774 | once to a single output file in @emph{unit-at-a-time} mode allows | |
d1bd0ded GK |
3775 | the compiler to use information gained from all of the files when |
3776 | compiling each of them. | |
3777 | ||
147d1cd3 JQ |
3778 | Not all optimizations are controlled directly by a flag. Only |
3779 | optimizations that have a flag are listed. | |
74291a4b | 3780 | |
2642624b | 3781 | @table @gcctabopt |
74291a4b MM |
3782 | @item -O |
3783 | @itemx -O1 | |
cd3bb277 JM |
3784 | @opindex O |
3785 | @opindex O1 | |
74291a4b MM |
3786 | Optimize. Optimizing compilation takes somewhat more time, and a lot |
3787 | more memory for a large function. | |
3788 | ||
630d3d5a | 3789 | With @option{-O}, the compiler tries to reduce code size and execution |
9c34dbbf ZW |
3790 | time, without performing any optimizations that take a great deal of |
3791 | compilation time. | |
74291a4b | 3792 | |
daf2f129 | 3793 | @option{-O} turns on the following optimization flags: |
9a94f7f3 JM |
3794 | @gccoptlist{-fdefer-pop @gol |
3795 | -fmerge-constants @gol | |
3796 | -fthread-jumps @gol | |
3797 | -floop-optimize @gol | |
9a94f7f3 JM |
3798 | -fif-conversion @gol |
3799 | -fif-conversion2 @gol | |
3800 | -fdelayed-branch @gol | |
3801 | -fguess-branch-probability @gol | |
fad893da JQ |
3802 | -fcprop-registers} |
3803 | ||
3804 | @option{-O} also turns on @option{-fomit-frame-pointer} on machines | |
3805 | where doing so does not interfere with debugging. | |
3806 | ||
74291a4b | 3807 | @item -O2 |
cd3bb277 | 3808 | @opindex O2 |
0c2d1a2a | 3809 | Optimize even more. GCC performs nearly all supported optimizations |
74291a4b | 3810 | that do not involve a space-speed tradeoff. The compiler does not |
630d3d5a JM |
3811 | perform loop unrolling or function inlining when you specify @option{-O2}. |
3812 | As compared to @option{-O}, this option increases both compilation time | |
74291a4b MM |
3813 | and the performance of the generated code. |
3814 | ||
fad893da JQ |
3815 | @option{-O2} turns on all optimization flags specified by @option{-O}. It |
3816 | also turns on the following optimization flags: | |
9a94f7f3 JM |
3817 | @gccoptlist{-fforce-mem @gol |
3818 | -foptimize-sibling-calls @gol | |
3819 | -fstrength-reduce @gol | |
3820 | -fcse-follow-jumps -fcse-skip-blocks @gol | |
3821 | -frerun-cse-after-loop -frerun-loop-opt @gol | |
f5f2e3cd | 3822 | -fgcse -fgcse-lm -fgcse-sm -fgcse-las @gol |
9a94f7f3 JM |
3823 | -fdelete-null-pointer-checks @gol |
3824 | -fexpensive-optimizations @gol | |
f5f2e3cd | 3825 | -fregmove @gol |
9a94f7f3 JM |
3826 | -fschedule-insns -fschedule-insns2 @gol |
3827 | -fsched-interblock -fsched-spec @gol | |
3828 | -fcaller-saves @gol | |
3829 | -fpeephole2 @gol | |
3830 | -freorder-blocks -freorder-functions @gol | |
3831 | -fstrict-aliasing @gol | |
23a44080 | 3832 | -funit-at-a-time @gol |
9a94f7f3 | 3833 | -falign-functions -falign-jumps @gol |
b684a3df JH |
3834 | -falign-loops -falign-labels @gol |
3835 | -fcrossjumping} | |
74291a4b | 3836 | |
081ca317 BL |
3837 | Please note the warning under @option{-fgcse} about |
3838 | invoking @option{-O2} on programs that use computed gotos. | |
3839 | ||
74291a4b | 3840 | @item -O3 |
cd3bb277 | 3841 | @opindex O3 |
630d3d5a | 3842 | Optimize yet more. @option{-O3} turns on all optimizations specified by |
dafc5b82 | 3843 | @option{-O2} and also turns on the @option{-finline-functions}, |
db643b91 SH |
3844 | @option{-fweb}, @option{-frename-registers} |
3845 | and @option{-fgcse-after-reload} options. | |
74291a4b MM |
3846 | |
3847 | @item -O0 | |
cd3bb277 | 3848 | @opindex O0 |
fad893da | 3849 | Do not optimize. This is the default. |
74291a4b | 3850 | |
c6aded7c | 3851 | @item -Os |
cd3bb277 | 3852 | @opindex Os |
630d3d5a | 3853 | Optimize for size. @option{-Os} enables all @option{-O2} optimizations that |
c6aded7c AG |
3854 | do not typically increase code size. It also performs further |
3855 | optimizations designed to reduce code size. | |
3856 | ||
fad893da | 3857 | @option{-Os} disables the following optimization flags: |
9a94f7f3 | 3858 | @gccoptlist{-falign-functions -falign-jumps -falign-loops @gol |
750054a2 | 3859 | -falign-labels -freorder-blocks -freorder-blocks-and-partition -fprefetch-loop-arrays} |
fad893da | 3860 | |
630d3d5a | 3861 | If you use multiple @option{-O} options, with or without level numbers, |
74291a4b MM |
3862 | the last such option is the one that is effective. |
3863 | @end table | |
3864 | ||
630d3d5a | 3865 | Options of the form @option{-f@var{flag}} specify machine-independent |
74291a4b | 3866 | flags. Most flags have both positive and negative forms; the negative |
147d1cd3 JQ |
3867 | form of @option{-ffoo} would be @option{-fno-foo}. In the table |
3868 | below, only one of the forms is listed---the one you typically will | |
3869 | use. You can figure out the other form by either removing @samp{no-} | |
3870 | or adding it. | |
3871 | ||
3872 | The following options control specific optimizations. They are either | |
3873 | activated by @option{-O} options or are related to ones that are. You | |
3874 | can use the following flags in the rare cases when ``fine-tuning'' of | |
3875 | optimizations to be performed is desired. | |
74291a4b | 3876 | |
2642624b | 3877 | @table @gcctabopt |
74291a4b | 3878 | @item -fno-default-inline |
cd3bb277 | 3879 | @opindex fno-default-inline |
74291a4b MM |
3880 | Do not make member functions inline by default merely because they are |
3881 | defined inside the class scope (C++ only). Otherwise, when you specify | |
630d3d5a | 3882 | @w{@option{-O}}, member functions defined inside class scope are compiled |
74291a4b MM |
3883 | inline by default; i.e., you don't need to add @samp{inline} in front of |
3884 | the member function name. | |
3885 | ||
3886 | @item -fno-defer-pop | |
cd3bb277 | 3887 | @opindex fno-defer-pop |
74291a4b MM |
3888 | Always pop the arguments to each function call as soon as that function |
3889 | returns. For machines which must pop arguments after a function call, | |
3890 | the compiler normally lets arguments accumulate on the stack for several | |
3891 | function calls and pops them all at once. | |
3892 | ||
38df970e JQ |
3893 | Disabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
3894 | ||
74291a4b | 3895 | @item -fforce-mem |
cd3bb277 | 3896 | @opindex fforce-mem |
74291a4b MM |
3897 | Force memory operands to be copied into registers before doing |
3898 | arithmetic on them. This produces better code by making all memory | |
3899 | references potential common subexpressions. When they are not common | |
3900 | subexpressions, instruction combination should eliminate the separate | |
38df970e JQ |
3901 | register-load. |
3902 | ||
3903 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. | |
74291a4b MM |
3904 | |
3905 | @item -fforce-addr | |
cd3bb277 | 3906 | @opindex fforce-addr |
74291a4b MM |
3907 | Force memory address constants to be copied into registers before |
3908 | doing arithmetic on them. This may produce better code just as | |
630d3d5a | 3909 | @option{-fforce-mem} may. |
74291a4b MM |
3910 | |
3911 | @item -fomit-frame-pointer | |
cd3bb277 | 3912 | @opindex fomit-frame-pointer |
74291a4b MM |
3913 | Don't keep the frame pointer in a register for functions that |
3914 | don't need one. This avoids the instructions to save, set up and | |
3915 | restore frame pointers; it also makes an extra register available | |
3916 | in many functions. @strong{It also makes debugging impossible on | |
3917 | some machines.} | |
3918 | ||
8aeea6e6 | 3919 | On some machines, such as the VAX, this flag has no effect, because |
74291a4b MM |
3920 | the standard calling sequence automatically handles the frame pointer |
3921 | and nothing is saved by pretending it doesn't exist. The | |
3922 | machine-description macro @code{FRAME_POINTER_REQUIRED} controls | |
3923 | whether a target machine supports this flag. @xref{Registers,,Register | |
b11cc610 | 3924 | Usage, gccint, GNU Compiler Collection (GCC) Internals}. |
74291a4b | 3925 | |
38df970e JQ |
3926 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
3927 | ||
1aaef9c1 | 3928 | @item -foptimize-sibling-calls |
cd3bb277 | 3929 | @opindex foptimize-sibling-calls |
1aaef9c1 JH |
3930 | Optimize sibling and tail recursive calls. |
3931 | ||
38df970e JQ |
3932 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
3933 | ||
74291a4b | 3934 | @item -fno-inline |
cd3bb277 | 3935 | @opindex fno-inline |
74291a4b MM |
3936 | Don't pay attention to the @code{inline} keyword. Normally this option |
3937 | is used to keep the compiler from expanding any functions inline. | |
3938 | Note that if you are not optimizing, no functions can be expanded inline. | |
3939 | ||
3940 | @item -finline-functions | |
cd3bb277 | 3941 | @opindex finline-functions |
74291a4b MM |
3942 | Integrate all simple functions into their callers. The compiler |
3943 | heuristically decides which functions are simple enough to be worth | |
3944 | integrating in this way. | |
3945 | ||
3946 | If all calls to a given function are integrated, and the function is | |
3947 | declared @code{static}, then the function is normally not output as | |
3948 | assembler code in its own right. | |
3949 | ||
38df970e JQ |
3950 | Enabled at level @option{-O3}. |
3951 | ||
efa3896a | 3952 | @item -finline-limit=@var{n} |
cd3bb277 | 3953 | @opindex finline-limit |
2dd76960 | 3954 | By default, GCC limits the size of functions that can be inlined. This flag |
f9e814f1 | 3955 | allows the control of this limit for functions that are explicitly marked as |
3364c33b | 3956 | inline (i.e., marked with the inline keyword or defined within the class |
02f52e19 | 3957 | definition in c++). @var{n} is the size of functions that can be inlined in |
f9e814f1 | 3958 | number of pseudo instructions (not counting parameter handling). The default |
93ee12c4 GP |
3959 | value of @var{n} is 600. |
3960 | Increasing this value can result in more inlined code at | |
f9e814f1 | 3961 | the cost of compilation time and memory consumption. Decreasing usually makes |
02f52e19 AJ |
3962 | the compilation faster and less code will be inlined (which presumably |
3963 | means slower programs). This option is particularly useful for programs that | |
aee96fe9 | 3964 | use inlining heavily such as those based on recursive templates with C++. |
f9e814f1 | 3965 | |
bc522472 KG |
3966 | Inlining is actually controlled by a number of parameters, which may be |
3967 | specified individually by using @option{--param @var{name}=@var{value}}. | |
daf2f129 | 3968 | The @option{-finline-limit=@var{n}} option sets some of these parameters |
bc522472 KG |
3969 | as follows: |
3970 | ||
3971 | @table @gcctabopt | |
bc522472 KG |
3972 | @item max-inline-insns-single |
3973 | is set to @var{n}/2. | |
6d7fe8b3 | 3974 | @item max-inline-insns-auto |
bc522472 KG |
3975 | is set to @var{n}/2. |
3976 | @item min-inline-insns | |
3977 | is set to 130 or @var{n}/4, whichever is smaller. | |
3978 | @item max-inline-insns-rtl | |
3979 | is set to @var{n}. | |
3980 | @end table | |
3981 | ||
f7a01847 | 3982 | See below for a documentation of the individual |
bc522472 KG |
3983 | parameters controlling inlining. |
3984 | ||
f9e814f1 TP |
3985 | @emph{Note:} pseudo instruction represents, in this particular context, an |
3986 | abstract measurement of function's size. In no way, it represents a count | |
3987 | of assembly instructions and as such its exact meaning might change from one | |
3988 | release to an another. | |
3989 | ||
74291a4b | 3990 | @item -fkeep-inline-functions |
cd3bb277 | 3991 | @opindex fkeep-inline-functions |
74291a4b MM |
3992 | Even if all calls to a given function are integrated, and the function |
3993 | is declared @code{static}, nevertheless output a separate run-time | |
3994 | callable version of the function. This switch does not affect | |
3995 | @code{extern inline} functions. | |
3996 | ||
3997 | @item -fkeep-static-consts | |
cd3bb277 | 3998 | @opindex fkeep-static-consts |
74291a4b MM |
3999 | Emit variables declared @code{static const} when optimization isn't turned |
4000 | on, even if the variables aren't referenced. | |
4001 | ||
0c2d1a2a | 4002 | GCC enables this option by default. If you want to force the compiler to |
74291a4b | 4003 | check if the variable was referenced, regardless of whether or not |
630d3d5a | 4004 | optimization is turned on, use the @option{-fno-keep-static-consts} option. |
74291a4b | 4005 | |
201556f0 JJ |
4006 | @item -fmerge-constants |
4007 | Attempt to merge identical constants (string constants and floating point | |
3364c33b | 4008 | constants) across compilation units. |
201556f0 | 4009 | |
3364c33b JQ |
4010 | This option is the default for optimized compilation if the assembler and |
4011 | linker support it. Use @option{-fno-merge-constants} to inhibit this | |
4012 | behavior. | |
201556f0 | 4013 | |
38df970e JQ |
4014 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
4015 | ||
201556f0 JJ |
4016 | @item -fmerge-all-constants |
4017 | Attempt to merge identical constants and identical variables. | |
4018 | ||
4019 | This option implies @option{-fmerge-constants}. In addition to | |
4020 | @option{-fmerge-constants} this considers e.g. even constant initialized | |
4021 | arrays or initialized constant variables with integral or floating point | |
4022 | types. Languages like C or C++ require each non-automatic variable to | |
4023 | have distinct location, so using this option will result in non-conforming | |
c21cd8b1 | 4024 | behavior. |
201556f0 | 4025 | |
e5626198 AZ |
4026 | @item -fmodulo-sched |
4027 | @opindex fmodulo-sched | |
4028 | Perform swing modulo scheduling immediately before the first scheduling | |
4029 | pass. This pass looks at innermost loops and reorders their | |
4030 | instructions by overlapping different iterations. | |
4031 | ||
ed8d2920 MM |
4032 | @item -fnew-ra |
4033 | @opindex fnew-ra | |
4034 | Use a graph coloring register allocator. Currently this option is meant | |
7db956db DH |
4035 | only for testing. Users should not specify this option, since it is not |
4036 | yet ready for production use. | |
ed8d2920 | 4037 | |
e03b7153 RS |
4038 | @item -fno-branch-count-reg |
4039 | @opindex fno-branch-count-reg | |
4040 | Do not use ``decrement and branch'' instructions on a count register, | |
4041 | but instead generate a sequence of instructions that decrement a | |
4042 | register, compare it against zero, then branch based upon the result. | |
4043 | This option is only meaningful on architectures that support such | |
4044 | instructions, which include x86, PowerPC, IA-64 and S/390. | |
4045 | ||
38df970e JQ |
4046 | The default is @option{-fbranch-count-reg}, enabled when |
4047 | @option{-fstrength-reduce} is enabled. | |
4048 | ||
74291a4b | 4049 | @item -fno-function-cse |
cd3bb277 | 4050 | @opindex fno-function-cse |
74291a4b MM |
4051 | Do not put function addresses in registers; make each instruction that |
4052 | calls a constant function contain the function's address explicitly. | |
4053 | ||
4054 | This option results in less efficient code, but some strange hacks | |
4055 | that alter the assembler output may be confused by the optimizations | |
4056 | performed when this option is not used. | |
4057 | ||
38df970e JQ |
4058 | The default is @option{-ffunction-cse} |
4059 | ||
27b41650 KG |
4060 | @item -fno-zero-initialized-in-bss |
4061 | @opindex fno-zero-initialized-in-bss | |
4062 | If the target supports a BSS section, GCC by default puts variables that | |
4063 | are initialized to zero into BSS@. This can save space in the resulting | |
4064 | code. | |
4065 | ||
4066 | This option turns off this behavior because some programs explicitly | |
4067 | rely on variables going to the data section. E.g., so that the | |
4068 | resulting executable can find the beginning of that section and/or make | |
4069 | assumptions based on that. | |
4070 | ||
4071 | The default is @option{-fzero-initialized-in-bss}. | |
e03b7153 | 4072 | |
6de9cd9a DN |
4073 | @item -fbounds-check |
4074 | @opindex fbounds-check | |
4075 | For front-ends that support it, generate additional code to check that | |
4076 | indices used to access arrays are within the declared range. This is | |
4077 | currently only supported by the Java and Fortran front-ends, where | |
4078 | this option defaults to true and false respectively. | |
4079 | ||
4080 | @item -fmudflap -fmudflapth -fmudflapir | |
4081 | @opindex fmudflap | |
4082 | @opindex fmudflapth | |
4083 | @opindex fmudflapir | |
4084 | @cindex bounds checking | |
4085 | @cindex mudflap | |
4086 | For front-ends that support it (C and C++), instrument all risky | |
4087 | pointer/array dereferencing operations, some standard library | |
4088 | string/heap functions, and some other associated constructs with | |
4089 | range/validity tests. Modules so instrumented should be immune to | |
4090 | buffer overflows, invalid heap use, and some other classes of C/C++ | |
4091 | programming errors. The instrumentation relies on a separate runtime | |
4092 | library (@file{libmudflap}), which will be linked into a program if | |
4093 | @option{-fmudflap} is given at link time. Run-time behavior of the | |
4094 | instrumented program is controlled by the @env{MUDFLAP_OPTIONS} | |
4095 | environment variable. See @code{env MUDFLAP_OPTIONS=-help a.out} | |
4096 | for its options. | |
4097 | ||
4098 | Use @option{-fmudflapth} instead of @option{-fmudflap} to compile and to | |
4099 | link if your program is multi-threaded. Use @option{-fmudflapir}, in | |
4100 | addition to @option{-fmudflap} or @option{-fmudflapth}, if | |
4101 | instrumentation should ignore pointer reads. This produces less | |
4102 | instrumentation (and therefore faster execution) and still provides | |
4103 | some protection against outright memory corrupting writes, but allows | |
4104 | erroneously read data to propagate within a program. | |
4105 | ||
74291a4b | 4106 | @item -fstrength-reduce |
cd3bb277 | 4107 | @opindex fstrength-reduce |
74291a4b MM |
4108 | Perform the optimizations of loop strength reduction and |
4109 | elimination of iteration variables. | |
4110 | ||
38df970e JQ |
4111 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4112 | ||
74291a4b | 4113 | @item -fthread-jumps |
cd3bb277 | 4114 | @opindex fthread-jumps |
74291a4b MM |
4115 | Perform optimizations where we check to see if a jump branches to a |
4116 | location where another comparison subsumed by the first is found. If | |
4117 | so, the first branch is redirected to either the destination of the | |
4118 | second branch or a point immediately following it, depending on whether | |
4119 | the condition is known to be true or false. | |
4120 | ||
38df970e JQ |
4121 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
4122 | ||
74291a4b | 4123 | @item -fcse-follow-jumps |
cd3bb277 | 4124 | @opindex fcse-follow-jumps |
74291a4b MM |
4125 | In common subexpression elimination, scan through jump instructions |
4126 | when the target of the jump is not reached by any other path. For | |
4127 | example, when CSE encounters an @code{if} statement with an | |
4128 | @code{else} clause, CSE will follow the jump when the condition | |
4129 | tested is false. | |
4130 | ||
38df970e JQ |
4131 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4132 | ||
74291a4b | 4133 | @item -fcse-skip-blocks |
cd3bb277 | 4134 | @opindex fcse-skip-blocks |
630d3d5a | 4135 | This is similar to @option{-fcse-follow-jumps}, but causes CSE to |
74291a4b MM |
4136 | follow jumps which conditionally skip over blocks. When CSE |
4137 | encounters a simple @code{if} statement with no else clause, | |
630d3d5a | 4138 | @option{-fcse-skip-blocks} causes CSE to follow the jump around the |
74291a4b MM |
4139 | body of the @code{if}. |
4140 | ||
38df970e JQ |
4141 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4142 | ||
74291a4b | 4143 | @item -frerun-cse-after-loop |
cd3bb277 | 4144 | @opindex frerun-cse-after-loop |
74291a4b MM |
4145 | Re-run common subexpression elimination after loop optimizations has been |
4146 | performed. | |
4147 | ||
38df970e JQ |
4148 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4149 | ||
6d6d0fa0 | 4150 | @item -frerun-loop-opt |
cd3bb277 | 4151 | @opindex frerun-loop-opt |
6d6d0fa0 JL |
4152 | Run the loop optimizer twice. |
4153 | ||
38df970e JQ |
4154 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4155 | ||
7506f491 | 4156 | @item -fgcse |
cd3bb277 | 4157 | @opindex fgcse |
7506f491 DE |
4158 | Perform a global common subexpression elimination pass. |
4159 | This pass also performs global constant and copy propagation. | |
4160 | ||
081ca317 BL |
4161 | @emph{Note:} When compiling a program using computed gotos, a GCC |
4162 | extension, you may get better runtime performance if you disable | |
3364c33b | 4163 | the global common subexpression elimination pass by adding |
081ca317 BL |
4164 | @option{-fno-gcse} to the command line. |
4165 | ||
38df970e JQ |
4166 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4167 | ||
a13d4ebf | 4168 | @item -fgcse-lm |
cd3bb277 | 4169 | @opindex fgcse-lm |
695ac33f | 4170 | When @option{-fgcse-lm} is enabled, global common subexpression elimination will |
767094dd | 4171 | attempt to move loads which are only killed by stores into themselves. This |
a13d4ebf | 4172 | allows a loop containing a load/store sequence to be changed to a load outside |
02f52e19 | 4173 | the loop, and a copy/store within the loop. |
a13d4ebf | 4174 | |
38df970e JQ |
4175 | Enabled by default when gcse is enabled. |
4176 | ||
a13d4ebf | 4177 | @item -fgcse-sm |
cd3bb277 | 4178 | @opindex fgcse-sm |
f5f2e3cd MH |
4179 | When @option{-fgcse-sm} is enabled, a store motion pass is run after |
4180 | global common subexpression elimination. This pass will attempt to move | |
4181 | stores out of loops. When used in conjunction with @option{-fgcse-lm}, | |
4182 | loops containing a load/store sequence can be changed to a load before | |
4183 | the loop and a store after the loop. | |
4184 | ||
4185 | Enabled by default when gcse is enabled. | |
4186 | ||
4187 | @item -fgcse-las | |
4188 | @opindex fgcse-las | |
4189 | When @option{-fgcse-las} is enabled, the global common subexpression | |
4190 | elimination pass eliminates redundant loads that come after stores to the | |
2206e783 | 4191 | same memory location (both partial and full redundancies). |
a13d4ebf | 4192 | |
38df970e JQ |
4193 | Enabled by default when gcse is enabled. |
4194 | ||
db643b91 SH |
4195 | @item -fgcse-after-reload |
4196 | @opindex fgcse-after-reload | |
4197 | When @option{-fgcse-after-reload} is enabled, a redundant load elimination | |
4198 | pass is performed after reload. The purpose of this pass is to cleanup | |
4199 | redundant spilling. | |
4200 | ||
96327cdc JH |
4201 | @item -floop-optimize |
4202 | @opindex floop-optimize | |
4203 | Perform loop optimizations: move constant expressions out of loops, simplify | |
4204 | exit test conditions and optionally do strength-reduction and loop unrolling as | |
4205 | well. | |
4206 | ||
38df970e JQ |
4207 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
4208 | ||
5e962776 ZD |
4209 | @item -floop-optimize2 |
4210 | @opindex floop-optimize2 | |
4211 | Perform loop optimizations using the new loop optimizer. The optimizations | |
4212 | (loop unrolling, peeling and unswitching, loop invariant motion) are enabled | |
4213 | by separate flags. | |
4214 | ||
96327cdc JH |
4215 | @item -fcrossjumping |
4216 | @opindex crossjumping | |
4217 | Perform cross-jumping transformation. This transformation unifies equivalent code and save code size. The | |
4218 | resulting code may or may not perform better than without cross-jumping. | |
4219 | ||
38df970e JQ |
4220 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
4221 | ||
2c4b77f3 JH |
4222 | @item -fif-conversion |
4223 | @opindex if-conversion | |
4224 | Attempt to transform conditional jumps into branch-less equivalents. This | |
4225 | include use of conditional moves, min, max, set flags and abs instructions, and | |
4226 | some tricks doable by standard arithmetics. The use of conditional execution | |
4227 | on chips where it is available is controlled by @code{if-conversion2}. | |
4228 | ||
38df970e JQ |
4229 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
4230 | ||
2c4b77f3 JH |
4231 | @item -fif-conversion2 |
4232 | @opindex if-conversion2 | |
4233 | Use conditional execution (where available) to transform conditional jumps into | |
4234 | branch-less equivalents. | |
4235 | ||
38df970e JQ |
4236 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
4237 | ||
b6d24183 | 4238 | @item -fdelete-null-pointer-checks |
cd3bb277 | 4239 | @opindex fdelete-null-pointer-checks |
9c34dbbf ZW |
4240 | Use global dataflow analysis to identify and eliminate useless checks |
4241 | for null pointers. The compiler assumes that dereferencing a null | |
4242 | pointer would have halted the program. If a pointer is checked after | |
4243 | it has already been dereferenced, it cannot be null. | |
4244 | ||
4245 | In some environments, this assumption is not true, and programs can | |
4246 | safely dereference null pointers. Use | |
4247 | @option{-fno-delete-null-pointer-checks} to disable this optimization | |
4248 | for programs which depend on that behavior. | |
b6d24183 | 4249 | |
38df970e JQ |
4250 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4251 | ||
74291a4b | 4252 | @item -fexpensive-optimizations |
cd3bb277 | 4253 | @opindex fexpensive-optimizations |
74291a4b MM |
4254 | Perform a number of minor optimizations that are relatively expensive. |
4255 | ||
38df970e JQ |
4256 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4257 | ||
639726ba | 4258 | @item -foptimize-register-move |
59d40964 | 4259 | @itemx -fregmove |
cd3bb277 JM |
4260 | @opindex foptimize-register-move |
4261 | @opindex fregmove | |
9ec36da5 JL |
4262 | Attempt to reassign register numbers in move instructions and as |
4263 | operands of other simple instructions in order to maximize the amount of | |
56159047 | 4264 | register tying. This is especially helpful on machines with two-operand |
38df970e | 4265 | instructions. |
9ec36da5 | 4266 | |
bedc7537 | 4267 | Note @option{-fregmove} and @option{-foptimize-register-move} are the same |
9ec36da5 JL |
4268 | optimization. |
4269 | ||
38df970e JQ |
4270 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4271 | ||
74291a4b | 4272 | @item -fdelayed-branch |
cd3bb277 | 4273 | @opindex fdelayed-branch |
74291a4b MM |
4274 | If supported for the target machine, attempt to reorder instructions |
4275 | to exploit instruction slots available after delayed branch | |
4276 | instructions. | |
4277 | ||
38df970e JQ |
4278 | Enabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. |
4279 | ||
74291a4b | 4280 | @item -fschedule-insns |
cd3bb277 | 4281 | @opindex fschedule-insns |
74291a4b MM |
4282 | If supported for the target machine, attempt to reorder instructions to |
4283 | eliminate execution stalls due to required data being unavailable. This | |
4284 | helps machines that have slow floating point or memory load instructions | |
4285 | by allowing other instructions to be issued until the result of the load | |
4286 | or floating point instruction is required. | |
4287 | ||
38df970e JQ |
4288 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4289 | ||
74291a4b | 4290 | @item -fschedule-insns2 |
cd3bb277 | 4291 | @opindex fschedule-insns2 |
630d3d5a | 4292 | Similar to @option{-fschedule-insns}, but requests an additional pass of |
74291a4b MM |
4293 | instruction scheduling after register allocation has been done. This is |
4294 | especially useful on machines with a relatively small number of | |
4295 | registers and where memory load instructions take more than one cycle. | |
4296 | ||
38df970e JQ |
4297 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4298 | ||
e03b7153 RS |
4299 | @item -fno-sched-interblock |
4300 | @opindex fno-sched-interblock | |
4301 | Don't schedule instructions across basic blocks. This is normally | |
4302 | enabled by default when scheduling before register allocation, i.e.@: | |
4303 | with @option{-fschedule-insns} or at @option{-O2} or higher. | |
4304 | ||
4305 | @item -fno-sched-spec | |
4306 | @opindex fno-sched-spec | |
4307 | Don't allow speculative motion of non-load instructions. This is normally | |
4308 | enabled by default when scheduling before register allocation, i.e.@: | |
4309 | with @option{-fschedule-insns} or at @option{-O2} or higher. | |
4310 | ||
4311 | @item -fsched-spec-load | |
4312 | @opindex fsched-spec-load | |
4313 | Allow speculative motion of some load instructions. This only makes | |
4314 | sense when scheduling before register allocation, i.e.@: with | |
4315 | @option{-fschedule-insns} or at @option{-O2} or higher. | |
4316 | ||
4317 | @item -fsched-spec-load-dangerous | |
4318 | @opindex fsched-spec-load-dangerous | |
4319 | Allow speculative motion of more load instructions. This only makes | |
4320 | sense when scheduling before register allocation, i.e.@: with | |
4321 | @option{-fschedule-insns} or at @option{-O2} or higher. | |
4322 | ||
569fa502 DN |
4323 | @item -fsched-stalled-insns=@var{n} |
4324 | @opindex fsched-stalled-insns | |
4325 | Define how many insns (if any) can be moved prematurely from the queue | |
4326 | of stalled insns into the ready list, during the second scheduling pass. | |
4327 | ||
4328 | @item -fsched-stalled-insns-dep=@var{n} | |
4329 | @opindex fsched-stalled-insns-dep | |
daf2f129 JM |
4330 | Define how many insn groups (cycles) will be examined for a dependency |
4331 | on a stalled insn that is candidate for premature removal from the queue | |
4332 | of stalled insns. Has an effect only during the second scheduling pass, | |
569fa502 DN |
4333 | and only if @option{-fsched-stalled-insns} is used and its value is not zero. |
4334 | ||
b9422b69 JH |
4335 | @item -fsched2-use-superblocks |
4336 | @opindex fsched2-use-superblocks | |
61aeb06f | 4337 | When scheduling after register allocation, do use superblock scheduling |
62b9c42c | 4338 | algorithm. Superblock scheduling allows motion across basic block boundaries |
b9422b69 | 4339 | resulting on faster schedules. This option is experimental, as not all machine |
62b9c42c | 4340 | descriptions used by GCC model the CPU closely enough to avoid unreliable |
daf2f129 | 4341 | results from the algorithm. |
b9422b69 JH |
4342 | |
4343 | This only makes sense when scheduling after register allocation, i.e.@: with | |
4344 | @option{-fschedule-insns2} or at @option{-O2} or higher. | |
4345 | ||
4346 | @item -fsched2-use-traces | |
4347 | @opindex fsched2-use-traces | |
4348 | Use @option{-fsched2-use-superblocks} algorithm when scheduling after register | |
4349 | allocation and additionally perform code duplication in order to increase the | |
4350 | size of superblocks using tracer pass. See @option{-ftracer} for details on | |
4351 | trace formation. | |
4352 | ||
62b9c42c | 4353 | This mode should produce faster but significantly longer programs. Also |
b9422b69 JH |
4354 | without @code{-fbranch-probabilities} the traces constructed may not match the |
4355 | reality and hurt the performance. This only makes | |
4356 | sense when scheduling after register allocation, i.e.@: with | |
4357 | @option{-fschedule-insns2} or at @option{-O2} or higher. | |
4358 | ||
74291a4b | 4359 | @item -fcaller-saves |
cd3bb277 | 4360 | @opindex fcaller-saves |
74291a4b MM |
4361 | Enable values to be allocated in registers that will be clobbered by |
4362 | function calls, by emitting extra instructions to save and restore the | |
4363 | registers around such calls. Such allocation is done only when it | |
4364 | seems to result in better code than would otherwise be produced. | |
4365 | ||
81610a0d HPN |
4366 | This option is always enabled by default on certain machines, usually |
4367 | those which have no call-preserved registers to use instead. | |
4368 | ||
38df970e | 4369 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
74291a4b | 4370 | |
6de9cd9a DN |
4371 | @item -ftree-pre |
4372 | Perform Partial Redundancy Elimination (PRE) on trees. This flag is | |
4373 | enabled by default at -O and higher. | |
ff2ad0f7 DN |
4374 | |
4375 | @item -ftree-fre | |
4376 | Perform Full Redundancy Elimination (FRE) on trees. The difference | |
4377 | between FRE and PRE is that FRE only considers expressions | |
4378 | that are computed on all paths leading to the redundant computation. | |
4379 | This analysis faster than PRE, though it exposes fewer redundancies. | |
4380 | This flag is enabled by default at -O and higher. | |
6de9cd9a DN |
4381 | |
4382 | @item -ftree-ccp | |
4383 | Perform sparse conditional constant propagation (CCP) on trees. This flag | |
4384 | is enabled by default at -O and higher. | |
4385 | ||
4386 | @item -ftree-dce | |
4387 | Perform dead code elimination (DCE) on trees. This flag is enabled by | |
4388 | default at -O and higher. | |
4389 | ||
4390 | @item -ftree-dominator-opts | |
4391 | Perform dead code elimination (DCE) on trees. This flag is enabled by | |
4392 | default at -O and higher. | |
4393 | ||
4394 | @item -ftree-ch | |
4395 | Perform loop header copying on trees. This is beneficial since it increases | |
4396 | effectivity of code motion optimizations. It also saves one jump. This flag | |
4397 | is enabled by default at -O and higher. It is not enabled for -Os, since it | |
4398 | usually increases code size. | |
4399 | ||
c66b6c66 ZD |
4400 | @item -ftree-loop-optimize |
4401 | Perform loop optimizations on trees. This flag is enabled by default at -O | |
4402 | and higher. | |
4403 | ||
6de9cd9a DN |
4404 | @item -ftree-sra |
4405 | Perform scalar replacement of aggregates. This pass replaces structure | |
4406 | references with scalars to prevent committing structures to memory too | |
4407 | early. This flag is enabled by default at -O and higher. | |
4408 | ||
4409 | @item -ftree-copyrename | |
f26c1794 EC |
4410 | Perform copy renaming on trees. This pass attempts to rename compiler |
4411 | temporaries to other variables at copy locations, usually resulting in | |
4412 | variable names which more closely resemble the original variables. This flag | |
6de9cd9a DN |
4413 | is enabled by default at -O and higher. |
4414 | ||
4415 | @item -ftree-ter | |
4416 | Perform temporary expression replacement during the SSA->normal phase. Single | |
f26c1794 EC |
4417 | use/single def temporaries are replaced at their use location with their |
4418 | defining expression. This results in non-GIMPLE code, but gives the expanders | |
6de9cd9a DN |
4419 | much more complex trees to work on resulting in better RTL generation. This is |
4420 | enabled by default at -O and higher. | |
4421 | ||
4422 | @item -ftree-lrs | |
f26c1794 EC |
4423 | Perform live range splitting during the SSA->normal phase. Distinct live |
4424 | ranges of a variable are split into unique variables, allowing for better | |
6de9cd9a DN |
4425 | optimization later. This is enabled by default at -O and higher. |
4426 | ||
4427 | @item -ftracer | |
4428 | @opindex ftracer | |
4429 | Perform tail duplication to enlarge superblock size. This transformation | |
4430 | simplifies the control flow of the function allowing other optimizations to do | |
4431 | better job. | |
4432 | ||
4433 | @item -funroll-loops | |
4434 | @opindex funroll-loops | |
4435 | Unroll loops whose number of iterations can be determined at compile | |
4436 | time or upon entry to the loop. @option{-funroll-loops} implies both | |
4437 | @option{-fstrength-reduce} and @option{-frerun-cse-after-loop}. This | |
4438 | option makes code larger, and may or may not make it run faster. | |
4439 | ||
4440 | @item -funroll-all-loops | |
4441 | @opindex funroll-all-loops | |
4442 | Unroll all loops, even if their number of iterations is uncertain when | |
4443 | the loop is entered. This usually makes programs run more slowly. | |
4444 | @option{-funroll-all-loops} implies the same options as | |
4445 | @option{-funroll-loops}, | |
4446 | ||
4447 | @item -fprefetch-loop-arrays | |
4448 | @opindex fprefetch-loop-arrays | |
4449 | If supported by the target machine, generate instructions to prefetch | |
4450 | memory to improve the performance of loops that access large arrays. | |
4451 | ||
e5eb27e5 | 4452 | @item -fmove-all-movables |
cd3bb277 | 4453 | @opindex fmove-all-movables |
e5eb27e5 JL |
4454 | Forces all invariant computations in loops to be moved |
4455 | outside the loop. | |
4456 | ||
4457 | @item -freduce-all-givs | |
cd3bb277 | 4458 | @opindex freduce-all-givs |
e5eb27e5 JL |
4459 | Forces all general-induction variables in loops to be |
4460 | strength-reduced. | |
4461 | ||
4462 | @emph{Note:} When compiling programs written in Fortran, | |
630d3d5a | 4463 | @option{-fmove-all-movables} and @option{-freduce-all-givs} are enabled |
e5eb27e5 JL |
4464 | by default when you use the optimizer. |
4465 | ||
4466 | These options may generate better or worse code; results are highly | |
4467 | dependent on the structure of loops within the source code. | |
4468 | ||
4469 | These two options are intended to be removed someday, once | |
4470 | they have helped determine the efficacy of various | |
4471 | approaches to improving loop optimizations. | |
4472 | ||
962e6e00 JM |
4473 | Please contact @w{@email{gcc@@gcc.gnu.org}}, and describe how use of |
4474 | these options affects the performance of your production code. | |
4475 | Examples of code that runs @emph{slower} when these options are | |
4476 | @emph{enabled} are very valuable. | |
e5eb27e5 | 4477 | |
74291a4b | 4478 | @item -fno-peephole |
6cfc0341 | 4479 | @itemx -fno-peephole2 |
cd3bb277 | 4480 | @opindex fno-peephole |
6cfc0341 RH |
4481 | @opindex fno-peephole2 |
4482 | Disable any machine-specific peephole optimizations. The difference | |
630d3d5a | 4483 | between @option{-fno-peephole} and @option{-fno-peephole2} is in how they |
6cfc0341 RH |
4484 | are implemented in the compiler; some targets use one, some use the |
4485 | other, a few use both. | |
861bb6c1 | 4486 | |
38df970e JQ |
4487 | @option{-fpeephole} is enabled by default. |
4488 | @option{-fpeephole2} enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. | |
4489 | ||
454d0cc7 | 4490 | @item -fno-guess-branch-probability |
cd3bb277 | 4491 | @opindex fno-guess-branch-probability |
9c34dbbf ZW |
4492 | Do not guess branch probabilities using a randomized model. |
4493 | ||
2dd76960 | 4494 | Sometimes GCC will opt to use a randomized model to guess branch |
9c34dbbf ZW |
4495 | probabilities, when none are available from either profiling feedback |
4496 | (@option{-fprofile-arcs}) or @samp{__builtin_expect}. This means that | |
4497 | different runs of the compiler on the same program may produce different | |
4498 | object code. | |
4499 | ||
4500 | In a hard real-time system, people don't want different runs of the | |
4501 | compiler to produce code that has different behavior; minimizing | |
4502 | non-determinism is of paramount import. This switch allows users to | |
4503 | reduce non-determinism, possibly at the expense of inferior | |
4504 | optimization. | |
454d0cc7 | 4505 | |
38df970e JQ |
4506 | The default is @option{-fguess-branch-probability} at levels |
4507 | @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. | |
4508 | ||
194734e9 JH |
4509 | @item -freorder-blocks |
4510 | @opindex freorder-blocks | |
4511 | Reorder basic blocks in the compiled function in order to reduce number of | |
4512 | taken branches and improve code locality. | |
4513 | ||
3f8b659d | 4514 | Enabled at levels @option{-O2}, @option{-O3}. |
38df970e | 4515 | |
750054a2 CT |
4516 | @item -freorder-blocks-and-partition |
4517 | @opindex freorder-blocks-and-partition | |
4518 | In addition to reordering basic blocks in the compiled function, in order | |
4519 | to reduce number of taken branches, partitions hot and cold basic blocks | |
4520 | into separate sections of the assembly and .o files, to improve | |
4521 | paging and cache locality performance. | |
4522 | ||
194734e9 JH |
4523 | @item -freorder-functions |
4524 | @opindex freorder-functions | |
4525 | Reorder basic blocks in the compiled function in order to reduce number of | |
4526 | taken branches and improve code locality. This is implemented by using special | |
3a4bdd05 RH |
4527 | subsections @code{.text.hot} for most frequently executed functions and |
4528 | @code{.text.unlikely} for unlikely executed functions. Reordering is done by | |
194734e9 | 4529 | the linker so object file format must support named sections and linker must |
3364c33b | 4530 | place them in a reasonable way. |
194734e9 JH |
4531 | |
4532 | Also profile feedback must be available in to make this option effective. See | |
4533 | @option{-fprofile-arcs} for details. | |
4534 | ||
38df970e JQ |
4535 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
4536 | ||
41472af8 | 4537 | @item -fstrict-aliasing |
cd3bb277 | 4538 | @opindex fstrict-aliasing |
41472af8 MM |
4539 | Allows the compiler to assume the strictest aliasing rules applicable to |
4540 | the language being compiled. For C (and C++), this activates | |
4541 | optimizations based on the type of expressions. In particular, an | |
4542 | object of one type is assumed never to reside at the same address as an | |
4543 | object of a different type, unless the types are almost the same. For | |
4544 | example, an @code{unsigned int} can alias an @code{int}, but not a | |
4545 | @code{void*} or a @code{double}. A character type may alias any other | |
02f52e19 | 4546 | type. |
41472af8 MM |
4547 | |
4548 | Pay special attention to code like this: | |
3ab51846 | 4549 | @smallexample |
02f52e19 | 4550 | union a_union @{ |
41472af8 MM |
4551 | int i; |
4552 | double d; | |
4553 | @}; | |
4554 | ||
4555 | int f() @{ | |
4556 | a_union t; | |
4557 | t.d = 3.0; | |
4558 | return t.i; | |
4559 | @} | |
3ab51846 | 4560 | @end smallexample |
41472af8 MM |
4561 | The practice of reading from a different union member than the one most |
4562 | recently written to (called ``type-punning'') is common. Even with | |
630d3d5a | 4563 | @option{-fstrict-aliasing}, type-punning is allowed, provided the memory |
41472af8 MM |
4564 | is accessed through the union type. So, the code above will work as |
4565 | expected. However, this code might not: | |
3ab51846 | 4566 | @smallexample |
02f52e19 | 4567 | int f() @{ |
41472af8 MM |
4568 | a_union t; |
4569 | int* ip; | |
4570 | t.d = 3.0; | |
4571 | ip = &t.i; | |
4572 | return *ip; | |
4573 | @} | |
3ab51846 | 4574 | @end smallexample |
41472af8 | 4575 | |
41472af8 MM |
4576 | Every language that wishes to perform language-specific alias analysis |
4577 | should define a function that computes, given an @code{tree} | |
4578 | node, an alias set for the node. Nodes in different alias sets are not | |
4579 | allowed to alias. For an example, see the C front-end function | |
4580 | @code{c_get_alias_set}. | |
41472af8 | 4581 | |
38df970e | 4582 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}. |
852b81bb | 4583 | |
efa3896a GK |
4584 | @item -falign-functions |
4585 | @itemx -falign-functions=@var{n} | |
cd3bb277 | 4586 | @opindex falign-functions |
efa3896a GK |
4587 | Align the start of functions to the next power-of-two greater than |
4588 | @var{n}, skipping up to @var{n} bytes. For instance, | |
630d3d5a JM |
4589 | @option{-falign-functions=32} aligns functions to the next 32-byte |
4590 | boundary, but @option{-falign-functions=24} would align to the next | |
efa3896a GK |
4591 | 32-byte boundary only if this can be done by skipping 23 bytes or less. |
4592 | ||
630d3d5a | 4593 | @option{-fno-align-functions} and @option{-falign-functions=1} are |
efa3896a GK |
4594 | equivalent and mean that functions will not be aligned. |
4595 | ||
4596 | Some assemblers only support this flag when @var{n} is a power of two; | |
4597 | in that case, it is rounded up. | |
4598 | ||
561913cb | 4599 | If @var{n} is not specified or is zero, use a machine-dependent default. |
efa3896a | 4600 | |
38df970e JQ |
4601 | Enabled at levels @option{-O2}, @option{-O3}. |
4602 | ||
efa3896a GK |
4603 | @item -falign-labels |
4604 | @itemx -falign-labels=@var{n} | |
cd3bb277 | 4605 | @opindex falign-labels |
efa3896a | 4606 | Align all branch targets to a power-of-two boundary, skipping up to |
630d3d5a | 4607 | @var{n} bytes like @option{-falign-functions}. This option can easily |
efa3896a GK |
4608 | make code slower, because it must insert dummy operations for when the |
4609 | branch target is reached in the usual flow of the code. | |
4610 | ||
561913cb AP |
4611 | @option{-fno-align-labels} and @option{-falign-labels=1} are |
4612 | equivalent and mean that labels will not be aligned. | |
4613 | ||
630d3d5a | 4614 | If @option{-falign-loops} or @option{-falign-jumps} are applicable and |
efa3896a GK |
4615 | are greater than this value, then their values are used instead. |
4616 | ||
561913cb AP |
4617 | If @var{n} is not specified or is zero, use a machine-dependent default |
4618 | which is very likely to be @samp{1}, meaning no alignment. | |
efa3896a | 4619 | |
38df970e JQ |
4620 | Enabled at levels @option{-O2}, @option{-O3}. |
4621 | ||
efa3896a GK |
4622 | @item -falign-loops |
4623 | @itemx -falign-loops=@var{n} | |
cd3bb277 | 4624 | @opindex falign-loops |
efa3896a | 4625 | Align loops to a power-of-two boundary, skipping up to @var{n} bytes |
630d3d5a | 4626 | like @option{-falign-functions}. The hope is that the loop will be |
efa3896a GK |
4627 | executed many times, which will make up for any execution of the dummy |
4628 | operations. | |
4629 | ||
561913cb AP |
4630 | @option{-fno-align-loops} and @option{-falign-loops=1} are |
4631 | equivalent and mean that loops will not be aligned. | |
4632 | ||
4633 | If @var{n} is not specified or is zero, use a machine-dependent default. | |
efa3896a | 4634 | |
38df970e JQ |
4635 | Enabled at levels @option{-O2}, @option{-O3}. |
4636 | ||
efa3896a GK |
4637 | @item -falign-jumps |
4638 | @itemx -falign-jumps=@var{n} | |
cd3bb277 | 4639 | @opindex falign-jumps |
efa3896a GK |
4640 | Align branch targets to a power-of-two boundary, for branch targets |
4641 | where the targets can only be reached by jumping, skipping up to @var{n} | |
630d3d5a | 4642 | bytes like @option{-falign-functions}. In this case, no dummy operations |
efa3896a GK |
4643 | need be executed. |
4644 | ||
561913cb AP |
4645 | @option{-fno-align-jumps} and @option{-falign-jumps=1} are |
4646 | equivalent and mean that loops will not be aligned. | |
4647 | ||
4648 | If @var{n} is not specified or is zero, use a machine-dependent default. | |
efa3896a | 4649 | |
38df970e JQ |
4650 | Enabled at levels @option{-O2}, @option{-O3}. |
4651 | ||
7797ff53 PB |
4652 | @item -funit-at-a-time |
4653 | @opindex funit-at-a-time | |
4654 | Parse the whole compilation unit before starting to produce code. | |
4655 | This allows some extra optimizations to take place but consumes | |
4656 | more memory (in general). There are some compatibility issues | |
4657 | with @emph{unit-at-at-time} mode: | |
4658 | @itemize @bullet | |
4659 | @item | |
4660 | enabling @emph{unit-at-a-time} mode may change the order | |
4661 | in which functions, variables, and top-level @code{asm} statements | |
4662 | are emitted, and will likely break code relying on some particular | |
4663 | ordering. The majority of such top-level @code{asm} statements, | |
4664 | though, can be replaced by @code{section} attributes. | |
4665 | ||
4666 | @item | |
4667 | @emph{unit-at-a-time} mode removes unreferenced static variables | |
4668 | and functions are removed. This may result in undefined references | |
4669 | when an @code{asm} statement refers directly to variables or functions | |
4670 | that are otherwise unused. In that case either the variable/function | |
4671 | shall be listed as an operand of the @code{asm} statement operand or, | |
4672 | in the case of top-level @code{asm} statements the attribute @code{used} | |
4673 | shall be used on the declaration. | |
4674 | ||
4675 | @item | |
4676 | Static functions now can use non-standard passing conventions that | |
4677 | may break @code{asm} statements calling functions directly. Again, | |
4678 | attribute @code{used} will prevent this behavior. | |
4679 | @end itemize | |
4680 | ||
4681 | As a temporary workaround, @option{-fno-unit-at-a-time} can be used, | |
f26c1794 | 4682 | but this scheme may not be supported by future releases of GCC. |
7797ff53 PB |
4683 | |
4684 | Enabled at levels @option{-O2}, @option{-O3}. | |
4685 | ||
7260e9a0 JH |
4686 | @item -fweb |
4687 | @opindex fweb | |
4688 | Constructs webs as commonly used for register allocation purposes and assign | |
962e6e00 | 4689 | each web individual pseudo register. This allows the register allocation pass |
7260e9a0 JH |
4690 | to operate on pseudos directly, but also strengthens several other optimization |
4691 | passes, such as CSE, loop optimizer and trivial dead code remover. It can, | |
4692 | however, make debugging impossible, since variables will no longer stay in a | |
4693 | ``home register''. | |
4694 | ||
38d396e5 PB |
4695 | Enabled at levels @option{-O2}, @option{-O3}, @option{-Os}, |
4696 | on targets where the default format for debugging information supports | |
4697 | variable tracking. | |
d4463dfc JQ |
4698 | |
4699 | @item -fno-cprop-registers | |
4700 | @opindex fno-cprop-registers | |
4701 | After register allocation and post-register allocation instruction splitting, | |
4702 | we perform a copy-propagation pass to try to reduce scheduling dependencies | |
4703 | and occasionally eliminate the copy. | |
4704 | ||
4705 | Disabled at levels @option{-O}, @option{-O2}, @option{-O3}, @option{-Os}. | |
4706 | ||
a8a5f53a JH |
4707 | @item -fprofile-generate |
4708 | @opindex fprofile-generate | |
a8a5f53a | 4709 | |
33adcb6c MM |
4710 | Enable options usually used for instrumenting application to produce |
4711 | profile useful for later recompilation with profile feedback based | |
4712 | optimization. You must use @code{-fprofile-generate} both when | |
4713 | compiling and when linking your program. | |
4714 | ||
4715 | The following options are enabled: @code{-fprofile-arcs}, @code{-fprofile-values}, @code{-fvpt}. | |
a8a5f53a JH |
4716 | |
4717 | @item -fprofile-use | |
4718 | @opindex fprofile-use | |
4719 | Enable profile feedback directed optimizations, and optimizations | |
4720 | generally profitable only with profile feedback available. | |
4721 | ||
4722 | The following options are enabled: @code{-fbranch-probabilities}, | |
4723 | @code{-fvpt}, @code{-funroll-loops}, @code{-fpeel-loops}, @code{-ftracer}. | |
4724 | ||
d4463dfc JQ |
4725 | @end table |
4726 | ||
4727 | The following options control compiler behavior regarding floating | |
4728 | point arithmetic. These options trade off between speed and | |
4729 | correctness. All must be specifically enabled. | |
4730 | ||
4731 | @table @gcctabopt | |
4732 | @item -ffloat-store | |
4733 | @opindex ffloat-store | |
4734 | Do not store floating point variables in registers, and inhibit other | |
4735 | options that might change whether a floating point value is taken from a | |
4736 | register or memory. | |
4737 | ||
4738 | @cindex floating point precision | |
4739 | This option prevents undesirable excess precision on machines such as | |
4740 | the 68000 where the floating registers (of the 68881) keep more | |
4741 | precision than a @code{double} is supposed to have. Similarly for the | |
4742 | x86 architecture. For most programs, the excess precision does only | |
4743 | good, but a few programs rely on the precise definition of IEEE floating | |
4744 | point. Use @option{-ffloat-store} for such programs, after modifying | |
4745 | them to store all pertinent intermediate computations into variables. | |
4746 | ||
4747 | @item -ffast-math | |
4748 | @opindex ffast-math | |
4749 | Sets @option{-fno-math-errno}, @option{-funsafe-math-optimizations}, @* | |
039c3d42 RS |
4750 | @option{-fno-trapping-math}, @option{-ffinite-math-only}, |
4751 | @option{-fno-rounding-math} and @option{-fno-signaling-nans}. | |
d4463dfc JQ |
4752 | |
4753 | This option causes the preprocessor macro @code{__FAST_MATH__} to be defined. | |
4754 | ||
4755 | This option should never be turned on by any @option{-O} option since | |
4756 | it can result in incorrect output for programs which depend on | |
4757 | an exact implementation of IEEE or ISO rules/specifications for | |
4758 | math functions. | |
4759 | ||
4760 | @item -fno-math-errno | |
4761 | @opindex fno-math-errno | |
4762 | Do not set ERRNO after calling math functions that are executed | |
4763 | with a single instruction, e.g., sqrt. A program that relies on | |
4764 | IEEE exceptions for math error handling may want to use this flag | |
4765 | for speed while maintaining IEEE arithmetic compatibility. | |
4766 | ||
4767 | This option should never be turned on by any @option{-O} option since | |
4768 | it can result in incorrect output for programs which depend on | |
4769 | an exact implementation of IEEE or ISO rules/specifications for | |
4770 | math functions. | |
4771 | ||
4772 | The default is @option{-fmath-errno}. | |
4773 | ||
4774 | @item -funsafe-math-optimizations | |
4775 | @opindex funsafe-math-optimizations | |
4776 | Allow optimizations for floating-point arithmetic that (a) assume | |
4777 | that arguments and results are valid and (b) may violate IEEE or | |
4778 | ANSI standards. When used at link-time, it may include libraries | |
4779 | or startup files that change the default FPU control word or other | |
4780 | similar optimizations. | |
4781 | ||
4782 | This option should never be turned on by any @option{-O} option since | |
4783 | it can result in incorrect output for programs which depend on | |
4784 | an exact implementation of IEEE or ISO rules/specifications for | |
4785 | math functions. | |
4786 | ||
4787 | The default is @option{-fno-unsafe-math-optimizations}. | |
4788 | ||
4789 | @item -ffinite-math-only | |
4790 | @opindex ffinite-math-only | |
4791 | Allow optimizations for floating-point arithmetic that assume | |
4792 | that arguments and results are not NaNs or +-Infs. | |
4793 | ||
4794 | This option should never be turned on by any @option{-O} option since | |
4795 | it can result in incorrect output for programs which depend on | |
4796 | an exact implementation of IEEE or ISO rules/specifications. | |
4797 | ||
4798 | The default is @option{-fno-finite-math-only}. | |
4799 | ||
4800 | @item -fno-trapping-math | |
4801 | @opindex fno-trapping-math | |
4802 | Compile code assuming that floating-point operations cannot generate | |
4803 | user-visible traps. These traps include division by zero, overflow, | |
4804 | underflow, inexact result and invalid operation. This option implies | |
4805 | @option{-fno-signaling-nans}. Setting this option may allow faster | |
4806 | code if one relies on ``non-stop'' IEEE arithmetic, for example. | |
4807 | ||
4808 | This option should never be turned on by any @option{-O} option since | |
4809 | it can result in incorrect output for programs which depend on | |
4810 | an exact implementation of IEEE or ISO rules/specifications for | |
4811 | math functions. | |
4812 | ||
4813 | The default is @option{-ftrapping-math}. | |
4814 | ||
039c3d42 RS |
4815 | @item -frounding-math |
4816 | @opindex frounding-math | |
4817 | Disable transformations and optimizations that assume default floating | |
4818 | point rounding behavior. This is round-to-zero for all floating point | |
4819 | to integer conversions, and round-to-nearest for all other arithmetic | |
4820 | truncations. This option should be specified for programs that change | |
4821 | the FP rounding mode dynamically, or that may be executed with a | |
4822 | non-default rounding mode. This option disables constant folding of | |
4823 | floating point expressions at compile-time (which may be affected by | |
4824 | rounding mode) and arithmetic transformations that are unsafe in the | |
4825 | presence of sign-dependent rounding modes. | |
4826 | ||
4827 | The default is @option{-fno-rounding-math}. | |
4828 | ||
4829 | This option is experimental and does not currently guarantee to | |
4830 | disable all GCC optimizations that are affected by rounding mode. | |
2dd76960 | 4831 | Future versions of GCC may provide finer control of this setting |
039c3d42 RS |
4832 | using C99's @code{FENV_ACCESS} pragma. This command line option |
4833 | will be used to specify the default state for @code{FENV_ACCESS}. | |
4834 | ||
d4463dfc JQ |
4835 | @item -fsignaling-nans |
4836 | @opindex fsignaling-nans | |
4837 | Compile code assuming that IEEE signaling NaNs may generate user-visible | |
4838 | traps during floating-point operations. Setting this option disables | |
4839 | optimizations that may change the number of exceptions visible with | |
4840 | signaling NaNs. This option implies @option{-ftrapping-math}. | |
4841 | ||
4842 | This option causes the preprocessor macro @code{__SUPPORT_SNAN__} to | |
4843 | be defined. | |
4844 | ||
4845 | The default is @option{-fno-signaling-nans}. | |
4846 | ||
4847 | This option is experimental and does not currently guarantee to | |
4848 | disable all GCC optimizations that affect signaling NaN behavior. | |
4849 | ||
4850 | @item -fsingle-precision-constant | |
4851 | @opindex fsingle-precision-constant | |
4852 | Treat floating point constant as single precision constant instead of | |
4853 | implicitly converting it to double precision constant. | |
4854 | ||
4855 | ||
4856 | @end table | |
4857 | ||
4858 | The following options control optimizations that may improve | |
4859 | performance, but are not enabled by any @option{-O} options. This | |
4860 | section includes experimental options that may produce broken code. | |
4861 | ||
4862 | @table @gcctabopt | |
4863 | @item -fbranch-probabilities | |
4864 | @opindex fbranch-probabilities | |
4865 | After running a program compiled with @option{-fprofile-arcs} | |
4866 | (@pxref{Debugging Options,, Options for Debugging Your Program or | |
4867 | @command{gcc}}), you can compile it a second time using | |
4868 | @option{-fbranch-probabilities}, to improve optimizations based on | |
4869 | the number of times each branch was taken. When the program | |
4870 | compiled with @option{-fprofile-arcs} exits it saves arc execution | |
a4878735 | 4871 | counts to a file called @file{@var{sourcename}.gcda} for each source |
d4463dfc JQ |
4872 | file The information in this data file is very dependent on the |
4873 | structure of the generated code, so you must use the same source code | |
4874 | and the same optimization options for both compilations. | |
4875 | ||
daf2f129 | 4876 | With @option{-fbranch-probabilities}, GCC puts a |
d4463dfc JQ |
4877 | @samp{REG_BR_PROB} note on each @samp{JUMP_INSN} and @samp{CALL_INSN}. |
4878 | These can be used to improve optimization. Currently, they are only | |
4879 | used in one place: in @file{reorg.c}, instead of guessing which path a | |
4880 | branch is mostly to take, the @samp{REG_BR_PROB} values are used to | |
4881 | exactly determine which path is taken more often. | |
4882 | ||
fc5eb4a1 ZD |
4883 | @item -fprofile-values |
4884 | @opindex fprofile-values | |
4885 | If combined with @option{-fprofile-arcs}, it adds code so that some | |
4886 | data about values of expressions in the program is gathered. | |
4887 | ||
6e885ee3 ZD |
4888 | With @option{-fbranch-probabilities}, it reads back the data gathered |
4889 | from profiling values of expressions and adds @samp{REG_VALUE_PROFILE} | |
4890 | notes to instructions for their later usage in optimizations. | |
4891 | ||
7797ff53 | 4892 | Enabled with @option{-fprofile-generate} and @option{-fprofile-use}. |
8d3b3fb7 | 4893 | |
fca9dc00 ZD |
4894 | @item -fvpt |
4895 | @opindex fvpt | |
4896 | If combined with @option{-fprofile-arcs}, it instructs the compiler to add | |
4897 | a code to gather information about values of expressions. | |
4898 | ||
4899 | With @option{-fbranch-probabilities}, it reads back the data gathered | |
4900 | and actually performs the optimizations based on them. | |
4901 | Currently the optimizations include specialization of division operation | |
4902 | using the knowledge about the value of the denominator. | |
4903 | ||
7797ff53 | 4904 | Enabled with @option{-fprofile-generate} and @option{-fprofile-use}. |
8d3b3fb7 | 4905 | |
a7b1dc36 PB |
4906 | @item -frename-registers |
4907 | @opindex frename-registers | |
4908 | Attempt to avoid false dependencies in scheduled code by making use | |
4909 | of registers left over after register allocation. This optimization | |
4910 | will most benefit processors with lots of registers. Depending on the | |
4911 | debug information format adopted by the target, however, it can | |
4912 | make debugging impossible, since variables will no longer stay in | |
4913 | a ``home register''. | |
4914 | ||
4915 | Not enabled by default at any level because it has known bugs. | |
4916 | ||
d4463dfc JQ |
4917 | @item -fnew-ra |
4918 | @opindex fnew-ra | |
4919 | Use a graph coloring register allocator. Currently this option is meant | |
4920 | for testing, so we are interested to hear about miscompilations with | |
4921 | @option{-fnew-ra}. | |
4922 | ||
4923 | @item -ftracer | |
4924 | @opindex ftracer | |
4925 | Perform tail duplication to enlarge superblock size. This transformation | |
4926 | simplifies the control flow of the function allowing other optimizations to do | |
4927 | better job. | |
4928 | ||
7797ff53 | 4929 | Enabled with @option{-fprofile-use}. |
8d3b3fb7 | 4930 | |
d4463dfc JQ |
4931 | @item -funroll-loops |
4932 | @opindex funroll-loops | |
b17d5d7c ZD |
4933 | Unroll loops whose number of iterations can be determined at compile time or |
4934 | upon entry to the loop. @option{-funroll-loops} implies | |
4935 | @option{-frerun-cse-after-loop}. It also turns on complete loop peeling | |
4936 | (i.e. complete removal of loops with small constant number of iterations). | |
4937 | This option makes code larger, and may or may not make it run faster. | |
d4463dfc | 4938 | |
7797ff53 | 4939 | Enabled with @option{-fprofile-use}. |
8d3b3fb7 | 4940 | |
d4463dfc JQ |
4941 | @item -funroll-all-loops |
4942 | @opindex funroll-all-loops | |
4943 | Unroll all loops, even if their number of iterations is uncertain when | |
4944 | the loop is entered. This usually makes programs run more slowly. | |
4945 | @option{-funroll-all-loops} implies the same options as | |
b17d5d7c ZD |
4946 | @option{-funroll-loops}. |
4947 | ||
4948 | @item -fpeel-loops | |
4949 | @opindex fpeel-loops | |
4950 | Peels the loops for that there is enough information that they do not | |
4951 | roll much (from profile feedback). It also turns on complete loop peeling | |
4952 | (i.e. complete removal of loops with small constant number of iterations). | |
4953 | ||
7797ff53 | 4954 | Enabled with @option{-fprofile-use}. |
8d3b3fb7 | 4955 | |
5e962776 ZD |
4956 | @item -fmove-loop-invariants |
4957 | @opindex fmove-loop-invariants | |
4958 | Enables the loop invariant motion pass in the new loop optimizer. Enabled | |
4959 | at level @option{-O1} | |
4960 | ||
b17d5d7c ZD |
4961 | @item -funswitch-loops |
4962 | @opindex funswitch-loops | |
4963 | Move branches with loop invariant conditions out of the loop, with duplicates | |
4964 | of the loop on both branches (modified according to result of the condition). | |
4965 | ||
4966 | @item -fold-unroll-loops | |
4967 | @opindex fold-unroll-loops | |
4968 | Unroll loops whose number of iterations can be determined at compile | |
4969 | time or upon entry to the loop, using the old loop unroller whose loop | |
4970 | recognition is based on notes from frontend. @option{-fold-unroll-loops} implies | |
4971 | both @option{-fstrength-reduce} and @option{-frerun-cse-after-loop}. This | |
4972 | option makes code larger, and may or may not make it run faster. | |
4973 | ||
4974 | @item -fold-unroll-all-loops | |
4975 | @opindex fold-unroll-all-loops | |
4976 | Unroll all loops, even if their number of iterations is uncertain when | |
4977 | the loop is entered. This is done using the old loop unroller whose loop | |
4978 | recognition is based on notes from frontend. This usually makes programs run more slowly. | |
4979 | @option{-fold-unroll-all-loops} implies the same options as | |
4980 | @option{-fold-unroll-loops}. | |
daf2f129 | 4981 | |
d4463dfc JQ |
4982 | @item -fprefetch-loop-arrays |
4983 | @opindex fprefetch-loop-arrays | |
4984 | If supported by the target machine, generate instructions to prefetch | |
4985 | memory to improve the performance of loops that access large arrays. | |
4986 | ||
4987 | Disabled at level @option{-Os}. | |
4988 | ||
4989 | @item -ffunction-sections | |
4990 | @itemx -fdata-sections | |
4991 | @opindex ffunction-sections | |
4992 | @opindex fdata-sections | |
4993 | Place each function or data item into its own section in the output | |
4994 | file if the target supports arbitrary sections. The name of the | |
4995 | function or the name of the data item determines the section's name | |
4996 | in the output file. | |
4997 | ||
4998 | Use these options on systems where the linker can perform optimizations | |
f401d0f5 JDA |
4999 | to improve locality of reference in the instruction space. Most systems |
5000 | using the ELF object format and SPARC processors running Solaris 2 have | |
5001 | linkers with such optimizations. AIX may have these optimizations in | |
5002 | the future. | |
d4463dfc JQ |
5003 | |
5004 | Only use these options when there are significant benefits from doing | |
5005 | so. When you specify these options, the assembler and linker will | |
5006 | create larger object and executable files and will also be slower. | |
5007 | You will not be able to use @code{gprof} on all systems if you | |
5008 | specify this option and you may have problems with debugging if | |
5009 | you specify both this option and @option{-g}. | |
5010 | ||
fe3ad572 SC |
5011 | @item -fbranch-target-load-optimize |
5012 | @opindex fbranch-target-load-optimize | |
5013 | Perform branch target register load optimization before prologue / epilogue | |
5014 | threading. | |
5015 | The use of target registers can typically be exposed only during reload, | |
5016 | thus hoisting loads out of loops and doing inter-block scheduling needs | |
5017 | a separate optimization pass. | |
5018 | ||
5019 | @item -fbranch-target-load-optimize2 | |
5020 | @opindex fbranch-target-load-optimize2 | |
5021 | Perform branch target register load optimization after prologue / epilogue | |
5022 | threading. | |
5023 | ||
1194fc79 R |
5024 | @item -fbtr-bb-exclusive |
5025 | @opindex fbtr-bb-exclusive | |
8d3b3fb7 | 5026 | When performing branch target register load optimization, don't reuse |
1194fc79 R |
5027 | branch target registers in within any basic block. |
5028 | ||
3af64fd6 | 5029 | @item --param @var{name}=@var{value} |
cd3bb277 | 5030 | @opindex param |
3af64fd6 MM |
5031 | In some places, GCC uses various constants to control the amount of |
5032 | optimization that is done. For example, GCC will not inline functions | |
5033 | that contain more that a certain number of instructions. You can | |
5034 | control some of these constants on the command-line using the | |
630d3d5a | 5035 | @option{--param} option. |
3af64fd6 | 5036 | |
b00567b0 ILT |
5037 | The names of specific parameters, and the meaning of the values, are |
5038 | tied to the internals of the compiler, and are subject to change | |
5039 | without notice in future releases. | |
5040 | ||
4fe9b91c | 5041 | In each case, the @var{value} is an integer. The allowable choices for |
3af64fd6 MM |
5042 | @var{name} are given in the following table: |
5043 | ||
5044 | @table @gcctabopt | |
5f24e0dc RH |
5045 | @item max-crossjump-edges |
5046 | The maximum number of incoming edges to consider for crossjumping. | |
d203738b | 5047 | The algorithm used by @option{-fcrossjumping} is @math{O(N^2)} in |
5f24e0dc RH |
5048 | the number of edges incoming to each block. Increasing values mean |
5049 | more aggressive optimization, making the compile time increase with | |
5050 | probably small improvement in executable size. | |
5051 | ||
1c4c47db JO |
5052 | @item max-delay-slot-insn-search |
5053 | The maximum number of instructions to consider when looking for an | |
5054 | instruction to fill a delay slot. If more than this arbitrary number of | |
5055 | instructions is searched, the time savings from filling the delay slot | |
5056 | will be minimal so stop searching. Increasing values mean more | |
5057 | aggressive optimization, making the compile time increase with probably | |
5058 | small improvement in executable run time. | |
5059 | ||
5060 | @item max-delay-slot-live-search | |
5061 | When trying to fill delay slots, the maximum number of instructions to | |
5062 | consider when searching for a block with valid live register | |
5063 | information. Increasing this arbitrarily chosen value means more | |
5064 | aggressive optimization, increasing the compile time. This parameter | |
5065 | should be removed when the delay slot code is rewritten to maintain the | |
5066 | control-flow graph. | |
33d3b05b MM |
5067 | |
5068 | @item max-gcse-memory | |
5069 | The approximate maximum amount of memory that will be allocated in | |
5070 | order to perform the global common subexpression elimination | |
5071 | optimization. If more memory than specified is required, the | |
5072 | optimization will not be done. | |
3af64fd6 | 5073 | |
740f35a0 | 5074 | @item max-gcse-passes |
8d3b3fb7 | 5075 | The maximum number of passes of GCSE to run. The default is 1. |
740f35a0 | 5076 | |
4a121cc3 | 5077 | @item max-pending-list-length |
0c688a7d | 5078 | The maximum number of pending dependencies scheduling will allow |
4a121cc3 AM |
5079 | before flushing the current state and starting over. Large functions |
5080 | with few branches or calls can create excessively large lists which | |
5081 | needlessly consume memory and resources. | |
5082 | ||
bc522472 KG |
5083 | @item max-inline-insns-single |
5084 | Several parameters control the tree inliner used in gcc. | |
2dd76960 | 5085 | This number sets the maximum number of instructions (counted in GCC's |
daf2f129 | 5086 | internal representation) in a single function that the tree inliner |
bc522472 KG |
5087 | will consider for inlining. This only affects functions declared |
5088 | inline and methods implemented in a class declaration (C++). | |
1f95c733 | 5089 | The default value is 500. |
bc522472 KG |
5090 | |
5091 | @item max-inline-insns-auto | |
5092 | When you use @option{-finline-functions} (included in @option{-O3}), | |
5093 | a lot of functions that would otherwise not be considered for inlining | |
5094 | by the compiler will be investigated. To those functions, a different | |
5095 | (more restrictive) limit compared to functions declared inline can | |
5096 | be applied. | |
3b75d796 | 5097 | The default value is 120. |
bc522472 | 5098 | |
b58b1157 JH |
5099 | @item large-function-insns |
5100 | The limit specifying really large functions. For functions greater than this | |
5101 | limit inlining is constrained by @option{--param large-function-growth}. | |
a2b172fb | 5102 | This parameter is useful primarily to avoid extreme compilation time caused by non-linear |
b58b1157 JH |
5103 | algorithms used by the backend. |
5104 | This parameter is ignored when @option{-funit-at-a-time} is not used. | |
3b75d796 | 5105 | The default value is 3000. |
b58b1157 JH |
5106 | |
5107 | @item large-function-growth | |
e53e0c56 | 5108 | Specifies maximal growth of large function caused by inlining in percents. |
b58b1157 JH |
5109 | This parameter is ignored when @option{-funit-at-a-time} is not used. |
5110 | The default value is 200. | |
5111 | ||
5112 | @item inline-unit-growth | |
5113 | Specifies maximal overall growth of the compilation unit caused by inlining. | |
5114 | This parameter is ignored when @option{-funit-at-a-time} is not used. | |
5115 | The default value is 150. | |
5116 | ||
6de9cd9a DN |
5117 | @item max-inline-insns-recursive |
5118 | @itemx max-inline-insns-recursive-auto | |
5119 | Specifies maximum number of instructions out-of-line copy of self recursive inline | |
5120 | function can grow into by performing recursive inlining. | |
5121 | ||
5122 | For functions declared inline @option{--param max-inline-insns-recursive} is | |
5123 | taken into acount. For function not declared inline, recursive inlining | |
5124 | happens only when @option{-finline-functions} (included in @option{-O3}) is | |
5125 | enabled and @option{--param max-inline-insns-recursive-auto} is used. The | |
5126 | default value is 500. | |
5127 | ||
5128 | @item max-inline-recursive-depth | |
5129 | @itemx max-inline-recursive-depth-auto | |
5130 | Specifies maximum recursion depth used by the recursive inlining. | |
5131 | ||
5132 | For functions declared inline @option{--param max-inline-recursive-depth} is | |
5133 | taken into acount. For function not declared inline, recursive inlining | |
5134 | happens only when @option{-finline-functions} (included in @option{-O3}) is | |
5135 | enabled and @option{--param max-inline-recursive-depth-auto} is used. The | |
5136 | default value is 500. | |
5137 | ||
bc522472 KG |
5138 | @item max-inline-insns-rtl |
5139 | For languages that use the RTL inliner (this happens at a later stage | |
daf2f129 | 5140 | than tree inlining), you can set the maximum allowable size (counted |
bc522472 KG |
5141 | in RTL instructions) for the RTL inliner with this parameter. |
5142 | The default value is 600. | |
5143 | ||
03e9dbc9 MM |
5144 | @item max-unrolled-insns |
5145 | The maximum number of instructions that a loop should have if that loop | |
5146 | is unrolled, and if the loop is unrolled, it determines how many times | |
5147 | the loop code is unrolled. | |
5148 | ||
b17d5d7c ZD |
5149 | @item max-average-unrolled-insns |
5150 | The maximum number of instructions biased by probabilities of their execution | |
5151 | that a loop should have if that loop is unrolled, and if the loop is unrolled, | |
5152 | it determines how many times the loop code is unrolled. | |
5153 | ||
5154 | @item max-unroll-times | |
5155 | The maximum number of unrollings of a single loop. | |
5156 | ||
5157 | @item max-peeled-insns | |
5158 | The maximum number of instructions that a loop should have if that loop | |
5159 | is peeled, and if the loop is peeled, it determines how many times | |
5160 | the loop code is peeled. | |
5161 | ||
5162 | @item max-peel-times | |
5163 | The maximum number of peelings of a single loop. | |
5164 | ||
5165 | @item max-completely-peeled-insns | |
5166 | The maximum number of insns of a completely peeled loop. | |
5167 | ||
5168 | @item max-completely-peel-times | |
5169 | The maximum number of iterations of a loop to be suitable for complete peeling. | |
5170 | ||
01a132bb ZD |
5171 | @item max-unswitch-insns |
5172 | The maximum number of insns of an unswitched loop. | |
5173 | ||
5174 | @item max-unswitch-level | |
5175 | The maximum number of branches unswitched in a single loop. | |
5176 | ||
194734e9 JH |
5177 | @item hot-bb-count-fraction |
5178 | Select fraction of the maximal count of repetitions of basic block in program | |
5179 | given basic block needs to have to be considered hot. | |
5180 | ||
5181 | @item hot-bb-frequency-fraction | |
5182 | Select fraction of the maximal frequency of executions of basic block in | |
5183 | function given basic block needs to have to be considered hot | |
5c856b23 JH |
5184 | |
5185 | @item tracer-dynamic-coverage | |
5186 | @itemx tracer-dynamic-coverage-feedback | |
5187 | ||
3364c33b JQ |
5188 | This value is used to limit superblock formation once the given percentage of |
5189 | executed instructions is covered. This limits unnecessary code size | |
5190 | expansion. | |
5c856b23 JH |
5191 | |
5192 | The @option{tracer-dynamic-coverage-feedback} is used only when profile | |
5193 | feedback is available. The real profiles (as opposed to statically estimated | |
5194 | ones) are much less balanced allowing the threshold to be larger value. | |
5195 | ||
5196 | @item tracer-max-code-growth | |
5197 | Stop tail duplication once code growth has reached given percentage. This is | |
3364c33b | 5198 | rather hokey argument, as most of the duplicates will be eliminated later in |
5c856b23 JH |
5199 | cross jumping, so it may be set to much higher values than is the desired code |
5200 | growth. | |
5201 | ||
5202 | @item tracer-min-branch-ratio | |
5203 | ||
5204 | Stop reverse growth when the reverse probability of best edge is less than this | |
5205 | threshold (in percent). | |
5206 | ||
5207 | @item tracer-min-branch-ratio | |
5208 | @itemx tracer-min-branch-ratio-feedback | |
5209 | ||
5210 | Stop forward growth if the best edge do have probability lower than this | |
5211 | threshold. | |
5212 | ||
3364c33b | 5213 | Similarly to @option{tracer-dynamic-coverage} two values are present, one for |
5c856b23 JH |
5214 | compilation for profile feedback and one for compilation without. The value |
5215 | for compilation with profile feedback needs to be more conservative (higher) in | |
5216 | order to make tracer effective. | |
5217 | ||
c48ec590 ZD |
5218 | @item max-cse-path-length |
5219 | ||
8d3b3fb7 | 5220 | Maximum number of basic blocks on path that cse considers. The default is 10. |
c48ec590 | 5221 | |
6de9cd9a DN |
5222 | @item global-var-threshold |
5223 | ||
5224 | Counts the number of function calls (N) and the number of | |
5225 | call-clobbered variables (V). If NxV is larger than this limit, a | |
5226 | single artificial variable will be created to represent all the | |
5227 | call-clobbered variables at function call sites. This artificial | |
5228 | variable will then be made to alias every call-clobbered variable. | |
5229 | (done as int * size_t on the host machine; beware overflow). | |
5230 | ||
5231 | @item max-aliased-vops | |
5232 | ||
5233 | Maxiumum number of virtual operands allowed to represent aliases | |
5234 | before triggering the alias grouping heuristic. Alias grouping | |
5235 | reduces compile times and memory consumption needed for aliasing at | |
5236 | the expense of precision loss in alias information. | |
5237 | ||
3788cc17 ZW |
5238 | @item ggc-min-expand |
5239 | ||
5240 | GCC uses a garbage collector to manage its own memory allocation. This | |
5241 | parameter specifies the minimum percentage by which the garbage | |
5242 | collector's heap should be allowed to expand between collections. | |
5243 | Tuning this may improve compilation speed; it has no effect on code | |
5244 | generation. | |
5245 | ||
9ac121af | 5246 | The default is 30% + 70% * (RAM/1GB) with an upper bound of 100% when |
16226f1e KG |
5247 | RAM >= 1GB. If @code{getrlimit} is available, the notion of "RAM" is |
5248 | the smallest of actual RAM, RLIMIT_RSS, RLIMIT_DATA and RLIMIT_AS. If | |
5249 | GCC is not able to calculate RAM on a particular platform, the lower | |
5250 | bound of 30% is used. Setting this parameter and | |
737c38d1 GK |
5251 | @option{ggc-min-heapsize} to zero causes a full collection to occur at |
5252 | every opportunity. This is extremely slow, but can be useful for | |
5253 | debugging. | |
3788cc17 ZW |
5254 | |
5255 | @item ggc-min-heapsize | |
5256 | ||
5257 | Minimum size of the garbage collector's heap before it begins bothering | |
5258 | to collect garbage. The first collection occurs after the heap expands | |
5259 | by @option{ggc-min-expand}% beyond @option{ggc-min-heapsize}. Again, | |
5260 | tuning this may improve compilation speed, and has no effect on code | |
5261 | generation. | |
5262 | ||
9ac121af | 5263 | The default is RAM/8, with a lower bound of 4096 (four megabytes) and an |
16226f1e KG |
5264 | upper bound of 131072 (128 megabytes). If @code{getrlimit} is |
5265 | available, the notion of "RAM" is the smallest of actual RAM, | |
5266 | RLIMIT_RSS, RLIMIT_DATA and RLIMIT_AS. If GCC is not able to calculate | |
9ac121af KG |
5267 | RAM on a particular platform, the lower bound is used. Setting this |
5268 | parameter very large effectively disables garbage collection. Setting | |
5269 | this parameter and @option{ggc-min-expand} to zero causes a full | |
5270 | collection to occur at every opportunity. | |
3788cc17 | 5271 | |
0bcf8261 JH |
5272 | @item max-reload-search-insns |
5273 | The maximum number of instruction reload should look backward for equivalent | |
5274 | register. Increasing values mean more aggressive optimization, making the | |
5275 | compile time increase with probably slightly better performance. The default | |
5276 | value is 100. | |
5277 | ||
c65ecebc JH |
5278 | @item max-cselib-memory-location |
5279 | The maximum number of memory locations cselib should take into acount. | |
5280 | Increasing values mean more aggressive optimization, making the compile time | |
5281 | increase with probably slightly better performance. The default value is 500. | |
5282 | ||
26f74aa3 JH |
5283 | @item reorder-blocks-duplicate |
5284 | @itemx reorder-blocks-duplicate-feedback | |
5285 | ||
65d2d764 | 5286 | Used by basic block reordering pass to decide whether to use unconditional |
b222f49a | 5287 | branch or duplicate the code on its destination. Code is duplicated when its |
26f74aa3 | 5288 | estimated size is smaller than this value multiplied by the estimated size of |
65d2d764 | 5289 | unconditional jump in the hot spots of the program. |
26f74aa3 JH |
5290 | |
5291 | The @option{reorder-block-duplicate-feedback} is used only when profile | |
5292 | feedback is available and may be set to higher values than | |
5293 | @option{reorder-block-duplicate} since information about the hot spots is more | |
5294 | accurate. | |
f72c6b56 DE |
5295 | |
5296 | @item max-sched-region-blocks | |
5297 | The maximum number of blocks in a region to be considered for | |
5298 | interblock scheduling. The default value is 10. | |
5299 | ||
fbce7685 | 5300 | @item max-sched-region-insns |
f72c6b56 DE |
5301 | The maximum number of insns in a region to be considered for |
5302 | interblock scheduling. The default value is 100. | |
1c4c47db | 5303 | @end table |
74291a4b MM |
5304 | @end table |
5305 | ||
5306 | @node Preprocessor Options | |
5307 | @section Options Controlling the Preprocessor | |
5308 | @cindex preprocessor options | |
5309 | @cindex options, preprocessor | |
5310 | ||
5311 | These options control the C preprocessor, which is run on each C source | |
5312 | file before actual compilation. | |
5313 | ||
630d3d5a JM |
5314 | If you use the @option{-E} option, nothing is done except preprocessing. |
5315 | Some of these options make sense only together with @option{-E} because | |
74291a4b MM |
5316 | they cause the preprocessor output to be unsuitable for actual |
5317 | compilation. | |
5318 | ||
4977bab6 | 5319 | @table @gcctabopt |
cd3bb277 | 5320 | @opindex Wp |
40adaa27 NB |
5321 | You can use @option{-Wp,@var{option}} to bypass the compiler driver |
5322 | and pass @var{option} directly through to the preprocessor. If | |
5323 | @var{option} contains commas, it is split into multiple options at the | |
5324 | commas. However, many options are modified, translated or interpreted | |
5325 | by the compiler driver before being passed to the preprocessor, and | |
5326 | @option{-Wp} forcibly bypasses this phase. The preprocessor's direct | |
5327 | interface is undocumented and subject to change, so whenever possible | |
5328 | you should avoid using @option{-Wp} and let the driver handle the | |
5329 | options instead. | |
5330 | ||
4977bab6 ZW |
5331 | @item -Xpreprocessor @var{option} |
5332 | @opindex preprocessor | |
5333 | Pass @var{option} as an option to the preprocessor. You can use this to | |
5334 | supply system-specific preprocessor options which GCC does not know how to | |
5335 | recognize. | |
5336 | ||
5337 | If you want to pass an option that takes an argument, you must use | |
5338 | @option{-Xpreprocessor} twice, once for the option and once for the argument. | |
5339 | @end table | |
5340 | ||
40adaa27 | 5341 | @include cppopts.texi |
74291a4b MM |
5342 | |
5343 | @node Assembler Options | |
5344 | @section Passing Options to the Assembler | |
5345 | ||
5346 | @c prevent bad page break with this line | |
5347 | You can pass options to the assembler. | |
5348 | ||
2642624b | 5349 | @table @gcctabopt |
aee96fe9 | 5350 | @item -Wa,@var{option} |
cd3bb277 | 5351 | @opindex Wa |
74291a4b MM |
5352 | Pass @var{option} as an option to the assembler. If @var{option} |
5353 | contains commas, it is split into multiple options at the commas. | |
4977bab6 ZW |
5354 | |
5355 | @item -Xassembler @var{option} | |
5356 | @opindex Xassembler | |
5357 | Pass @var{option} as an option to the assembler. You can use this to | |
5358 | supply system-specific assembler options which GCC does not know how to | |
5359 | recognize. | |
5360 | ||
5361 | If you want to pass an option that takes an argument, you must use | |
5362 | @option{-Xassembler} twice, once for the option and once for the argument. | |
5363 | ||
74291a4b MM |
5364 | @end table |
5365 | ||
5366 | @node Link Options | |
5367 | @section Options for Linking | |
5368 | @cindex link options | |
5369 | @cindex options, linking | |
5370 | ||
5371 | These options come into play when the compiler links object files into | |
5372 | an executable output file. They are meaningless if the compiler is | |
5373 | not doing a link step. | |
5374 | ||
2642624b | 5375 | @table @gcctabopt |
74291a4b MM |
5376 | @cindex file names |
5377 | @item @var{object-file-name} | |
5378 | A file name that does not end in a special recognized suffix is | |
5379 | considered to name an object file or library. (Object files are | |
5380 | distinguished from libraries by the linker according to the file | |
5381 | contents.) If linking is done, these object files are used as input | |
5382 | to the linker. | |
5383 | ||
5384 | @item -c | |
5385 | @itemx -S | |
5386 | @itemx -E | |
cd3bb277 JM |
5387 | @opindex c |
5388 | @opindex S | |
5389 | @opindex E | |
74291a4b MM |
5390 | If any of these options is used, then the linker is not run, and |
5391 | object file names should not be used as arguments. @xref{Overall | |
5392 | Options}. | |
5393 | ||
5394 | @cindex Libraries | |
5395 | @item -l@var{library} | |
4275c4c4 | 5396 | @itemx -l @var{library} |
cd3bb277 | 5397 | @opindex l |
4275c4c4 JS |
5398 | Search the library named @var{library} when linking. (The second |
5399 | alternative with the library as a separate argument is only for | |
5400 | POSIX compliance and is not recommended.) | |
74291a4b MM |
5401 | |
5402 | It makes a difference where in the command you write this option; the | |
4275c4c4 | 5403 | linker searches and processes libraries and object files in the order they |
74291a4b MM |
5404 | are specified. Thus, @samp{foo.o -lz bar.o} searches library @samp{z} |
5405 | after file @file{foo.o} but before @file{bar.o}. If @file{bar.o} refers | |
5406 | to functions in @samp{z}, those functions may not be loaded. | |
5407 | ||
5408 | The linker searches a standard list of directories for the library, | |
5409 | which is actually a file named @file{lib@var{library}.a}. The linker | |
5410 | then uses this file as if it had been specified precisely by name. | |
5411 | ||
5412 | The directories searched include several standard system directories | |
630d3d5a | 5413 | plus any that you specify with @option{-L}. |
74291a4b MM |
5414 | |
5415 | Normally the files found this way are library files---archive files | |
5416 | whose members are object files. The linker handles an archive file by | |
5417 | scanning through it for members which define symbols that have so far | |
5418 | been referenced but not defined. But if the file that is found is an | |
5419 | ordinary object file, it is linked in the usual fashion. The only | |
630d3d5a JM |
5420 | difference between using an @option{-l} option and specifying a file name |
5421 | is that @option{-l} surrounds @var{library} with @samp{lib} and @samp{.a} | |
74291a4b MM |
5422 | and searches several directories. |
5423 | ||
5424 | @item -lobjc | |
cd3bb277 | 5425 | @opindex lobjc |
630d3d5a | 5426 | You need this special case of the @option{-l} option in order to |
2147b154 | 5427 | link an Objective-C program. |
74291a4b MM |
5428 | |
5429 | @item -nostartfiles | |
cd3bb277 | 5430 | @opindex nostartfiles |
74291a4b | 5431 | Do not use the standard system startup files when linking. |
bedc7537 NC |
5432 | The standard system libraries are used normally, unless @option{-nostdlib} |
5433 | or @option{-nodefaultlibs} is used. | |
74291a4b MM |
5434 | |
5435 | @item -nodefaultlibs | |
cd3bb277 | 5436 | @opindex nodefaultlibs |
74291a4b MM |
5437 | Do not use the standard system libraries when linking. |
5438 | Only the libraries you specify will be passed to the linker. | |
bedc7537 | 5439 | The standard startup files are used normally, unless @option{-nostartfiles} |
8f99553f JM |
5440 | is used. The compiler may generate calls to @code{memcmp}, |
5441 | @code{memset}, @code{memcpy} and @code{memmove}. | |
5442 | These entries are usually resolved by entries in | |
4754172c CM |
5443 | libc. These entry points should be supplied through some other |
5444 | mechanism when this option is specified. | |
74291a4b MM |
5445 | |
5446 | @item -nostdlib | |
cd3bb277 | 5447 | @opindex nostdlib |
74291a4b MM |
5448 | Do not use the standard system startup files or libraries when linking. |
5449 | No startup files and only the libraries you specify will be passed to | |
8f99553f JM |
5450 | the linker. The compiler may generate calls to @code{memcmp}, @code{memset}, |
5451 | @code{memcpy} and @code{memmove}. | |
5452 | These entries are usually resolved by entries in | |
4754172c CM |
5453 | libc. These entry points should be supplied through some other |
5454 | mechanism when this option is specified. | |
74291a4b | 5455 | |
630d3d5a JM |
5456 | @cindex @option{-lgcc}, use with @option{-nostdlib} |
5457 | @cindex @option{-nostdlib} and unresolved references | |
5458 | @cindex unresolved references and @option{-nostdlib} | |
5459 | @cindex @option{-lgcc}, use with @option{-nodefaultlibs} | |
5460 | @cindex @option{-nodefaultlibs} and unresolved references | |
5461 | @cindex unresolved references and @option{-nodefaultlibs} | |
5462 | One of the standard libraries bypassed by @option{-nostdlib} and | |
5463 | @option{-nodefaultlibs} is @file{libgcc.a}, a library of internal subroutines | |
0c2d1a2a | 5464 | that GCC uses to overcome shortcomings of particular machines, or special |
74291a4b | 5465 | needs for some languages. |
b11cc610 JM |
5466 | (@xref{Interface,,Interfacing to GCC Output,gccint,GNU Compiler |
5467 | Collection (GCC) Internals}, | |
74291a4b | 5468 | for more discussion of @file{libgcc.a}.) |
74291a4b | 5469 | In most cases, you need @file{libgcc.a} even when you want to avoid |
630d3d5a JM |
5470 | other standard libraries. In other words, when you specify @option{-nostdlib} |
5471 | or @option{-nodefaultlibs} you should usually specify @option{-lgcc} as well. | |
0c2d1a2a | 5472 | This ensures that you have no unresolved references to internal GCC |
74291a4b | 5473 | library subroutines. (For example, @samp{__main}, used to ensure C++ |
b11cc610 JM |
5474 | constructors will be called; @pxref{Collect2,,@code{collect2}, gccint, |
5475 | GNU Compiler Collection (GCC) Internals}.) | |
74291a4b | 5476 | |
24a4dd31 JJ |
5477 | @item -pie |
5478 | @opindex pie | |
5479 | Produce a position independent executable on targets which support it. | |
5480 | For predictable results, you must also specify the same set of options | |
5481 | that were used to generate code (@option{-fpie}, @option{-fPIE}, | |
5482 | or model suboptions) when you specify this option. | |
5483 | ||
74291a4b | 5484 | @item -s |
cd3bb277 | 5485 | @opindex s |
74291a4b MM |
5486 | Remove all symbol table and relocation information from the executable. |
5487 | ||
5488 | @item -static | |
cd3bb277 | 5489 | @opindex static |
74291a4b MM |
5490 | On systems that support dynamic linking, this prevents linking with the shared |
5491 | libraries. On other systems, this option has no effect. | |
5492 | ||
5493 | @item -shared | |
cd3bb277 | 5494 | @opindex shared |
74291a4b | 5495 | Produce a shared object which can then be linked with other objects to |
1d3b0e2c | 5496 | form an executable. Not all systems support this option. For predictable |
02f52e19 | 5497 | results, you must also specify the same set of options that were used to |
630d3d5a | 5498 | generate code (@option{-fpic}, @option{-fPIC}, or model suboptions) |
2642624b | 5499 | when you specify this option.@footnote{On some systems, @samp{gcc -shared} |
767094dd | 5500 | needs to build supplementary stub code for constructors to work. On |
2642624b | 5501 | multi-libbed systems, @samp{gcc -shared} must select the correct support |
1d3b0e2c | 5502 | libraries to link against. Failing to supply the correct flags may lead |
767094dd | 5503 | to subtle defects. Supplying them in cases where they are not necessary |
1d3b0e2c | 5504 | is innocuous.} |
74291a4b | 5505 | |
9db0819e RH |
5506 | @item -shared-libgcc |
5507 | @itemx -static-libgcc | |
cd3bb277 JM |
5508 | @opindex shared-libgcc |
5509 | @opindex static-libgcc | |
9db0819e RH |
5510 | On systems that provide @file{libgcc} as a shared library, these options |
5511 | force the use of either the shared or static version respectively. | |
5512 | If no shared version of @file{libgcc} was built when the compiler was | |
5513 | configured, these options have no effect. | |
5514 | ||
5515 | There are several situations in which an application should use the | |
5516 | shared @file{libgcc} instead of the static version. The most common | |
5517 | of these is when the application wishes to throw and catch exceptions | |
5518 | across different shared libraries. In that case, each of the libraries | |
5519 | as well as the application itself should use the shared @file{libgcc}. | |
5520 | ||
5c181756 AO |
5521 | Therefore, the G++ and GCJ drivers automatically add |
5522 | @option{-shared-libgcc} whenever you build a shared library or a main | |
5523 | executable, because C++ and Java programs typically use exceptions, so | |
5524 | this is the right thing to do. | |
5525 | ||
5526 | If, instead, you use the GCC driver to create shared libraries, you may | |
5527 | find that they will not always be linked with the shared @file{libgcc}. | |
d3144423 EB |
5528 | If GCC finds, at its configuration time, that you have a non-GNU linker |
5529 | or a GNU linker that does not support option @option{--eh-frame-hdr}, | |
5530 | it will link the shared version of @file{libgcc} into shared libraries | |
5531 | by default. Otherwise, it will take advantage of the linker and optimize | |
5532 | away the linking with the shared version of @file{libgcc}, linking with | |
5533 | the static version of libgcc by default. This allows exceptions to | |
5534 | propagate through such shared libraries, without incurring relocation | |
5535 | costs at library load time. | |
5c181756 AO |
5536 | |
5537 | However, if a library or main executable is supposed to throw or catch | |
5538 | exceptions, you must link it using the G++ or GCJ driver, as appropriate | |
5539 | for the languages used in the program, or using the option | |
5540 | @option{-shared-libgcc}, such that it is linked with the shared | |
049f6ec9 | 5541 | @file{libgcc}. |
9db0819e | 5542 | |
74291a4b | 5543 | @item -symbolic |
cd3bb277 | 5544 | @opindex symbolic |
74291a4b MM |
5545 | Bind references to global symbols when building a shared object. Warn |
5546 | about any unresolved references (unless overridden by the link editor | |
5547 | option @samp{-Xlinker -z -Xlinker defs}). Only a few systems support | |
5548 | this option. | |
5549 | ||
5550 | @item -Xlinker @var{option} | |
cd3bb277 | 5551 | @opindex Xlinker |
74291a4b | 5552 | Pass @var{option} as an option to the linker. You can use this to |
0c2d1a2a | 5553 | supply system-specific linker options which GCC does not know how to |
74291a4b MM |
5554 | recognize. |
5555 | ||
5556 | If you want to pass an option that takes an argument, you must use | |
630d3d5a JM |
5557 | @option{-Xlinker} twice, once for the option and once for the argument. |
5558 | For example, to pass @option{-assert definitions}, you must write | |
74291a4b | 5559 | @samp{-Xlinker -assert -Xlinker definitions}. It does not work to write |
630d3d5a | 5560 | @option{-Xlinker "-assert definitions"}, because this passes the entire |
74291a4b MM |
5561 | string as a single argument, which is not what the linker expects. |
5562 | ||
aee96fe9 | 5563 | @item -Wl,@var{option} |
cd3bb277 | 5564 | @opindex Wl |
74291a4b MM |
5565 | Pass @var{option} as an option to the linker. If @var{option} contains |
5566 | commas, it is split into multiple options at the commas. | |
5567 | ||
5568 | @item -u @var{symbol} | |
cd3bb277 | 5569 | @opindex u |
74291a4b | 5570 | Pretend the symbol @var{symbol} is undefined, to force linking of |
630d3d5a | 5571 | library modules to define it. You can use @option{-u} multiple times with |
74291a4b MM |
5572 | different symbols to force loading of additional library modules. |
5573 | @end table | |
5574 | ||
5575 | @node Directory Options | |
5576 | @section Options for Directory Search | |
5577 | @cindex directory options | |
5578 | @cindex options, directory search | |
5579 | @cindex search path | |
5580 | ||
5581 | These options specify directories to search for header files, for | |
5582 | libraries and for parts of the compiler: | |
5583 | ||
2642624b | 5584 | @table @gcctabopt |
74291a4b | 5585 | @item -I@var{dir} |
cd3bb277 | 5586 | @opindex I |
861bb6c1 JL |
5587 | Add the directory @var{dir} to the head of the list of directories to be |
5588 | searched for header files. This can be used to override a system header | |
5589 | file, substituting your own version, since these directories are | |
d0a5eb32 RK |
5590 | searched before the system header file directories. However, you should |
5591 | not use this option to add directories that contain vendor-supplied | |
767094dd | 5592 | system header files (use @option{-isystem} for that). If you use more than |
630d3d5a | 5593 | one @option{-I} option, the directories are scanned in left-to-right |
74291a4b MM |
5594 | order; the standard system directories come after. |
5595 | ||
dbead49c | 5596 | If a standard system include directory, or a directory specified with |
48209ce5 JDA |
5597 | @option{-isystem}, is also specified with @option{-I}, the @option{-I} |
5598 | option will be ignored. The directory will still be searched but as a | |
5599 | system directory at its normal position in the system include chain. | |
5600 | This is to ensure that GCC's procedure to fix buggy system headers and | |
3364c33b | 5601 | the ordering for the include_next directive are not inadvertently changed. |
48209ce5 JDA |
5602 | If you really need to change the search order for system directories, |
5603 | use the @option{-nostdinc} and/or @option{-isystem} options. | |
dbead49c | 5604 | |
4bed3787 MS |
5605 | @item -iquote@var{dir} |
5606 | @opindex iquote | |
5607 | Add the directory @var{dir} to the head of the list of directories to | |
5608 | be searched for header files only for the case of @samp{#include | |
5609 | "@var{file}"}; they are not searched for @samp{#include <@var{file}>}, | |
5610 | otherwise just like @option{-I}. | |
74291a4b MM |
5611 | |
5612 | @item -L@var{dir} | |
cd3bb277 | 5613 | @opindex L |
74291a4b | 5614 | Add directory @var{dir} to the list of directories to be searched |
630d3d5a | 5615 | for @option{-l}. |
74291a4b MM |
5616 | |
5617 | @item -B@var{prefix} | |
cd3bb277 | 5618 | @opindex B |
74291a4b MM |
5619 | This option specifies where to find the executables, libraries, |
5620 | include files, and data files of the compiler itself. | |
5621 | ||
5622 | The compiler driver program runs one or more of the subprograms | |
5623 | @file{cpp}, @file{cc1}, @file{as} and @file{ld}. It tries | |
5624 | @var{prefix} as a prefix for each program it tries to run, both with and | |
5625 | without @samp{@var{machine}/@var{version}/} (@pxref{Target Options}). | |
5626 | ||
5627 | For each subprogram to be run, the compiler driver first tries the | |
630d3d5a | 5628 | @option{-B} prefix, if any. If that name is not found, or if @option{-B} |
74291a4b | 5629 | was not specified, the driver tries two standard prefixes, which are |
8e5f33ff | 5630 | @file{/usr/lib/gcc/} and @file{/usr/local/lib/gcc/}. If neither of |
74291a4b MM |
5631 | those results in a file name that is found, the unmodified program |
5632 | name is searched for using the directories specified in your | |
bedc7537 | 5633 | @env{PATH} environment variable. |
74291a4b | 5634 | |
07804c3b NC |
5635 | The compiler will check to see if the path provided by the @option{-B} |
5636 | refers to a directory, and if necessary it will add a directory | |
5637 | separator character at the end of the path. | |
5638 | ||
630d3d5a | 5639 | @option{-B} prefixes that effectively specify directory names also apply |
74291a4b | 5640 | to libraries in the linker, because the compiler translates these |
630d3d5a | 5641 | options into @option{-L} options for the linker. They also apply to |
74291a4b | 5642 | includes files in the preprocessor, because the compiler translates these |
630d3d5a | 5643 | options into @option{-isystem} options for the preprocessor. In this case, |
74291a4b MM |
5644 | the compiler appends @samp{include} to the prefix. |
5645 | ||
5646 | The run-time support file @file{libgcc.a} can also be searched for using | |
630d3d5a | 5647 | the @option{-B} prefix, if needed. If it is not found there, the two |
74291a4b MM |
5648 | standard prefixes above are tried, and that is all. The file is left |
5649 | out of the link if it is not found by those means. | |
5650 | ||
630d3d5a | 5651 | Another way to specify a prefix much like the @option{-B} prefix is to use |
bedc7537 | 5652 | the environment variable @env{GCC_EXEC_PREFIX}. @xref{Environment |
74291a4b | 5653 | Variables}. |
861bb6c1 | 5654 | |
07804c3b | 5655 | As a special kludge, if the path provided by @option{-B} is |
bf4eebe0 NC |
5656 | @file{[dir/]stage@var{N}/}, where @var{N} is a number in the range 0 to |
5657 | 9, then it will be replaced by @file{[dir/]include}. This is to help | |
7dac2f89 | 5658 | with boot-strapping the compiler. |
07804c3b | 5659 | |
861bb6c1 | 5660 | @item -specs=@var{file} |
cd3bb277 | 5661 | @opindex specs |
861bb6c1 JL |
5662 | Process @var{file} after the compiler reads in the standard @file{specs} |
5663 | file, in order to override the defaults that the @file{gcc} driver | |
5664 | program uses when determining what switches to pass to @file{cc1}, | |
5665 | @file{cc1plus}, @file{as}, @file{ld}, etc. More than one | |
630d3d5a | 5666 | @option{-specs=@var{file}} can be specified on the command line, and they |
861bb6c1 | 5667 | are processed in order, from left to right. |
4bed3787 MS |
5668 | |
5669 | @item -I- | |
5670 | @opindex I- | |
5671 | This option has been deprecated. Please use @option{-iquote} instead for | |
5672 | @option{-I} directories before the @option{-I-} and remove the @option{-I-}. | |
5673 | Any directories you specify with @option{-I} options before the @option{-I-} | |
5674 | option are searched only for the case of @samp{#include "@var{file}"}; | |
5675 | they are not searched for @samp{#include <@var{file}>}. | |
5676 | ||
5677 | If additional directories are specified with @option{-I} options after | |
5678 | the @option{-I-}, these directories are searched for all @samp{#include} | |
5679 | directives. (Ordinarily @emph{all} @option{-I} directories are used | |
5680 | this way.) | |
5681 | ||
5682 | In addition, the @option{-I-} option inhibits the use of the current | |
5683 | directory (where the current input file came from) as the first search | |
5684 | directory for @samp{#include "@var{file}"}. There is no way to | |
5685 | override this effect of @option{-I-}. With @option{-I.} you can specify | |
5686 | searching the directory which was current when the compiler was | |
5687 | invoked. That is not exactly the same as what the preprocessor does | |
5688 | by default, but it is often satisfactory. | |
5689 | ||
5690 | @option{-I-} does not inhibit the use of the standard system directories | |
5691 | for header files. Thus, @option{-I-} and @option{-nostdinc} are | |
5692 | independent. | |
74291a4b MM |
5693 | @end table |
5694 | ||
ee457005 JM |
5695 | @c man end |
5696 | ||
a743d340 NC |
5697 | @node Spec Files |
5698 | @section Specifying subprocesses and the switches to pass to them | |
5699 | @cindex Spec Files | |
d2d42a91 | 5700 | |
bedc7537 | 5701 | @command{gcc} is a driver program. It performs its job by invoking a |
a743d340 NC |
5702 | sequence of other programs to do the work of compiling, assembling and |
5703 | linking. GCC interprets its command-line parameters and uses these to | |
5704 | deduce which programs it should invoke, and which command-line options | |
c21cd8b1 | 5705 | it ought to place on their command lines. This behavior is controlled |
a743d340 NC |
5706 | by @dfn{spec strings}. In most cases there is one spec string for each |
5707 | program that GCC can invoke, but a few programs have multiple spec | |
c21cd8b1 | 5708 | strings to control their behavior. The spec strings built into GCC can |
630d3d5a | 5709 | be overridden by using the @option{-specs=} command-line switch to specify |
a743d340 NC |
5710 | a spec file. |
5711 | ||
5712 | @dfn{Spec files} are plaintext files that are used to construct spec | |
5713 | strings. They consist of a sequence of directives separated by blank | |
5714 | lines. The type of directive is determined by the first non-whitespace | |
5715 | character on the line and it can be one of the following: | |
5716 | ||
5717 | @table @code | |
5718 | @item %@var{command} | |
5719 | Issues a @var{command} to the spec file processor. The commands that can | |
02f52e19 | 5720 | appear here are: |
a743d340 NC |
5721 | |
5722 | @table @code | |
5723 | @item %include <@var{file}> | |
5724 | @cindex %include | |
5725 | Search for @var{file} and insert its text at the current point in the | |
5726 | specs file. | |
5727 | ||
5728 | @item %include_noerr <@var{file}> | |
5729 | @cindex %include_noerr | |
5730 | Just like @samp{%include}, but do not generate an error message if the include | |
5731 | file cannot be found. | |
5732 | ||
5733 | @item %rename @var{old_name} @var{new_name} | |
5734 | @cindex %rename | |
5735 | Rename the spec string @var{old_name} to @var{new_name}. | |
5736 | ||
5737 | @end table | |
5738 | ||
5739 | @item *[@var{spec_name}]: | |
5740 | This tells the compiler to create, override or delete the named spec | |
5741 | string. All lines after this directive up to the next directive or | |
5742 | blank line are considered to be the text for the spec string. If this | |
5743 | results in an empty string then the spec will be deleted. (Or, if the | |
5744 | spec did not exist, then nothing will happened.) Otherwise, if the spec | |
5745 | does not currently exist a new spec will be created. If the spec does | |
5746 | exist then its contents will be overridden by the text of this | |
5747 | directive, unless the first character of that text is the @samp{+} | |
5748 | character, in which case the text will be appended to the spec. | |
5749 | ||
5750 | @item [@var{suffix}]: | |
5751 | Creates a new @samp{[@var{suffix}] spec} pair. All lines after this directive | |
5752 | and up to the next directive or blank line are considered to make up the | |
02f52e19 | 5753 | spec string for the indicated suffix. When the compiler encounters an |
a743d340 NC |
5754 | input file with the named suffix, it will processes the spec string in |
5755 | order to work out how to compile that file. For example: | |
5756 | ||
5757 | @smallexample | |
5758 | .ZZ: | |
5759 | z-compile -input %i | |
5760 | @end smallexample | |
5761 | ||
5762 | This says that any input file whose name ends in @samp{.ZZ} should be | |
5763 | passed to the program @samp{z-compile}, which should be invoked with the | |
630d3d5a | 5764 | command-line switch @option{-input} and with the result of performing the |
a743d340 NC |
5765 | @samp{%i} substitution. (See below.) |
5766 | ||
5767 | As an alternative to providing a spec string, the text that follows a | |
5768 | suffix directive can be one of the following: | |
5769 | ||
5770 | @table @code | |
5771 | @item @@@var{language} | |
5772 | This says that the suffix is an alias for a known @var{language}. This is | |
bedc7537 | 5773 | similar to using the @option{-x} command-line switch to GCC to specify a |
a743d340 NC |
5774 | language explicitly. For example: |
5775 | ||
5776 | @smallexample | |
5777 | .ZZ: | |
5778 | @@c++ | |
5779 | @end smallexample | |
5780 | ||
5781 | Says that .ZZ files are, in fact, C++ source files. | |
5782 | ||
5783 | @item #@var{name} | |
5784 | This causes an error messages saying: | |
5785 | ||
5786 | @smallexample | |
5787 | @var{name} compiler not installed on this system. | |
5788 | @end smallexample | |
5789 | @end table | |
5790 | ||
5791 | GCC already has an extensive list of suffixes built into it. | |
5792 | This directive will add an entry to the end of the list of suffixes, but | |
5793 | since the list is searched from the end backwards, it is effectively | |
5794 | possible to override earlier entries using this technique. | |
5795 | ||
5796 | @end table | |
5797 | ||
5798 | GCC has the following spec strings built into it. Spec files can | |
5799 | override these strings or create their own. Note that individual | |
02f52e19 | 5800 | targets can also add their own spec strings to this list. |
a743d340 NC |
5801 | |
5802 | @smallexample | |
5803 | asm Options to pass to the assembler | |
5804 | asm_final Options to pass to the assembler post-processor | |
5805 | cpp Options to pass to the C preprocessor | |
5806 | cc1 Options to pass to the C compiler | |
5807 | cc1plus Options to pass to the C++ compiler | |
5808 | endfile Object files to include at the end of the link | |
5809 | link Options to pass to the linker | |
5810 | lib Libraries to include on the command line to the linker | |
5811 | libgcc Decides which GCC support library to pass to the linker | |
5812 | linker Sets the name of the linker | |
5813 | predefines Defines to be passed to the C preprocessor | |
310668e8 JM |
5814 | signed_char Defines to pass to CPP to say whether @code{char} is signed |
5815 | by default | |
a743d340 NC |
5816 | startfile Object files to include at the start of the link |
5817 | @end smallexample | |
5818 | ||
5819 | Here is a small example of a spec file: | |
5820 | ||
5821 | @smallexample | |
5822 | %rename lib old_lib | |
5823 | ||
5824 | *lib: | |
5825 | --start-group -lgcc -lc -leval1 --end-group %(old_lib) | |
5826 | @end smallexample | |
5827 | ||
5828 | This example renames the spec called @samp{lib} to @samp{old_lib} and | |
5829 | then overrides the previous definition of @samp{lib} with a new one. | |
5830 | The new definition adds in some extra command-line options before | |
5831 | including the text of the old definition. | |
5832 | ||
5833 | @dfn{Spec strings} are a list of command-line options to be passed to their | |
5834 | corresponding program. In addition, the spec strings can contain | |
5835 | @samp{%}-prefixed sequences to substitute variable text or to | |
5836 | conditionally insert text into the command line. Using these constructs | |
5837 | it is possible to generate quite complex command lines. | |
5838 | ||
5839 | Here is a table of all defined @samp{%}-sequences for spec | |
5840 | strings. Note that spaces are not generated automatically around the | |
5841 | results of expanding these sequences. Therefore you can concatenate them | |
02f52e19 | 5842 | together or combine them with constant text in a single argument. |
a743d340 NC |
5843 | |
5844 | @table @code | |
5845 | @item %% | |
5846 | Substitute one @samp{%} into the program name or argument. | |
5847 | ||
5848 | @item %i | |
5849 | Substitute the name of the input file being processed. | |
5850 | ||
5851 | @item %b | |
5852 | Substitute the basename of the input file being processed. | |
5853 | This is the substring up to (and not including) the last period | |
5854 | and not including the directory. | |
5855 | ||
371e300b NC |
5856 | @item %B |
5857 | This is the same as @samp{%b}, but include the file suffix (text after | |
5858 | the last period). | |
5859 | ||
a743d340 NC |
5860 | @item %d |
5861 | Marks the argument containing or following the @samp{%d} as a | |
5862 | temporary file name, so that that file will be deleted if GCC exits | |
5863 | successfully. Unlike @samp{%g}, this contributes no text to the | |
02f52e19 | 5864 | argument. |
a743d340 NC |
5865 | |
5866 | @item %g@var{suffix} | |
5867 | Substitute a file name that has suffix @var{suffix} and is chosen | |
5868 | once per compilation, and mark the argument in the same way as | |
5869 | @samp{%d}. To reduce exposure to denial-of-service attacks, the file | |
02f52e19 | 5870 | name is now chosen in a way that is hard to predict even when previously |
695ac33f | 5871 | chosen file names are known. For example, @samp{%g.s @dots{} %g.o @dots{} %g.s} |
a743d340 NC |
5872 | might turn into @samp{ccUVUUAU.s ccXYAXZ12.o ccUVUUAU.s}. @var{suffix} matches |
5873 | the regexp @samp{[.A-Za-z]*} or the special string @samp{%O}, which is | |
5874 | treated exactly as if @samp{%O} had been preprocessed. Previously, @samp{%g} | |
5875 | was simply substituted with a file name chosen once per compilation, | |
5876 | without regard to any appended suffix (which was therefore treated | |
5877 | just like ordinary text), making such attacks more likely to succeed. | |
5878 | ||
5879 | @item %u@var{suffix} | |
5880 | Like @samp{%g}, but generates a new temporary file name even if | |
5881 | @samp{%u@var{suffix}} was already seen. | |
5882 | ||
5883 | @item %U@var{suffix} | |
5884 | Substitutes the last file name generated with @samp{%u@var{suffix}}, generating a | |
5885 | new one if there is no such last file name. In the absence of any | |
5886 | @samp{%u@var{suffix}}, this is just like @samp{%g@var{suffix}}, except they don't share | |
695ac33f | 5887 | the same suffix @emph{space}, so @samp{%g.s @dots{} %U.s @dots{} %g.s @dots{} %U.s} |
a743d340 NC |
5888 | would involve the generation of two distinct file names, one |
5889 | for each @samp{%g.s} and another for each @samp{%U.s}. Previously, @samp{%U} was | |
5890 | simply substituted with a file name chosen for the previous @samp{%u}, | |
5891 | without regard to any appended suffix. | |
5892 | ||
4977bab6 | 5893 | @item %j@var{suffix} |
aee96fe9 | 5894 | Substitutes the name of the @code{HOST_BIT_BUCKET}, if any, and if it is |
371e300b NC |
5895 | writable, and if save-temps is off; otherwise, substitute the name |
5896 | of a temporary file, just like @samp{%u}. This temporary file is not | |
5897 | meant for communication between processes, but rather as a junk | |
5898 | disposal mechanism. | |
5899 | ||
4977bab6 ZW |
5900 | @item %|@var{suffix} |
5901 | @itemx %m@var{suffix} | |
5902 | Like @samp{%g}, except if @option{-pipe} is in effect. In that case | |
5903 | @samp{%|} substitutes a single dash and @samp{%m} substitutes nothing at | |
5904 | all. These are the two most common ways to instruct a program that it | |
5905 | should read from standard input or write to standard output. If you | |
5906 | need something more elaborate you can use an @samp{%@{pipe:@code{X}@}} | |
5907 | construct: see for example @file{f/lang-specs.h}. | |
5908 | ||
371e300b NC |
5909 | @item %.@var{SUFFIX} |
5910 | Substitutes @var{.SUFFIX} for the suffixes of a matched switch's args | |
767094dd | 5911 | when it is subsequently output with @samp{%*}. @var{SUFFIX} is |
371e300b NC |
5912 | terminated by the next space or %. |
5913 | ||
a743d340 NC |
5914 | @item %w |
5915 | Marks the argument containing or following the @samp{%w} as the | |
5916 | designated output file of this compilation. This puts the argument | |
5917 | into the sequence of arguments that @samp{%o} will substitute later. | |
5918 | ||
5919 | @item %o | |
5920 | Substitutes the names of all the output files, with spaces | |
5921 | automatically placed around them. You should write spaces | |
5922 | around the @samp{%o} as well or the results are undefined. | |
5923 | @samp{%o} is for use in the specs for running the linker. | |
5924 | Input files whose names have no recognized suffix are not compiled | |
5925 | at all, but they are included among the output files, so they will | |
5926 | be linked. | |
5927 | ||
5928 | @item %O | |
5929 | Substitutes the suffix for object files. Note that this is | |
5930 | handled specially when it immediately follows @samp{%g, %u, or %U}, | |
5931 | because of the need for those to form complete file names. The | |
5932 | handling is such that @samp{%O} is treated exactly as if it had already | |
5933 | been substituted, except that @samp{%g, %u, and %U} do not currently | |
5934 | support additional @var{suffix} characters following @samp{%O} as they would | |
5935 | following, for example, @samp{.o}. | |
5936 | ||
5937 | @item %p | |
5938 | Substitutes the standard macro predefinitions for the | |
5939 | current target machine. Use this when running @code{cpp}. | |
5940 | ||
5941 | @item %P | |
5942 | Like @samp{%p}, but puts @samp{__} before and after the name of each | |
5943 | predefined macro, except for macros that start with @samp{__} or with | |
c1030c7c | 5944 | @samp{_@var{L}}, where @var{L} is an uppercase letter. This is for ISO |
161d7b59 | 5945 | C@. |
a743d340 NC |
5946 | |
5947 | @item %I | |
047d636f DJ |
5948 | Substitute any of @option{-iprefix} (made from @env{GCC_EXEC_PREFIX}), |
5949 | @option{-isysroot} (made from @env{TARGET_SYSTEM_ROOT}), and | |
5950 | @option{-isystem} (made from @env{COMPILER_PATH} and @option{-B} options) | |
5951 | as necessary. | |
a743d340 NC |
5952 | |
5953 | @item %s | |
5954 | Current argument is the name of a library or startup file of some sort. | |
5955 | Search for that file in a standard list of directories and substitute | |
02f52e19 | 5956 | the full name found. |
a743d340 NC |
5957 | |
5958 | @item %e@var{str} | |
5959 | Print @var{str} as an error message. @var{str} is terminated by a newline. | |
5960 | Use this when inconsistent options are detected. | |
5961 | ||
a743d340 NC |
5962 | @item %(@var{name}) |
5963 | Substitute the contents of spec string @var{name} at this point. | |
5964 | ||
5965 | @item %[@var{name}] | |
630d3d5a | 5966 | Like @samp{%(@dots{})} but put @samp{__} around @option{-D} arguments. |
a743d340 NC |
5967 | |
5968 | @item %x@{@var{option}@} | |
5969 | Accumulate an option for @samp{%X}. | |
5970 | ||
5971 | @item %X | |
630d3d5a | 5972 | Output the accumulated linker options specified by @option{-Wl} or a @samp{%x} |
a743d340 NC |
5973 | spec string. |
5974 | ||
5975 | @item %Y | |
630d3d5a | 5976 | Output the accumulated assembler options specified by @option{-Wa}. |
a743d340 NC |
5977 | |
5978 | @item %Z | |
630d3d5a | 5979 | Output the accumulated preprocessor options specified by @option{-Wp}. |
a743d340 | 5980 | |
a743d340 NC |
5981 | @item %a |
5982 | Process the @code{asm} spec. This is used to compute the | |
5983 | switches to be passed to the assembler. | |
5984 | ||
5985 | @item %A | |
5986 | Process the @code{asm_final} spec. This is a spec string for | |
5987 | passing switches to an assembler post-processor, if such a program is | |
5988 | needed. | |
5989 | ||
5990 | @item %l | |
5991 | Process the @code{link} spec. This is the spec for computing the | |
5992 | command line passed to the linker. Typically it will make use of the | |
5993 | @samp{%L %G %S %D and %E} sequences. | |
5994 | ||
5995 | @item %D | |
630d3d5a | 5996 | Dump out a @option{-L} option for each directory that GCC believes might |
a743d340 | 5997 | contain startup files. If the target supports multilibs then the |
02f52e19 | 5998 | current multilib directory will be prepended to each of these paths. |
a743d340 | 5999 | |
371e300b | 6000 | @item %M |
c771326b | 6001 | Output the multilib directory with directory separators replaced with |
695ac33f JM |
6002 | @samp{_}. If multilib directories are not set, or the multilib directory is |
6003 | @file{.} then this option emits nothing. | |
371e300b | 6004 | |
a743d340 NC |
6005 | @item %L |
6006 | Process the @code{lib} spec. This is a spec string for deciding which | |
02f52e19 | 6007 | libraries should be included on the command line to the linker. |
a743d340 NC |
6008 | |
6009 | @item %G | |
6010 | Process the @code{libgcc} spec. This is a spec string for deciding | |
02f52e19 | 6011 | which GCC support library should be included on the command line to the linker. |
a743d340 NC |
6012 | |
6013 | @item %S | |
6014 | Process the @code{startfile} spec. This is a spec for deciding which | |
6015 | object files should be the first ones passed to the linker. Typically | |
02f52e19 | 6016 | this might be a file named @file{crt0.o}. |
a743d340 NC |
6017 | |
6018 | @item %E | |
6019 | Process the @code{endfile} spec. This is a spec string that specifies | |
02f52e19 | 6020 | the last object files that will be passed to the linker. |
a743d340 NC |
6021 | |
6022 | @item %C | |
6023 | Process the @code{cpp} spec. This is used to construct the arguments | |
6024 | to be passed to the C preprocessor. | |
6025 | ||
a743d340 NC |
6026 | @item %1 |
6027 | Process the @code{cc1} spec. This is used to construct the options to be | |
6028 | passed to the actual C compiler (@samp{cc1}). | |
6029 | ||
6030 | @item %2 | |
6031 | Process the @code{cc1plus} spec. This is used to construct the options to be | |
6032 | passed to the actual C++ compiler (@samp{cc1plus}). | |
6033 | ||
6034 | @item %* | |
6035 | Substitute the variable part of a matched option. See below. | |
6036 | Note that each comma in the substituted string is replaced by | |
6037 | a single space. | |
6038 | ||
4977bab6 ZW |
6039 | @item %<@code{S} |
6040 | Remove all occurrences of @code{-S} from the command line. Note---this | |
6041 | command is position dependent. @samp{%} commands in the spec string | |
6042 | before this one will see @code{-S}, @samp{%} commands in the spec string | |
6043 | after this one will not. | |
6044 | ||
f3226a90 JT |
6045 | @item %:@var{function}(@var{args}) |
6046 | Call the named function @var{function}, passing it @var{args}. | |
6047 | @var{args} is first processed as a nested spec string, then split | |
6048 | into an argument vector in the usual fashion. The function returns | |
6049 | a string which is processed as if it had appeared literally as part | |
6050 | of the current spec. | |
6051 | ||
6052 | The following built-in spec functions are provided: | |
6053 | ||
6054 | @table @code | |
6055 | @item @code{if-exists} | |
6056 | The @code{if-exists} spec function takes one argument, an absolute | |
6057 | pathname to a file. If the file exists, @code{if-exists} returns the | |
6058 | pathname. Here is a small example of its usage: | |
6059 | ||
6060 | @smallexample | |
6061 | *startfile: | |
6062 | crt0%O%s %:if-exists(crti%O%s) crtbegin%O%s | |
6063 | @end smallexample | |
152a5a9c JT |
6064 | |
6065 | @item @code{if-exists-else} | |
6066 | The @code{if-exists-else} spec function is similar to the @code{if-exists} | |
6067 | spec function, except that it takes two arguments. The first argument is | |
6068 | an absolute pathname to a file. If the file exists, @code{if-exists-else} | |
6069 | returns the pathname. If it does not exist, it returns the second argument. | |
6070 | This way, @code{if-exists-else} can be used to select one file or another, | |
6071 | based on the existence of the first. Here is a small example of its usage: | |
6072 | ||
daf2f129 | 6073 | @smallexample |
152a5a9c | 6074 | *startfile: |
f5034c5e JM |
6075 | crt0%O%s %:if-exists(crti%O%s) \ |
6076 | %:if-exists-else(crtbeginT%O%s crtbegin%O%s) | |
152a5a9c | 6077 | @end smallexample |
daf2f129 | 6078 | @end table |
f3226a90 | 6079 | |
a743d340 | 6080 | @item %@{@code{S}@} |
161d7b59 | 6081 | Substitutes the @code{-S} switch, if that switch was given to GCC@. |
a743d340 NC |
6082 | If that switch was not specified, this substitutes nothing. Note that |
6083 | the leading dash is omitted when specifying this option, and it is | |
6084 | automatically inserted if the substitution is performed. Thus the spec | |
630d3d5a JM |
6085 | string @samp{%@{foo@}} would match the command-line option @option{-foo} |
6086 | and would output the command line option @option{-foo}. | |
a743d340 NC |
6087 | |
6088 | @item %W@{@code{S}@} | |
6089 | Like %@{@code{S}@} but mark last argument supplied within as a file to be | |
02f52e19 | 6090 | deleted on failure. |
a743d340 NC |
6091 | |
6092 | @item %@{@code{S}*@} | |
6093 | Substitutes all the switches specified to GCC whose names start | |
6094 | with @code{-S}, but which also take an argument. This is used for | |
695ac33f | 6095 | switches like @option{-o}, @option{-D}, @option{-I}, etc. |
630d3d5a | 6096 | GCC considers @option{-o foo} as being |
a743d340 | 6097 | one switch whose names starts with @samp{o}. %@{o*@} would substitute this |
02f52e19 | 6098 | text, including the space. Thus two arguments would be generated. |
a743d340 | 6099 | |
371e300b NC |
6100 | @item %@{@code{S}*&@code{T}*@} |
6101 | Like %@{@code{S}*@}, but preserve order of @code{S} and @code{T} options | |
6102 | (the order of @code{S} and @code{T} in the spec is not significant). | |
6103 | There can be any number of ampersand-separated variables; for each the | |
6104 | wild card is optional. Useful for CPP as @samp{%@{D*&U*&A*@}}. | |
6105 | ||
a743d340 | 6106 | @item %@{@code{S}:@code{X}@} |
4977bab6 | 6107 | Substitutes @code{X}, if the @samp{-S} switch was given to GCC@. |
a743d340 NC |
6108 | |
6109 | @item %@{!@code{S}:@code{X}@} | |
4977bab6 | 6110 | Substitutes @code{X}, if the @samp{-S} switch was @emph{not} given to GCC@. |
a743d340 | 6111 | |
4977bab6 ZW |
6112 | @item %@{@code{S}*:@code{X}@} |
6113 | Substitutes @code{X} if one or more switches whose names start with | |
6114 | @code{-S} are specified to GCC@. Normally @code{X} is substituted only | |
6115 | once, no matter how many such switches appeared. However, if @code{%*} | |
6116 | appears somewhere in @code{X}, then @code{X} will be substituted once | |
6117 | for each matching switch, with the @code{%*} replaced by the part of | |
6118 | that switch that matched the @code{*}. | |
a743d340 NC |
6119 | |
6120 | @item %@{.@code{S}:@code{X}@} | |
4977bab6 | 6121 | Substitutes @code{X}, if processing a file with suffix @code{S}. |
a743d340 NC |
6122 | |
6123 | @item %@{!.@code{S}:@code{X}@} | |
4977bab6 | 6124 | Substitutes @code{X}, if @emph{not} processing a file with suffix @code{S}. |
a743d340 NC |
6125 | |
6126 | @item %@{@code{S}|@code{P}:@code{X}@} | |
4977bab6 ZW |
6127 | Substitutes @code{X} if either @code{-S} or @code{-P} was given to GCC@. |
6128 | This may be combined with @samp{!}, @samp{.}, and @code{*} sequences as well, | |
6129 | although they have a stronger binding than the @samp{|}. If @code{%*} | |
6130 | appears in @code{X}, all of the alternatives must be starred, and only | |
6131 | the first matching alternative is substituted. | |
6132 | ||
6133 | For example, a spec string like this: | |
a743d340 NC |
6134 | |
6135 | @smallexample | |
6136 | %@{.c:-foo@} %@{!.c:-bar@} %@{.c|d:-baz@} %@{!.c|d:-boggle@} | |
6137 | @end smallexample | |
6138 | ||
6139 | will output the following command-line options from the following input | |
6140 | command-line options: | |
6141 | ||
6142 | @smallexample | |
6143 | fred.c -foo -baz | |
6144 | jim.d -bar -boggle | |
6145 | -d fred.c -foo -baz -boggle | |
6146 | -d jim.d -bar -baz -boggle | |
6147 | @end smallexample | |
6148 | ||
4977bab6 ZW |
6149 | @item %@{S:X; T:Y; :D@} |
6150 | ||
c0cbdbd9 KH |
6151 | If @code{S} was given to GCC, substitutes @code{X}; else if @code{T} was |
6152 | given to GCC, substitutes @code{Y}; else substitutes @code{D}. There can | |
daf2f129 | 6153 | be as many clauses as you need. This may be combined with @code{.}, |
4977bab6 ZW |
6154 | @code{!}, @code{|}, and @code{*} as needed. |
6155 | ||
6156 | ||
a743d340 NC |
6157 | @end table |
6158 | ||
4977bab6 ZW |
6159 | The conditional text @code{X} in a %@{@code{S}:@code{X}@} or similar |
6160 | construct may contain other nested @samp{%} constructs or spaces, or | |
6161 | even newlines. They are processed as usual, as described above. | |
6162 | Trailing white space in @code{X} is ignored. White space may also | |
6163 | appear anywhere on the left side of the colon in these constructs, | |
6164 | except between @code{.} or @code{*} and the corresponding word. | |
a743d340 | 6165 | |
4977bab6 ZW |
6166 | The @option{-O}, @option{-f}, @option{-m}, and @option{-W} switches are |
6167 | handled specifically in these constructs. If another value of | |
6168 | @option{-O} or the negated form of a @option{-f}, @option{-m}, or | |
6169 | @option{-W} switch is found later in the command line, the earlier | |
6170 | switch value is ignored, except with @{@code{S}*@} where @code{S} is | |
6171 | just one letter, which passes all matching options. | |
a743d340 | 6172 | |
4977bab6 ZW |
6173 | The character @samp{|} at the beginning of the predicate text is used to |
6174 | indicate that a command should be piped to the following command, but | |
6175 | only if @option{-pipe} is specified. | |
a743d340 NC |
6176 | |
6177 | It is built into GCC which switches take arguments and which do not. | |
6178 | (You might think it would be useful to generalize this to allow each | |
6179 | compiler's spec to say which switches take arguments. But this cannot | |
6180 | be done in a consistent fashion. GCC cannot even decide which input | |
6181 | files have been specified without knowing which switches take arguments, | |
6182 | and it must know which input files to compile in order to tell which | |
02f52e19 | 6183 | compilers to run). |
a743d340 | 6184 | |
630d3d5a | 6185 | GCC also knows implicitly that arguments starting in @option{-l} are to be |
a743d340 NC |
6186 | treated as compiler output files, and passed to the linker in their |
6187 | proper position among the other output files. | |
6188 | ||
ee457005 JM |
6189 | @c man begin OPTIONS |
6190 | ||
74291a4b MM |
6191 | @node Target Options |
6192 | @section Specifying Target Machine and Compiler Version | |
6193 | @cindex target options | |
6194 | @cindex cross compiling | |
6195 | @cindex specifying machine version | |
6196 | @cindex specifying compiler version and target machine | |
6197 | @cindex compiler version, specifying | |
6198 | @cindex target machine, specifying | |
6199 | ||
37a4aa31 GK |
6200 | The usual way to run GCC is to run the executable called @file{gcc}, or |
6201 | @file{<machine>-gcc} when cross-compiling, or | |
6202 | @file{<machine>-gcc-<version>} to run a version other than the one that | |
6203 | was installed last. Sometimes this is inconvenient, so GCC provides | |
6204 | options that will switch to another cross-compiler or version. | |
74291a4b | 6205 | |
2642624b | 6206 | @table @gcctabopt |
74291a4b | 6207 | @item -b @var{machine} |
cd3bb277 | 6208 | @opindex b |
74291a4b | 6209 | The argument @var{machine} specifies the target machine for compilation. |
74291a4b MM |
6210 | |
6211 | The value to use for @var{machine} is the same as was specified as the | |
0c2d1a2a | 6212 | machine type when configuring GCC as a cross-compiler. For |
74291a4b MM |
6213 | example, if a cross-compiler was configured with @samp{configure |
6214 | i386v}, meaning to compile for an 80386 running System V, then you | |
630d3d5a | 6215 | would specify @option{-b i386v} to run that cross compiler. |
74291a4b | 6216 | |
37a4aa31 GK |
6217 | @item -V @var{version} |
6218 | @opindex V | |
6219 | The argument @var{version} specifies which version of GCC to run. | |
6220 | This is useful when multiple versions are installed. For example, | |
6221 | @var{version} might be @samp{2.0}, meaning to run GCC version 2.0. | |
74291a4b MM |
6222 | @end table |
6223 | ||
37a4aa31 GK |
6224 | The @option{-V} and @option{-b} options work by running the |
6225 | @file{<machine>-gcc-<version>} executable, so there's no real reason to | |
6226 | use them if you can just run that directly. | |
74291a4b MM |
6227 | |
6228 | @node Submodel Options | |
6229 | @section Hardware Models and Configurations | |
6230 | @cindex submodel options | |
6231 | @cindex specifying hardware config | |
6232 | @cindex hardware models and configurations, specifying | |
6233 | @cindex machine dependent options | |
6234 | ||
630d3d5a | 6235 | Earlier we discussed the standard option @option{-b} which chooses among |
74291a4b | 6236 | different installed compilers for completely different target |
8aeea6e6 | 6237 | machines, such as VAX vs.@: 68000 vs.@: 80386. |
74291a4b MM |
6238 | |
6239 | In addition, each of these target machine types can have its own | |
6240 | special options, starting with @samp{-m}, to choose among various | |
6241 | hardware models or configurations---for example, 68010 vs 68020, | |
6242 | floating coprocessor or none. A single installed version of the | |
6243 | compiler can compile for any model or configuration, according to the | |
6244 | options specified. | |
6245 | ||
6246 | Some configurations of the compiler also support additional special | |
6247 | options, usually for compatibility with other compilers on the same | |
6248 | platform. | |
6249 | ||
74291a4b MM |
6250 | These options are defined by the macro @code{TARGET_SWITCHES} in the |
6251 | machine description. The default for the options is also defined by | |
6252 | that macro, which enables you to change the defaults. | |
74291a4b | 6253 | |
39bc1876 NS |
6254 | @c This list is ordered alphanumerically by subsection name. |
6255 | @c It should be the same order and spelling as these options are listed | |
6256 | @c in Machine Dependent Options | |
6257 | ||
74291a4b | 6258 | @menu |
39bc1876 | 6259 | * ARC Options:: |
74291a4b | 6260 | * ARM Options:: |
39bc1876 NS |
6261 | * AVR Options:: |
6262 | * CRIS Options:: | |
48aec0bc | 6263 | * Darwin Options:: |
74291a4b | 6264 | * DEC Alpha Options:: |
d7c23cdc | 6265 | * DEC Alpha/VMS Options:: |
39bc1876 | 6266 | * FRV Options:: |
74291a4b | 6267 | * H8/300 Options:: |
39bc1876 NS |
6268 | * HPPA Options:: |
6269 | * i386 and x86-64 Options:: | |
6270 | * IA-64 Options:: | |
6271 | * M32R/D Options:: | |
6272 | * M680x0 Options:: | |
6273 | * M68hc1x Options:: | |
6274 | * MCore Options:: | |
6275 | * MIPS Options:: | |
6276 | * MMIX Options:: | |
6277 | * MN10300 Options:: | |
6278 | * NS32K Options:: | |
6279 | * PDP-11 Options:: | |
6280 | * PowerPC Options:: | |
6281 | * RS/6000 and PowerPC Options:: | |
6282 | * S/390 and zSeries Options:: | |
74291a4b | 6283 | * SH Options:: |
39bc1876 | 6284 | * SPARC Options:: |
74291a4b | 6285 | * System V Options:: |
282a61e6 | 6286 | * TMS320C3x/C4x Options:: |
f84271d9 | 6287 | * V850 Options:: |
39bc1876 NS |
6288 | * VAX Options:: |
6289 | * x86-64 Options:: | |
69a0611f | 6290 | * Xstormy16 Options:: |
03984308 | 6291 | * Xtensa Options:: |
39bc1876 | 6292 | * zSeries Options:: |
74291a4b MM |
6293 | @end menu |
6294 | ||
39bc1876 NS |
6295 | @node ARC Options |
6296 | @subsection ARC Options | |
6297 | @cindex ARC Options | |
74291a4b | 6298 | |
39bc1876 | 6299 | These options are defined for ARC implementations: |
74291a4b | 6300 | |
2642624b | 6301 | @table @gcctabopt |
39bc1876 NS |
6302 | @item -EL |
6303 | @opindex EL | |
6304 | Compile code for little endian mode. This is the default. | |
74cf1c6d | 6305 | |
39bc1876 NS |
6306 | @item -EB |
6307 | @opindex EB | |
6308 | Compile code for big endian mode. | |
74291a4b | 6309 | |
39bc1876 NS |
6310 | @item -mmangle-cpu |
6311 | @opindex mmangle-cpu | |
6312 | Prepend the name of the cpu to all public symbol names. | |
6313 | In multiple-processor systems, there are many ARC variants with different | |
6314 | instruction and register set characteristics. This flag prevents code | |
6315 | compiled for one cpu to be linked with code compiled for another. | |
6316 | No facility exists for handling variants that are ``almost identical''. | |
6317 | This is an all or nothing option. | |
74291a4b | 6318 | |
39bc1876 NS |
6319 | @item -mcpu=@var{cpu} |
6320 | @opindex mcpu | |
6321 | Compile code for ARC variant @var{cpu}. | |
6322 | Which variants are supported depend on the configuration. | |
6323 | All variants support @option{-mcpu=base}, this is the default. | |
74291a4b | 6324 | |
39bc1876 NS |
6325 | @item -mtext=@var{text-section} |
6326 | @itemx -mdata=@var{data-section} | |
6327 | @itemx -mrodata=@var{readonly-data-section} | |
6328 | @opindex mtext | |
6329 | @opindex mdata | |
6330 | @opindex mrodata | |
6331 | Put functions, data, and readonly data in @var{text-section}, | |
6332 | @var{data-section}, and @var{readonly-data-section} respectively | |
6333 | by default. This can be overridden with the @code{section} attribute. | |
6334 | @xref{Variable Attributes}. | |
74291a4b | 6335 | |
39bc1876 | 6336 | @end table |
74291a4b | 6337 | |
39bc1876 NS |
6338 | @node ARM Options |
6339 | @subsection ARM Options | |
6340 | @cindex ARM options | |
74291a4b | 6341 | |
39bc1876 NS |
6342 | These @samp{-m} options are defined for Advanced RISC Machines (ARM) |
6343 | architectures: | |
74cf1c6d | 6344 | |
39bc1876 NS |
6345 | @table @gcctabopt |
6346 | @item -mabi=@var{name} | |
6347 | @opindex mabi | |
6348 | Generate code for the specified ABI. Permissible values are: @samp{apcs-gnu}, | |
6349 | @samp{atpcs}, @samp{aapcs} and @samp{iwmmxt}. | |
74cf1c6d | 6350 | |
39bc1876 NS |
6351 | @item -mapcs-frame |
6352 | @opindex mapcs-frame | |
6353 | Generate a stack frame that is compliant with the ARM Procedure Call | |
6354 | Standard for all functions, even if this is not strictly necessary for | |
6355 | correct execution of the code. Specifying @option{-fomit-frame-pointer} | |
6356 | with this option will cause the stack frames not to be generated for | |
6357 | leaf functions. The default is @option{-mno-apcs-frame}. | |
74291a4b | 6358 | |
39bc1876 NS |
6359 | @item -mapcs |
6360 | @opindex mapcs | |
6361 | This is a synonym for @option{-mapcs-frame}. | |
74291a4b | 6362 | |
39bc1876 NS |
6363 | @ignore |
6364 | @c not currently implemented | |
6365 | @item -mapcs-stack-check | |
6366 | @opindex mapcs-stack-check | |
6367 | Generate code to check the amount of stack space available upon entry to | |
6368 | every function (that actually uses some stack space). If there is | |
6369 | insufficient space available then either the function | |
6370 | @samp{__rt_stkovf_split_small} or @samp{__rt_stkovf_split_big} will be | |
6371 | called, depending upon the amount of stack space required. The run time | |
6372 | system is required to provide these functions. The default is | |
6373 | @option{-mno-apcs-stack-check}, since this produces smaller code. | |
74cf1c6d | 6374 | |
39bc1876 NS |
6375 | @c not currently implemented |
6376 | @item -mapcs-float | |
6377 | @opindex mapcs-float | |
6378 | Pass floating point arguments using the float point registers. This is | |
6379 | one of the variants of the APCS@. This option is recommended if the | |
6380 | target hardware has a floating point unit or if a lot of floating point | |
6381 | arithmetic is going to be performed by the code. The default is | |
6382 | @option{-mno-apcs-float}, since integer only code is slightly increased in | |
6383 | size if @option{-mapcs-float} is used. | |
74291a4b | 6384 | |
39bc1876 NS |
6385 | @c not currently implemented |
6386 | @item -mapcs-reentrant | |
6387 | @opindex mapcs-reentrant | |
6388 | Generate reentrant, position independent code. The default is | |
6389 | @option{-mno-apcs-reentrant}. | |
6390 | @end ignore | |
74291a4b | 6391 | |
39bc1876 NS |
6392 | @item -mthumb-interwork |
6393 | @opindex mthumb-interwork | |
6394 | Generate code which supports calling between the ARM and Thumb | |
6395 | instruction sets. Without this option the two instruction sets cannot | |
6396 | be reliably used inside one program. The default is | |
6397 | @option{-mno-thumb-interwork}, since slightly larger code is generated | |
6398 | when @option{-mthumb-interwork} is specified. | |
6399 | ||
6400 | @item -mno-sched-prolog | |
6401 | @opindex mno-sched-prolog | |
6402 | Prevent the reordering of instructions in the function prolog, or the | |
6403 | merging of those instruction with the instructions in the function's | |
6404 | body. This means that all functions will start with a recognizable set | |
6405 | of instructions (or in fact one of a choice from a small set of | |
6406 | different function prologues), and this information can be used to | |
6407 | locate the start if functions inside an executable piece of code. The | |
6408 | default is @option{-msched-prolog}. | |
6409 | ||
6410 | @item -mhard-float | |
6411 | @opindex mhard-float | |
6412 | Generate output containing floating point instructions. This is the | |
6413 | default. | |
861bb6c1 | 6414 | |
74291a4b | 6415 | @item -msoft-float |
cd3bb277 | 6416 | @opindex msoft-float |
74291a4b | 6417 | Generate output containing library calls for floating point. |
39bc1876 | 6418 | @strong{Warning:} the requisite libraries are not available for all ARM |
74291a4b | 6419 | targets. Normally the facilities of the machine's usual C compiler are |
39bc1876 NS |
6420 | used, but this cannot be done directly in cross-compilation. You must make |
6421 | your own arrangements to provide suitable library functions for | |
6422 | cross-compilation. | |
74291a4b | 6423 | |
39bc1876 NS |
6424 | @option{-msoft-float} changes the calling convention in the output file; |
6425 | therefore, it is only useful if you compile @emph{all} of a program with | |
6426 | this option. In particular, you need to compile @file{libgcc.a}, the | |
6427 | library that comes with GCC, with @option{-msoft-float} in order for | |
6428 | this to work. | |
74291a4b | 6429 | |
39bc1876 NS |
6430 | @item -mfloat-abi=@var{name} |
6431 | @opindex mfloat-abi | |
6432 | Specifies which ABI to use for floating point values. Permissible values | |
6433 | are: @samp{soft}, @samp{softfp} and @samp{hard}. | |
74291a4b | 6434 | |
39bc1876 NS |
6435 | @samp{soft} and @samp{hard} are equivalent to @option{-msoft-float} |
6436 | and @option{-mhard-float} respectively. @samp{softfp} allows the generation | |
6437 | of floating point instructions, but still uses the soft-float calling | |
6438 | conventions. | |
74291a4b | 6439 | |
39bc1876 NS |
6440 | @item -mlittle-endian |
6441 | @opindex mlittle-endian | |
6442 | Generate code for a processor running in little-endian mode. This is | |
6443 | the default for all standard configurations. | |
74291a4b | 6444 | |
39bc1876 NS |
6445 | @item -mbig-endian |
6446 | @opindex mbig-endian | |
6447 | Generate code for a processor running in big-endian mode; the default is | |
6448 | to compile code for a little-endian processor. | |
74291a4b | 6449 | |
39bc1876 NS |
6450 | @item -mwords-little-endian |
6451 | @opindex mwords-little-endian | |
6452 | This option only applies when generating code for big-endian processors. | |
6453 | Generate code for a little-endian word order but a big-endian byte | |
6454 | order. That is, a byte order of the form @samp{32107654}. Note: this | |
6455 | option should only be used if you require compatibility with code for | |
6456 | big-endian ARM processors generated by versions of the compiler prior to | |
6457 | 2.8. | |
74291a4b | 6458 | |
39bc1876 NS |
6459 | @item -mcpu=@var{name} |
6460 | @opindex mcpu | |
6461 | This specifies the name of the target ARM processor. GCC uses this name | |
6462 | to determine what kind of instructions it can emit when generating | |
6463 | assembly code. Permissible names are: @samp{arm2}, @samp{arm250}, | |
6464 | @samp{arm3}, @samp{arm6}, @samp{arm60}, @samp{arm600}, @samp{arm610}, | |
6465 | @samp{arm620}, @samp{arm7}, @samp{arm7m}, @samp{arm7d}, @samp{arm7dm}, | |
6466 | @samp{arm7di}, @samp{arm7dmi}, @samp{arm70}, @samp{arm700}, | |
6467 | @samp{arm700i}, @samp{arm710}, @samp{arm710c}, @samp{arm7100}, | |
6468 | @samp{arm7500}, @samp{arm7500fe}, @samp{arm7tdmi}, @samp{arm8}, | |
6469 | @samp{strongarm}, @samp{strongarm110}, @samp{strongarm1100}, | |
6470 | @samp{arm8}, @samp{arm810}, @samp{arm9}, @samp{arm9e}, @samp{arm920}, | |
6471 | @samp{arm920t}, @samp{arm926ejs}, @samp{arm940t}, @samp{arm9tdmi}, | |
6472 | @samp{arm10tdmi}, @samp{arm1020t}, @samp{arm1026ejs}, | |
6473 | @samp{arm1136js}, @samp{arm1136jfs} ,@samp{xscale}, @samp{iwmmxt}, | |
6474 | @samp{ep9312}. | |
74291a4b | 6475 | |
39bc1876 NS |
6476 | @itemx -mtune=@var{name} |
6477 | @opindex mtune | |
6478 | This option is very similar to the @option{-mcpu=} option, except that | |
6479 | instead of specifying the actual target processor type, and hence | |
6480 | restricting which instructions can be used, it specifies that GCC should | |
6481 | tune the performance of the code as if the target were of the type | |
6482 | specified in this option, but still choosing the instructions that it | |
6483 | will generate based on the cpu specified by a @option{-mcpu=} option. | |
6484 | For some ARM implementations better performance can be obtained by using | |
6485 | this option. | |
861bb6c1 | 6486 | |
39bc1876 NS |
6487 | @item -march=@var{name} |
6488 | @opindex march | |
6489 | This specifies the name of the target ARM architecture. GCC uses this | |
6490 | name to determine what kind of instructions it can emit when generating | |
6491 | assembly code. This option can be used in conjunction with or instead | |
6492 | of the @option{-mcpu=} option. Permissible names are: @samp{armv2}, | |
6493 | @samp{armv2a}, @samp{armv3}, @samp{armv3m}, @samp{armv4}, @samp{armv4t}, | |
6494 | @samp{armv5}, @samp{armv5t}, @samp{armv5te}, @samp{armv6}, @samp{armv6j}, | |
6495 | @samp{iwmmxt}, @samp{ep9312}. | |
861bb6c1 | 6496 | |
39bc1876 NS |
6497 | @item -mfpu=@var{name} |
6498 | @itemx -mfpe=@var{number} | |
6499 | @itemx -mfp=@var{number} | |
6500 | @opindex mfpu | |
6501 | @opindex mfpe | |
6502 | @opindex mfp | |
6503 | This specifies what floating point hardware (or hardware emulation) is | |
6504 | available on the target. Permissible names are: @samp{fpa}, @samp{fpe2}, | |
6505 | @samp{fpe3}, @samp{maverick}, @samp{vfp}. @option{-mfp} and @option{-mfpe} | |
6506 | are synonyms for @option{-mfpu}=@samp{fpe}@var{number}, for compatibility | |
6507 | with older versions of GCC@. | |
861bb6c1 | 6508 | |
39bc1876 NS |
6509 | If @option{-msoft-float} is specified this specifies the format of |
6510 | floating point values. | |
fb868474 | 6511 | |
39bc1876 NS |
6512 | @item -mstructure-size-boundary=@var{n} |
6513 | @opindex mstructure-size-boundary | |
6514 | The size of all structures and unions will be rounded up to a multiple | |
6515 | of the number of bits set by this option. Permissible values are 8, 32 | |
6516 | and 64. The default value varies for different toolchains. For the COFF | |
6517 | targeted toolchain the default value is 8. A value of 64 is only allowed | |
6518 | if the underlying ABI supports it. | |
b71733d5 | 6519 | |
39bc1876 NS |
6520 | Specifying the larger number can produce faster, more efficient code, but |
6521 | can also increase the size of the program. Different values are potentially | |
6522 | incompatible. Code compiled with one value cannot necessarily expect to | |
6523 | work with code or libraries compiled with another value, if they exchange | |
6524 | information using structures or unions. | |
24f9c4df | 6525 | |
39bc1876 NS |
6526 | @item -mabort-on-noreturn |
6527 | @opindex mabort-on-noreturn | |
6528 | Generate a call to the function @code{abort} at the end of a | |
6529 | @code{noreturn} function. It will be executed if the function tries to | |
6530 | return. | |
24f9c4df | 6531 | |
39bc1876 NS |
6532 | @item -mlong-calls |
6533 | @itemx -mno-long-calls | |
6534 | @opindex mlong-calls | |
6535 | @opindex mno-long-calls | |
6536 | Tells the compiler to perform function calls by first loading the | |
6537 | address of the function into a register and then performing a subroutine | |
6538 | call on this register. This switch is needed if the target function | |
6539 | will lie outside of the 64 megabyte addressing range of the offset based | |
6540 | version of subroutine call instruction. | |
24f9c4df | 6541 | |
39bc1876 NS |
6542 | Even if this switch is enabled, not all function calls will be turned |
6543 | into long calls. The heuristic is that static functions, functions | |
6544 | which have the @samp{short-call} attribute, functions that are inside | |
6545 | the scope of a @samp{#pragma no_long_calls} directive and functions whose | |
6546 | definitions have already been compiled within the current compilation | |
6547 | unit, will not be turned into long calls. The exception to this rule is | |
6548 | that weak function definitions, functions with the @samp{long-call} | |
6549 | attribute or the @samp{section} attribute, and functions that are within | |
6550 | the scope of a @samp{#pragma long_calls} directive, will always be | |
6551 | turned into long calls. | |
24f9c4df | 6552 | |
39bc1876 NS |
6553 | This feature is not enabled by default. Specifying |
6554 | @option{-mno-long-calls} will restore the default behavior, as will | |
6555 | placing the function calls within the scope of a @samp{#pragma | |
6556 | long_calls_off} directive. Note these switches have no effect on how | |
6557 | the compiler generates code to handle function calls via function | |
6558 | pointers. | |
24f9c4df | 6559 | |
39bc1876 NS |
6560 | @item -mnop-fun-dllimport |
6561 | @opindex mnop-fun-dllimport | |
6562 | Disable support for the @code{dllimport} attribute. | |
74291a4b | 6563 | |
39bc1876 NS |
6564 | @item -msingle-pic-base |
6565 | @opindex msingle-pic-base | |
6566 | Treat the register used for PIC addressing as read-only, rather than | |
6567 | loading it in the prologue for each function. The run-time system is | |
6568 | responsible for initializing this register with an appropriate value | |
6569 | before execution begins. | |
2856c3e3 | 6570 | |
39bc1876 NS |
6571 | @item -mpic-register=@var{reg} |
6572 | @opindex mpic-register | |
6573 | Specify the register to be used for PIC addressing. The default is R10 | |
6574 | unless stack-checking is enabled, when R9 is used. | |
2856c3e3 | 6575 | |
39bc1876 NS |
6576 | @item -mcirrus-fix-invalid-insns |
6577 | @opindex mcirrus-fix-invalid-insns | |
6578 | @opindex mno-cirrus-fix-invalid-insns | |
6579 | Insert NOPs into the instruction stream to in order to work around | |
6580 | problems with invalid Maverick instruction combinations. This option | |
6581 | is only valid if the @option{-mcpu=ep9312} option has been used to | |
6582 | enable generation of instructions for the Cirrus Maverick floating | |
6583 | point co-processor. This option is not enabled by default, since the | |
6584 | problem is only present in older Maverick implementations. The default | |
6585 | can be re-enabled by use of the @option{-mno-cirrus-fix-invalid-insns} | |
6586 | switch. | |
2856c3e3 | 6587 | |
39bc1876 NS |
6588 | @item -mpoke-function-name |
6589 | @opindex mpoke-function-name | |
6590 | Write the name of each function into the text section, directly | |
6591 | preceding the function prologue. The generated code is similar to this: | |
2856c3e3 | 6592 | |
39bc1876 NS |
6593 | @smallexample |
6594 | t0 | |
6595 | .ascii "arm_poke_function_name", 0 | |
6596 | .align | |
6597 | t1 | |
6598 | .word 0xff000000 + (t1 - t0) | |
6599 | arm_poke_function_name | |
6600 | mov ip, sp | |
6601 | stmfd sp!, @{fp, ip, lr, pc@} | |
6602 | sub fp, ip, #4 | |
6603 | @end smallexample | |
f077f169 | 6604 | |
39bc1876 NS |
6605 | When performing a stack backtrace, code can inspect the value of |
6606 | @code{pc} stored at @code{fp + 0}. If the trace function then looks at | |
6607 | location @code{pc - 12} and the top 8 bits are set, then we know that | |
6608 | there is a function name embedded immediately preceding this location | |
6609 | and has length @code{((pc[-3]) & 0xff000000)}. | |
2856c3e3 | 6610 | |
39bc1876 NS |
6611 | @item -mthumb |
6612 | @opindex mthumb | |
6613 | Generate code for the 16-bit Thumb instruction set. The default is to | |
6614 | use the 32-bit ARM instruction set. | |
8a0b86f5 | 6615 | |
39bc1876 NS |
6616 | @item -mtpcs-frame |
6617 | @opindex mtpcs-frame | |
6618 | Generate a stack frame that is compliant with the Thumb Procedure Call | |
6619 | Standard for all non-leaf functions. (A leaf function is one that does | |
6620 | not call any other functions.) The default is @option{-mno-tpcs-frame}. | |
058edcdb | 6621 | |
39bc1876 NS |
6622 | @item -mtpcs-leaf-frame |
6623 | @opindex mtpcs-leaf-frame | |
6624 | Generate a stack frame that is compliant with the Thumb Procedure Call | |
6625 | Standard for all leaf functions. (A leaf function is one that does | |
6626 | not call any other functions.) The default is @option{-mno-apcs-leaf-frame}. | |
2856c3e3 | 6627 | |
39bc1876 NS |
6628 | @item -mcallee-super-interworking |
6629 | @opindex mcallee-super-interworking | |
6630 | Gives all externally visible functions in the file being compiled an ARM | |
6631 | instruction set header which switches to Thumb mode before executing the | |
6632 | rest of the function. This allows these functions to be called from | |
6633 | non-interworking code. | |
6634 | ||
6635 | @item -mcaller-super-interworking | |
6636 | @opindex mcaller-super-interworking | |
6637 | Allows calls via function pointers (including virtual functions) to | |
6638 | execute correctly regardless of whether the target code has been | |
6639 | compiled for interworking or not. There is a small overhead in the cost | |
6640 | of executing a function pointer if this option is enabled. | |
2856c3e3 SC |
6641 | |
6642 | @end table | |
6643 | ||
39bc1876 NS |
6644 | @node AVR Options |
6645 | @subsection AVR Options | |
6646 | @cindex AVR Options | |
74291a4b | 6647 | |
39bc1876 | 6648 | These options are defined for AVR implementations: |
74291a4b | 6649 | |
2642624b | 6650 | @table @gcctabopt |
39bc1876 NS |
6651 | @item -mmcu=@var{mcu} |
6652 | @opindex mmcu | |
6653 | Specify ATMEL AVR instruction set or MCU type. | |
74291a4b | 6654 | |
39bc1876 NS |
6655 | Instruction set avr1 is for the minimal AVR core, not supported by the C |
6656 | compiler, only for assembler programs (MCU types: at90s1200, attiny10, | |
6657 | attiny11, attiny12, attiny15, attiny28). | |
74291a4b | 6658 | |
39bc1876 NS |
6659 | Instruction set avr2 (default) is for the classic AVR core with up to |
6660 | 8K program memory space (MCU types: at90s2313, at90s2323, attiny22, | |
6661 | at90s2333, at90s2343, at90s4414, at90s4433, at90s4434, at90s8515, | |
6662 | at90c8534, at90s8535). | |
74291a4b | 6663 | |
39bc1876 NS |
6664 | Instruction set avr3 is for the classic AVR core with up to 128K program |
6665 | memory space (MCU types: atmega103, atmega603, at43usb320, at76c711). | |
74291a4b | 6666 | |
39bc1876 NS |
6667 | Instruction set avr4 is for the enhanced AVR core with up to 8K program |
6668 | memory space (MCU types: atmega8, atmega83, atmega85). | |
74291a4b | 6669 | |
39bc1876 NS |
6670 | Instruction set avr5 is for the enhanced AVR core with up to 128K program |
6671 | memory space (MCU types: atmega16, atmega161, atmega163, atmega32, atmega323, | |
6672 | atmega64, atmega128, at43usb355, at94k). | |
74291a4b | 6673 | |
39bc1876 NS |
6674 | @item -msize |
6675 | @opindex msize | |
6676 | Output instruction sizes to the asm file. | |
74291a4b | 6677 | |
39bc1876 NS |
6678 | @item -minit-stack=@var{N} |
6679 | @opindex minit-stack | |
6680 | Specify the initial stack address, which may be a symbol or numeric value, | |
6681 | @samp{__stack} is the default. | |
74291a4b | 6682 | |
39bc1876 NS |
6683 | @item -mno-interrupts |
6684 | @opindex mno-interrupts | |
6685 | Generated code is not compatible with hardware interrupts. | |
6686 | Code size will be smaller. | |
74291a4b | 6687 | |
39bc1876 NS |
6688 | @item -mcall-prologues |
6689 | @opindex mcall-prologues | |
6690 | Functions prologues/epilogues expanded as call to appropriate | |
6691 | subroutines. Code size will be smaller. | |
74291a4b | 6692 | |
39bc1876 NS |
6693 | @item -mno-tablejump |
6694 | @opindex mno-tablejump | |
6695 | Do not generate tablejump insns which sometimes increase code size. | |
74291a4b | 6696 | |
39bc1876 NS |
6697 | @item -mtiny-stack |
6698 | @opindex mtiny-stack | |
6699 | Change only the low 8 bits of the stack pointer. | |
74291a4b | 6700 | |
39bc1876 NS |
6701 | @item -mint8 |
6702 | @opindex mint8 | |
6703 | Assume int to be 8 bit integer. This affects the sizes of all types: A | |
6704 | char will be 1 byte, an int will be 1 byte, an long will be 2 bytes | |
6705 | and long long will be 4 bytes. Please note that this option does not | |
6706 | comply to the C standards, but it will provide you with smaller code | |
6707 | size. | |
6708 | @end table | |
74291a4b | 6709 | |
39bc1876 NS |
6710 | @node CRIS Options |
6711 | @subsection CRIS Options | |
6712 | @cindex CRIS Options | |
74291a4b | 6713 | |
39bc1876 | 6714 | These options are defined specifically for the CRIS ports. |
74291a4b | 6715 | |
39bc1876 NS |
6716 | @table @gcctabopt |
6717 | @item -march=@var{architecture-type} | |
6718 | @itemx -mcpu=@var{architecture-type} | |
6719 | @opindex march | |
6720 | @opindex mcpu | |
6721 | Generate code for the specified architecture. The choices for | |
6722 | @var{architecture-type} are @samp{v3}, @samp{v8} and @samp{v10} for | |
6723 | respectively ETRAX@w{ }4, ETRAX@w{ }100, and ETRAX@w{ }100@w{ }LX. | |
6724 | Default is @samp{v0} except for cris-axis-linux-gnu, where the default is | |
6725 | @samp{v10}. | |
c219ddf7 | 6726 | |
39bc1876 NS |
6727 | @item -mtune=@var{architecture-type} |
6728 | @opindex mtune | |
6729 | Tune to @var{architecture-type} everything applicable about the generated | |
6730 | code, except for the ABI and the set of available instructions. The | |
6731 | choices for @var{architecture-type} are the same as for | |
6732 | @option{-march=@var{architecture-type}}. | |
54284728 | 6733 | |
39bc1876 NS |
6734 | @item -mmax-stack-frame=@var{n} |
6735 | @opindex mmax-stack-frame | |
6736 | Warn when the stack frame of a function exceeds @var{n} bytes. | |
54284728 | 6737 | |
39bc1876 NS |
6738 | @item -melinux-stacksize=@var{n} |
6739 | @opindex melinux-stacksize | |
6740 | Only available with the @samp{cris-axis-aout} target. Arranges for | |
6741 | indications in the program to the kernel loader that the stack of the | |
6742 | program should be set to @var{n} bytes. | |
54284728 | 6743 | |
39bc1876 NS |
6744 | @item -metrax4 |
6745 | @itemx -metrax100 | |
6746 | @opindex metrax4 | |
6747 | @opindex metrax100 | |
6748 | The options @option{-metrax4} and @option{-metrax100} are synonyms for | |
6749 | @option{-march=v3} and @option{-march=v8} respectively. | |
c0498f43 | 6750 | |
39bc1876 NS |
6751 | @item -mmul-bug-workaround |
6752 | @itemx -mno-mul-bug-workaround | |
6753 | @opindex mmul-bug-workaround | |
6754 | @opindex mno-mul-bug-workaround | |
6755 | Work around a bug in the @code{muls} and @code{mulu} instructions for CPU | |
6756 | models where it applies. This option is active by default. | |
c0498f43 | 6757 | |
39bc1876 NS |
6758 | @item -mpdebug |
6759 | @opindex mpdebug | |
6760 | Enable CRIS-specific verbose debug-related information in the assembly | |
6761 | code. This option also has the effect to turn off the @samp{#NO_APP} | |
6762 | formatted-code indicator to the assembler at the beginning of the | |
6763 | assembly file. | |
c0498f43 | 6764 | |
39bc1876 NS |
6765 | @item -mcc-init |
6766 | @opindex mcc-init | |
6767 | Do not use condition-code results from previous instruction; always emit | |
6768 | compare and test instructions before use of condition codes. | |
74291a4b | 6769 | |
39bc1876 NS |
6770 | @item -mno-side-effects |
6771 | @opindex mno-side-effects | |
6772 | Do not emit instructions with side-effects in addressing modes other than | |
6773 | post-increment. | |
238b11b5 | 6774 | |
39bc1876 NS |
6775 | @item -mstack-align |
6776 | @itemx -mno-stack-align | |
6777 | @itemx -mdata-align | |
6778 | @itemx -mno-data-align | |
6779 | @itemx -mconst-align | |
6780 | @itemx -mno-const-align | |
6781 | @opindex mstack-align | |
6782 | @opindex mno-stack-align | |
6783 | @opindex mdata-align | |
6784 | @opindex mno-data-align | |
6785 | @opindex mconst-align | |
6786 | @opindex mno-const-align | |
6787 | These options (no-options) arranges (eliminate arrangements) for the | |
6788 | stack-frame, individual data and constants to be aligned for the maximum | |
6789 | single data access size for the chosen CPU model. The default is to | |
6790 | arrange for 32-bit alignment. ABI details such as structure layout are | |
6791 | not affected by these options. | |
238b11b5 | 6792 | |
39bc1876 NS |
6793 | @item -m32-bit |
6794 | @itemx -m16-bit | |
6795 | @itemx -m8-bit | |
6796 | @opindex m32-bit | |
6797 | @opindex m16-bit | |
6798 | @opindex m8-bit | |
6799 | Similar to the stack- data- and const-align options above, these options | |
6800 | arrange for stack-frame, writable data and constants to all be 32-bit, | |
6801 | 16-bit or 8-bit aligned. The default is 32-bit alignment. | |
238b11b5 | 6802 | |
39bc1876 NS |
6803 | @item -mno-prologue-epilogue |
6804 | @itemx -mprologue-epilogue | |
6805 | @opindex mno-prologue-epilogue | |
6806 | @opindex mprologue-epilogue | |
6807 | With @option{-mno-prologue-epilogue}, the normal function prologue and | |
6808 | epilogue that sets up the stack-frame are omitted and no return | |
6809 | instructions or return sequences are generated in the code. Use this | |
6810 | option only together with visual inspection of the compiled code: no | |
6811 | warnings or errors are generated when call-saved registers must be saved, | |
6812 | or storage for local variable needs to be allocated. | |
238b11b5 | 6813 | |
39bc1876 NS |
6814 | @item -mno-gotplt |
6815 | @itemx -mgotplt | |
6816 | @opindex mno-gotplt | |
6817 | @opindex mgotplt | |
6818 | With @option{-fpic} and @option{-fPIC}, don't generate (do generate) | |
6819 | instruction sequences that load addresses for functions from the PLT part | |
6820 | of the GOT rather than (traditional on other architectures) calls to the | |
6821 | PLT. The default is @option{-mgotplt}. | |
238b11b5 | 6822 | |
39bc1876 NS |
6823 | @item -maout |
6824 | @opindex maout | |
6825 | Legacy no-op option only recognized with the cris-axis-aout target. | |
c0498f43 | 6826 | |
39bc1876 NS |
6827 | @item -melf |
6828 | @opindex melf | |
6829 | Legacy no-op option only recognized with the cris-axis-elf and | |
6830 | cris-axis-linux-gnu targets. | |
74291a4b | 6831 | |
39bc1876 NS |
6832 | @item -melinux |
6833 | @opindex melinux | |
6834 | Only recognized with the cris-axis-aout target, where it selects a | |
6835 | GNU/linux-like multilib, include files and instruction set for | |
6836 | @option{-march=v8}. | |
ded17aad | 6837 | |
39bc1876 NS |
6838 | @item -mlinux |
6839 | @opindex mlinux | |
6840 | Legacy no-op option only recognized with the cris-axis-linux-gnu target. | |
ded17aad | 6841 | |
39bc1876 NS |
6842 | @item -sim |
6843 | @opindex sim | |
6844 | This option, recognized for the cris-axis-aout and cris-axis-elf arranges | |
6845 | to link with input-output functions from a simulator library. Code, | |
6846 | initialized data and zero-initialized data are allocated consecutively. | |
74291a4b | 6847 | |
39bc1876 NS |
6848 | @item -sim2 |
6849 | @opindex sim2 | |
6850 | Like @option{-sim}, but pass linker options to locate initialized data at | |
6851 | 0x40000000 and zero-initialized data at 0x80000000. | |
74291a4b MM |
6852 | @end table |
6853 | ||
39bc1876 NS |
6854 | @node Darwin Options |
6855 | @subsection Darwin Options | |
6856 | @cindex Darwin options | |
74291a4b | 6857 | |
39bc1876 NS |
6858 | These options are defined for all architectures running the Darwin operating |
6859 | system. They are useful for compatibility with other Mac OS compilers. | |
74291a4b | 6860 | |
2642624b | 6861 | @table @gcctabopt |
39bc1876 NS |
6862 | @item -F@var{dir} |
6863 | @opindex F | |
6864 | Add the framework directory @var{dir} to the head of the list of | |
6865 | directories to be searched for header files. These directories are | |
6866 | interleaved with those specified by @option{-I} options and are | |
6867 | scanned in a left-to-right order. | |
5848830f | 6868 | |
39bc1876 NS |
6869 | A framework directory is a directory with frameworks in it. A |
6870 | framework is a directory with a @samp{"Headers"} and/or | |
6871 | @samp{"PrivateHeaders"} directory contained directly in it that ends | |
6872 | in @samp{".framework"}. The name of a framework is the name of this | |
6873 | directory excluding the @samp{".framework"}. Headers associated with | |
6874 | the framework are found in one of those two directories, with | |
6875 | @samp{"Headers"} being searched first. A subframework is a framework | |
6876 | directory that is in a framework's @samp{"Frameworks"} directory. | |
6877 | Includes of subframework headers can only appear in a header of a | |
6878 | framework that contains the subframework, or in a sibling subframework | |
6879 | header. Two subframeworks are siblings if they occur in the same | |
6880 | framework. A subframework should not have the same name as a | |
6881 | framework, a warning will be issued if this is violated. Currently a | |
6882 | subframework cannot have subframeworks, in the future, the mechanism | |
6883 | may be extended to support this. The standard frameworks can be found | |
6884 | in @samp{"/System/Library/Frameworks"}, @samp{"/Library/Frameworks"} | |
6885 | and @samp{"/Local/Library/Frameworks"}. An example include looks like | |
6886 | @code{#include <Framework/header.h>}, where @samp{Framework} denotes | |
6887 | the name of the framework and header.h is found in the | |
6888 | @samp{"PrivateHeaders"} or @samp{"Headers"} directory. | |
157a620e | 6889 | |
39bc1876 NS |
6890 | @item -all_load |
6891 | @opindex all_load | |
6892 | Loads all members of static archive libraries. | |
6893 | See man ld(1) for more information. | |
74291a4b | 6894 | |
39bc1876 NS |
6895 | @item -arch_errors_fatal |
6896 | @opindex arch_errors_fatal | |
6897 | Cause the errors having to do with files that have the wrong architecture | |
6898 | to be fatal. | |
157a620e | 6899 | |
39bc1876 NS |
6900 | @item -bind_at_load |
6901 | @opindex bind_at_load | |
6902 | Causes the output file to be marked such that the dynamic linker will | |
6903 | bind all undefined references when the file is loaded or launched. | |
157a620e | 6904 | |
39bc1876 NS |
6905 | @item -bundle |
6906 | @opindex bundle | |
6907 | Produce a Mach-o bundle format file. | |
6908 | See man ld(1) for more information. | |
157a620e | 6909 | |
39bc1876 NS |
6910 | @item -bundle_loader @var{executable} |
6911 | @opindex bundle_loader | |
6912 | This specifies the @var{executable} that will be loading the build | |
6913 | output file being linked. See man ld(1) for more information. | |
157a620e | 6914 | |
39bc1876 NS |
6915 | @item -allowable_client @var{client_name} |
6916 | @itemx -arch_only | |
157a620e | 6917 | |
39bc1876 NS |
6918 | @itemx -client_name |
6919 | @itemx -compatibility_version | |
6920 | @itemx -current_version | |
6921 | @itemx -dependency-file | |
6922 | @itemx -dylib_file | |
6923 | @itemx -dylinker_install_name | |
6924 | @itemx -dynamic | |
6925 | @itemx -dynamiclib | |
6926 | @itemx -exported_symbols_list | |
6927 | @itemx -filelist | |
6928 | @itemx -flat_namespace | |
6929 | @itemx -force_cpusubtype_ALL | |
6930 | @itemx -force_flat_namespace | |
6931 | @itemx -headerpad_max_install_names | |
6932 | @itemx -image_base | |
6933 | @itemx -init | |
6934 | @itemx -install_name | |
6935 | @itemx -keep_private_externs | |
6936 | @itemx -multi_module | |
6937 | @itemx -multiply_defined | |
6938 | @itemx -multiply_defined_unused | |
6939 | @itemx -noall_load | |
6940 | @itemx -nofixprebinding | |
6941 | @itemx -nomultidefs | |
6942 | @itemx -noprebind | |
6943 | @itemx -noseglinkedit | |
6944 | @itemx -pagezero_size | |
6945 | @itemx -prebind | |
6946 | @itemx -prebind_all_twolevel_modules | |
6947 | @itemx -private_bundle | |
6948 | @itemx -read_only_relocs | |
6949 | @itemx -sectalign | |
6950 | @itemx -sectobjectsymbols | |
6951 | @itemx -whyload | |
6952 | @itemx -seg1addr | |
6953 | @itemx -sectcreate | |
6954 | @itemx -sectobjectsymbols | |
6955 | @itemx -sectorder | |
6956 | @itemx -seg_addr_table | |
6957 | @itemx -seg_addr_table_filename | |
6958 | @itemx -seglinkedit | |
6959 | @itemx -segprot | |
6960 | @itemx -segs_read_only_addr | |
6961 | @itemx -segs_read_write_addr | |
6962 | @itemx -single_module | |
6963 | @itemx -static | |
6964 | @itemx -sub_library | |
6965 | @itemx -sub_umbrella | |
6966 | @itemx -twolevel_namespace | |
6967 | @itemx -umbrella | |
6968 | @itemx -undefined | |
6969 | @itemx -unexported_symbols_list | |
6970 | @itemx -weak_reference_mismatches | |
6971 | @itemx -whatsloaded | |
74291a4b | 6972 | |
39bc1876 NS |
6973 | @opindex allowable_client |
6974 | @opindex arch_only | |
6975 | @opindex client_name | |
6976 | @opindex compatibility_version | |
6977 | @opindex current_version | |
6978 | @opindex dependency-file | |
6979 | @opindex dylib_file | |
6980 | @opindex dylinker_install_name | |
6981 | @opindex dynamic | |
6982 | @opindex dynamiclib | |
6983 | @opindex exported_symbols_list | |
6984 | @opindex filelist | |
6985 | @opindex flat_namespace | |
6986 | @opindex force_cpusubtype_ALL | |
6987 | @opindex force_flat_namespace | |
6988 | @opindex headerpad_max_install_names | |
6989 | @opindex image_base | |
6990 | @opindex init | |
6991 | @opindex install_name | |
6992 | @opindex keep_private_externs | |
6993 | @opindex multi_module | |
6994 | @opindex multiply_defined | |
6995 | @opindex multiply_defined_unused | |
6996 | @opindex noall_load | |
6997 | @opindex nofixprebinding | |
6998 | @opindex nomultidefs | |
6999 | @opindex noprebind | |
7000 | @opindex noseglinkedit | |
7001 | @opindex pagezero_size | |
7002 | @opindex prebind | |
7003 | @opindex prebind_all_twolevel_modules | |
7004 | @opindex private_bundle | |
7005 | @opindex read_only_relocs | |
7006 | @opindex sectalign | |
7007 | @opindex sectobjectsymbols | |
7008 | @opindex whyload | |
7009 | @opindex seg1addr | |
7010 | @opindex sectcreate | |
7011 | @opindex sectobjectsymbols | |
7012 | @opindex sectorder | |
7013 | @opindex seg_addr_table | |
7014 | @opindex seg_addr_table_filename | |
7015 | @opindex seglinkedit | |
7016 | @opindex segprot | |
7017 | @opindex segs_read_only_addr | |
7018 | @opindex segs_read_write_addr | |
7019 | @opindex single_module | |
7020 | @opindex static | |
7021 | @opindex sub_library | |
7022 | @opindex sub_umbrella | |
7023 | @opindex twolevel_namespace | |
7024 | @opindex umbrella | |
7025 | @opindex undefined | |
7026 | @opindex unexported_symbols_list | |
7027 | @opindex weak_reference_mismatches | |
7028 | @opindex whatsloaded | |
7029 | ||
7030 | These options are available for Darwin linker. Darwin linker man page | |
7031 | describes them in detail. | |
7032 | @end table | |
7033 | ||
7034 | @node DEC Alpha Options | |
7035 | @subsection DEC Alpha Options | |
7036 | ||
7037 | These @samp{-m} options are defined for the DEC Alpha implementations: | |
7038 | ||
7039 | @table @gcctabopt | |
7040 | @item -mno-soft-float | |
7041 | @itemx -msoft-float | |
7042 | @opindex mno-soft-float | |
cd3bb277 | 7043 | @opindex msoft-float |
39bc1876 NS |
7044 | Use (do not use) the hardware floating-point instructions for |
7045 | floating-point operations. When @option{-msoft-float} is specified, | |
7046 | functions in @file{libgcc.a} will be used to perform floating-point | |
7047 | operations. Unless they are replaced by routines that emulate the | |
7048 | floating-point operations, or compiled in such a way as to call such | |
7049 | emulations routines, these routines will issue floating-point | |
7050 | operations. If you are compiling for an Alpha without floating-point | |
7051 | operations, you must ensure that the library is built so as not to call | |
7052 | them. | |
74291a4b | 7053 | |
39bc1876 NS |
7054 | Note that Alpha implementations without floating-point operations are |
7055 | required to have floating-point registers. | |
74291a4b | 7056 | |
39bc1876 NS |
7057 | @item -mfp-reg |
7058 | @itemx -mno-fp-regs | |
7059 | @opindex mfp-reg | |
7060 | @opindex mno-fp-regs | |
7061 | Generate code that uses (does not use) the floating-point register set. | |
7062 | @option{-mno-fp-regs} implies @option{-msoft-float}. If the floating-point | |
7063 | register set is not used, floating point operands are passed in integer | |
7064 | registers as if they were integers and floating-point results are passed | |
7065 | in @code{$0} instead of @code{$f0}. This is a non-standard calling sequence, | |
7066 | so any function with a floating-point argument or return value called by code | |
7067 | compiled with @option{-mno-fp-regs} must also be compiled with that | |
7068 | option. | |
9b66ebb1 | 7069 | |
39bc1876 NS |
7070 | A typical use of this option is building a kernel that does not use, |
7071 | and hence need not save and restore, any floating-point registers. | |
9b66ebb1 | 7072 | |
39bc1876 NS |
7073 | @item -mieee |
7074 | @opindex mieee | |
7075 | The Alpha architecture implements floating-point hardware optimized for | |
7076 | maximum performance. It is mostly compliant with the IEEE floating | |
7077 | point standard. However, for full compliance, software assistance is | |
7078 | required. This option generates code fully IEEE compliant code | |
7079 | @emph{except} that the @var{inexact-flag} is not maintained (see below). | |
7080 | If this option is turned on, the preprocessor macro @code{_IEEE_FP} is | |
7081 | defined during compilation. The resulting code is less efficient but is | |
7082 | able to correctly support denormalized numbers and exceptional IEEE | |
7083 | values such as not-a-number and plus/minus infinity. Other Alpha | |
7084 | compilers call this option @option{-ieee_with_no_inexact}. | |
74291a4b | 7085 | |
39bc1876 NS |
7086 | @item -mieee-with-inexact |
7087 | @opindex mieee-with-inexact | |
7088 | This is like @option{-mieee} except the generated code also maintains | |
7089 | the IEEE @var{inexact-flag}. Turning on this option causes the | |
7090 | generated code to implement fully-compliant IEEE math. In addition to | |
7091 | @code{_IEEE_FP}, @code{_IEEE_FP_EXACT} is defined as a preprocessor | |
7092 | macro. On some Alpha implementations the resulting code may execute | |
7093 | significantly slower than the code generated by default. Since there is | |
7094 | very little code that depends on the @var{inexact-flag}, you should | |
7095 | normally not specify this option. Other Alpha compilers call this | |
7096 | option @option{-ieee_with_inexact}. | |
74291a4b | 7097 | |
39bc1876 NS |
7098 | @item -mfp-trap-mode=@var{trap-mode} |
7099 | @opindex mfp-trap-mode | |
7100 | This option controls what floating-point related traps are enabled. | |
7101 | Other Alpha compilers call this option @option{-fptm @var{trap-mode}}. | |
7102 | The trap mode can be set to one of four values: | |
74291a4b | 7103 | |
39bc1876 NS |
7104 | @table @samp |
7105 | @item n | |
7106 | This is the default (normal) setting. The only traps that are enabled | |
7107 | are the ones that cannot be disabled in software (e.g., division by zero | |
7108 | trap). | |
62b10bbc | 7109 | |
39bc1876 NS |
7110 | @item u |
7111 | In addition to the traps enabled by @samp{n}, underflow traps are enabled | |
7112 | as well. | |
157a620e | 7113 | |
39bc1876 NS |
7114 | @item su |
7115 | Like @samp{su}, but the instructions are marked to be safe for software | |
7116 | completion (see Alpha architecture manual for details). | |
157a620e | 7117 | |
39bc1876 NS |
7118 | @item sui |
7119 | Like @samp{su}, but inexact traps are enabled as well. | |
7120 | @end table | |
9b66ebb1 | 7121 | |
39bc1876 NS |
7122 | @item -mfp-rounding-mode=@var{rounding-mode} |
7123 | @opindex mfp-rounding-mode | |
7124 | Selects the IEEE rounding mode. Other Alpha compilers call this option | |
7125 | @option{-fprm @var{rounding-mode}}. The @var{rounding-mode} can be one | |
7126 | of: | |
157a620e | 7127 | |
39bc1876 NS |
7128 | @table @samp |
7129 | @item n | |
7130 | Normal IEEE rounding mode. Floating point numbers are rounded towards | |
7131 | the nearest machine number or towards the even machine number in case | |
7132 | of a tie. | |
5848830f | 7133 | |
39bc1876 NS |
7134 | @item m |
7135 | Round towards minus infinity. | |
157a620e | 7136 | |
39bc1876 NS |
7137 | @item c |
7138 | Chopped rounding mode. Floating point numbers are rounded towards zero. | |
f5a1b0d2 | 7139 | |
39bc1876 NS |
7140 | @item d |
7141 | Dynamic rounding mode. A field in the floating point control register | |
7142 | (@var{fpcr}, see Alpha architecture reference manual) controls the | |
7143 | rounding mode in effect. The C library initializes this register for | |
7144 | rounding towards plus infinity. Thus, unless your program modifies the | |
7145 | @var{fpcr}, @samp{d} corresponds to round towards plus infinity. | |
7146 | @end table | |
c27ba912 | 7147 | |
39bc1876 NS |
7148 | @item -mtrap-precision=@var{trap-precision} |
7149 | @opindex mtrap-precision | |
7150 | In the Alpha architecture, floating point traps are imprecise. This | |
7151 | means without software assistance it is impossible to recover from a | |
7152 | floating trap and program execution normally needs to be terminated. | |
7153 | GCC can generate code that can assist operating system trap handlers | |
7154 | in determining the exact location that caused a floating point trap. | |
7155 | Depending on the requirements of an application, different levels of | |
7156 | precisions can be selected: | |
c27ba912 | 7157 | |
39bc1876 NS |
7158 | @table @samp |
7159 | @item p | |
7160 | Program precision. This option is the default and means a trap handler | |
7161 | can only identify which program caused a floating point exception. | |
c27ba912 | 7162 | |
39bc1876 NS |
7163 | @item f |
7164 | Function precision. The trap handler can determine the function that | |
7165 | caused a floating point exception. | |
62b10bbc | 7166 | |
39bc1876 NS |
7167 | @item i |
7168 | Instruction precision. The trap handler can determine the exact | |
7169 | instruction that caused a floating point exception. | |
7170 | @end table | |
ed0e6530 | 7171 | |
39bc1876 NS |
7172 | Other Alpha compilers provide the equivalent options called |
7173 | @option{-scope_safe} and @option{-resumption_safe}. | |
ed0e6530 | 7174 | |
39bc1876 NS |
7175 | @item -mieee-conformant |
7176 | @opindex mieee-conformant | |
7177 | This option marks the generated code as IEEE conformant. You must not | |
7178 | use this option unless you also specify @option{-mtrap-precision=i} and either | |
7179 | @option{-mfp-trap-mode=su} or @option{-mfp-trap-mode=sui}. Its only effect | |
7180 | is to emit the line @samp{.eflag 48} in the function prologue of the | |
7181 | generated assembly file. Under DEC Unix, this has the effect that | |
7182 | IEEE-conformant math library routines will be linked in. | |
9b6b54e2 | 7183 | |
39bc1876 NS |
7184 | @item -mbuild-constants |
7185 | @opindex mbuild-constants | |
7186 | Normally GCC examines a 32- or 64-bit integer constant to | |
7187 | see if it can construct it from smaller constants in two or three | |
7188 | instructions. If it cannot, it will output the constant as a literal and | |
7189 | generate code to load it from the data segment at runtime. | |
74291a4b | 7190 | |
39bc1876 NS |
7191 | Use this option to require GCC to construct @emph{all} integer constants |
7192 | using code, even if it takes more instructions (the maximum is six). | |
157a620e | 7193 | |
39bc1876 NS |
7194 | You would typically use this option to build a shared library dynamic |
7195 | loader. Itself a shared library, it must relocate itself in memory | |
7196 | before it can find the variables and constants in its own data segment. | |
7197 | ||
7198 | @item -malpha-as | |
7199 | @itemx -mgas | |
7200 | @opindex malpha-as | |
7201 | @opindex mgas | |
7202 | Select whether to generate code to be assembled by the vendor-supplied | |
7203 | assembler (@option{-malpha-as}) or by the GNU assembler @option{-mgas}. | |
7204 | ||
7205 | @item -mbwx | |
7206 | @itemx -mno-bwx | |
7207 | @itemx -mcix | |
7208 | @itemx -mno-cix | |
7209 | @itemx -mfix | |
7210 | @itemx -mno-fix | |
7211 | @itemx -mmax | |
7212 | @itemx -mno-max | |
7213 | @opindex mbwx | |
7214 | @opindex mno-bwx | |
7215 | @opindex mcix | |
7216 | @opindex mno-cix | |
7217 | @opindex mfix | |
7218 | @opindex mno-fix | |
7219 | @opindex mmax | |
7220 | @opindex mno-max | |
7221 | Indicate whether GCC should generate code to use the optional BWX, | |
7222 | CIX, FIX and MAX instruction sets. The default is to use the instruction | |
7223 | sets supported by the CPU type specified via @option{-mcpu=} option or that | |
7224 | of the CPU on which GCC was built if none was specified. | |
157a620e | 7225 | |
39bc1876 NS |
7226 | @item -mfloat-vax |
7227 | @itemx -mfloat-ieee | |
7228 | @opindex mfloat-vax | |
7229 | @opindex mfloat-ieee | |
7230 | Generate code that uses (does not use) VAX F and G floating point | |
7231 | arithmetic instead of IEEE single and double precision. | |
157a620e | 7232 | |
39bc1876 NS |
7233 | @item -mexplicit-relocs |
7234 | @itemx -mno-explicit-relocs | |
7235 | @opindex mexplicit-relocs | |
7236 | @opindex mno-explicit-relocs | |
7237 | Older Alpha assemblers provided no way to generate symbol relocations | |
7238 | except via assembler macros. Use of these macros does not allow | |
7239 | optimal instruction scheduling. GNU binutils as of version 2.12 | |
7240 | supports a new syntax that allows the compiler to explicitly mark | |
7241 | which relocations should apply to which instructions. This option | |
7242 | is mostly useful for debugging, as GCC detects the capabilities of | |
7243 | the assembler when it is built and sets the default accordingly. | |
157a620e | 7244 | |
39bc1876 NS |
7245 | @item -msmall-data |
7246 | @itemx -mlarge-data | |
7247 | @opindex msmall-data | |
7248 | @opindex mlarge-data | |
7249 | When @option{-mexplicit-relocs} is in effect, static data is | |
7250 | accessed via @dfn{gp-relative} relocations. When @option{-msmall-data} | |
7251 | is used, objects 8 bytes long or smaller are placed in a @dfn{small data area} | |
7252 | (the @code{.sdata} and @code{.sbss} sections) and are accessed via | |
7253 | 16-bit relocations off of the @code{$gp} register. This limits the | |
7254 | size of the small data area to 64KB, but allows the variables to be | |
7255 | directly accessed via a single instruction. | |
62b10bbc | 7256 | |
39bc1876 NS |
7257 | The default is @option{-mlarge-data}. With this option the data area |
7258 | is limited to just below 2GB. Programs that require more than 2GB of | |
7259 | data must use @code{malloc} or @code{mmap} to allocate the data in the | |
7260 | heap instead of in the program's data segment. | |
62b10bbc | 7261 | |
39bc1876 NS |
7262 | When generating code for shared libraries, @option{-fpic} implies |
7263 | @option{-msmall-data} and @option{-fPIC} implies @option{-mlarge-data}. | |
4bdc1ac7 | 7264 | |
39bc1876 NS |
7265 | @item -msmall-text |
7266 | @itemx -mlarge-text | |
7267 | @opindex msmall-text | |
7268 | @opindex mlarge-text | |
7269 | When @option{-msmall-text} is used, the compiler assumes that the | |
7270 | code of the entire program (or shared library) fits in 4MB, and is | |
7271 | thus reachable with a branch instruction. When @option{-msmall-data} | |
7272 | is used, the compiler can assume that all local symbols share the | |
7273 | same @code{$gp} value, and thus reduce the number of instructions | |
7274 | required for a function call from 4 to 1. | |
157a620e | 7275 | |
39bc1876 | 7276 | The default is @option{-mlarge-text}. |
d2d42a91 | 7277 | |
39bc1876 NS |
7278 | @item -mcpu=@var{cpu_type} |
7279 | @opindex mcpu | |
7280 | Set the instruction set and instruction scheduling parameters for | |
7281 | machine type @var{cpu_type}. You can specify either the @samp{EV} | |
7282 | style name or the corresponding chip number. GCC supports scheduling | |
7283 | parameters for the EV4, EV5 and EV6 family of processors and will | |
7284 | choose the default values for the instruction set from the processor | |
7285 | you specify. If you do not specify a processor type, GCC will default | |
7286 | to the processor on which the compiler was built. | |
6d6d0fa0 | 7287 | |
39bc1876 | 7288 | Supported values for @var{cpu_type} are |
6d6d0fa0 | 7289 | |
39bc1876 NS |
7290 | @table @samp |
7291 | @item ev4 | |
7292 | @itemx ev45 | |
7293 | @itemx 21064 | |
7294 | Schedules as an EV4 and has no instruction set extensions. | |
ecff22ab | 7295 | |
39bc1876 NS |
7296 | @item ev5 |
7297 | @itemx 21164 | |
7298 | Schedules as an EV5 and has no instruction set extensions. | |
705ac34f | 7299 | |
39bc1876 NS |
7300 | @item ev56 |
7301 | @itemx 21164a | |
7302 | Schedules as an EV5 and supports the BWX extension. | |
705ac34f | 7303 | |
39bc1876 NS |
7304 | @item pca56 |
7305 | @itemx 21164pc | |
7306 | @itemx 21164PC | |
7307 | Schedules as an EV5 and supports the BWX and MAX extensions. | |
c474f76b | 7308 | |
39bc1876 NS |
7309 | @item ev6 |
7310 | @itemx 21264 | |
7311 | Schedules as an EV6 and supports the BWX, FIX, and MAX extensions. | |
ecff22ab | 7312 | |
39bc1876 NS |
7313 | @item ev67 |
7314 | @itemx 21264a | |
7315 | Schedules as an EV6 and supports the BWX, CIX, FIX, and MAX extensions. | |
6d6d0fa0 JL |
7316 | @end table |
7317 | ||
39bc1876 NS |
7318 | @item -mtune=@var{cpu_type} |
7319 | @opindex mtune | |
7320 | Set only the instruction scheduling parameters for machine type | |
7321 | @var{cpu_type}. The instruction set is not changed. | |
ecff22ab | 7322 | |
39bc1876 NS |
7323 | @item -mmemory-latency=@var{time} |
7324 | @opindex mmemory-latency | |
7325 | Sets the latency the scheduler should assume for typical memory | |
7326 | references as seen by the application. This number is highly | |
7327 | dependent on the memory access patterns used by the application | |
7328 | and the size of the external cache on the machine. | |
861bb6c1 | 7329 | |
39bc1876 | 7330 | Valid options for @var{time} are |
6975bd2c | 7331 | |
39bc1876 NS |
7332 | @table @samp |
7333 | @item @var{number} | |
7334 | A decimal number representing clock cycles. | |
98180123 | 7335 | |
39bc1876 NS |
7336 | @item L1 |
7337 | @itemx L2 | |
7338 | @itemx L3 | |
7339 | @itemx main | |
7340 | The compiler contains estimates of the number of clock cycles for | |
7341 | ``typical'' EV4 & EV5 hardware for the Level 1, 2 & 3 caches | |
7342 | (also called Dcache, Scache, and Bcache), as well as to main memory. | |
7343 | Note that L3 is only valid for EV5. | |
de41e41c | 7344 | |
39bc1876 NS |
7345 | @end table |
7346 | @end table | |
861bb6c1 | 7347 | |
39bc1876 NS |
7348 | @node DEC Alpha/VMS Options |
7349 | @subsection DEC Alpha/VMS Options | |
861bb6c1 | 7350 | |
39bc1876 | 7351 | These @samp{-m} options are defined for the DEC Alpha/VMS implementations: |
861bb6c1 | 7352 | |
39bc1876 NS |
7353 | @table @gcctabopt |
7354 | @item -mvms-return-codes | |
7355 | @opindex mvms-return-codes | |
7356 | Return VMS condition codes from main. The default is to return POSIX | |
7357 | style condition (e.g.@ error) codes. | |
7358 | @end table | |
861bb6c1 | 7359 | |
39bc1876 NS |
7360 | @node FRV Options |
7361 | @subsection FRV Options | |
7362 | @cindex FRV Options | |
861bb6c1 | 7363 | |
39bc1876 NS |
7364 | @table @gcctabopt |
7365 | @item -mgpr-32 | |
7366 | @opindex mgpr-32 | |
861bb6c1 | 7367 | |
39bc1876 | 7368 | Only use the first 32 general purpose registers. |
861bb6c1 | 7369 | |
39bc1876 NS |
7370 | @item -mgpr-64 |
7371 | @opindex mgpr-64 | |
861bb6c1 | 7372 | |
39bc1876 | 7373 | Use all 64 general purpose registers. |
861bb6c1 | 7374 | |
39bc1876 NS |
7375 | @item -mfpr-32 |
7376 | @opindex mfpr-32 | |
861bb6c1 | 7377 | |
39bc1876 | 7378 | Use only the first 32 floating point registers. |
ad126521 | 7379 | |
39bc1876 NS |
7380 | @item -mfpr-64 |
7381 | @opindex mfpr-64 | |
ad126521 | 7382 | |
39bc1876 | 7383 | Use all 64 floating point registers |
ad126521 | 7384 | |
39bc1876 NS |
7385 | @item -mhard-float |
7386 | @opindex mhard-float | |
ad126521 | 7387 | |
39bc1876 | 7388 | Use hardware instructions for floating point operations. |
ad126521 | 7389 | |
39bc1876 NS |
7390 | @item -msoft-float |
7391 | @opindex msoft-float | |
ad126521 | 7392 | |
39bc1876 | 7393 | Use library routines for floating point operations. |
ad126521 | 7394 | |
39bc1876 NS |
7395 | @item -malloc-cc |
7396 | @opindex malloc-cc | |
ad126521 | 7397 | |
39bc1876 | 7398 | Dynamically allocate condition code registers. |
ad126521 | 7399 | |
39bc1876 NS |
7400 | @item -mfixed-cc |
7401 | @opindex mfixed-cc | |
861bb6c1 | 7402 | |
39bc1876 NS |
7403 | Do not try to dynamically allocate condition code registers, only |
7404 | use @code{icc0} and @code{fcc0}. | |
74291a4b | 7405 | |
39bc1876 NS |
7406 | @item -mdword |
7407 | @opindex mdword | |
74291a4b | 7408 | |
39bc1876 | 7409 | Change ABI to use double word insns. |
74291a4b | 7410 | |
39bc1876 NS |
7411 | @item -mno-dword |
7412 | @opindex mno-dword | |
74291a4b | 7413 | |
39bc1876 | 7414 | Do not use double word instructions. |
74291a4b | 7415 | |
39bc1876 NS |
7416 | @item -mdouble |
7417 | @opindex mdouble | |
74291a4b | 7418 | |
39bc1876 | 7419 | Use floating point double instructions. |
7fe90e7b | 7420 | |
39bc1876 NS |
7421 | @item -mno-double |
7422 | @opindex mno-double | |
74291a4b | 7423 | |
39bc1876 | 7424 | Do not use floating point double instructions. |
74291a4b | 7425 | |
39bc1876 NS |
7426 | @item -mmedia |
7427 | @opindex mmedia | |
74291a4b | 7428 | |
39bc1876 | 7429 | Use media instructions. |
9c34dbbf | 7430 | |
39bc1876 NS |
7431 | @item -mno-media |
7432 | @opindex mno-media | |
74291a4b | 7433 | |
39bc1876 | 7434 | Do not use media instructions. |
74291a4b | 7435 | |
39bc1876 NS |
7436 | @item -mmuladd |
7437 | @opindex mmuladd | |
9c34dbbf | 7438 | |
39bc1876 | 7439 | Use multiply and add/subtract instructions. |
66188a7e | 7440 | |
39bc1876 NS |
7441 | @item -mno-muladd |
7442 | @opindex mno-muladd | |
74291a4b | 7443 | |
39bc1876 | 7444 | Do not use multiply and add/subtract instructions. |
74291a4b | 7445 | |
39bc1876 NS |
7446 | @item -mlibrary-pic |
7447 | @opindex mlibrary-pic | |
0ac081f6 | 7448 | |
39bc1876 | 7449 | Generate position-independent EABI code. |
6c8875e5 | 7450 | |
39bc1876 NS |
7451 | @item -macc-4 |
7452 | @opindex macc-4 | |
6c8875e5 | 7453 | |
39bc1876 | 7454 | Use only the first four media accumulator registers. |
6c8875e5 | 7455 | |
39bc1876 NS |
7456 | @item -macc-8 |
7457 | @opindex macc-8 | |
993f19a8 | 7458 | |
39bc1876 | 7459 | Use all eight media accumulator registers. |
5da702b1 | 7460 | |
39bc1876 NS |
7461 | @item -mpack |
7462 | @opindex mpack | |
74291a4b | 7463 | |
39bc1876 | 7464 | Pack VLIW instructions. |
74291a4b | 7465 | |
39bc1876 NS |
7466 | @item -mno-pack |
7467 | @opindex mno-pack | |
74291a4b | 7468 | |
39bc1876 | 7469 | Do not pack VLIW instructions. |
7fe90e7b | 7470 | |
39bc1876 NS |
7471 | @item -mno-eflags |
7472 | @opindex mno-eflags | |
74291a4b | 7473 | |
39bc1876 | 7474 | Do not mark ABI switches in e_flags. |
861bb6c1 | 7475 | |
39bc1876 NS |
7476 | @item -mcond-move |
7477 | @opindex mcond-move | |
6184e8a4 | 7478 | |
39bc1876 | 7479 | Enable the use of conditional-move instructions (default). |
74291a4b | 7480 | |
39bc1876 NS |
7481 | This switch is mainly for debugging the compiler and will likely be removed |
7482 | in a future version. | |
74291a4b | 7483 | |
39bc1876 NS |
7484 | @item -mno-cond-move |
7485 | @opindex mno-cond-move | |
74291a4b | 7486 | |
39bc1876 | 7487 | Disable the use of conditional-move instructions. |
861bb6c1 | 7488 | |
39bc1876 NS |
7489 | This switch is mainly for debugging the compiler and will likely be removed |
7490 | in a future version. | |
861bb6c1 | 7491 | |
39bc1876 NS |
7492 | @item -mscc |
7493 | @opindex mscc | |
74291a4b | 7494 | |
39bc1876 | 7495 | Enable the use of conditional set instructions (default). |
74291a4b | 7496 | |
39bc1876 NS |
7497 | This switch is mainly for debugging the compiler and will likely be removed |
7498 | in a future version. | |
74291a4b | 7499 | |
39bc1876 NS |
7500 | @item -mno-scc |
7501 | @opindex mno-scc | |
74291a4b | 7502 | |
39bc1876 | 7503 | Disable the use of conditional set instructions. |
74291a4b | 7504 | |
39bc1876 NS |
7505 | This switch is mainly for debugging the compiler and will likely be removed |
7506 | in a future version. | |
74291a4b | 7507 | |
39bc1876 NS |
7508 | @item -mcond-exec |
7509 | @opindex mcond-exec | |
74291a4b | 7510 | |
39bc1876 | 7511 | Enable the use of conditional execution (default). |
74291a4b | 7512 | |
39bc1876 NS |
7513 | This switch is mainly for debugging the compiler and will likely be removed |
7514 | in a future version. | |
ab82a49f | 7515 | |
39bc1876 NS |
7516 | @item -mno-cond-exec |
7517 | @opindex mno-cond-exec | |
79ae11c4 | 7518 | |
39bc1876 | 7519 | Disable the use of conditional execution. |
daf2f129 | 7520 | |
39bc1876 NS |
7521 | This switch is mainly for debugging the compiler and will likely be removed |
7522 | in a future version. | |
cbe26ab8 | 7523 | |
39bc1876 NS |
7524 | @item -mvliw-branch |
7525 | @opindex mvliw-branch | |
7526 | ||
7527 | Run a pass to pack branches into VLIW instructions (default). | |
7528 | ||
7529 | This switch is mainly for debugging the compiler and will likely be removed | |
7530 | in a future version. | |
7531 | ||
7532 | @item -mno-vliw-branch | |
7533 | @opindex mno-vliw-branch | |
7534 | ||
7535 | Do not run a pass to pack branches into VLIW instructions. | |
7536 | ||
7537 | This switch is mainly for debugging the compiler and will likely be removed | |
7538 | in a future version. | |
74291a4b | 7539 | |
39bc1876 NS |
7540 | @item -mmulti-cond-exec |
7541 | @opindex mmulti-cond-exec | |
74291a4b | 7542 | |
39bc1876 NS |
7543 | Enable optimization of @code{&&} and @code{||} in conditional execution |
7544 | (default). | |
74291a4b | 7545 | |
39bc1876 NS |
7546 | This switch is mainly for debugging the compiler and will likely be removed |
7547 | in a future version. | |
74291a4b | 7548 | |
39bc1876 NS |
7549 | @item -mno-multi-cond-exec |
7550 | @opindex mno-multi-cond-exec | |
74291a4b | 7551 | |
39bc1876 | 7552 | Disable optimization of @code{&&} and @code{||} in conditional execution. |
48180d68 | 7553 | |
39bc1876 NS |
7554 | This switch is mainly for debugging the compiler and will likely be removed |
7555 | in a future version. | |
edf1b3f3 | 7556 | |
39bc1876 NS |
7557 | @item -mnested-cond-exec |
7558 | @opindex mnested-cond-exec | |
9904592e | 7559 | |
39bc1876 | 7560 | Enable nested conditional execution optimizations (default). |
9904592e | 7561 | |
39bc1876 NS |
7562 | This switch is mainly for debugging the compiler and will likely be removed |
7563 | in a future version. | |
0ac081f6 | 7564 | |
39bc1876 NS |
7565 | @item -mno-nested-cond-exec |
7566 | @opindex mno-nested-cond-exec | |
76a773f3 | 7567 | |
39bc1876 | 7568 | Disable nested conditional execution optimizations. |
74291a4b | 7569 | |
39bc1876 NS |
7570 | This switch is mainly for debugging the compiler and will likely be removed |
7571 | in a future version. | |
74291a4b | 7572 | |
39bc1876 NS |
7573 | @item -mtomcat-stats |
7574 | @opindex mtomcat-stats | |
e9a25f70 | 7575 | |
39bc1876 | 7576 | Cause gas to print out tomcat statistics. |
e9a25f70 | 7577 | |
39bc1876 NS |
7578 | @item -mcpu=@var{cpu} |
7579 | @opindex mcpu | |
74291a4b | 7580 | |
39bc1876 NS |
7581 | Select the processor type for which to generate code. Possible values are |
7582 | @samp{simple}, @samp{tomcat}, @samp{fr500}, @samp{fr400}, @samp{fr300}, | |
7583 | @samp{frv}. | |
bff46771 | 7584 | |
39bc1876 | 7585 | @end table |
8d8269fa | 7586 | |
39bc1876 NS |
7587 | @node H8/300 Options |
7588 | @subsection H8/300 Options | |
74291a4b | 7589 | |
39bc1876 | 7590 | These @samp{-m} options are defined for the H8/300 implementations: |
74291a4b | 7591 | |
39bc1876 NS |
7592 | @table @gcctabopt |
7593 | @item -mrelax | |
7594 | @opindex mrelax | |
7595 | Shorten some address references at link time, when possible; uses the | |
7596 | linker option @option{-relax}. @xref{H8/300,, @code{ld} and the H8/300, | |
7597 | ld, Using ld}, for a fuller description. | |
74291a4b | 7598 | |
39bc1876 NS |
7599 | @item -mh |
7600 | @opindex mh | |
7601 | Generate code for the H8/300H@. | |
74291a4b | 7602 | |
39bc1876 NS |
7603 | @item -ms |
7604 | @opindex ms | |
7605 | Generate code for the H8S@. | |
74291a4b | 7606 | |
39bc1876 NS |
7607 | @item -mn |
7608 | @opindex mn | |
7609 | Generate code for the H8S and H8/300H in the normal mode. This switch | |
7610 | must be used either with -mh or -ms. | |
74291a4b | 7611 | |
39bc1876 NS |
7612 | @item -ms2600 |
7613 | @opindex ms2600 | |
7614 | Generate code for the H8S/2600. This switch must be used with @option{-ms}. | |
74291a4b | 7615 | |
39bc1876 NS |
7616 | @item -mint32 |
7617 | @opindex mint32 | |
7618 | Make @code{int} data 32 bits by default. | |
74291a4b | 7619 | |
39bc1876 NS |
7620 | @item -malign-300 |
7621 | @opindex malign-300 | |
7622 | On the H8/300H and H8S, use the same alignment rules as for the H8/300. | |
7623 | The default for the H8/300H and H8S is to align longs and floats on 4 | |
7624 | byte boundaries. | |
7625 | @option{-malign-300} causes them to be aligned on 2 byte boundaries. | |
7626 | This option has no effect on the H8/300. | |
7627 | @end table | |
f5a1b0d2 | 7628 | |
39bc1876 NS |
7629 | @node HPPA Options |
7630 | @subsection HPPA Options | |
7631 | @cindex HPPA Options | |
a5c76ee6 | 7632 | |
39bc1876 | 7633 | These @samp{-m} options are defined for the HPPA family of computers: |
a5c76ee6 | 7634 | |
39bc1876 NS |
7635 | @table @gcctabopt |
7636 | @item -march=@var{architecture-type} | |
7637 | @opindex march | |
7638 | Generate code for the specified architecture. The choices for | |
7639 | @var{architecture-type} are @samp{1.0} for PA 1.0, @samp{1.1} for PA | |
7640 | 1.1, and @samp{2.0} for PA 2.0 processors. Refer to | |
7641 | @file{/usr/lib/sched.models} on an HP-UX system to determine the proper | |
7642 | architecture option for your machine. Code compiled for lower numbered | |
7643 | architectures will run on higher numbered architectures, but not the | |
7644 | other way around. | |
7645 | ||
7646 | PA 2.0 support currently requires gas snapshot 19990413 or later. The | |
7647 | next release of binutils (current is 2.9.1) will probably contain PA 2.0 | |
7648 | support. | |
7649 | ||
7650 | @item -mpa-risc-1-0 | |
7651 | @itemx -mpa-risc-1-1 | |
7652 | @itemx -mpa-risc-2-0 | |
7653 | @opindex mpa-risc-1-0 | |
7654 | @opindex mpa-risc-1-1 | |
7655 | @opindex mpa-risc-2-0 | |
7656 | Synonyms for @option{-march=1.0}, @option{-march=1.1}, and @option{-march=2.0} respectively. | |
5a26b329 | 7657 | |
39bc1876 NS |
7658 | @item -mbig-switch |
7659 | @opindex mbig-switch | |
7660 | Generate code suitable for big switch tables. Use this option only if | |
7661 | the assembler/linker complain about out of range branches within a switch | |
7662 | table. | |
efdba735 | 7663 | |
39bc1876 NS |
7664 | @item -mjump-in-delay |
7665 | @opindex mjump-in-delay | |
7666 | Fill delay slots of function calls with unconditional jump instructions | |
7667 | by modifying the return pointer for the function call to be the target | |
7668 | of the conditional jump. | |
a5c76ee6 | 7669 | |
39bc1876 NS |
7670 | @item -mdisable-fpregs |
7671 | @opindex mdisable-fpregs | |
7672 | Prevent floating point registers from being used in any manner. This is | |
7673 | necessary for compiling kernels which perform lazy context switching of | |
7674 | floating point registers. If you use this option and attempt to perform | |
7675 | floating point operations, the compiler will abort. | |
0a379b7a | 7676 | |
39bc1876 NS |
7677 | @item -mdisable-indexing |
7678 | @opindex mdisable-indexing | |
7679 | Prevent the compiler from using indexing address modes. This avoids some | |
7680 | rather obscure problems when compiling MIG generated code under MACH@. | |
f5a1b0d2 | 7681 | |
39bc1876 NS |
7682 | @item -mno-space-regs |
7683 | @opindex mno-space-regs | |
7684 | Generate code that assumes the target has no space registers. This allows | |
7685 | GCC to generate faster indirect calls and use unscaled index address modes. | |
d2d42a91 | 7686 | |
39bc1876 | 7687 | Such code is suitable for level 0 PA systems and kernels. |
d2d42a91 | 7688 | |
39bc1876 NS |
7689 | @item -mfast-indirect-calls |
7690 | @opindex mfast-indirect-calls | |
7691 | Generate code that assumes calls never cross space boundaries. This | |
7692 | allows GCC to emit code which performs faster indirect calls. | |
f08a3544 | 7693 | |
39bc1876 NS |
7694 | This option will not work in the presence of shared libraries or nested |
7695 | functions. | |
f08a3544 | 7696 | |
39bc1876 NS |
7697 | @item -mlong-load-store |
7698 | @opindex mlong-load-store | |
7699 | Generate 3-instruction load and store sequences as sometimes required by | |
7700 | the HP-UX 10 linker. This is equivalent to the @samp{+k} option to | |
7701 | the HP compilers. | |
61c85ff1 | 7702 | |
39bc1876 NS |
7703 | @item -mportable-runtime |
7704 | @opindex mportable-runtime | |
7705 | Use the portable calling conventions proposed by HP for ELF systems. | |
61c85ff1 | 7706 | |
39bc1876 NS |
7707 | @item -mgas |
7708 | @opindex mgas | |
7709 | Enable the use of assembler directives only GAS understands. | |
61c85ff1 | 7710 | |
39bc1876 NS |
7711 | @item -mschedule=@var{cpu-type} |
7712 | @opindex mschedule | |
7713 | Schedule code according to the constraints for the machine type | |
7714 | @var{cpu-type}. The choices for @var{cpu-type} are @samp{700} | |
7715 | @samp{7100}, @samp{7100LC}, @samp{7200}, @samp{7300} and @samp{8000}. Refer | |
7716 | to @file{/usr/lib/sched.models} on an HP-UX system to determine the | |
7717 | proper scheduling option for your machine. The default scheduling is | |
7718 | @samp{8000}. | |
61c85ff1 | 7719 | |
39bc1876 NS |
7720 | @item -mlinker-opt |
7721 | @opindex mlinker-opt | |
7722 | Enable the optimization pass in the HP-UX linker. Note this makes symbolic | |
7723 | debugging impossible. It also triggers a bug in the HP-UX 8 and HP-UX 9 | |
7724 | linkers in which they give bogus error messages when linking some programs. | |
61c85ff1 | 7725 | |
39bc1876 NS |
7726 | @item -msoft-float |
7727 | @opindex msoft-float | |
7728 | Generate output containing library calls for floating point. | |
7729 | @strong{Warning:} the requisite libraries are not available for all HPPA | |
7730 | targets. Normally the facilities of the machine's usual C compiler are | |
7731 | used, but this cannot be done directly in cross-compilation. You must make | |
7732 | your own arrangements to provide suitable library functions for | |
7733 | cross-compilation. The embedded target @samp{hppa1.1-*-pro} | |
7734 | does provide software floating point support. | |
31775d31 | 7735 | |
39bc1876 NS |
7736 | @option{-msoft-float} changes the calling convention in the output file; |
7737 | therefore, it is only useful if you compile @emph{all} of a program with | |
7738 | this option. In particular, you need to compile @file{libgcc.a}, the | |
7739 | library that comes with GCC, with @option{-msoft-float} in order for | |
7740 | this to work. | |
61c85ff1 | 7741 | |
39bc1876 NS |
7742 | @item -msio |
7743 | @opindex msio | |
7744 | Generate the predefine, @code{_SIO}, for server IO. The default is | |
7745 | @option{-mwsio}. This generates the predefines, @code{__hp9000s700}, | |
7746 | @code{__hp9000s700__} and @code{_WSIO}, for workstation IO. These | |
7747 | options are available under HP-UX and HI-UX. | |
7748 | ||
7749 | @item -mgnu-ld | |
7750 | @opindex gnu-ld | |
7751 | Use GNU ld specific options. This passes @option{-shared} to ld when | |
7752 | building a shared library. It is the default when GCC is configured, | |
7753 | explicitly or implicitly, with the GNU linker. This option does not | |
7754 | have any affect on which ld is called, it only changes what parameters | |
7755 | are passed to that ld. The ld that is called is determined by the | |
7756 | @option{--with-ld} configure option, GCC's program search path, and | |
7757 | finally by the user's @env{PATH}. The linker used by GCC can be printed | |
7758 | using @samp{which `gcc -print-prog-name=ld`}. | |
48aec0bc | 7759 | |
39bc1876 NS |
7760 | @item -mhp-ld |
7761 | @opindex hp-ld | |
7762 | Use HP ld specific options. This passes @option{-b} to ld when building | |
7763 | a shared library and passes @option{+Accept TypeMismatch} to ld on all | |
7764 | links. It is the default when GCC is configured, explicitly or | |
7765 | implicitly, with the HP linker. This option does not have any affect on | |
7766 | which ld is called, it only changes what parameters are passed to that | |
7767 | ld. The ld that is called is determined by the @option{--with-ld} | |
7768 | configure option, GCC's program search path, and finally by the user's | |
7769 | @env{PATH}. The linker used by GCC can be printed using @samp{which | |
7770 | `gcc -print-prog-name=ld`}. | |
48aec0bc | 7771 | |
39bc1876 NS |
7772 | @item -mfdpic |
7773 | @opindex mfdpic | |
48aec0bc | 7774 | |
39bc1876 NS |
7775 | Select the FDPIC ABI, that uses function descriptors to represent |
7776 | pointers to functions. Without any PIC/PIE-related options, it | |
7777 | implies @option{-fPIE}. With @option{-fpic} or @option{-fpie}, it | |
7778 | assumes GOT entries and small data are within a 12-bit range from the | |
7779 | GOT base address; with @option{-fPIC} or @option{-fPIE}, GOT offsets | |
7780 | are computed with 32 bits. | |
74291a4b | 7781 | |
39bc1876 NS |
7782 | @item -minline-plt |
7783 | @opindex minline-plt | |
7dac2f89 | 7784 | |
39bc1876 NS |
7785 | Enable inlining of PLT entries in function calls to functions that are |
7786 | not known to bind locally. It has no effect without @option{-mfdpic}. | |
7787 | It's enabled by default if optimizing for speed and compiling for | |
7788 | shared libraries (i.e., @option{-fPIC} or @option{-fpic}), or when an | |
7789 | optimization option such as @option{-O3} or above is present in the | |
7790 | command line. | |
5a4b3afd | 7791 | |
39bc1876 NS |
7792 | @item -mgprel-ro |
7793 | @opindex mgprel-ro | |
5a4b3afd | 7794 | |
39bc1876 NS |
7795 | Enable the use of @code{GPREL} relocations in the FDPIC ABI for data |
7796 | that is known to be in read-only sections. It's enabled by default, | |
7797 | except for @option{-fpic} or @option{-fpie}: even though it may help | |
7798 | make the global offset table smaller, it trades 1 instruction for 4. | |
7799 | With @option{-fPIC} or @option{-fPIE}, it trades 3 instructions for 4, | |
7800 | one of which may be shared by multiple symbols, and it avoids the need | |
7801 | for a GOT entry for the referenced symbol, so it's more likely to be a | |
7802 | win. If it is not, @option{-mno-gprel-ro} can be used to disable it. | |
a27fb29b | 7803 | |
39bc1876 NS |
7804 | @item -multilib-library-pic |
7805 | @opindex multilib-library-pic | |
a27fb29b | 7806 | |
39bc1876 NS |
7807 | Link with the (library, not FD) pic libraries. It's implied by |
7808 | @option{-mlibrary-pic}, as well as by @option{-fPIC} and | |
7809 | @option{-fpic} without @option{-mfdpic}. You should never have to use | |
7810 | it explicitly. | |
a27fb29b | 7811 | |
39bc1876 NS |
7812 | @item -mlinked-fp |
7813 | @opindex mlinked-fp | |
a27fb29b | 7814 | |
39bc1876 NS |
7815 | Follow the EABI requirement of always creating a frame pointer whenever |
7816 | a stack frame is allocated. This option is enabled by default and can | |
7817 | be disabled with @option{-mno-linked-fp}. | |
a27fb29b | 7818 | |
39bc1876 NS |
7819 | @item -mlong-calls |
7820 | @opindex mno-long-calls | |
7821 | Generate code that uses long call sequences. This ensures that a call | |
7822 | is always able to reach linker generated stubs. The default is to generate | |
7823 | long calls only when the distance from the call site to the beginning | |
7824 | of the function or translation unit, as the case may be, exceeds a | |
7825 | predefined limit set by the branch type being used. The limits for | |
7826 | normal calls are 7,600,000 and 240,000 bytes, respectively for the | |
7827 | PA 2.0 and PA 1.X architectures. Sibcalls are always limited at | |
7828 | 240,000 bytes. | |
a27fb29b | 7829 | |
39bc1876 NS |
7830 | Distances are measured from the beginning of functions when using the |
7831 | @option{-ffunction-sections} option, or when using the @option{-mgas} | |
7832 | and @option{-mno-portable-runtime} options together under HP-UX with | |
7833 | the SOM linker. | |
7dac2f89 | 7834 | |
39bc1876 NS |
7835 | It is normally not desirable to use this option as it will degrade |
7836 | performance. However, it may be useful in large applications, | |
7837 | particularly when partial linking is used to build the application. | |
74291a4b | 7838 | |
39bc1876 NS |
7839 | The types of long calls used depends on the capabilities of the |
7840 | assembler and linker, and the type of code being generated. The | |
7841 | impact on systems that support long absolute calls, and long pic | |
7842 | symbol-difference or pc-relative calls should be relatively small. | |
7843 | However, an indirect call is used on 32-bit ELF systems in pic code | |
7844 | and it is quite long. | |
74291a4b | 7845 | |
39bc1876 NS |
7846 | @item -nolibdld |
7847 | @opindex nolibdld | |
7848 | Suppress the generation of link options to search libdld.sl when the | |
7849 | @option{-static} option is specified on HP-UX 10 and later. | |
7850 | ||
7851 | @item -static | |
7852 | @opindex static | |
7853 | The HP-UX implementation of setlocale in libc has a dependency on | |
7854 | libdld.sl. There isn't an archive version of libdld.sl. Thus, | |
7855 | when the @option{-static} option is specified, special link options | |
7856 | are needed to resolve this dependency. | |
7857 | ||
7858 | On HP-UX 10 and later, the GCC driver adds the necessary options to | |
7859 | link with libdld.sl when the @option{-static} option is specified. | |
7860 | This causes the resulting binary to be dynamic. On the 64-bit port, | |
7861 | the linkers generate dynamic binaries by default in any case. The | |
7862 | @option{-nolibdld} option can be used to prevent the GCC driver from | |
7863 | adding these link options. | |
7864 | ||
7865 | @item -threads | |
7866 | @opindex threads | |
7867 | Add support for multithreading with the @dfn{dce thread} library | |
7868 | under HP-UX. This option sets flags for both the preprocessor and | |
7869 | linker. | |
7870 | @end table | |
7871 | ||
7872 | @node i386 and x86-64 Options | |
7873 | @subsection Intel 386 and AMD x86-64 Options | |
7874 | @cindex i386 Options | |
7875 | @cindex x86-64 Options | |
7876 | @cindex Intel 386 Options | |
7877 | @cindex AMD x86-64 Options | |
7878 | ||
7879 | These @samp{-m} options are defined for the i386 and x86-64 family of | |
7880 | computers: | |
7881 | ||
7882 | @table @gcctabopt | |
7883 | @item -mtune=@var{cpu-type} | |
7884 | @opindex mtune | |
7885 | Tune to @var{cpu-type} everything applicable about the generated code, except | |
7886 | for the ABI and the set of available instructions. The choices for | |
7887 | @var{cpu-type} are: | |
7888 | @table @emph | |
7889 | @item i386 | |
7890 | Original Intel's i386 CPU. | |
7891 | @item i486 | |
7892 | Intel's i486 CPU. (No scheduling is implemented for this chip.) | |
7893 | @item i586, pentium | |
7894 | Intel Pentium CPU with no MMX support. | |
7895 | @item pentium-mmx | |
7896 | Intel PentiumMMX CPU based on Pentium core with MMX instruction set support. | |
7897 | @item i686, pentiumpro | |
7898 | Intel PentiumPro CPU. | |
7899 | @item pentium2 | |
7900 | Intel Pentium2 CPU based on PentiumPro core with MMX instruction set support. | |
7901 | @item pentium3, pentium3m | |
7902 | Intel Pentium3 CPU based on PentiumPro core with MMX and SSE instruction set | |
7903 | support. | |
7904 | @item pentium-m | |
7905 | Low power version of Intel Pentium3 CPU with MMX, SSE and SSE2 instruction set | |
7906 | support. Used by Centrino notebooks. | |
7907 | @item pentium4, pentium4m | |
7908 | Intel Pentium4 CPU with MMX, SSE and SSE2 instruction set support. | |
7909 | @item prescott | |
7910 | Improved version of Intel Pentium4 CPU with MMX, SSE, SSE2 and SSE3 instruction | |
7911 | set support. | |
7912 | @item nocona | |
7913 | Improved version of Intel Pentium4 CPU with 64-bit extensions, MMX, SSE, | |
7914 | SSE2 and SSE3 instruction set support. | |
7915 | @item k6 | |
7916 | AMD K6 CPU with MMX instruction set support. | |
7917 | @item k6-2, k6-3 | |
7918 | Improved versions of AMD K6 CPU with MMX and 3dNOW! instruction set support. | |
7919 | @item athlon, athlon-tbird | |
7920 | AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and SSE prefetch instructions | |
7921 | support. | |
7922 | @item athlon-4, athlon-xp, athlon-mp | |
7923 | Improved AMD Athlon CPU with MMX, 3dNOW!, enhanced 3dNOW! and full SSE | |
7924 | instruction set support. | |
7925 | @item k8, opteron, athlon64, athlon-fx | |
7926 | AMD K8 core based CPUs with x86-64 instruction set support. (This supersets | |
7927 | MMX, SSE, SSE2, 3dNOW!, enhanced 3dNOW! and 64-bit instruction set extensions.) | |
7928 | @item winchip-c6 | |
7929 | IDT Winchip C6 CPU, dealt in same way as i486 with additional MMX instruction | |
7930 | set support. | |
7931 | @item winchip2 | |
7932 | IDT Winchip2 CPU, dealt in same way as i486 with additional MMX and 3dNOW! | |
7933 | instruction set support. | |
7934 | @item c3 | |
7935 | Via C3 CPU with MMX and 3dNOW! instruction set support. (No scheduling is | |
7936 | implemented for this chip.) | |
7937 | @item c3-2 | |
7938 | Via C3-2 CPU with MMX and SSE instruction set support. (No scheduling is | |
7939 | implemented for this chip.) | |
7940 | @end table | |
7941 | ||
7942 | While picking a specific @var{cpu-type} will schedule things appropriately | |
7943 | for that particular chip, the compiler will not generate any code that | |
7944 | does not run on the i386 without the @option{-march=@var{cpu-type}} option | |
7945 | being used. | |
7946 | ||
7947 | @item -march=@var{cpu-type} | |
7948 | @opindex march | |
7949 | Generate instructions for the machine type @var{cpu-type}. The choices | |
7950 | for @var{cpu-type} are the same as for @option{-mtune}. Moreover, | |
7951 | specifying @option{-march=@var{cpu-type}} implies @option{-mtune=@var{cpu-type}}. | |
74291a4b | 7952 | |
39bc1876 NS |
7953 | @item -mcpu=@var{cpu-type} |
7954 | @opindex mcpu | |
7955 | A deprecated synonym for @option{-mtune}. | |
3398f47f | 7956 | |
39bc1876 NS |
7957 | @item -m386 |
7958 | @itemx -m486 | |
7959 | @itemx -mpentium | |
7960 | @itemx -mpentiumpro | |
7961 | @opindex m386 | |
7962 | @opindex m486 | |
7963 | @opindex mpentium | |
7964 | @opindex mpentiumpro | |
7965 | These options are synonyms for @option{-mtune=i386}, @option{-mtune=i486}, | |
7966 | @option{-mtune=pentium}, and @option{-mtune=pentiumpro} respectively. | |
7967 | These synonyms are deprecated. | |
74291a4b | 7968 | |
39bc1876 NS |
7969 | @item -mfpmath=@var{unit} |
7970 | @opindex march | |
7971 | Generate floating point arithmetics for selected unit @var{unit}. The choices | |
7972 | for @var{unit} are: | |
2d2a50c3 | 7973 | |
39bc1876 NS |
7974 | @table @samp |
7975 | @item 387 | |
7976 | Use the standard 387 floating point coprocessor present majority of chips and | |
7977 | emulated otherwise. Code compiled with this option will run almost everywhere. | |
7978 | The temporary results are computed in 80bit precision instead of precision | |
7979 | specified by the type resulting in slightly different results compared to most | |
7980 | of other chips. See @option{-ffloat-store} for more detailed description. | |
74291a4b | 7981 | |
39bc1876 | 7982 | This is the default choice for i386 compiler. |
74291a4b | 7983 | |
39bc1876 NS |
7984 | @item sse |
7985 | Use scalar floating point instructions present in the SSE instruction set. | |
7986 | This instruction set is supported by Pentium3 and newer chips, in the AMD line | |
7987 | by Athlon-4, Athlon-xp and Athlon-mp chips. The earlier version of SSE | |
7988 | instruction set supports only single precision arithmetics, thus the double and | |
7989 | extended precision arithmetics is still done using 387. Later version, present | |
7990 | only in Pentium4 and the future AMD x86-64 chips supports double precision | |
7991 | arithmetics too. | |
a27fb29b | 7992 | |
39bc1876 NS |
7993 | For i387 you need to use @option{-march=@var{cpu-type}}, @option{-msse} or |
7994 | @option{-msse2} switches to enable SSE extensions and make this option | |
7995 | effective. For x86-64 compiler, these extensions are enabled by default. | |
3398f47f | 7996 | |
39bc1876 NS |
7997 | The resulting code should be considerably faster in the majority of cases and avoid |
7998 | the numerical instability problems of 387 code, but may break some existing | |
7999 | code that expects temporaries to be 80bit. | |
cd3f11a6 | 8000 | |
39bc1876 | 8001 | This is the default choice for the x86-64 compiler. |
74291a4b | 8002 | |
39bc1876 NS |
8003 | @item sse,387 |
8004 | Attempt to utilize both instruction sets at once. This effectively double the | |
8005 | amount of available registers and on chips with separate execution units for | |
8006 | 387 and SSE the execution resources too. Use this option with care, as it is | |
8007 | still experimental, because the GCC register allocator does not model separate | |
8008 | functional units well resulting in instable performance. | |
8009 | @end table | |
ee692410 | 8010 | |
39bc1876 NS |
8011 | @item -masm=@var{dialect} |
8012 | @opindex masm=@var{dialect} | |
8013 | Output asm instructions using selected @var{dialect}. Supported choices are | |
8014 | @samp{intel} or @samp{att} (the default one). | |
ee692410 | 8015 | |
39bc1876 NS |
8016 | @item -mieee-fp |
8017 | @itemx -mno-ieee-fp | |
8018 | @opindex mieee-fp | |
8019 | @opindex mno-ieee-fp | |
8020 | Control whether or not the compiler uses IEEE floating point | |
8021 | comparisons. These handle correctly the case where the result of a | |
8022 | comparison is unordered. | |
ee692410 | 8023 | |
39bc1876 NS |
8024 | @item -msoft-float |
8025 | @opindex msoft-float | |
8026 | Generate output containing library calls for floating point. | |
8027 | @strong{Warning:} the requisite libraries are not part of GCC@. | |
8028 | Normally the facilities of the machine's usual C compiler are used, but | |
8029 | this can't be done directly in cross-compilation. You must make your | |
8030 | own arrangements to provide suitable library functions for | |
8031 | cross-compilation. | |
ee692410 | 8032 | |
39bc1876 NS |
8033 | On machines where a function returns floating point results in the 80387 |
8034 | register stack, some floating point opcodes may be emitted even if | |
8035 | @option{-msoft-float} is used. | |
ee692410 | 8036 | |
39bc1876 NS |
8037 | @item -mno-fp-ret-in-387 |
8038 | @opindex mno-fp-ret-in-387 | |
8039 | Do not use the FPU registers for return values of functions. | |
ee692410 | 8040 | |
39bc1876 NS |
8041 | The usual calling convention has functions return values of types |
8042 | @code{float} and @code{double} in an FPU register, even if there | |
8043 | is no FPU@. The idea is that the operating system should emulate | |
8044 | an FPU@. | |
5a4b3afd | 8045 | |
39bc1876 NS |
8046 | The option @option{-mno-fp-ret-in-387} causes such values to be returned |
8047 | in ordinary CPU registers instead. | |
5a4b3afd | 8048 | |
39bc1876 NS |
8049 | @item -mno-fancy-math-387 |
8050 | @opindex mno-fancy-math-387 | |
8051 | Some 387 emulators do not support the @code{sin}, @code{cos} and | |
8052 | @code{sqrt} instructions for the 387. Specify this option to avoid | |
8053 | generating those instructions. This option is the default on FreeBSD, | |
8054 | OpenBSD and NetBSD@. This option is overridden when @option{-march} | |
8055 | indicates that the target cpu will always have an FPU and so the | |
8056 | instruction will not need emulation. As of revision 2.6.1, these | |
8057 | instructions are not generated unless you also use the | |
8058 | @option{-funsafe-math-optimizations} switch. | |
5a4b3afd | 8059 | |
39bc1876 NS |
8060 | @item -malign-double |
8061 | @itemx -mno-align-double | |
8062 | @opindex malign-double | |
8063 | @opindex mno-align-double | |
8064 | Control whether GCC aligns @code{double}, @code{long double}, and | |
8065 | @code{long long} variables on a two word boundary or a one word | |
8066 | boundary. Aligning @code{double} variables on a two word boundary will | |
8067 | produce code that runs somewhat faster on a @samp{Pentium} at the | |
8068 | expense of more memory. | |
5a4b3afd | 8069 | |
39bc1876 NS |
8070 | @strong{Warning:} if you use the @option{-malign-double} switch, |
8071 | structures containing the above types will be aligned differently than | |
8072 | the published application binary interface specifications for the 386 | |
8073 | and will not be binary compatible with structures in code compiled | |
8074 | without that switch. | |
5a4b3afd | 8075 | |
39bc1876 NS |
8076 | @item -m96bit-long-double |
8077 | @itemx -m128bit-long-double | |
8078 | @opindex m96bit-long-double | |
8079 | @opindex m128bit-long-double | |
8080 | These switches control the size of @code{long double} type. The i386 | |
8081 | application binary interface specifies the size to be 96 bits, | |
8082 | so @option{-m96bit-long-double} is the default in 32 bit mode. | |
5a4b3afd | 8083 | |
39bc1876 NS |
8084 | Modern architectures (Pentium and newer) would prefer @code{long double} |
8085 | to be aligned to an 8 or 16 byte boundary. In arrays or structures | |
8086 | conforming to the ABI, this would not be possible. So specifying a | |
8087 | @option{-m128bit-long-double} will align @code{long double} | |
8088 | to a 16 byte boundary by padding the @code{long double} with an additional | |
8089 | 32 bit zero. | |
5a4b3afd | 8090 | |
39bc1876 NS |
8091 | In the x86-64 compiler, @option{-m128bit-long-double} is the default choice as |
8092 | its ABI specifies that @code{long double} is to be aligned on 16 byte boundary. | |
5a4b3afd | 8093 | |
39bc1876 NS |
8094 | Notice that neither of these options enable any extra precision over the x87 |
8095 | standard of 80 bits for a @code{long double}. | |
5a4b3afd | 8096 | |
39bc1876 NS |
8097 | @strong{Warning:} if you override the default value for your target ABI, the |
8098 | structures and arrays containing @code{long double} variables will change | |
8099 | their size as well as function calling convention for function taking | |
8100 | @code{long double} will be modified. Hence they will not be binary | |
8101 | compatible with arrays or structures in code compiled without that switch. | |
5a4b3afd | 8102 | |
5a4b3afd | 8103 | |
39bc1876 NS |
8104 | @item -msvr3-shlib |
8105 | @itemx -mno-svr3-shlib | |
8106 | @opindex msvr3-shlib | |
8107 | @opindex mno-svr3-shlib | |
8108 | Control whether GCC places uninitialized local variables into the | |
8109 | @code{bss} or @code{data} segments. @option{-msvr3-shlib} places them | |
8110 | into @code{bss}. These options are meaningful only on System V Release 3. | |
5a4b3afd | 8111 | |
39bc1876 NS |
8112 | @item -mrtd |
8113 | @opindex mrtd | |
8114 | Use a different function-calling convention, in which functions that | |
8115 | take a fixed number of arguments return with the @code{ret} @var{num} | |
8116 | instruction, which pops their arguments while returning. This saves one | |
8117 | instruction in the caller since there is no need to pop the arguments | |
8118 | there. | |
5a4b3afd | 8119 | |
39bc1876 NS |
8120 | You can specify that an individual function is called with this calling |
8121 | sequence with the function attribute @samp{stdcall}. You can also | |
8122 | override the @option{-mrtd} option by using the function attribute | |
8123 | @samp{cdecl}. @xref{Function Attributes}. | |
74291a4b | 8124 | |
39bc1876 NS |
8125 | @strong{Warning:} this calling convention is incompatible with the one |
8126 | normally used on Unix, so you cannot use it if you need to call | |
8127 | libraries compiled with the Unix compiler. | |
74291a4b | 8128 | |
39bc1876 NS |
8129 | Also, you must provide function prototypes for all functions that |
8130 | take variable numbers of arguments (including @code{printf}); | |
8131 | otherwise incorrect code will be generated for calls to those | |
8132 | functions. | |
02f52e19 | 8133 | |
39bc1876 NS |
8134 | In addition, seriously incorrect code will result if you call a |
8135 | function with too many arguments. (Normally, extra arguments are | |
8136 | harmlessly ignored.) | |
1cf959cb | 8137 | |
39bc1876 NS |
8138 | @item -mregparm=@var{num} |
8139 | @opindex mregparm | |
8140 | Control how many registers are used to pass integer arguments. By | |
8141 | default, no registers are used to pass arguments, and at most 3 | |
8142 | registers can be used. You can control this behavior for a specific | |
8143 | function by using the function attribute @samp{regparm}. | |
8144 | @xref{Function Attributes}. | |
1cf959cb | 8145 | |
39bc1876 NS |
8146 | @strong{Warning:} if you use this switch, and |
8147 | @var{num} is nonzero, then you must build all modules with the same | |
8148 | value, including any libraries. This includes the system libraries and | |
8149 | startup modules. | |
5a4b3afd | 8150 | |
39bc1876 NS |
8151 | @item -mpreferred-stack-boundary=@var{num} |
8152 | @opindex mpreferred-stack-boundary | |
8153 | Attempt to keep the stack boundary aligned to a 2 raised to @var{num} | |
8154 | byte boundary. If @option{-mpreferred-stack-boundary} is not specified, | |
8155 | the default is 4 (16 bytes or 128 bits), except when optimizing for code | |
8156 | size (@option{-Os}), in which case the default is the minimum correct | |
8157 | alignment (4 bytes for x86, and 8 bytes for x86-64). | |
5a4b3afd | 8158 | |
39bc1876 NS |
8159 | On Pentium and PentiumPro, @code{double} and @code{long double} values |
8160 | should be aligned to an 8 byte boundary (see @option{-malign-double}) or | |
8161 | suffer significant run time performance penalties. On Pentium III, the | |
8162 | Streaming SIMD Extension (SSE) data type @code{__m128} suffers similar | |
8163 | penalties if it is not 16 byte aligned. | |
5a4b3afd | 8164 | |
39bc1876 NS |
8165 | To ensure proper alignment of this values on the stack, the stack boundary |
8166 | must be as aligned as that required by any value stored on the stack. | |
8167 | Further, every function must be generated such that it keeps the stack | |
8168 | aligned. Thus calling a function compiled with a higher preferred | |
8169 | stack boundary from a function compiled with a lower preferred stack | |
8170 | boundary will most likely misalign the stack. It is recommended that | |
8171 | libraries that use callbacks always use the default setting. | |
5a4b3afd | 8172 | |
39bc1876 NS |
8173 | This extra alignment does consume extra stack space, and generally |
8174 | increases code size. Code that is sensitive to stack space usage, such | |
8175 | as embedded systems and operating system kernels, may want to reduce the | |
8176 | preferred alignment to @option{-mpreferred-stack-boundary=2}. | |
5a4b3afd | 8177 | |
39bc1876 NS |
8178 | @item -mmmx |
8179 | @itemx -mno-mmx | |
8180 | @item -msse | |
8181 | @itemx -mno-sse | |
8182 | @item -msse2 | |
8183 | @itemx -mno-sse2 | |
8184 | @item -msse3 | |
8185 | @itemx -mno-sse3 | |
8186 | @item -m3dnow | |
8187 | @itemx -mno-3dnow | |
8188 | @opindex mmmx | |
8189 | @opindex mno-mmx | |
8190 | @opindex msse | |
8191 | @opindex mno-sse | |
8192 | @opindex m3dnow | |
8193 | @opindex mno-3dnow | |
8194 | These switches enable or disable the use of built-in functions that allow | |
8195 | direct access to the MMX, SSE, SSE2, SSE3 and 3Dnow extensions of the | |
8196 | instruction set. | |
74291a4b | 8197 | |
39bc1876 NS |
8198 | @xref{X86 Built-in Functions}, for details of the functions enabled |
8199 | and disabled by these switches. | |
74291a4b | 8200 | |
39bc1876 NS |
8201 | To have SSE/SSE2 instructions generated automatically from floating-point |
8202 | code, see @option{-mfpmath=sse}. | |
74291a4b | 8203 | |
39bc1876 NS |
8204 | @item -mpush-args |
8205 | @itemx -mno-push-args | |
8206 | @opindex mpush-args | |
8207 | @opindex mno-push-args | |
8208 | Use PUSH operations to store outgoing parameters. This method is shorter | |
8209 | and usually equally fast as method using SUB/MOV operations and is enabled | |
8210 | by default. In some cases disabling it may improve performance because of | |
8211 | improved scheduling and reduced dependencies. | |
74291a4b | 8212 | |
39bc1876 NS |
8213 | @item -maccumulate-outgoing-args |
8214 | @opindex maccumulate-outgoing-args | |
8215 | If enabled, the maximum amount of space required for outgoing arguments will be | |
8216 | computed in the function prologue. This is faster on most modern CPUs | |
8217 | because of reduced dependencies, improved scheduling and reduced stack usage | |
8218 | when preferred stack boundary is not equal to 2. The drawback is a notable | |
8219 | increase in code size. This switch implies @option{-mno-push-args}. | |
63357d93 | 8220 | |
39bc1876 NS |
8221 | @item -mthreads |
8222 | @opindex mthreads | |
8223 | Support thread-safe exception handling on @samp{Mingw32}. Code that relies | |
8224 | on thread-safe exception handling must compile and link all code with the | |
8225 | @option{-mthreads} option. When compiling, @option{-mthreads} defines | |
8226 | @option{-D_MT}; when linking, it links in a special thread helper library | |
8227 | @option{-lmingwthrd} which cleans up per thread exception handling data. | |
5ef1a99d | 8228 | |
39bc1876 NS |
8229 | @item -mno-align-stringops |
8230 | @opindex mno-align-stringops | |
8231 | Do not align destination of inlined string operations. This switch reduces | |
8232 | code size and improves performance in case the destination is already aligned, | |
8233 | but GCC doesn't know about it. | |
46490403 | 8234 | |
39bc1876 NS |
8235 | @item -minline-all-stringops |
8236 | @opindex minline-all-stringops | |
8237 | By default GCC inlines string operations only when destination is known to be | |
8238 | aligned at least to 4 byte boundary. This enables more inlining, increase code | |
8239 | size, but may improve performance of code that depends on fast memcpy, strlen | |
8240 | and memset for short lengths. | |
c235ddf2 | 8241 | |
39bc1876 NS |
8242 | @item -momit-leaf-frame-pointer |
8243 | @opindex momit-leaf-frame-pointer | |
8244 | Don't keep the frame pointer in a register for leaf functions. This | |
8245 | avoids the instructions to save, set up and restore frame pointers and | |
8246 | makes an extra register available in leaf functions. The option | |
8247 | @option{-fomit-frame-pointer} removes the frame pointer for all functions | |
8248 | which might make debugging harder. | |
c235ddf2 | 8249 | |
39bc1876 NS |
8250 | @item -mtls-direct-seg-refs |
8251 | @itemx -mno-tls-direct-seg-refs | |
8252 | @opindex mtls-direct-seg-refs | |
8253 | Controls whether TLS variables may be accessed with offsets from the | |
8254 | TLS segment register (@code{%gs} for 32-bit, @code{%fs} for 64-bit), | |
8255 | or whether the thread base pointer must be added. Whether or not this | |
8256 | is legal depends on the operating system, and whether it maps the | |
8257 | segment to cover the entire TLS area. | |
beadc644 | 8258 | |
39bc1876 NS |
8259 | For systems that use GNU libc, the default is on. |
8260 | @end table | |
af34e51e | 8261 | |
39bc1876 NS |
8262 | These @samp{-m} switches are supported in addition to the above |
8263 | on AMD x86-64 processors in 64-bit environments. | |
50d32cf6 | 8264 | |
39bc1876 NS |
8265 | @table @gcctabopt |
8266 | @item -m32 | |
8267 | @itemx -m64 | |
8268 | @opindex m32 | |
8269 | @opindex m64 | |
8270 | Generate code for a 32-bit or 64-bit environment. | |
8271 | The 32-bit environment sets int, long and pointer to 32 bits and | |
8272 | generates code that runs on any i386 system. | |
8273 | The 64-bit environment sets int to 32 bits and long and pointer | |
8274 | to 64 bits and generates code for AMD's x86-64 architecture. | |
50d32cf6 | 8275 | |
39bc1876 NS |
8276 | @item -mno-red-zone |
8277 | @opindex no-red-zone | |
8278 | Do not use a so called red zone for x86-64 code. The red zone is mandated | |
8279 | by the x86-64 ABI, it is a 128-byte area beyond the location of the | |
8280 | stack pointer that will not be modified by signal or interrupt handlers | |
8281 | and therefore can be used for temporary data without adjusting the stack | |
8282 | pointer. The flag @option{-mno-red-zone} disables this red zone. | |
dc884a86 | 8283 | |
39bc1876 NS |
8284 | @item -mcmodel=small |
8285 | @opindex mcmodel=small | |
8286 | Generate code for the small code model: the program and its symbols must | |
8287 | be linked in the lower 2 GB of the address space. Pointers are 64 bits. | |
8288 | Programs can be statically or dynamically linked. This is the default | |
8289 | code model. | |
dc884a86 | 8290 | |
39bc1876 NS |
8291 | @item -mcmodel=kernel |
8292 | @opindex mcmodel=kernel | |
8293 | Generate code for the kernel code model. The kernel runs in the | |
8294 | negative 2 GB of the address space. | |
8295 | This model has to be used for Linux kernel code. | |
8296 | ||
8297 | @item -mcmodel=medium | |
8298 | @opindex mcmodel=medium | |
8299 | Generate code for the medium model: The program is linked in the lower 2 | |
8300 | GB of the address space but symbols can be located anywhere in the | |
8301 | address space. Programs can be statically or dynamically linked, but | |
8302 | building of shared libraries are not supported with the medium model. | |
8303 | ||
8304 | @item -mcmodel=large | |
8305 | @opindex mcmodel=large | |
8306 | Generate code for the large model: This model makes no assumptions | |
8307 | about addresses and sizes of sections. Currently GCC does not implement | |
8308 | this model. | |
74291a4b MM |
8309 | @end table |
8310 | ||
39bc1876 NS |
8311 | @node IA-64 Options |
8312 | @subsection IA-64 Options | |
8313 | @cindex IA-64 Options | |
74291a4b | 8314 | |
39bc1876 | 8315 | These are the @samp{-m} options defined for the Intel IA-64 architecture. |
74291a4b | 8316 | |
2642624b | 8317 | @table @gcctabopt |
39bc1876 NS |
8318 | @item -mbig-endian |
8319 | @opindex mbig-endian | |
8320 | Generate code for a big endian target. This is the default for HP-UX@. | |
6f670fde | 8321 | |
39bc1876 NS |
8322 | @item -mlittle-endian |
8323 | @opindex mlittle-endian | |
8324 | Generate code for a little endian target. This is the default for AIX5 | |
8325 | and GNU/Linux. | |
a9f3e1a4 | 8326 | |
39bc1876 NS |
8327 | @item -mgnu-as |
8328 | @itemx -mno-gnu-as | |
8329 | @opindex mgnu-as | |
8330 | @opindex mno-gnu-as | |
8331 | Generate (or don't) code for the GNU assembler. This is the default. | |
8332 | @c Also, this is the default if the configure option @option{--with-gnu-as} | |
8333 | @c is used. | |
9d913bbf | 8334 | |
39bc1876 NS |
8335 | @item -mgnu-ld |
8336 | @itemx -mno-gnu-ld | |
8337 | @opindex mgnu-ld | |
8338 | @opindex mno-gnu-ld | |
8339 | Generate (or don't) code for the GNU linker. This is the default. | |
8340 | @c Also, this is the default if the configure option @option{--with-gnu-ld} | |
8341 | @c is used. | |
a9f3e1a4 | 8342 | |
39bc1876 NS |
8343 | @item -mno-pic |
8344 | @opindex mno-pic | |
8345 | Generate code that does not use a global pointer register. The result | |
8346 | is not position independent code, and violates the IA-64 ABI@. | |
74291a4b | 8347 | |
39bc1876 NS |
8348 | @item -mvolatile-asm-stop |
8349 | @itemx -mno-volatile-asm-stop | |
8350 | @opindex mvolatile-asm-stop | |
8351 | @opindex mno-volatile-asm-stop | |
8352 | Generate (or don't) a stop bit immediately before and after volatile asm | |
8353 | statements. | |
965f5423 | 8354 | |
39bc1876 NS |
8355 | @item -mb-step |
8356 | @opindex mb-step | |
8357 | Generate code that works around Itanium B step errata. | |
965f5423 | 8358 | |
39bc1876 NS |
8359 | @item -mregister-names |
8360 | @itemx -mno-register-names | |
8361 | @opindex mregister-names | |
8362 | @opindex mno-register-names | |
8363 | Generate (or don't) @samp{in}, @samp{loc}, and @samp{out} register names for | |
8364 | the stacked registers. This may make assembler output more readable. | |
965f5423 | 8365 | |
39bc1876 NS |
8366 | @item -mno-sdata |
8367 | @itemx -msdata | |
8368 | @opindex mno-sdata | |
8369 | @opindex msdata | |
8370 | Disable (or enable) optimizations that use the small data section. This may | |
8371 | be useful for working around optimizer bugs. | |
8372 | ||
8373 | @item -mconstant-gp | |
8374 | @opindex mconstant-gp | |
8375 | Generate code that uses a single constant global pointer value. This is | |
8376 | useful when compiling kernel code. | |
8377 | ||
8378 | @item -mauto-pic | |
8379 | @opindex mauto-pic | |
8380 | Generate code that is self-relocatable. This implies @option{-mconstant-gp}. | |
8381 | This is useful when compiling firmware code. | |
8382 | ||
8383 | @item -minline-float-divide-min-latency | |
8384 | @opindex minline-float-divide-min-latency | |
8385 | Generate code for inline divides of floating point values | |
8386 | using the minimum latency algorithm. | |
965f5423 | 8387 | |
39bc1876 NS |
8388 | @item -minline-float-divide-max-throughput |
8389 | @opindex minline-float-divide-max-throughput | |
8390 | Generate code for inline divides of floating point values | |
8391 | using the maximum throughput algorithm. | |
965f5423 | 8392 | |
39bc1876 NS |
8393 | @item -minline-int-divide-min-latency |
8394 | @opindex minline-int-divide-min-latency | |
8395 | Generate code for inline divides of integer values | |
8396 | using the minimum latency algorithm. | |
965f5423 | 8397 | |
39bc1876 NS |
8398 | @item -minline-int-divide-max-throughput |
8399 | @opindex minline-int-divide-max-throughput | |
8400 | Generate code for inline divides of integer values | |
8401 | using the maximum throughput algorithm. | |
965f5423 | 8402 | |
39bc1876 NS |
8403 | @item -mno-dwarf2-asm |
8404 | @itemx -mdwarf2-asm | |
8405 | @opindex mno-dwarf2-asm | |
8406 | @opindex mdwarf2-asm | |
8407 | Don't (or do) generate assembler code for the DWARF2 line number debugging | |
8408 | info. This may be useful when not using the GNU assembler. | |
965f5423 | 8409 | |
39bc1876 NS |
8410 | @item -mfixed-range=@var{register-range} |
8411 | @opindex mfixed-range | |
8412 | Generate code treating the given register range as fixed registers. | |
8413 | A fixed register is one that the register allocator can not use. This is | |
8414 | useful when compiling kernel code. A register range is specified as | |
8415 | two registers separated by a dash. Multiple register ranges can be | |
8416 | specified separated by a comma. | |
04e149ab | 8417 | |
39bc1876 NS |
8418 | @item -mearly-stop-bits |
8419 | @itemx -mno-early-stop-bits | |
8420 | @opindex mearly-stop-bits | |
8421 | @opindex mno-early-stop-bits | |
8422 | Allow stop bits to be placed earlier than immediately preceding the | |
8423 | instruction that triggered the stop bit. This can improve instruction | |
8424 | scheduling, but does not always do so. | |
8425 | @end table | |
74291a4b | 8426 | |
39bc1876 NS |
8427 | @node M32R/D Options |
8428 | @subsection M32R/D Options | |
8429 | @cindex M32R/D options | |
74291a4b | 8430 | |
39bc1876 | 8431 | These @option{-m} options are defined for Renesas M32R/D architectures: |
74291a4b | 8432 | |
39bc1876 NS |
8433 | @table @gcctabopt |
8434 | @item -m32r2 | |
8435 | @opindex m32r2 | |
8436 | Generate code for the M32R/2@. | |
74291a4b | 8437 | |
39bc1876 NS |
8438 | @item -m32rx |
8439 | @opindex m32rx | |
8440 | Generate code for the M32R/X@. | |
74291a4b | 8441 | |
39bc1876 NS |
8442 | @item -m32r |
8443 | @opindex m32r | |
8444 | Generate code for the M32R@. This is the default. | |
74291a4b | 8445 | |
39bc1876 NS |
8446 | @item -mmodel=small |
8447 | @opindex mmodel=small | |
8448 | Assume all objects live in the lower 16MB of memory (so that their addresses | |
8449 | can be loaded with the @code{ld24} instruction), and assume all subroutines | |
8450 | are reachable with the @code{bl} instruction. | |
8451 | This is the default. | |
74291a4b | 8452 | |
39bc1876 NS |
8453 | The addressability of a particular object can be set with the |
8454 | @code{model} attribute. | |
74291a4b | 8455 | |
39bc1876 NS |
8456 | @item -mmodel=medium |
8457 | @opindex mmodel=medium | |
8458 | Assume objects may be anywhere in the 32-bit address space (the compiler | |
8459 | will generate @code{seth/add3} instructions to load their addresses), and | |
8460 | assume all subroutines are reachable with the @code{bl} instruction. | |
194734e9 | 8461 | |
39bc1876 NS |
8462 | @item -mmodel=large |
8463 | @opindex mmodel=large | |
8464 | Assume objects may be anywhere in the 32-bit address space (the compiler | |
8465 | will generate @code{seth/add3} instructions to load their addresses), and | |
8466 | assume subroutines may not be reachable with the @code{bl} instruction | |
8467 | (the compiler will generate the much slower @code{seth/add3/jl} | |
8468 | instruction sequence). | |
a5f3dd66 | 8469 | |
39bc1876 NS |
8470 | @item -msdata=none |
8471 | @opindex msdata=none | |
8472 | Disable use of the small data area. Variables will be put into | |
8473 | one of @samp{.data}, @samp{bss}, or @samp{.rodata} (unless the | |
8474 | @code{section} attribute has been specified). | |
8475 | This is the default. | |
a5f3dd66 | 8476 | |
39bc1876 NS |
8477 | The small data area consists of sections @samp{.sdata} and @samp{.sbss}. |
8478 | Objects may be explicitly put in the small data area with the | |
8479 | @code{section} attribute using one of these sections. | |
daf2f129 | 8480 | |
39bc1876 NS |
8481 | @item -msdata=sdata |
8482 | @opindex msdata=sdata | |
8483 | Put small global and static data in the small data area, but do not | |
8484 | generate special code to reference them. | |
2b589241 | 8485 | |
39bc1876 NS |
8486 | @item -msdata=use |
8487 | @opindex msdata=use | |
8488 | Put small global and static data in the small data area, and generate | |
8489 | special instructions to reference them. | |
2b589241 | 8490 | |
39bc1876 NS |
8491 | @item -G @var{num} |
8492 | @opindex G | |
8493 | @cindex smaller data references | |
8494 | Put global and static objects less than or equal to @var{num} bytes | |
8495 | into the small data or bss sections instead of the normal data or bss | |
8496 | sections. The default value of @var{num} is 8. | |
8497 | The @option{-msdata} option must be set to one of @samp{sdata} or @samp{use} | |
8498 | for this option to have any effect. | |
74291a4b | 8499 | |
39bc1876 NS |
8500 | All modules should be compiled with the same @option{-G @var{num}} value. |
8501 | Compiling with different values of @var{num} may or may not work; if it | |
8502 | doesn't the linker will give an error message---incorrect code will not be | |
8503 | generated. | |
74291a4b | 8504 | |
39bc1876 NS |
8505 | @item -mdebug |
8506 | @opindex mdebug | |
8507 | Makes the M32R specific code in the compiler display some statistics | |
8508 | that might help in debugging programs. | |
74291a4b | 8509 | |
39bc1876 NS |
8510 | @item -malign-loops |
8511 | @opindex malign-loops | |
8512 | Align all loops to a 32-byte boundary. | |
74291a4b | 8513 | |
39bc1876 NS |
8514 | @item -mno-align-loops |
8515 | @opindex mno-align-loops | |
8516 | Do not enforce a 32-byte alignment for loops. This is the default. | |
74291a4b | 8517 | |
39bc1876 NS |
8518 | @item -missue-rate=@var{number} |
8519 | @opindex missue-rate=@var{number} | |
8520 | Issue @var{number} instructions per cycle. @var{number} can only be 1 | |
8521 | or 2. | |
74291a4b | 8522 | |
39bc1876 NS |
8523 | @item -mbranch-cost=@var{number} |
8524 | @opindex mbranch-cost=@var{number} | |
8525 | @var{number} can only be 1 or 2. If it is 1 then branches will be | |
8526 | preferred over conditional code, if it is 2, then the opposite will | |
8527 | apply. | |
74291a4b | 8528 | |
39bc1876 NS |
8529 | @item -mflush-trap=@var{number} |
8530 | @opindex mflush-trap=@var{number} | |
8531 | Specifies the trap number to use to flush the cache. The default is | |
8532 | 12. Valid numbers are between 0 and 15 inclusive. | |
74291a4b | 8533 | |
39bc1876 NS |
8534 | @item -mno-flush-trap |
8535 | @opindex mno-flush-trap | |
8536 | Specifies that the cache cannot be flushed by using a trap. | |
74291a4b | 8537 | |
39bc1876 NS |
8538 | @item -mflush-func=@var{name} |
8539 | @opindex mflush-func=@var{name} | |
8540 | Specifies the name of the operating system function to call to flush | |
8541 | the cache. The default is @emph{_flush_cache}, but a function call | |
8542 | will only be used if a trap is not available. | |
3af4bd89 | 8543 | |
39bc1876 NS |
8544 | @item -mno-flush-func |
8545 | @opindex mno-flush-func | |
8546 | Indicates that there is no OS function for flushing the cache. | |
3af4bd89 | 8547 | |
39bc1876 | 8548 | @end table |
3af4bd89 | 8549 | |
39bc1876 NS |
8550 | @node M680x0 Options |
8551 | @subsection M680x0 Options | |
8552 | @cindex M680x0 options | |
f22a97d2 | 8553 | |
39bc1876 NS |
8554 | These are the @samp{-m} options defined for the 68000 series. The default |
8555 | values for these options depends on which style of 68000 was selected when | |
8556 | the compiler was configured; the defaults for the most common choices are | |
8557 | given below. | |
1255c85c | 8558 | |
39bc1876 NS |
8559 | @table @gcctabopt |
8560 | @item -m68000 | |
8561 | @itemx -mc68000 | |
8562 | @opindex m68000 | |
8563 | @opindex mc68000 | |
8564 | Generate output for a 68000. This is the default | |
8565 | when the compiler is configured for 68000-based systems. | |
1255c85c | 8566 | |
39bc1876 NS |
8567 | Use this option for microcontrollers with a 68000 or EC000 core, |
8568 | including the 68008, 68302, 68306, 68307, 68322, 68328 and 68356. | |
7eafc329 | 8569 | |
39bc1876 NS |
8570 | @item -m68020 |
8571 | @itemx -mc68020 | |
8572 | @opindex m68020 | |
8573 | @opindex mc68020 | |
8574 | Generate output for a 68020. This is the default | |
8575 | when the compiler is configured for 68020-based systems. | |
f73ad30e | 8576 | |
39bc1876 NS |
8577 | @item -m68881 |
8578 | @opindex m68881 | |
8579 | Generate output containing 68881 instructions for floating point. | |
8580 | This is the default for most 68020 systems unless @option{--nfp} was | |
8581 | specified when the compiler was configured. | |
f73ad30e | 8582 | |
39bc1876 NS |
8583 | @item -m68030 |
8584 | @opindex m68030 | |
8585 | Generate output for a 68030. This is the default when the compiler is | |
8586 | configured for 68030-based systems. | |
79f05c19 | 8587 | |
39bc1876 NS |
8588 | @item -m68040 |
8589 | @opindex m68040 | |
8590 | Generate output for a 68040. This is the default when the compiler is | |
8591 | configured for 68040-based systems. | |
79f05c19 | 8592 | |
39bc1876 NS |
8593 | This option inhibits the use of 68881/68882 instructions that have to be |
8594 | emulated by software on the 68040. Use this option if your 68040 does not | |
8595 | have code to emulate those instructions. | |
762e166b | 8596 | |
39bc1876 NS |
8597 | @item -m68060 |
8598 | @opindex m68060 | |
8599 | Generate output for a 68060. This is the default when the compiler is | |
8600 | configured for 68060-based systems. | |
74dc3e94 | 8601 | |
39bc1876 NS |
8602 | This option inhibits the use of 68020 and 68881/68882 instructions that |
8603 | have to be emulated by software on the 68060. Use this option if your 68060 | |
8604 | does not have code to emulate those instructions. | |
74dc3e94 | 8605 | |
39bc1876 NS |
8606 | @item -mcpu32 |
8607 | @opindex mcpu32 | |
8608 | Generate output for a CPU32. This is the default | |
8609 | when the compiler is configured for CPU32-based systems. | |
3af4bd89 | 8610 | |
39bc1876 NS |
8611 | Use this option for microcontrollers with a |
8612 | CPU32 or CPU32+ core, including the 68330, 68331, 68332, 68333, 68334, | |
8613 | 68336, 68340, 68341, 68349 and 68360. | |
14f73b5a | 8614 | |
39bc1876 NS |
8615 | @item -m5200 |
8616 | @opindex m5200 | |
8617 | Generate output for a 520X ``coldfire'' family cpu. This is the default | |
8618 | when the compiler is configured for 520X-based systems. | |
14f73b5a | 8619 | |
39bc1876 NS |
8620 | Use this option for microcontroller with a 5200 core, including |
8621 | the MCF5202, MCF5203, MCF5204 and MCF5202. | |
a7701995 | 8622 | |
a7701995 | 8623 | |
39bc1876 NS |
8624 | @item -m68020-40 |
8625 | @opindex m68020-40 | |
8626 | Generate output for a 68040, without using any of the new instructions. | |
8627 | This results in code which can run relatively efficiently on either a | |
8628 | 68020/68881 or a 68030 or a 68040. The generated code does use the | |
8629 | 68881 instructions that are emulated on the 68040. | |
a7701995 | 8630 | |
39bc1876 NS |
8631 | @item -m68020-60 |
8632 | @opindex m68020-60 | |
8633 | Generate output for a 68060, without using any of the new instructions. | |
8634 | This results in code which can run relatively efficiently on either a | |
8635 | 68020/68881 or a 68030 or a 68040. The generated code does use the | |
8636 | 68881 instructions that are emulated on the 68060. | |
a7701995 | 8637 | |
39bc1876 NS |
8638 | @item -msoft-float |
8639 | @opindex msoft-float | |
8640 | Generate output containing library calls for floating point. | |
8641 | @strong{Warning:} the requisite libraries are not available for all m68k | |
8642 | targets. Normally the facilities of the machine's usual C compiler are | |
8643 | used, but this can't be done directly in cross-compilation. You must | |
8644 | make your own arrangements to provide suitable library functions for | |
8645 | cross-compilation. The embedded targets @samp{m68k-*-aout} and | |
8646 | @samp{m68k-*-coff} do provide software floating point support. | |
14f73b5a | 8647 | |
39bc1876 NS |
8648 | @item -mshort |
8649 | @opindex mshort | |
8650 | Consider type @code{int} to be 16 bits wide, like @code{short int}. | |
8651 | Additionally, parameters passed on the stack are also aligned to a | |
8652 | 16-bit boundary even on targets whose API mandates promotion to 32-bit. | |
74291a4b | 8653 | |
39bc1876 NS |
8654 | @item -mnobitfield |
8655 | @opindex mnobitfield | |
8656 | Do not use the bit-field instructions. The @option{-m68000}, @option{-mcpu32} | |
8657 | and @option{-m5200} options imply @w{@option{-mnobitfield}}. | |
74291a4b | 8658 | |
39bc1876 NS |
8659 | @item -mbitfield |
8660 | @opindex mbitfield | |
8661 | Do use the bit-field instructions. The @option{-m68020} option implies | |
8662 | @option{-mbitfield}. This is the default if you use a configuration | |
8663 | designed for a 68020. | |
8664 | ||
8665 | @item -mrtd | |
8666 | @opindex mrtd | |
8667 | Use a different function-calling convention, in which functions | |
8668 | that take a fixed number of arguments return with the @code{rtd} | |
8669 | instruction, which pops their arguments while returning. This | |
8670 | saves one instruction in the caller since there is no need to pop | |
8671 | the arguments there. | |
ea3bfbfe | 8672 | |
39bc1876 NS |
8673 | This calling convention is incompatible with the one normally |
8674 | used on Unix, so you cannot use it if you need to call libraries | |
8675 | compiled with the Unix compiler. | |
74291a4b | 8676 | |
39bc1876 NS |
8677 | Also, you must provide function prototypes for all functions that |
8678 | take variable numbers of arguments (including @code{printf}); | |
8679 | otherwise incorrect code will be generated for calls to those | |
8680 | functions. | |
861bb6c1 | 8681 | |
39bc1876 NS |
8682 | In addition, seriously incorrect code will result if you call a |
8683 | function with too many arguments. (Normally, extra arguments are | |
8684 | harmlessly ignored.) | |
74291a4b | 8685 | |
39bc1876 NS |
8686 | The @code{rtd} instruction is supported by the 68010, 68020, 68030, |
8687 | 68040, 68060 and CPU32 processors, but not by the 68000 or 5200. | |
74291a4b | 8688 | |
39bc1876 NS |
8689 | @item -malign-int |
8690 | @itemx -mno-align-int | |
8691 | @opindex malign-int | |
8692 | @opindex mno-align-int | |
8693 | Control whether GCC aligns @code{int}, @code{long}, @code{long long}, | |
8694 | @code{float}, @code{double}, and @code{long double} variables on a 32-bit | |
8695 | boundary (@option{-malign-int}) or a 16-bit boundary (@option{-mno-align-int}). | |
8696 | Aligning variables on 32-bit boundaries produces code that runs somewhat | |
8697 | faster on processors with 32-bit busses at the expense of more memory. | |
74291a4b | 8698 | |
39bc1876 NS |
8699 | @strong{Warning:} if you use the @option{-malign-int} switch, GCC will |
8700 | align structures containing the above types differently than | |
8701 | most published application binary interface specifications for the m68k. | |
74291a4b | 8702 | |
39bc1876 NS |
8703 | @item -mpcrel |
8704 | @opindex mpcrel | |
8705 | Use the pc-relative addressing mode of the 68000 directly, instead of | |
8706 | using a global offset table. At present, this option implies @option{-fpic}, | |
8707 | allowing at most a 16-bit offset for pc-relative addressing. @option{-fPIC} is | |
8708 | not presently supported with @option{-mpcrel}, though this could be supported for | |
8709 | 68020 and higher processors. | |
74291a4b | 8710 | |
39bc1876 NS |
8711 | @item -mno-strict-align |
8712 | @itemx -mstrict-align | |
8713 | @opindex mno-strict-align | |
8714 | @opindex mstrict-align | |
8715 | Do not (do) assume that unaligned memory references will be handled by | |
8716 | the system. | |
74291a4b | 8717 | |
39bc1876 NS |
8718 | @item -msep-data |
8719 | Generate code that allows the data segment to be located in a different | |
8720 | area of memory from the text segment. This allows for execute in place in | |
8721 | an environment without virtual memory management. This option implies -fPIC. | |
74291a4b | 8722 | |
39bc1876 NS |
8723 | @item -mno-sep-data |
8724 | Generate code that assumes that the data segment follows the text segment. | |
8725 | This is the default. | |
74291a4b | 8726 | |
39bc1876 NS |
8727 | @item -mid-shared-library |
8728 | Generate code that supports shared libraries via the library ID method. | |
8729 | This allows for execute in place and shared libraries in an environment | |
8730 | without virtual memory management. This option implies -fPIC. | |
74291a4b | 8731 | |
39bc1876 NS |
8732 | @item -mno-id-shared-library |
8733 | Generate code that doesn't assume ID based shared libraries are being used. | |
8734 | This is the default. | |
74291a4b | 8735 | |
39bc1876 NS |
8736 | @item -mshared-library-id=n |
8737 | Specified the identification number of the ID based shared library being | |
8738 | compiled. Specifying a value of 0 will generate more compact code, specifying | |
8739 | other values will force the allocation of that number to the current | |
8740 | library but is no more space or time efficient than omitting this option. | |
74291a4b | 8741 | |
39bc1876 | 8742 | @end table |
74291a4b | 8743 | |
39bc1876 NS |
8744 | @node M68hc1x Options |
8745 | @subsection M68hc1x Options | |
8746 | @cindex M68hc1x options | |
74291a4b | 8747 | |
39bc1876 NS |
8748 | These are the @samp{-m} options defined for the 68hc11 and 68hc12 |
8749 | microcontrollers. The default values for these options depends on | |
8750 | which style of microcontroller was selected when the compiler was configured; | |
8751 | the defaults for the most common choices are given below. | |
c219e1da | 8752 | |
39bc1876 NS |
8753 | @table @gcctabopt |
8754 | @item -m6811 | |
8755 | @itemx -m68hc11 | |
8756 | @opindex m6811 | |
8757 | @opindex m68hc11 | |
8758 | Generate output for a 68HC11. This is the default | |
8759 | when the compiler is configured for 68HC11-based systems. | |
c5d3d49b | 8760 | |
39bc1876 NS |
8761 | @item -m6812 |
8762 | @itemx -m68hc12 | |
8763 | @opindex m6812 | |
8764 | @opindex m68hc12 | |
8765 | Generate output for a 68HC12. This is the default | |
8766 | when the compiler is configured for 68HC12-based systems. | |
c5d3d49b | 8767 | |
39bc1876 NS |
8768 | @item -m68S12 |
8769 | @itemx -m68hcs12 | |
8770 | @opindex m68S12 | |
8771 | @opindex m68hcs12 | |
8772 | Generate output for a 68HCS12. | |
c5d3d49b | 8773 | |
39bc1876 NS |
8774 | @item -mauto-incdec |
8775 | @opindex mauto-incdec | |
8776 | Enable the use of 68HC12 pre and post auto-increment and auto-decrement | |
8777 | addressing modes. | |
34208acf | 8778 | |
39bc1876 NS |
8779 | @item -minmax |
8780 | @itemx -nominmax | |
8781 | @opindex minmax | |
8782 | @opindex mnominmax | |
8783 | Enable the use of 68HC12 min and max instructions. | |
34208acf | 8784 | |
39bc1876 NS |
8785 | @item -mlong-calls |
8786 | @itemx -mno-long-calls | |
8787 | @opindex mlong-calls | |
8788 | @opindex mno-long-calls | |
8789 | Treat all calls as being far away (near). If calls are assumed to be | |
8790 | far away, the compiler will use the @code{call} instruction to | |
8791 | call a function and the @code{rtc} instruction for returning. | |
34208acf | 8792 | |
39bc1876 NS |
8793 | @item -mshort |
8794 | @opindex mshort | |
8795 | Consider type @code{int} to be 16 bits wide, like @code{short int}. | |
34208acf | 8796 | |
39bc1876 NS |
8797 | @item -msoft-reg-count=@var{count} |
8798 | @opindex msoft-reg-count | |
8799 | Specify the number of pseudo-soft registers which are used for the | |
8800 | code generation. The maximum number is 32. Using more pseudo-soft | |
8801 | register may or may not result in better code depending on the program. | |
8802 | The default is 4 for 68HC11 and 2 for 68HC12. | |
34208acf | 8803 | |
39bc1876 | 8804 | @end table |
34208acf | 8805 | |
39bc1876 NS |
8806 | @node MCore Options |
8807 | @subsection MCore Options | |
8808 | @cindex MCore options | |
34208acf | 8809 | |
39bc1876 NS |
8810 | These are the @samp{-m} options defined for the Motorola M*Core |
8811 | processors. | |
34208acf | 8812 | |
39bc1876 | 8813 | @table @gcctabopt |
34208acf | 8814 | |
39bc1876 NS |
8815 | @item -mhardlit |
8816 | @itemx -mno-hardlit | |
8817 | @opindex mhardlit | |
8818 | @opindex mno-hardlit | |
8819 | Inline constants into the code stream if it can be done in two | |
8820 | instructions or less. | |
34208acf | 8821 | |
39bc1876 NS |
8822 | @item -mdiv |
8823 | @itemx -mno-div | |
8824 | @opindex mdiv | |
8825 | @opindex mno-div | |
8826 | Use the divide instruction. (Enabled by default). | |
a02aa5b0 | 8827 | |
39bc1876 NS |
8828 | @item -mrelax-immediate |
8829 | @itemx -mno-relax-immediate | |
8830 | @opindex mrelax-immediate | |
8831 | @opindex mno-relax-immediate | |
8832 | Allow arbitrary sized immediates in bit operations. | |
a02aa5b0 | 8833 | |
39bc1876 NS |
8834 | @item -mwide-bitfields |
8835 | @itemx -mno-wide-bitfields | |
8836 | @opindex mwide-bitfields | |
8837 | @opindex mno-wide-bitfields | |
8838 | Always treat bit-fields as int-sized. | |
a02aa5b0 | 8839 | |
39bc1876 NS |
8840 | @item -m4byte-functions |
8841 | @itemx -mno-4byte-functions | |
8842 | @opindex m4byte-functions | |
8843 | @opindex mno-4byte-functions | |
8844 | Force all functions to be aligned to a four byte boundary. | |
a02aa5b0 | 8845 | |
39bc1876 NS |
8846 | @item -mcallgraph-data |
8847 | @itemx -mno-callgraph-data | |
8848 | @opindex mcallgraph-data | |
8849 | @opindex mno-callgraph-data | |
8850 | Emit callgraph information. | |
f401d0f5 | 8851 | |
39bc1876 NS |
8852 | @item -mslow-bytes |
8853 | @itemx -mno-slow-bytes | |
8854 | @opindex mslow-bytes | |
8855 | @opindex mno-slow-bytes | |
8856 | Prefer word access when reading byte quantities. | |
f401d0f5 | 8857 | |
39bc1876 NS |
8858 | @item -mlittle-endian |
8859 | @itemx -mbig-endian | |
8860 | @opindex mlittle-endian | |
8861 | @opindex mbig-endian | |
8862 | Generate code for a little endian target. | |
f401d0f5 | 8863 | |
39bc1876 NS |
8864 | @item -m210 |
8865 | @itemx -m340 | |
8866 | @opindex m210 | |
8867 | @opindex m340 | |
8868 | Generate code for the 210 processor. | |
74291a4b MM |
8869 | @end table |
8870 | ||
39bc1876 NS |
8871 | @node MIPS Options |
8872 | @subsection MIPS Options | |
8873 | @cindex MIPS options | |
74291a4b | 8874 | |
2642624b | 8875 | @table @gcctabopt |
74291a4b | 8876 | |
39bc1876 NS |
8877 | @item -EB |
8878 | @opindex EB | |
8879 | Generate big-endian code. | |
74291a4b | 8880 | |
39bc1876 NS |
8881 | @item -EL |
8882 | @opindex EL | |
8883 | Generate little-endian code. This is the default for @samp{mips*el-*-*} | |
8884 | configurations. | |
74291a4b | 8885 | |
39bc1876 NS |
8886 | @item -march=@var{arch} |
8887 | @opindex march | |
8888 | Generate code that will run on @var{arch}, which can be the name of a | |
8889 | generic MIPS ISA, or the name of a particular processor. | |
8890 | The ISA names are: | |
8891 | @samp{mips1}, @samp{mips2}, @samp{mips3}, @samp{mips4}, | |
8892 | @samp{mips32}, @samp{mips32r2}, and @samp{mips64}. | |
8893 | The processor names are: | |
8894 | @samp{4kc}, @samp{4kp}, @samp{5kc}, @samp{20kc}, | |
8895 | @samp{m4k}, | |
8896 | @samp{r2000}, @samp{r3000}, @samp{r3900}, @samp{r4000}, @samp{r4400}, | |
8897 | @samp{r4600}, @samp{r4650}, @samp{r6000}, @samp{r8000}, @samp{rm7000}, | |
8898 | @samp{rm9000}, | |
8899 | @samp{orion}, | |
8900 | @samp{sb1}, | |
8901 | @samp{vr4100}, @samp{vr4111}, @samp{vr4120}, @samp{vr4130}, @samp{vr4300}, | |
8902 | @samp{vr5000}, @samp{vr5400} and @samp{vr5500}. | |
8903 | The special value @samp{from-abi} selects the | |
8904 | most compatible architecture for the selected ABI (that is, | |
8905 | @samp{mips1} for 32-bit ABIs and @samp{mips3} for 64-bit ABIs)@. | |
74291a4b | 8906 | |
39bc1876 NS |
8907 | In processor names, a final @samp{000} can be abbreviated as @samp{k} |
8908 | (for example, @samp{-march=r2k}). Prefixes are optional, and | |
8909 | @samp{vr} may be written @samp{r}. | |
74291a4b | 8910 | |
39bc1876 NS |
8911 | GCC defines two macros based on the value of this option. The first |
8912 | is @samp{_MIPS_ARCH}, which gives the name of target architecture, as | |
8913 | a string. The second has the form @samp{_MIPS_ARCH_@var{foo}}, | |
8914 | where @var{foo} is the capitalized value of @samp{_MIPS_ARCH}@. | |
8915 | For example, @samp{-march=r2000} will set @samp{_MIPS_ARCH} | |
8916 | to @samp{"r2000"} and define the macro @samp{_MIPS_ARCH_R2000}. | |
74291a4b | 8917 | |
39bc1876 NS |
8918 | Note that the @samp{_MIPS_ARCH} macro uses the processor names given |
8919 | above. In other words, it will have the full prefix and will not | |
8920 | abbreviate @samp{000} as @samp{k}. In the case of @samp{from-abi}, | |
8921 | the macro names the resolved architecture (either @samp{"mips1"} or | |
8922 | @samp{"mips3"}). It names the default architecture when no | |
8923 | @option{-march} option is given. | |
74291a4b | 8924 | |
39bc1876 NS |
8925 | @item -mtune=@var{arch} |
8926 | @opindex mtune | |
8927 | Optimize for @var{arch}. Among other things, this option controls | |
8928 | the way instructions are scheduled, and the perceived cost of arithmetic | |
8929 | operations. The list of @var{arch} values is the same as for | |
8930 | @option{-march}. | |
74291a4b | 8931 | |
39bc1876 NS |
8932 | When this option is not used, GCC will optimize for the processor |
8933 | specified by @option{-march}. By using @option{-march} and | |
8934 | @option{-mtune} together, it is possible to generate code that will | |
8935 | run on a family of processors, but optimize the code for one | |
8936 | particular member of that family. | |
74291a4b | 8937 | |
39bc1876 NS |
8938 | @samp{-mtune} defines the macros @samp{_MIPS_TUNE} and |
8939 | @samp{_MIPS_TUNE_@var{foo}}, which work in the same way as the | |
8940 | @samp{-march} ones described above. | |
74291a4b | 8941 | |
39bc1876 NS |
8942 | @item -mips1 |
8943 | @opindex mips1 | |
8944 | Equivalent to @samp{-march=mips1}. | |
74291a4b | 8945 | |
39bc1876 NS |
8946 | @item -mips2 |
8947 | @opindex mips2 | |
8948 | Equivalent to @samp{-march=mips2}. | |
74291a4b | 8949 | |
39bc1876 NS |
8950 | @item -mips3 |
8951 | @opindex mips3 | |
8952 | Equivalent to @samp{-march=mips3}. | |
74291a4b | 8953 | |
39bc1876 NS |
8954 | @item -mips4 |
8955 | @opindex mips4 | |
8956 | Equivalent to @samp{-march=mips4}. | |
8957 | ||
8958 | @item -mips32 | |
8959 | @opindex mips32 | |
8960 | Equivalent to @samp{-march=mips32}. | |
74291a4b | 8961 | |
39bc1876 NS |
8962 | @item -mips32r2 |
8963 | @opindex mips32r2 | |
8964 | Equivalent to @samp{-march=mips32r2}. | |
74291a4b | 8965 | |
39bc1876 NS |
8966 | @item -mips64 |
8967 | @opindex mips64 | |
8968 | Equivalent to @samp{-march=mips64}. | |
74291a4b | 8969 | |
39bc1876 NS |
8970 | @item -mips16 |
8971 | @itemx -mno-mips16 | |
8972 | @opindex mips16 | |
8973 | @opindex mno-mips16 | |
8974 | Use (do not use) the MIPS16 ISA. | |
74291a4b | 8975 | |
39bc1876 NS |
8976 | @item -mabi=32 |
8977 | @itemx -mabi=o64 | |
8978 | @itemx -mabi=n32 | |
8979 | @itemx -mabi=64 | |
8980 | @itemx -mabi=eabi | |
8981 | @opindex mabi=32 | |
8982 | @opindex mabi=o64 | |
8983 | @opindex mabi=n32 | |
8984 | @opindex mabi=64 | |
8985 | @opindex mabi=eabi | |
8986 | Generate code for the given ABI@. | |
74291a4b | 8987 | |
39bc1876 NS |
8988 | Note that the EABI has a 32-bit and a 64-bit variant. GCC normally |
8989 | generates 64-bit code when you select a 64-bit architecture, but you | |
8990 | can use @option{-mgp32} to get 32-bit code instead. | |
74291a4b | 8991 | |
39bc1876 NS |
8992 | For information about the O64 ABI, see |
8993 | @w{@uref{http://gcc.gnu.org/projects/mipso64-abi.html}}. | |
74291a4b | 8994 | |
39bc1876 NS |
8995 | @item -mabicalls |
8996 | @itemx -mno-abicalls | |
8997 | @opindex mabicalls | |
8998 | @opindex mno-abicalls | |
8999 | Generate (do not generate) SVR4-style position-independent code. | |
9000 | @option{-mabicalls} is the default for SVR4-based systems. | |
74291a4b | 9001 | |
39bc1876 NS |
9002 | @item -mxgot |
9003 | @itemx -mno-xgot | |
9004 | @opindex mxgot | |
9005 | @opindex mno-xgot | |
9006 | Lift (do not lift) the usual restrictions on the size of the global | |
9007 | offset table. | |
74291a4b | 9008 | |
39bc1876 NS |
9009 | GCC normally uses a single instruction to load values from the GOT. |
9010 | While this is relatively efficient, it will only work if the GOT | |
9011 | is smaller than about 64k. Anything larger will cause the linker | |
9012 | to report an error such as: | |
74291a4b | 9013 | |
39bc1876 NS |
9014 | @cindex relocation truncated to fit (MIPS) |
9015 | @smallexample | |
9016 | relocation truncated to fit: R_MIPS_GOT16 foobar | |
9017 | @end smallexample | |
74291a4b | 9018 | |
39bc1876 NS |
9019 | If this happens, you should recompile your code with @option{-mxgot}. |
9020 | It should then work with very large GOTs, although it will also be | |
9021 | less efficient, since it will take three instructions to fetch the | |
9022 | value of a global symbol. | |
956d6950 | 9023 | |
39bc1876 NS |
9024 | Note that some linkers can create multiple GOTs. If you have such a |
9025 | linker, you should only need to use @option{-mxgot} when a single object | |
9026 | file accesses more than 64k's worth of GOT entries. Very few do. | |
956d6950 | 9027 | |
39bc1876 NS |
9028 | These options have no effect unless GCC is generating position |
9029 | independent code. | |
956d6950 | 9030 | |
39bc1876 NS |
9031 | @item -mgp32 |
9032 | @opindex mgp32 | |
9033 | Assume that general-purpose registers are 32 bits wide. | |
58605ba0 | 9034 | |
39bc1876 NS |
9035 | @item -mgp64 |
9036 | @opindex mgp64 | |
9037 | Assume that general-purpose registers are 64 bits wide. | |
58605ba0 | 9038 | |
39bc1876 NS |
9039 | @item -mfp32 |
9040 | @opindex mfp32 | |
9041 | Assume that floating-point registers are 32 bits wide. | |
58605ba0 | 9042 | |
39bc1876 NS |
9043 | @item -mfp64 |
9044 | @opindex mfp64 | |
9045 | Assume that floating-point registers are 64 bits wide. | |
58605ba0 | 9046 | |
39bc1876 NS |
9047 | @item -mhard-float |
9048 | @opindex mhard-float | |
9049 | Use floating-point coprocessor instructions. | |
58605ba0 | 9050 | |
39bc1876 NS |
9051 | @item -msoft-float |
9052 | @opindex msoft-float | |
9053 | Do not use floating-point coprocessor instructions. Implement | |
9054 | floating-point calculations using library calls instead. | |
3094247f | 9055 | |
39bc1876 NS |
9056 | @item -msingle-float |
9057 | @opindex msingle-float | |
9058 | Assume that the floating-point coprocessor only supports single-precision | |
9059 | operations. | |
3094247f | 9060 | |
39bc1876 NS |
9061 | @itemx -mdouble-float |
9062 | @opindex mdouble-float | |
9063 | Assume that the floating-point coprocessor supports double-precision | |
9064 | operations. This is the default. | |
956d6950 | 9065 | |
39bc1876 NS |
9066 | @item -mint64 |
9067 | @opindex mint64 | |
9068 | Force @code{int} and @code{long} types to be 64 bits wide. See | |
9069 | @option{-mlong32} for an explanation of the default and the way | |
9070 | that the pointer size is determined. | |
956d6950 | 9071 | |
39bc1876 NS |
9072 | @item -mlong64 |
9073 | @opindex mlong64 | |
9074 | Force @code{long} types to be 64 bits wide. See @option{-mlong32} for | |
9075 | an explanation of the default and the way that the pointer size is | |
9076 | determined. | |
956d6950 | 9077 | |
39bc1876 NS |
9078 | @item -mlong32 |
9079 | @opindex mlong32 | |
9080 | Force @code{long}, @code{int}, and pointer types to be 32 bits wide. | |
956d6950 | 9081 | |
39bc1876 NS |
9082 | The default size of @code{int}s, @code{long}s and pointers depends on |
9083 | the ABI@. All the supported ABIs use 32-bit @code{int}s. The n64 ABI | |
9084 | uses 64-bit @code{long}s, as does the 64-bit EABI; the others use | |
9085 | 32-bit @code{long}s. Pointers are the same size as @code{long}s, | |
9086 | or the same size as integer registers, whichever is smaller. | |
956d6950 | 9087 | |
39bc1876 NS |
9088 | @item -G @var{num} |
9089 | @opindex G | |
9090 | @cindex smaller data references (MIPS) | |
9091 | @cindex gp-relative references (MIPS) | |
9092 | Put global and static items less than or equal to @var{num} bytes into | |
9093 | the small data or bss section instead of the normal data or bss section. | |
9094 | This allows the data to be accessed using a single instruction. | |
9095 | ||
9096 | All modules should be compiled with the same @option{-G @var{num}} | |
9097 | value. | |
956d6950 | 9098 | |
39bc1876 NS |
9099 | @item -membedded-data |
9100 | @itemx -mno-embedded-data | |
9101 | @opindex membedded-data | |
9102 | @opindex mno-embedded-data | |
9103 | Allocate variables to the read-only data section first if possible, then | |
9104 | next in the small data section if possible, otherwise in data. This gives | |
9105 | slightly slower code than the default, but reduces the amount of RAM required | |
9106 | when executing, and thus may be preferred for some embedded systems. | |
58605ba0 | 9107 | |
39bc1876 NS |
9108 | @item -muninit-const-in-rodata |
9109 | @itemx -mno-uninit-const-in-rodata | |
9110 | @opindex muninit-const-in-rodata | |
9111 | @opindex mno-uninit-const-in-rodata | |
9112 | Put uninitialized @code{const} variables in the read-only data section. | |
9113 | This option is only meaningful in conjunction with @option{-membedded-data}. | |
4f69985c | 9114 | |
39bc1876 NS |
9115 | @item -msplit-addresses |
9116 | @itemx -mno-split-addresses | |
9117 | @opindex msplit-addresses | |
9118 | @opindex mno-split-addresses | |
9119 | Enable (disable) use of the @code{%hi()} and @code{%lo()} assembler | |
9120 | relocation operators. This option has been superceded by | |
9121 | @option{-mexplicit-relocs} but is retained for backwards compatibility. | |
58605ba0 | 9122 | |
39bc1876 NS |
9123 | @item -mexplicit-relocs |
9124 | @itemx -mno-explicit-relocs | |
9125 | @opindex mexplicit-relocs | |
9126 | @opindex mno-explicit-relocs | |
9127 | Use (do not use) assembler relocation operators when dealing with symbolic | |
9128 | addresses. The alternative, selected by @option{-mno-explicit-relocs}, | |
9129 | is to use assembler macros instead. | |
4f69985c | 9130 | |
39bc1876 NS |
9131 | @option{-mexplicit-relocs} is usually the default if GCC was configured |
9132 | to use an assembler that supports relocation operators. However, the | |
9133 | combination of @option{-mabicalls} and @option{-fno-unit-at-a-time} | |
9134 | implies @option{-mno-explicit-relocs} unless explicitly overridden. | |
9135 | This is because, when generating abicalls, the choice of relocation | |
9136 | depends on whether a symbol is local or global. In some rare cases, | |
9137 | GCC will not be able to decide this until the whole compilation unit | |
9138 | has been read. | |
4f69985c | 9139 | |
39bc1876 NS |
9140 | @item -mrnames |
9141 | @itemx -mno-rnames | |
9142 | @opindex mrnames | |
9143 | @opindex mno-rnames | |
9144 | Generate (do not generate) code that refers to registers using their | |
9145 | software names. The default is @option{-mno-rnames}, which tells GCC | |
9146 | to use hardware names like @samp{$4} instead of software names like | |
9147 | @samp{a0}. The only assembler known to support @option{-rnames} is | |
9148 | the Algorithmics assembler. | |
4f69985c | 9149 | |
39bc1876 NS |
9150 | @item -mcheck-zero-division |
9151 | @itemx -mno-check-zero-division | |
9152 | @opindex mcheck-zero-division | |
9153 | @opindex mno-check-zero-division | |
9154 | Trap (do not trap) on integer division by zero. The default is | |
9155 | @option{-mcheck-zero-division}. | |
4f69985c | 9156 | |
39bc1876 NS |
9157 | @item -mmemcpy |
9158 | @itemx -mno-memcpy | |
9159 | @opindex mmemcpy | |
9160 | @opindex mno-memcpy | |
9161 | Force (do not force) the use of @code{memcpy()} for non-trivial block | |
9162 | moves. The default is @option{-mno-memcpy}, which allows GCC to inline | |
9163 | most constant-sized copies. | |
74291a4b | 9164 | |
39bc1876 NS |
9165 | @item -mlong-calls |
9166 | @itemx -mno-long-calls | |
9167 | @opindex mlong-calls | |
9168 | @opindex mno-long-calls | |
9169 | Disable (do not disable) use of the @code{jal} instruction. Calling | |
9170 | functions using @code{jal} is more efficient but requires the caller | |
9171 | and callee to be in the same 256 megabyte segment. | |
d7c23cdc | 9172 | |
39bc1876 NS |
9173 | This option has no effect on abicalls code. The default is |
9174 | @option{-mno-long-calls}. | |
d7c23cdc | 9175 | |
39bc1876 NS |
9176 | @item -mmad |
9177 | @itemx -mno-mad | |
9178 | @opindex mmad | |
9179 | @opindex mno-mad | |
9180 | Enable (disable) use of the @code{mad}, @code{madu} and @code{mul} | |
9181 | instructions, as provided by the R4650 ISA. | |
d7c23cdc | 9182 | |
39bc1876 NS |
9183 | @item -mfused-madd |
9184 | @itemx -mno-fused-madd | |
9185 | @opindex mfused-madd | |
9186 | @opindex mno-fused-madd | |
9187 | Enable (disable) use of the floating point multiply-accumulate | |
9188 | instructions, when they are available. The default is | |
9189 | @option{-mfused-madd}. | |
74291a4b | 9190 | |
39bc1876 NS |
9191 | When multiply-accumulate instructions are used, the intermediate |
9192 | product is calculated to infinite precision and is not subject to | |
9193 | the FCSR Flush to Zero bit. This may be undesirable in some | |
9194 | circumstances. | |
74291a4b | 9195 | |
39bc1876 NS |
9196 | @item -nocpp |
9197 | @opindex nocpp | |
9198 | Tell the MIPS assembler to not run its preprocessor over user | |
9199 | assembler files (with a @samp{.s} suffix) when assembling them. | |
74291a4b | 9200 | |
39bc1876 NS |
9201 | @item -mfix-r4000 |
9202 | @itemx -mno-fix-r4000 | |
9203 | @opindex mfix-r4000 | |
9204 | @opindex mno-fix-r4000 | |
9205 | Work around certain R4000 CPU errata: | |
9206 | @itemize @minus | |
9207 | @item | |
9208 | A double-word or a variable shift may give an incorrect result if executed | |
9209 | immediately after starting an integer division. | |
9210 | @item | |
9211 | A double-word or a variable shift may give an incorrect result if executed | |
9212 | while an integer multiplication is in progress. | |
9213 | @item | |
9214 | An integer division may give an incorrect result if started in a delay slot | |
9215 | of a taken branch or a jump. | |
9216 | @end itemize | |
74291a4b | 9217 | |
39bc1876 NS |
9218 | @item -mfix-r4400 |
9219 | @itemx -mno-fix-r4400 | |
9220 | @opindex mfix-r4400 | |
9221 | @opindex mno-fix-r4400 | |
9222 | Work around certain R4400 CPU errata: | |
9223 | @itemize @minus | |
9224 | @item | |
9225 | A double-word or a variable shift may give an incorrect result if executed | |
9226 | immediately after starting an integer division. | |
9227 | @end itemize | |
dcb9d1f0 | 9228 | |
39bc1876 NS |
9229 | @item -mfix-vr4120 |
9230 | @itemx -mno-fix-vr4120 | |
9231 | @opindex mfix-vr4120 | |
9232 | Work around certain VR4120 errata: | |
9233 | @itemize @minus | |
9234 | @item | |
9235 | @code{dmultu} does not always produce the correct result. | |
9236 | @item | |
9237 | @code{div} and @code{ddiv} do not always produce the correct result if one | |
9238 | of the operands is negative. | |
9239 | @end itemize | |
9240 | The workarounds for the division errata rely on special functions in | |
9241 | @file{libgcc.a}. At present, these functions are only provided by | |
9242 | the @code{mips64vr*-elf} configurations. | |
39ba95b5 | 9243 | |
39bc1876 NS |
9244 | Other VR4120 errata require a nop to be inserted between certain pairs of |
9245 | instructions. These errata are handled by the assembler, not by GCC itself. | |
17f0f8fa | 9246 | |
39bc1876 NS |
9247 | @item -mfix-sb1 |
9248 | @itemx -mno-fix-sb1 | |
9249 | @opindex mfix-sb1 | |
9250 | Work around certain SB-1 CPU core errata. | |
9251 | (This flag currently works around the SB-1 revision 2 | |
9252 | ``F1'' and ``F2'' floating point errata.) | |
74291a4b | 9253 | |
39bc1876 NS |
9254 | @item -mflush-func=@var{func} |
9255 | @itemx -mno-flush-func | |
9256 | @opindex mflush-func | |
9257 | Specifies the function to call to flush the I and D caches, or to not | |
9258 | call any such function. If called, the function must take the same | |
9259 | arguments as the common @code{_flush_func()}, that is, the address of the | |
9260 | memory range for which the cache is being flushed, the size of the | |
9261 | memory range, and the number 3 (to flush both caches). The default | |
9262 | depends on the target GCC was configured for, but commonly is either | |
9263 | @samp{_flush_func} or @samp{__cpu_flush}. | |
74291a4b | 9264 | |
39bc1876 NS |
9265 | @item -mbranch-likely |
9266 | @itemx -mno-branch-likely | |
9267 | @opindex mbranch-likely | |
9268 | @opindex mno-branch-likely | |
9269 | Enable or disable use of Branch Likely instructions, regardless of the | |
9270 | default for the selected architecture. By default, Branch Likely | |
9271 | instructions may be generated if they are supported by the selected | |
9272 | architecture. An exception is for the MIPS32 and MIPS64 architectures | |
9273 | and processors which implement those architectures; for those, Branch | |
9274 | Likely instructions will not be generated by default because the MIPS32 | |
9275 | and MIPS64 architectures specifically deprecate their use. | |
74291a4b | 9276 | |
39bc1876 NS |
9277 | @item -mfp-exceptions |
9278 | @itemx -mno-fp-exceptions | |
9279 | @opindex mfp-exceptions | |
9280 | Specifies whether FP exceptions are enabled. This affects how we schedule | |
9281 | FP instructions for some processors. The default is that FP exceptions are | |
9282 | enabled. | |
74291a4b | 9283 | |
39bc1876 NS |
9284 | For instance, on the SB-1, if FP exceptions are disabled, and we are emitting |
9285 | 64-bit code, then we can use both FP pipes. Otherwise, we can only use one | |
9286 | FP pipe. | |
74291a4b | 9287 | |
39bc1876 NS |
9288 | @item -mvr4130-align |
9289 | @itemx -mno-vr4130-align | |
9290 | @opindex mvr4130-align | |
9291 | The VR4130 pipeline is two-way superscalar, but can only issue two | |
9292 | instructions together if the first one is 8-byte aligned. When this | |
9293 | option is enabled, GCC will align pairs of instructions that it | |
9294 | thinks should execute in parallel. | |
74291a4b | 9295 | |
39bc1876 NS |
9296 | This option only has an effect when optimizing for the VR4130. |
9297 | It normally makes code faster, but at the expense of making it bigger. | |
9298 | It is enabled by default at optimization level @option{-O3}. | |
9299 | @end table | |
3a8699c7 | 9300 | |
39bc1876 NS |
9301 | @node MMIX Options |
9302 | @subsection MMIX Options | |
9303 | @cindex MMIX Options | |
74291a4b | 9304 | |
39bc1876 | 9305 | These options are defined for the MMIX: |
74291a4b | 9306 | |
39bc1876 NS |
9307 | @table @gcctabopt |
9308 | @item -mlibfuncs | |
9309 | @itemx -mno-libfuncs | |
9310 | @opindex mlibfuncs | |
9311 | @opindex mno-libfuncs | |
9312 | Specify that intrinsic library functions are being compiled, passing all | |
9313 | values in registers, no matter the size. | |
3cadd778 | 9314 | |
39bc1876 NS |
9315 | @item -mepsilon |
9316 | @itemx -mno-epsilon | |
9317 | @opindex mepsilon | |
9318 | @opindex mno-epsilon | |
9319 | Generate floating-point comparison instructions that compare with respect | |
9320 | to the @code{rE} epsilon register. | |
3cadd778 | 9321 | |
39bc1876 NS |
9322 | @item -mabi=mmixware |
9323 | @itemx -mabi=gnu | |
9324 | @opindex mabi-mmixware | |
9325 | @opindex mabi=gnu | |
9326 | Generate code that passes function parameters and return values that (in | |
9327 | the called function) are seen as registers @code{$0} and up, as opposed to | |
9328 | the GNU ABI which uses global registers @code{$231} and up. | |
3cadd778 | 9329 | |
39bc1876 NS |
9330 | @item -mzero-extend |
9331 | @itemx -mno-zero-extend | |
9332 | @opindex mzero-extend | |
9333 | @opindex mno-zero-extend | |
9334 | When reading data from memory in sizes shorter than 64 bits, use (do not | |
9335 | use) zero-extending load instructions by default, rather than | |
9336 | sign-extending ones. | |
3cadd778 | 9337 | |
39bc1876 NS |
9338 | @item -mknuthdiv |
9339 | @itemx -mno-knuthdiv | |
9340 | @opindex mknuthdiv | |
9341 | @opindex mno-knuthdiv | |
9342 | Make the result of a division yielding a remainder have the same sign as | |
9343 | the divisor. With the default, @option{-mno-knuthdiv}, the sign of the | |
9344 | remainder follows the sign of the dividend. Both methods are | |
9345 | arithmetically valid, the latter being almost exclusively used. | |
74291a4b | 9346 | |
39bc1876 NS |
9347 | @item -mtoplevel-symbols |
9348 | @itemx -mno-toplevel-symbols | |
9349 | @opindex mtoplevel-symbols | |
9350 | @opindex mno-toplevel-symbols | |
9351 | Prepend (do not prepend) a @samp{:} to all global symbols, so the assembly | |
9352 | code can be used with the @code{PREFIX} assembly directive. | |
74291a4b | 9353 | |
39bc1876 NS |
9354 | @item -melf |
9355 | @opindex melf | |
9356 | Generate an executable in the ELF format, rather than the default | |
9357 | @samp{mmo} format used by the @command{mmix} simulator. | |
3d5a0820 | 9358 | |
39bc1876 NS |
9359 | @item -mbranch-predict |
9360 | @itemx -mno-branch-predict | |
9361 | @opindex mbranch-predict | |
9362 | @opindex mno-branch-predict | |
9363 | Use (do not use) the probable-branch instructions, when static branch | |
9364 | prediction indicates a probable branch. | |
3cadd778 | 9365 | |
39bc1876 NS |
9366 | @item -mbase-addresses |
9367 | @itemx -mno-base-addresses | |
9368 | @opindex mbase-addresses | |
9369 | @opindex mno-base-addresses | |
9370 | Generate (do not generate) code that uses @emph{base addresses}. Using a | |
9371 | base address automatically generates a request (handled by the assembler | |
9372 | and the linker) for a constant to be set up in a global register. The | |
9373 | register is used for one or more base address requests within the range 0 | |
9374 | to 255 from the value held in the register. The generally leads to short | |
9375 | and fast code, but the number of different data items that can be | |
9376 | addressed is limited. This means that a program that uses lots of static | |
9377 | data may require @option{-mno-base-addresses}. | |
3cadd778 | 9378 | |
39bc1876 NS |
9379 | @item -msingle-exit |
9380 | @itemx -mno-single-exit | |
9381 | @opindex msingle-exit | |
9382 | @opindex mno-single-exit | |
9383 | Force (do not force) generated code to have a single exit point in each | |
9384 | function. | |
9385 | @end table | |
3cadd778 | 9386 | |
39bc1876 NS |
9387 | @node MN10300 Options |
9388 | @subsection MN10300 Options | |
9389 | @cindex MN10300 options | |
3cadd778 | 9390 | |
39bc1876 | 9391 | These @option{-m} options are defined for Matsushita MN10300 architectures: |
3cadd778 | 9392 | |
39bc1876 NS |
9393 | @table @gcctabopt |
9394 | @item -mmult-bug | |
9395 | @opindex mmult-bug | |
9396 | Generate code to avoid bugs in the multiply instructions for the MN10300 | |
9397 | processors. This is the default. | |
c474f76b | 9398 | |
39bc1876 NS |
9399 | @item -mno-mult-bug |
9400 | @opindex mno-mult-bug | |
9401 | Do not generate code to avoid bugs in the multiply instructions for the | |
9402 | MN10300 processors. | |
3cadd778 | 9403 | |
39bc1876 NS |
9404 | @item -mam33 |
9405 | @opindex mam33 | |
9406 | Generate code which uses features specific to the AM33 processor. | |
3cadd778 | 9407 | |
39bc1876 NS |
9408 | @item -mno-am33 |
9409 | @opindex mno-am33 | |
9410 | Do not generate code which uses features specific to the AM33 processor. This | |
9411 | is the default. | |
1a66cd67 | 9412 | |
39bc1876 NS |
9413 | @item -mno-crt0 |
9414 | @opindex mno-crt0 | |
9415 | Do not link in the C run-time initialization object file. | |
93ca1662 | 9416 | |
39bc1876 NS |
9417 | @item -mrelax |
9418 | @opindex mrelax | |
9419 | Indicate to the linker that it should perform a relaxation optimization pass | |
9420 | to shorten branches, calls and absolute memory addresses. This option only | |
9421 | has an effect when used on the command line for the final link step. | |
9422 | ||
9423 | This option makes symbolic debugging impossible. | |
74291a4b MM |
9424 | @end table |
9425 | ||
39bc1876 NS |
9426 | @node NS32K Options |
9427 | @subsection NS32K Options | |
9428 | @cindex NS32K options | |
74291a4b | 9429 | |
39bc1876 NS |
9430 | These are the @samp{-m} options defined for the 32000 series. The default |
9431 | values for these options depends on which style of 32000 was selected when | |
9432 | the compiler was configured; the defaults for the most common choices are | |
9433 | given below. | |
74291a4b | 9434 | |
2642624b | 9435 | @table @gcctabopt |
39bc1876 NS |
9436 | @item -m32032 |
9437 | @itemx -m32032 | |
9438 | @opindex m32032 | |
9439 | @opindex m32032 | |
9440 | Generate output for a 32032. This is the default | |
9441 | when the compiler is configured for 32032 and 32016 based systems. | |
74291a4b | 9442 | |
39bc1876 NS |
9443 | @item -m32332 |
9444 | @itemx -m32332 | |
9445 | @opindex m32332 | |
9446 | @opindex m32332 | |
9447 | Generate output for a 32332. This is the default | |
9448 | when the compiler is configured for 32332-based systems. | |
74291a4b | 9449 | |
39bc1876 NS |
9450 | @item -m32532 |
9451 | @itemx -m32532 | |
9452 | @opindex m32532 | |
9453 | @opindex m32532 | |
9454 | Generate output for a 32532. This is the default | |
9455 | when the compiler is configured for 32532-based systems. | |
74291a4b | 9456 | |
39bc1876 NS |
9457 | @item -m32081 |
9458 | @opindex m32081 | |
9459 | Generate output containing 32081 instructions for floating point. | |
9460 | This is the default for all systems. | |
74291a4b | 9461 | |
39bc1876 NS |
9462 | @item -m32381 |
9463 | @opindex m32381 | |
9464 | Generate output containing 32381 instructions for floating point. This | |
9465 | also implies @option{-m32081}. The 32381 is only compatible with the 32332 | |
9466 | and 32532 cpus. This is the default for the pc532-netbsd configuration. | |
9467 | ||
9468 | @item -mmulti-add | |
9469 | @opindex mmulti-add | |
9470 | Try and generate multiply-add floating point instructions @code{polyF} | |
9471 | and @code{dotF}. This option is only available if the @option{-m32381} | |
9472 | option is in effect. Using these instructions requires changes to | |
9473 | register allocation which generally has a negative impact on | |
9474 | performance. This option should only be enabled when compiling code | |
9475 | particularly likely to make heavy use of multiply-add instructions. | |
9476 | ||
9477 | @item -mnomulti-add | |
9478 | @opindex mnomulti-add | |
9479 | Do not try and generate multiply-add floating point instructions | |
9480 | @code{polyF} and @code{dotF}. This is the default on all platforms. | |
74291a4b | 9481 | |
39bc1876 NS |
9482 | @item -msoft-float |
9483 | @opindex msoft-float | |
9484 | Generate output containing library calls for floating point. | |
9485 | @strong{Warning:} the requisite libraries may not be available. | |
282a61e6 | 9486 | |
39bc1876 NS |
9487 | @item -mieee-compare |
9488 | @itemx -mno-ieee-compare | |
9489 | @opindex mieee-compare | |
9490 | @opindex mno-ieee-compare | |
9491 | Control whether or not the compiler uses IEEE floating point | |
9492 | comparisons. These handle correctly the case where the result of a | |
9493 | comparison is unordered. | |
9494 | @strong{Warning:} the requisite kernel support may not be available. | |
282a61e6 | 9495 | |
39bc1876 NS |
9496 | @item -mnobitfield |
9497 | @opindex mnobitfield | |
9498 | Do not use the bit-field instructions. On some machines it is faster to | |
9499 | use shifting and masking operations. This is the default for the pc532. | |
282a61e6 | 9500 | |
39bc1876 NS |
9501 | @item -mbitfield |
9502 | @opindex mbitfield | |
9503 | Do use the bit-field instructions. This is the default for all platforms | |
9504 | except the pc532. | |
282a61e6 | 9505 | |
39bc1876 NS |
9506 | @item -mrtd |
9507 | @opindex mrtd | |
9508 | Use a different function-calling convention, in which functions | |
9509 | that take a fixed number of arguments return pop their | |
9510 | arguments on return with the @code{ret} instruction. | |
282a61e6 | 9511 | |
39bc1876 NS |
9512 | This calling convention is incompatible with the one normally |
9513 | used on Unix, so you cannot use it if you need to call libraries | |
9514 | compiled with the Unix compiler. | |
282a61e6 | 9515 | |
39bc1876 NS |
9516 | Also, you must provide function prototypes for all functions that |
9517 | take variable numbers of arguments (including @code{printf}); | |
9518 | otherwise incorrect code will be generated for calls to those | |
9519 | functions. | |
282a61e6 | 9520 | |
39bc1876 NS |
9521 | In addition, seriously incorrect code will result if you call a |
9522 | function with too many arguments. (Normally, extra arguments are | |
9523 | harmlessly ignored.) | |
282a61e6 | 9524 | |
39bc1876 | 9525 | This option takes its name from the 680x0 @code{rtd} instruction. |
282a61e6 | 9526 | |
282a61e6 | 9527 | |
39bc1876 NS |
9528 | @item -mregparam |
9529 | @opindex mregparam | |
9530 | Use a different function-calling convention where the first two arguments | |
9531 | are passed in registers. | |
282a61e6 | 9532 | |
39bc1876 NS |
9533 | This calling convention is incompatible with the one normally |
9534 | used on Unix, so you cannot use it if you need to call libraries | |
9535 | compiled with the Unix compiler. | |
282a61e6 | 9536 | |
39bc1876 NS |
9537 | @item -mnoregparam |
9538 | @opindex mnoregparam | |
9539 | Do not pass any arguments in registers. This is the default for all | |
9540 | targets. | |
282a61e6 | 9541 | |
39bc1876 NS |
9542 | @item -msb |
9543 | @opindex msb | |
9544 | It is OK to use the sb as an index register which is always loaded with | |
9545 | zero. This is the default for the pc532-netbsd target. | |
282a61e6 | 9546 | |
39bc1876 NS |
9547 | @item -mnosb |
9548 | @opindex mnosb | |
9549 | The sb register is not available for use or has not been initialized to | |
9550 | zero by the run time system. This is the default for all targets except | |
9551 | the pc532-netbsd. It is also implied whenever @option{-mhimem} or | |
9552 | @option{-fpic} is set. | |
282a61e6 | 9553 | |
39bc1876 NS |
9554 | @item -mhimem |
9555 | @opindex mhimem | |
9556 | Many ns32000 series addressing modes use displacements of up to 512MB@. | |
9557 | If an address is above 512MB then displacements from zero can not be used. | |
9558 | This option causes code to be generated which can be loaded above 512MB@. | |
9559 | This may be useful for operating systems or ROM code. | |
282a61e6 | 9560 | |
39bc1876 NS |
9561 | @item -mnohimem |
9562 | @opindex mnohimem | |
9563 | Assume code will be loaded in the first 512MB of virtual address space. | |
9564 | This is the default for all platforms. | |
282a61e6 MH |
9565 | |
9566 | @end table | |
9567 | ||
39bc1876 NS |
9568 | @node PDP-11 Options |
9569 | @subsection PDP-11 Options | |
9570 | @cindex PDP-11 Options | |
f84271d9 | 9571 | |
39bc1876 | 9572 | These options are defined for the PDP-11: |
f84271d9 | 9573 | |
2642624b | 9574 | @table @gcctabopt |
39bc1876 NS |
9575 | @item -mfpu |
9576 | @opindex mfpu | |
9577 | Use hardware FPP floating point. This is the default. (FIS floating | |
9578 | point on the PDP-11/40 is not supported.) | |
f84271d9 | 9579 | |
39bc1876 NS |
9580 | @item -msoft-float |
9581 | @opindex msoft-float | |
9582 | Do not use hardware floating point. | |
f84271d9 | 9583 | |
39bc1876 NS |
9584 | @item -mac0 |
9585 | @opindex mac0 | |
9586 | Return floating-point results in ac0 (fr0 in Unix assembler syntax). | |
f84271d9 | 9587 | |
39bc1876 NS |
9588 | @item -mno-ac0 |
9589 | @opindex mno-ac0 | |
9590 | Return floating-point results in memory. This is the default. | |
9591 | ||
9592 | @item -m40 | |
9593 | @opindex m40 | |
9594 | Generate code for a PDP-11/40. | |
9595 | ||
9596 | @item -m45 | |
9597 | @opindex m45 | |
9598 | Generate code for a PDP-11/45. This is the default. | |
f84271d9 | 9599 | |
39bc1876 NS |
9600 | @item -m10 |
9601 | @opindex m10 | |
9602 | Generate code for a PDP-11/10. | |
f84271d9 | 9603 | |
39bc1876 NS |
9604 | @item -mbcopy-builtin |
9605 | @opindex bcopy-builtin | |
9606 | Use inline @code{movstrhi} patterns for copying memory. This is the | |
9607 | default. | |
f84271d9 | 9608 | |
39bc1876 NS |
9609 | @item -mbcopy |
9610 | @opindex mbcopy | |
9611 | Do not use inline @code{movstrhi} patterns for copying memory. | |
02f52e19 | 9612 | |
39bc1876 NS |
9613 | @item -mint16 |
9614 | @itemx -mno-int32 | |
9615 | @opindex mint16 | |
9616 | @opindex mno-int32 | |
9617 | Use 16-bit @code{int}. This is the default. | |
48f0be1b | 9618 | |
39bc1876 NS |
9619 | @item -mint32 |
9620 | @itemx -mno-int16 | |
9621 | @opindex mint32 | |
9622 | @opindex mno-int16 | |
9623 | Use 32-bit @code{int}. | |
b4378319 | 9624 | |
39bc1876 NS |
9625 | @item -mfloat64 |
9626 | @itemx -mno-float32 | |
9627 | @opindex mfloat64 | |
9628 | @opindex mno-float32 | |
9629 | Use 64-bit @code{float}. This is the default. | |
b4378319 | 9630 | |
39bc1876 NS |
9631 | @item -mfloat32 |
9632 | @itemx -mno-float64 | |
9633 | @opindex mfloat32 | |
9634 | @opindex mno-float64 | |
9635 | Use 32-bit @code{float}. | |
daf2f129 | 9636 | |
39bc1876 NS |
9637 | @item -mabshi |
9638 | @opindex mabshi | |
9639 | Use @code{abshi2} pattern. This is the default. | |
232830b7 | 9640 | |
39bc1876 NS |
9641 | @item -mno-abshi |
9642 | @opindex mno-abshi | |
9643 | Do not use @code{abshi2} pattern. | |
b4378319 | 9644 | |
39bc1876 NS |
9645 | @item -mbranch-expensive |
9646 | @opindex mbranch-expensive | |
9647 | Pretend that branches are expensive. This is for experimenting with | |
9648 | code generation only. | |
b4378319 | 9649 | |
39bc1876 NS |
9650 | @item -mbranch-cheap |
9651 | @opindex mbranch-cheap | |
9652 | Do not pretend that branches are expensive. This is the default. | |
b4378319 | 9653 | |
39bc1876 NS |
9654 | @item -msplit |
9655 | @opindex msplit | |
9656 | Generate code for a system with split I&D. | |
b4378319 | 9657 | |
39bc1876 NS |
9658 | @item -mno-split |
9659 | @opindex mno-split | |
9660 | Generate code for a system without split I&D. This is the default. | |
f84271d9 | 9661 | |
39bc1876 NS |
9662 | @item -munix-asm |
9663 | @opindex munix-asm | |
9664 | Use Unix assembler syntax. This is the default when configured for | |
9665 | @samp{pdp11-*-bsd}. | |
56b2d7a7 | 9666 | |
39bc1876 NS |
9667 | @item -mdec-asm |
9668 | @opindex mdec-asm | |
9669 | Use DEC assembler syntax. This is the default when configured for any | |
9670 | PDP-11 target other than @samp{pdp11-*-bsd}. | |
9671 | @end table | |
56b2d7a7 | 9672 | |
39bc1876 NS |
9673 | @node PowerPC Options |
9674 | @subsection PowerPC Options | |
9675 | @cindex PowerPC options | |
56b2d7a7 | 9676 | |
39bc1876 | 9677 | These are listed under @xref{RS/6000 and PowerPC Options}. |
56b2d7a7 | 9678 | |
39bc1876 NS |
9679 | @node RS/6000 and PowerPC Options |
9680 | @subsection IBM RS/6000 and PowerPC Options | |
9681 | @cindex RS/6000 and PowerPC Options | |
9682 | @cindex IBM RS/6000 and PowerPC Options | |
56b2d7a7 | 9683 | |
39bc1876 NS |
9684 | These @samp{-m} options are defined for the IBM RS/6000 and PowerPC: |
9685 | @table @gcctabopt | |
9686 | @item -mpower | |
9687 | @itemx -mno-power | |
9688 | @itemx -mpower2 | |
9689 | @itemx -mno-power2 | |
9690 | @itemx -mpowerpc | |
9691 | @itemx -mno-powerpc | |
9692 | @itemx -mpowerpc-gpopt | |
9693 | @itemx -mno-powerpc-gpopt | |
9694 | @itemx -mpowerpc-gfxopt | |
9695 | @itemx -mno-powerpc-gfxopt | |
9696 | @itemx -mpowerpc64 | |
9697 | @itemx -mno-powerpc64 | |
9698 | @opindex mpower | |
9699 | @opindex mno-power | |
9700 | @opindex mpower2 | |
9701 | @opindex mno-power2 | |
9702 | @opindex mpowerpc | |
9703 | @opindex mno-powerpc | |
9704 | @opindex mpowerpc-gpopt | |
9705 | @opindex mno-powerpc-gpopt | |
9706 | @opindex mpowerpc-gfxopt | |
9707 | @opindex mno-powerpc-gfxopt | |
9708 | @opindex mpowerpc64 | |
9709 | @opindex mno-powerpc64 | |
9710 | GCC supports two related instruction set architectures for the | |
9711 | RS/6000 and PowerPC@. The @dfn{POWER} instruction set are those | |
9712 | instructions supported by the @samp{rios} chip set used in the original | |
9713 | RS/6000 systems and the @dfn{PowerPC} instruction set is the | |
9714 | architecture of the Motorola MPC5xx, MPC6xx, MPC8xx microprocessors, and | |
9715 | the IBM 4xx microprocessors. | |
56b2d7a7 | 9716 | |
39bc1876 NS |
9717 | Neither architecture is a subset of the other. However there is a |
9718 | large common subset of instructions supported by both. An MQ | |
9719 | register is included in processors supporting the POWER architecture. | |
56b2d7a7 | 9720 | |
39bc1876 NS |
9721 | You use these options to specify which instructions are available on the |
9722 | processor you are using. The default value of these options is | |
9723 | determined when configuring GCC@. Specifying the | |
9724 | @option{-mcpu=@var{cpu_type}} overrides the specification of these | |
9725 | options. We recommend you use the @option{-mcpu=@var{cpu_type}} option | |
9726 | rather than the options listed above. | |
56b2d7a7 | 9727 | |
39bc1876 NS |
9728 | The @option{-mpower} option allows GCC to generate instructions that |
9729 | are found only in the POWER architecture and to use the MQ register. | |
9730 | Specifying @option{-mpower2} implies @option{-power} and also allows GCC | |
9731 | to generate instructions that are present in the POWER2 architecture but | |
9732 | not the original POWER architecture. | |
83575957 | 9733 | |
39bc1876 NS |
9734 | The @option{-mpowerpc} option allows GCC to generate instructions that |
9735 | are found only in the 32-bit subset of the PowerPC architecture. | |
9736 | Specifying @option{-mpowerpc-gpopt} implies @option{-mpowerpc} and also allows | |
9737 | GCC to use the optional PowerPC architecture instructions in the | |
9738 | General Purpose group, including floating-point square root. Specifying | |
9739 | @option{-mpowerpc-gfxopt} implies @option{-mpowerpc} and also allows GCC to | |
9740 | use the optional PowerPC architecture instructions in the Graphics | |
9741 | group, including floating-point select. | |
83575957 | 9742 | |
39bc1876 NS |
9743 | The @option{-mpowerpc64} option allows GCC to generate the additional |
9744 | 64-bit instructions that are found in the full PowerPC64 architecture | |
9745 | and to treat GPRs as 64-bit, doubleword quantities. GCC defaults to | |
9746 | @option{-mno-powerpc64}. | |
83575957 | 9747 | |
39bc1876 NS |
9748 | If you specify both @option{-mno-power} and @option{-mno-powerpc}, GCC |
9749 | will use only the instructions in the common subset of both | |
9750 | architectures plus some special AIX common-mode calls, and will not use | |
9751 | the MQ register. Specifying both @option{-mpower} and @option{-mpowerpc} | |
9752 | permits GCC to use any instruction from either architecture and to | |
9753 | allow use of the MQ register; specify this for the Motorola MPC601. | |
83575957 | 9754 | |
39bc1876 NS |
9755 | @item -mnew-mnemonics |
9756 | @itemx -mold-mnemonics | |
9757 | @opindex mnew-mnemonics | |
9758 | @opindex mold-mnemonics | |
9759 | Select which mnemonics to use in the generated assembler code. With | |
9760 | @option{-mnew-mnemonics}, GCC uses the assembler mnemonics defined for | |
9761 | the PowerPC architecture. With @option{-mold-mnemonics} it uses the | |
9762 | assembler mnemonics defined for the POWER architecture. Instructions | |
9763 | defined in only one architecture have only one mnemonic; GCC uses that | |
9764 | mnemonic irrespective of which of these options is specified. | |
83575957 | 9765 | |
39bc1876 NS |
9766 | GCC defaults to the mnemonics appropriate for the architecture in |
9767 | use. Specifying @option{-mcpu=@var{cpu_type}} sometimes overrides the | |
9768 | value of these option. Unless you are building a cross-compiler, you | |
9769 | should normally not specify either @option{-mnew-mnemonics} or | |
9770 | @option{-mold-mnemonics}, but should instead accept the default. | |
83575957 | 9771 | |
39bc1876 NS |
9772 | @item -mcpu=@var{cpu_type} |
9773 | @opindex mcpu | |
9774 | Set architecture type, register usage, choice of mnemonics, and | |
9775 | instruction scheduling parameters for machine type @var{cpu_type}. | |
9776 | Supported values for @var{cpu_type} are @samp{401}, @samp{403}, | |
9777 | @samp{405}, @samp{405fp}, @samp{440}, @samp{440fp}, @samp{505}, | |
9778 | @samp{601}, @samp{602}, @samp{603}, @samp{603e}, @samp{604}, | |
9779 | @samp{604e}, @samp{620}, @samp{630}, @samp{740}, @samp{7400}, | |
9780 | @samp{7450}, @samp{750}, @samp{801}, @samp{821}, @samp{823}, | |
9781 | @samp{860}, @samp{970}, @samp{common}, @samp{ec603e}, @samp{G3}, | |
9782 | @samp{G4}, @samp{G5}, @samp{power}, @samp{power2}, @samp{power3}, | |
9783 | @samp{power4}, @samp{power5}, @samp{powerpc}, @samp{powerpc64}, | |
9784 | @samp{rios}, @samp{rios1}, @samp{rios2}, @samp{rsc}, and @samp{rs64a}. | |
83575957 | 9785 | |
39bc1876 NS |
9786 | @option{-mcpu=common} selects a completely generic processor. Code |
9787 | generated under this option will run on any POWER or PowerPC processor. | |
9788 | GCC will use only the instructions in the common subset of both | |
9789 | architectures, and will not use the MQ register. GCC assumes a generic | |
9790 | processor model for scheduling purposes. | |
83575957 | 9791 | |
39bc1876 NS |
9792 | @option{-mcpu=power}, @option{-mcpu=power2}, @option{-mcpu=powerpc}, and |
9793 | @option{-mcpu=powerpc64} specify generic POWER, POWER2, pure 32-bit | |
9794 | PowerPC (i.e., not MPC601), and 64-bit PowerPC architecture machine | |
9795 | types, with an appropriate, generic processor model assumed for | |
9796 | scheduling purposes. | |
83575957 | 9797 | |
39bc1876 NS |
9798 | The other options specify a specific processor. Code generated under |
9799 | those options will run best on that processor, and may not run at all on | |
9800 | others. | |
83575957 | 9801 | |
39bc1876 NS |
9802 | The @option{-mcpu} options automatically enable or disable the |
9803 | following options: @option{-maltivec}, @option{-mhard-float}, | |
9804 | @option{-mmfcrf}, @option{-mmultiple}, @option{-mnew-mnemonics}, | |
9805 | @option{-mpower}, @option{-mpower2}, @option{-mpowerpc64}, | |
9806 | @option{-mpowerpc-gpopt}, @option{-mpowerpc-gfxopt}, | |
9807 | @option{-mstring}. The particular options set for any particular CPU | |
9808 | will vary between compiler versions, depending on what setting seems | |
9809 | to produce optimal code for that CPU; it doesn't necessarily reflect | |
9810 | the actual hardware's capabilities. If you wish to set an individual | |
9811 | option to a particular value, you may specify it after the | |
9812 | @option{-mcpu} option, like @samp{-mcpu=970 -mno-altivec}. | |
5d7c2819 | 9813 | |
39bc1876 NS |
9814 | On AIX, the @option{-maltivec} and @option{-mpowerpc64} options are |
9815 | not enabled or disabled by the @option{-mcpu} option at present, since | |
9816 | AIX does not have full support for these options. You may still | |
9817 | enable or disable them individually if you're sure it'll work in your | |
9818 | environment. | |
83575957 | 9819 | |
39bc1876 NS |
9820 | @item -mtune=@var{cpu_type} |
9821 | @opindex mtune | |
9822 | Set the instruction scheduling parameters for machine type | |
9823 | @var{cpu_type}, but do not set the architecture type, register usage, or | |
9824 | choice of mnemonics, as @option{-mcpu=@var{cpu_type}} would. The same | |
9825 | values for @var{cpu_type} are used for @option{-mtune} as for | |
9826 | @option{-mcpu}. If both are specified, the code generated will use the | |
9827 | architecture, registers, and mnemonics set by @option{-mcpu}, but the | |
9828 | scheduling parameters set by @option{-mtune}. | |
83575957 | 9829 | |
39bc1876 NS |
9830 | @item -maltivec |
9831 | @itemx -mno-altivec | |
9832 | @opindex maltivec | |
9833 | @opindex mno-altivec | |
9834 | These switches enable or disable the use of built-in functions that | |
9835 | allow access to the AltiVec instruction set. You may also need to set | |
9836 | @option{-mabi=altivec} to adjust the current ABI with AltiVec ABI | |
9837 | enhancements. | |
83575957 | 9838 | |
39bc1876 NS |
9839 | @item -mabi=spe |
9840 | @opindex mabi=spe | |
9841 | Extend the current ABI with SPE ABI extensions. This does not change | |
9842 | the default ABI, instead it adds the SPE ABI extensions to the current | |
9843 | ABI@. | |
83575957 | 9844 | |
39bc1876 NS |
9845 | @item -mabi=no-spe |
9846 | @opindex mabi=no-spe | |
9847 | Disable Booke SPE ABI extensions for the current ABI. | |
83575957 | 9848 | |
39bc1876 NS |
9849 | @item -misel=@var{yes/no} |
9850 | @itemx -misel | |
9851 | @opindex misel | |
9852 | This switch enables or disables the generation of ISEL instructions. | |
83575957 | 9853 | |
39bc1876 NS |
9854 | @item -mspe=@var{yes/no} |
9855 | @itemx -mspe | |
9856 | @opindex mspe | |
9857 | This switch enables or disables the generation of SPE simd | |
9858 | instructions. | |
83575957 | 9859 | |
39bc1876 NS |
9860 | @item -mfloat-gprs=@var{yes/no} |
9861 | @itemx -mfloat-gprs | |
9862 | @opindex mfloat-gprs | |
9863 | This switch enables or disables the generation of floating point | |
9864 | operations on the general purpose registers for architectures that | |
9865 | support it. This option is currently only available on the MPC8540. | |
83575957 | 9866 | |
39bc1876 NS |
9867 | @item -mfull-toc |
9868 | @itemx -mno-fp-in-toc | |
9869 | @itemx -mno-sum-in-toc | |
9870 | @itemx -mminimal-toc | |
9871 | @opindex mfull-toc | |
9872 | @opindex mno-fp-in-toc | |
9873 | @opindex mno-sum-in-toc | |
9874 | @opindex mminimal-toc | |
9875 | Modify generation of the TOC (Table Of Contents), which is created for | |
9876 | every executable file. The @option{-mfull-toc} option is selected by | |
9877 | default. In that case, GCC will allocate at least one TOC entry for | |
9878 | each unique non-automatic variable reference in your program. GCC | |
9879 | will also place floating-point constants in the TOC@. However, only | |
9880 | 16,384 entries are available in the TOC@. | |
83575957 | 9881 | |
39bc1876 NS |
9882 | If you receive a linker error message that saying you have overflowed |
9883 | the available TOC space, you can reduce the amount of TOC space used | |
9884 | with the @option{-mno-fp-in-toc} and @option{-mno-sum-in-toc} options. | |
9885 | @option{-mno-fp-in-toc} prevents GCC from putting floating-point | |
9886 | constants in the TOC and @option{-mno-sum-in-toc} forces GCC to | |
9887 | generate code to calculate the sum of an address and a constant at | |
9888 | run-time instead of putting that sum into the TOC@. You may specify one | |
9889 | or both of these options. Each causes GCC to produce very slightly | |
9890 | slower and larger code at the expense of conserving TOC space. | |
83575957 | 9891 | |
39bc1876 NS |
9892 | If you still run out of space in the TOC even when you specify both of |
9893 | these options, specify @option{-mminimal-toc} instead. This option causes | |
9894 | GCC to make only one TOC entry for every file. When you specify this | |
9895 | option, GCC will produce code that is slower and larger but which | |
9896 | uses extremely little TOC space. You may wish to use this option | |
9897 | only on files that contain less frequently executed code. | |
83575957 | 9898 | |
39bc1876 NS |
9899 | @item -maix64 |
9900 | @itemx -maix32 | |
9901 | @opindex maix64 | |
9902 | @opindex maix32 | |
9903 | Enable 64-bit AIX ABI and calling convention: 64-bit pointers, 64-bit | |
9904 | @code{long} type, and the infrastructure needed to support them. | |
9905 | Specifying @option{-maix64} implies @option{-mpowerpc64} and | |
9906 | @option{-mpowerpc}, while @option{-maix32} disables the 64-bit ABI and | |
9907 | implies @option{-mno-powerpc64}. GCC defaults to @option{-maix32}. | |
83575957 | 9908 | |
39bc1876 NS |
9909 | @item -mxl-call |
9910 | @itemx -mno-xl-call | |
9911 | @opindex mxl-call | |
9912 | @opindex mno-xl-call | |
9913 | On AIX, pass floating-point arguments to prototyped functions beyond the | |
9914 | register save area (RSA) on the stack in addition to argument FPRs. The | |
9915 | AIX calling convention was extended but not initially documented to | |
9916 | handle an obscure K&R C case of calling a function that takes the | |
9917 | address of its arguments with fewer arguments than declared. AIX XL | |
9918 | compilers access floating point arguments which do not fit in the | |
9919 | RSA from the stack when a subroutine is compiled without | |
9920 | optimization. Because always storing floating-point arguments on the | |
9921 | stack is inefficient and rarely needed, this option is not enabled by | |
9922 | default and only is necessary when calling subroutines compiled by AIX | |
9923 | XL compilers without optimization. | |
83575957 | 9924 | |
39bc1876 NS |
9925 | @item -mpe |
9926 | @opindex mpe | |
9927 | Support @dfn{IBM RS/6000 SP} @dfn{Parallel Environment} (PE)@. Link an | |
9928 | application written to use message passing with special startup code to | |
9929 | enable the application to run. The system must have PE installed in the | |
9930 | standard location (@file{/usr/lpp/ppe.poe/}), or the @file{specs} file | |
9931 | must be overridden with the @option{-specs=} option to specify the | |
9932 | appropriate directory location. The Parallel Environment does not | |
9933 | support threads, so the @option{-mpe} option and the @option{-pthread} | |
9934 | option are incompatible. | |
83575957 | 9935 | |
39bc1876 NS |
9936 | @item -malign-natural |
9937 | @itemx -malign-power | |
9938 | @opindex malign-natural | |
9939 | @opindex malign-power | |
9940 | On AIX, Darwin, and 64-bit PowerPC GNU/Linux, the option | |
9941 | @option{-malign-natural} overrides the ABI-defined alignment of larger | |
9942 | types, such as floating-point doubles, on their natural size-based boundary. | |
9943 | The option @option{-malign-power} instructs GCC to follow the ABI-specified | |
9944 | alignment rules. GCC defaults to the standard alignment defined in the ABI. | |
83575957 | 9945 | |
39bc1876 NS |
9946 | @item -msoft-float |
9947 | @itemx -mhard-float | |
9948 | @opindex msoft-float | |
9949 | @opindex mhard-float | |
9950 | Generate code that does not use (uses) the floating-point register set. | |
9951 | Software floating point emulation is provided if you use the | |
9952 | @option{-msoft-float} option, and pass the option to GCC when linking. | |
83575957 | 9953 | |
39bc1876 NS |
9954 | @item -mmultiple |
9955 | @itemx -mno-multiple | |
9956 | @opindex mmultiple | |
9957 | @opindex mno-multiple | |
9958 | Generate code that uses (does not use) the load multiple word | |
9959 | instructions and the store multiple word instructions. These | |
9960 | instructions are generated by default on POWER systems, and not | |
9961 | generated on PowerPC systems. Do not use @option{-mmultiple} on little | |
9962 | endian PowerPC systems, since those instructions do not work when the | |
9963 | processor is in little endian mode. The exceptions are PPC740 and | |
9964 | PPC750 which permit the instructions usage in little endian mode. | |
83575957 | 9965 | |
39bc1876 NS |
9966 | @item -mstring |
9967 | @itemx -mno-string | |
9968 | @opindex mstring | |
9969 | @opindex mno-string | |
9970 | Generate code that uses (does not use) the load string instructions | |
9971 | and the store string word instructions to save multiple registers and | |
9972 | do small block moves. These instructions are generated by default on | |
9973 | POWER systems, and not generated on PowerPC systems. Do not use | |
9974 | @option{-mstring} on little endian PowerPC systems, since those | |
9975 | instructions do not work when the processor is in little endian mode. | |
9976 | The exceptions are PPC740 and PPC750 which permit the instructions | |
9977 | usage in little endian mode. | |
052a4b28 | 9978 | |
39bc1876 NS |
9979 | @item -mupdate |
9980 | @itemx -mno-update | |
9981 | @opindex mupdate | |
9982 | @opindex mno-update | |
9983 | Generate code that uses (does not use) the load or store instructions | |
9984 | that update the base register to the address of the calculated memory | |
9985 | location. These instructions are generated by default. If you use | |
9986 | @option{-mno-update}, there is a small window between the time that the | |
9987 | stack pointer is updated and the address of the previous frame is | |
9988 | stored, which means code that walks the stack frame across interrupts or | |
9989 | signals may get corrupted data. | |
052a4b28 | 9990 | |
39bc1876 NS |
9991 | @item -mfused-madd |
9992 | @itemx -mno-fused-madd | |
9993 | @opindex mfused-madd | |
9994 | @opindex mno-fused-madd | |
9995 | Generate code that uses (does not use) the floating point multiply and | |
9996 | accumulate instructions. These instructions are generated by default if | |
9997 | hardware floating is used. | |
3a69a7d5 | 9998 | |
39bc1876 NS |
9999 | @item -mno-bit-align |
10000 | @itemx -mbit-align | |
10001 | @opindex mno-bit-align | |
10002 | @opindex mbit-align | |
10003 | On System V.4 and embedded PowerPC systems do not (do) force structures | |
10004 | and unions that contain bit-fields to be aligned to the base type of the | |
10005 | bit-field. | |
3a69a7d5 | 10006 | |
39bc1876 NS |
10007 | For example, by default a structure containing nothing but 8 |
10008 | @code{unsigned} bit-fields of length 1 would be aligned to a 4 byte | |
10009 | boundary and have a size of 4 bytes. By using @option{-mno-bit-align}, | |
10010 | the structure would be aligned to a 1 byte boundary and be one byte in | |
10011 | size. | |
3a69a7d5 | 10012 | |
39bc1876 NS |
10013 | @item -mno-strict-align |
10014 | @itemx -mstrict-align | |
10015 | @opindex mno-strict-align | |
10016 | @opindex mstrict-align | |
10017 | On System V.4 and embedded PowerPC systems do not (do) assume that | |
10018 | unaligned memory references will be handled by the system. | |
3a69a7d5 | 10019 | |
39bc1876 NS |
10020 | @item -mrelocatable |
10021 | @itemx -mno-relocatable | |
10022 | @opindex mrelocatable | |
10023 | @opindex mno-relocatable | |
10024 | On embedded PowerPC systems generate code that allows (does not allow) | |
10025 | the program to be relocated to a different address at runtime. If you | |
10026 | use @option{-mrelocatable} on any module, all objects linked together must | |
10027 | be compiled with @option{-mrelocatable} or @option{-mrelocatable-lib}. | |
3a69a7d5 | 10028 | |
39bc1876 NS |
10029 | @item -mrelocatable-lib |
10030 | @itemx -mno-relocatable-lib | |
10031 | @opindex mrelocatable-lib | |
10032 | @opindex mno-relocatable-lib | |
10033 | On embedded PowerPC systems generate code that allows (does not allow) | |
10034 | the program to be relocated to a different address at runtime. Modules | |
10035 | compiled with @option{-mrelocatable-lib} can be linked with either modules | |
10036 | compiled without @option{-mrelocatable} and @option{-mrelocatable-lib} or | |
10037 | with modules compiled with the @option{-mrelocatable} options. | |
052a4b28 | 10038 | |
39bc1876 NS |
10039 | @item -mno-toc |
10040 | @itemx -mtoc | |
10041 | @opindex mno-toc | |
10042 | @opindex mtoc | |
10043 | On System V.4 and embedded PowerPC systems do not (do) assume that | |
10044 | register 2 contains a pointer to a global area pointing to the addresses | |
10045 | used in the program. | |
052a4b28 | 10046 | |
39bc1876 NS |
10047 | @item -mlittle |
10048 | @itemx -mlittle-endian | |
10049 | @opindex mlittle | |
10050 | @opindex mlittle-endian | |
10051 | On System V.4 and embedded PowerPC systems compile code for the | |
10052 | processor in little endian mode. The @option{-mlittle-endian} option is | |
10053 | the same as @option{-mlittle}. | |
052a4b28 | 10054 | |
39bc1876 NS |
10055 | @item -mbig |
10056 | @itemx -mbig-endian | |
10057 | @opindex mbig | |
10058 | @opindex mbig-endian | |
10059 | On System V.4 and embedded PowerPC systems compile code for the | |
10060 | processor in big endian mode. The @option{-mbig-endian} option is | |
10061 | the same as @option{-mbig}. | |
052a4b28 | 10062 | |
39bc1876 NS |
10063 | @item -mdynamic-no-pic |
10064 | @opindex mdynamic-no-pic | |
10065 | On Darwin and Mac OS X systems, compile code so that it is not | |
10066 | relocatable, but that its external references are relocatable. The | |
10067 | resulting code is suitable for applications, but not shared | |
10068 | libraries. | |
3a69a7d5 | 10069 | |
39bc1876 NS |
10070 | @item -mprioritize-restricted-insns=@var{priority} |
10071 | @opindex mprioritize-restricted-insns | |
10072 | This option controls the priority that is assigned to | |
10073 | dispatch-slot restricted instructions during the second scheduling | |
10074 | pass. The argument @var{priority} takes the value @var{0/1/2} to assign | |
10075 | @var{no/highest/second-highest} priority to dispatch slot restricted | |
10076 | instructions. | |
3a69a7d5 | 10077 | |
39bc1876 NS |
10078 | @item -msched-costly-dep=@var{dependence_type} |
10079 | @opindex msched-costly-dep | |
10080 | This option controls which dependences are considered costly | |
10081 | by the target during instruction scheduling. The argument | |
10082 | @var{dependence_type} takes one of the following values: | |
10083 | @var{no}: no dependence is costly, | |
10084 | @var{all}: all dependences are costly, | |
10085 | @var{true_store_to_load}: a true dependence from store to load is costly, | |
10086 | @var{store_to_load}: any dependence from store to load is costly, | |
10087 | @var{number}: any dependence which latency >= @var{number} is costly. | |
11338cda | 10088 | |
39bc1876 NS |
10089 | @item -minsert-sched-nops=@var{scheme} |
10090 | @opindex minsert-sched-nops | |
10091 | This option controls which nop insertion scheme will be used during | |
10092 | the second scheduling pass. The argument @var{scheme} takes one of the | |
10093 | following values: | |
10094 | @var{no}: Don't insert nops. | |
10095 | @var{pad}: Pad with nops any dispatch group which has vacant issue slots, | |
10096 | according to the scheduler's grouping. | |
10097 | @var{regroup_exact}: Insert nops to force costly dependent insns into | |
10098 | separate groups. Insert exactly as many nops as needed to force an insn | |
10099 | to a new group, according to the estimated processor grouping. | |
10100 | @var{number}: Insert nops to force costly dependent insns into | |
10101 | separate groups. Insert @var{number} nops to force an insn to a new group. | |
052a4b28 | 10102 | |
39bc1876 NS |
10103 | @item -mcall-sysv |
10104 | @opindex mcall-sysv | |
10105 | On System V.4 and embedded PowerPC systems compile code using calling | |
10106 | conventions that adheres to the March 1995 draft of the System V | |
10107 | Application Binary Interface, PowerPC processor supplement. This is the | |
10108 | default unless you configured GCC using @samp{powerpc-*-eabiaix}. | |
789a3090 | 10109 | |
39bc1876 NS |
10110 | @item -mcall-sysv-eabi |
10111 | @opindex mcall-sysv-eabi | |
10112 | Specify both @option{-mcall-sysv} and @option{-meabi} options. | |
789a3090 | 10113 | |
39bc1876 NS |
10114 | @item -mcall-sysv-noeabi |
10115 | @opindex mcall-sysv-noeabi | |
10116 | Specify both @option{-mcall-sysv} and @option{-mno-eabi} options. | |
789a3090 | 10117 | |
39bc1876 NS |
10118 | @item -mcall-solaris |
10119 | @opindex mcall-solaris | |
10120 | On System V.4 and embedded PowerPC systems compile code for the Solaris | |
10121 | operating system. | |
789a3090 | 10122 | |
39bc1876 NS |
10123 | @item -mcall-linux |
10124 | @opindex mcall-linux | |
10125 | On System V.4 and embedded PowerPC systems compile code for the | |
10126 | Linux-based GNU system. | |
789a3090 | 10127 | |
39bc1876 NS |
10128 | @item -mcall-gnu |
10129 | @opindex mcall-gnu | |
10130 | On System V.4 and embedded PowerPC systems compile code for the | |
10131 | Hurd-based GNU system. | |
789a3090 | 10132 | |
39bc1876 NS |
10133 | @item -mcall-netbsd |
10134 | @opindex mcall-netbsd | |
10135 | On System V.4 and embedded PowerPC systems compile code for the | |
10136 | NetBSD operating system. | |
789a3090 | 10137 | |
39bc1876 NS |
10138 | @item -maix-struct-return |
10139 | @opindex maix-struct-return | |
10140 | Return all structures in memory (as specified by the AIX ABI)@. | |
789a3090 | 10141 | |
39bc1876 NS |
10142 | @item -msvr4-struct-return |
10143 | @opindex msvr4-struct-return | |
10144 | Return structures smaller than 8 bytes in registers (as specified by the | |
10145 | SVR4 ABI)@. | |
789a3090 | 10146 | |
39bc1876 NS |
10147 | @item -mabi=altivec |
10148 | @opindex mabi=altivec | |
10149 | Extend the current ABI with AltiVec ABI extensions. This does not | |
10150 | change the default ABI, instead it adds the AltiVec ABI extensions to | |
10151 | the current ABI@. | |
789a3090 | 10152 | |
39bc1876 NS |
10153 | @item -mabi=no-altivec |
10154 | @opindex mabi=no-altivec | |
10155 | Disable AltiVec ABI extensions for the current ABI. | |
789a3090 | 10156 | |
39bc1876 NS |
10157 | @item -mprototype |
10158 | @itemx -mno-prototype | |
10159 | @opindex mprototype | |
10160 | @opindex mno-prototype | |
10161 | On System V.4 and embedded PowerPC systems assume that all calls to | |
10162 | variable argument functions are properly prototyped. Otherwise, the | |
10163 | compiler must insert an instruction before every non prototyped call to | |
10164 | set or clear bit 6 of the condition code register (@var{CR}) to | |
10165 | indicate whether floating point values were passed in the floating point | |
10166 | registers in case the function takes a variable arguments. With | |
10167 | @option{-mprototype}, only calls to prototyped variable argument functions | |
10168 | will set or clear the bit. | |
83575957 | 10169 | |
39bc1876 NS |
10170 | @item -msim |
10171 | @opindex msim | |
10172 | On embedded PowerPC systems, assume that the startup module is called | |
10173 | @file{sim-crt0.o} and that the standard C libraries are @file{libsim.a} and | |
10174 | @file{libc.a}. This is the default for @samp{powerpc-*-eabisim}. | |
10175 | configurations. | |
df6194d4 | 10176 | |
39bc1876 NS |
10177 | @item -mmvme |
10178 | @opindex mmvme | |
10179 | On embedded PowerPC systems, assume that the startup module is called | |
10180 | @file{crt0.o} and the standard C libraries are @file{libmvme.a} and | |
10181 | @file{libc.a}. | |
df6194d4 | 10182 | |
39bc1876 NS |
10183 | @item -mads |
10184 | @opindex mads | |
10185 | On embedded PowerPC systems, assume that the startup module is called | |
10186 | @file{crt0.o} and the standard C libraries are @file{libads.a} and | |
10187 | @file{libc.a}. | |
df6194d4 | 10188 | |
39bc1876 NS |
10189 | @item -myellowknife |
10190 | @opindex myellowknife | |
10191 | On embedded PowerPC systems, assume that the startup module is called | |
10192 | @file{crt0.o} and the standard C libraries are @file{libyk.a} and | |
10193 | @file{libc.a}. | |
df6194d4 | 10194 | |
39bc1876 NS |
10195 | @item -mvxworks |
10196 | @opindex mvxworks | |
10197 | On System V.4 and embedded PowerPC systems, specify that you are | |
10198 | compiling for a VxWorks system. | |
df6194d4 | 10199 | |
39bc1876 NS |
10200 | @item -mwindiss |
10201 | @opindex mwindiss | |
10202 | Specify that you are compiling for the WindISS simulation environment. | |
df6194d4 | 10203 | |
39bc1876 NS |
10204 | @item -memb |
10205 | @opindex memb | |
10206 | On embedded PowerPC systems, set the @var{PPC_EMB} bit in the ELF flags | |
10207 | header to indicate that @samp{eabi} extended relocations are used. | |
df6194d4 | 10208 | |
39bc1876 NS |
10209 | @item -meabi |
10210 | @itemx -mno-eabi | |
10211 | @opindex meabi | |
10212 | @opindex mno-eabi | |
10213 | On System V.4 and embedded PowerPC systems do (do not) adhere to the | |
10214 | Embedded Applications Binary Interface (eabi) which is a set of | |
10215 | modifications to the System V.4 specifications. Selecting @option{-meabi} | |
10216 | means that the stack is aligned to an 8 byte boundary, a function | |
10217 | @code{__eabi} is called to from @code{main} to set up the eabi | |
10218 | environment, and the @option{-msdata} option can use both @code{r2} and | |
10219 | @code{r13} to point to two separate small data areas. Selecting | |
10220 | @option{-mno-eabi} means that the stack is aligned to a 16 byte boundary, | |
10221 | do not call an initialization function from @code{main}, and the | |
10222 | @option{-msdata} option will only use @code{r13} to point to a single | |
10223 | small data area. The @option{-meabi} option is on by default if you | |
10224 | configured GCC using one of the @samp{powerpc*-*-eabi*} options. | |
df6194d4 | 10225 | |
39bc1876 NS |
10226 | @item -msdata=eabi |
10227 | @opindex msdata=eabi | |
10228 | On System V.4 and embedded PowerPC systems, put small initialized | |
10229 | @code{const} global and static data in the @samp{.sdata2} section, which | |
10230 | is pointed to by register @code{r2}. Put small initialized | |
10231 | non-@code{const} global and static data in the @samp{.sdata} section, | |
10232 | which is pointed to by register @code{r13}. Put small uninitialized | |
10233 | global and static data in the @samp{.sbss} section, which is adjacent to | |
10234 | the @samp{.sdata} section. The @option{-msdata=eabi} option is | |
10235 | incompatible with the @option{-mrelocatable} option. The | |
10236 | @option{-msdata=eabi} option also sets the @option{-memb} option. | |
df6194d4 | 10237 | |
39bc1876 NS |
10238 | @item -msdata=sysv |
10239 | @opindex msdata=sysv | |
10240 | On System V.4 and embedded PowerPC systems, put small global and static | |
10241 | data in the @samp{.sdata} section, which is pointed to by register | |
10242 | @code{r13}. Put small uninitialized global and static data in the | |
10243 | @samp{.sbss} section, which is adjacent to the @samp{.sdata} section. | |
10244 | The @option{-msdata=sysv} option is incompatible with the | |
10245 | @option{-mrelocatable} option. | |
df6194d4 | 10246 | |
39bc1876 | 10247 | @item -msdata=default |
df6194d4 | 10248 | @itemx -msdata |
39bc1876 | 10249 | @opindex msdata=default |
cd3bb277 | 10250 | @opindex msdata |
39bc1876 NS |
10251 | On System V.4 and embedded PowerPC systems, if @option{-meabi} is used, |
10252 | compile code the same as @option{-msdata=eabi}, otherwise compile code the | |
10253 | same as @option{-msdata=sysv}. | |
df6194d4 | 10254 | |
39bc1876 NS |
10255 | @item -msdata-data |
10256 | @opindex msdata-data | |
10257 | On System V.4 and embedded PowerPC systems, put small global and static | |
10258 | data in the @samp{.sdata} section. Put small uninitialized global and | |
10259 | static data in the @samp{.sbss} section. Do not use register @code{r13} | |
10260 | to address small data however. This is the default behavior unless | |
10261 | other @option{-msdata} options are used. | |
df6194d4 | 10262 | |
39bc1876 NS |
10263 | @item -msdata=none |
10264 | @itemx -mno-sdata | |
10265 | @opindex msdata=none | |
10266 | @opindex mno-sdata | |
10267 | On embedded PowerPC systems, put all initialized global and static data | |
10268 | in the @samp{.data} section, and all uninitialized data in the | |
10269 | @samp{.bss} section. | |
df6194d4 | 10270 | |
39bc1876 NS |
10271 | @item -G @var{num} |
10272 | @opindex G | |
10273 | @cindex smaller data references (PowerPC) | |
10274 | @cindex .sdata/.sdata2 references (PowerPC) | |
10275 | On embedded PowerPC systems, put global and static items less than or | |
10276 | equal to @var{num} bytes into the small data or bss sections instead of | |
10277 | the normal data or bss section. By default, @var{num} is 8. The | |
10278 | @option{-G @var{num}} switch is also passed to the linker. | |
10279 | All modules should be compiled with the same @option{-G @var{num}} value. | |
dcffbade | 10280 | |
39bc1876 NS |
10281 | @item -mregnames |
10282 | @itemx -mno-regnames | |
10283 | @opindex mregnames | |
10284 | @opindex mno-regnames | |
10285 | On System V.4 and embedded PowerPC systems do (do not) emit register | |
10286 | names in the assembly language output using symbolic forms. | |
dcffbade | 10287 | |
39bc1876 NS |
10288 | @item -mlongcall |
10289 | @itemx -mno-longcall | |
10290 | @opindex mlongcall | |
10291 | @opindex mno-longcall | |
10292 | Default to making all function calls indirectly, using a register, so | |
10293 | that functions which reside further than 32 megabytes (33,554,432 | |
10294 | bytes) from the current location can be called. This setting can be | |
10295 | overridden by the @code{shortcall} function attribute, or by | |
10296 | @code{#pragma longcall(0)}. | |
dcffbade | 10297 | |
39bc1876 NS |
10298 | Some linkers are capable of detecting out-of-range calls and generating |
10299 | glue code on the fly. On these systems, long calls are unnecessary and | |
10300 | generate slower code. As of this writing, the AIX linker can do this, | |
10301 | as can the GNU linker for PowerPC/64. It is planned to add this feature | |
10302 | to the GNU linker for 32-bit PowerPC systems as well. | |
df6194d4 | 10303 | |
39bc1876 NS |
10304 | On Darwin/PPC systems, @code{#pragma longcall} will generate ``jbsr |
10305 | callee, L42'', plus a ``branch island'' (glue code). The two target | |
10306 | addresses represent the callee and the ``branch island.'' The | |
10307 | Darwin/PPC linker will prefer the first address and generate a ``bl | |
10308 | callee'' if the PPC ``bl'' instruction will reach the callee directly; | |
10309 | otherwise, the linker will generate ``bl L42'' to call the ``branch | |
10310 | island.'' The ``branch island'' is appended to the body of the | |
10311 | calling function; it computes the full 32-bit address of the callee | |
10312 | and jumps to it. | |
df6194d4 | 10313 | |
39bc1876 NS |
10314 | On Mach-O (Darwin) systems, this option directs the compiler emit to |
10315 | the glue for every direct call, and the Darwin linker decides whether | |
10316 | to use or discard it. | |
10317 | ||
10318 | In the future, we may cause GCC to ignore all longcall specifications | |
10319 | when the linker is known to generate glue. | |
10320 | ||
10321 | @item -pthread | |
10322 | @opindex pthread | |
10323 | Adds support for multithreading with the @dfn{pthreads} library. | |
10324 | This option sets flags for both the preprocessor and linker. | |
30028c85 | 10325 | |
df6194d4 JW |
10326 | @end table |
10327 | ||
91abf72d HP |
10328 | @node S/390 and zSeries Options |
10329 | @subsection S/390 and zSeries Options | |
10330 | @cindex S/390 and zSeries Options | |
10331 | ||
10332 | These are the @samp{-m} options defined for the S/390 and zSeries architecture. | |
10333 | ||
10334 | @table @gcctabopt | |
10335 | @item -mhard-float | |
10336 | @itemx -msoft-float | |
10337 | @opindex mhard-float | |
10338 | @opindex msoft-float | |
10339 | Use (do not use) the hardware floating-point instructions and registers | |
10340 | for floating-point operations. When @option{-msoft-float} is specified, | |
10341 | functions in @file{libgcc.a} will be used to perform floating-point | |
10342 | operations. When @option{-mhard-float} is specified, the compiler | |
10343 | generates IEEE floating-point instructions. This is the default. | |
10344 | ||
10345 | @item -mbackchain | |
10346 | @itemx -mno-backchain | |
10347 | @opindex mbackchain | |
10348 | @opindex mno-backchain | |
f282ffb3 | 10349 | Generate (or do not generate) code which maintains an explicit |
91abf72d | 10350 | backchain within the stack frame that points to the caller's frame. |
590fcf48 UW |
10351 | This may be needed to allow debugging using tools that do not understand |
10352 | DWARF-2 call frame information. The default is not to generate the | |
10353 | backchain. | |
91abf72d HP |
10354 | |
10355 | @item -msmall-exec | |
10356 | @itemx -mno-small-exec | |
10357 | @opindex msmall-exec | |
10358 | @opindex mno-small-exec | |
f282ffb3 JM |
10359 | Generate (or do not generate) code using the @code{bras} instruction |
10360 | to do subroutine calls. | |
91abf72d HP |
10361 | This only works reliably if the total executable size does not |
10362 | exceed 64k. The default is to use the @code{basr} instruction instead, | |
10363 | which does not have this limitation. | |
10364 | ||
10365 | @item -m64 | |
10366 | @itemx -m31 | |
10367 | @opindex m64 | |
10368 | @opindex m31 | |
10369 | When @option{-m31} is specified, generate code compliant to the | |
95fef11f JM |
10370 | GNU/Linux for S/390 ABI@. When @option{-m64} is specified, generate |
10371 | code compliant to the GNU/Linux for zSeries ABI@. This allows GCC in | |
91abf72d | 10372 | particular to generate 64-bit instructions. For the @samp{s390} |
f282ffb3 | 10373 | targets, the default is @option{-m31}, while the @samp{s390x} |
91abf72d HP |
10374 | targets default to @option{-m64}. |
10375 | ||
1fec52be HP |
10376 | @item -mzarch |
10377 | @itemx -mesa | |
10378 | @opindex mzarch | |
10379 | @opindex mesa | |
daf2f129 JM |
10380 | When @option{-mzarch} is specified, generate code using the |
10381 | instructions available on z/Architecture. | |
10382 | When @option{-mesa} is specified, generate code using the | |
1fec52be HP |
10383 | instructions available on ESA/390. Note that @option{-mesa} is |
10384 | not possible with @option{-m64}. | |
95fef11f | 10385 | When generating code compliant to the GNU/Linux for S/390 ABI, |
f13e0d4e | 10386 | the default is @option{-mesa}. When generating code compliant |
95fef11f | 10387 | to the GNU/Linux for zSeries ABI, the default is @option{-mzarch}. |
1fec52be | 10388 | |
91abf72d HP |
10389 | @item -mmvcle |
10390 | @itemx -mno-mvcle | |
10391 | @opindex mmvcle | |
10392 | @opindex mno-mvcle | |
f282ffb3 | 10393 | Generate (or do not generate) code using the @code{mvcle} instruction |
3364c33b | 10394 | to perform block moves. When @option{-mno-mvcle} is specified, |
91abf72d HP |
10395 | use a @code{mvc} loop instead. This is the default. |
10396 | ||
10397 | @item -mdebug | |
10398 | @itemx -mno-debug | |
10399 | @opindex mdebug | |
10400 | @opindex mno-debug | |
10401 | Print (or do not print) additional debug information when compiling. | |
10402 | The default is to not print debug information. | |
10403 | ||
f13e0d4e | 10404 | @item -march=@var{cpu-type} |
1fec52be | 10405 | @opindex march |
f13e0d4e | 10406 | Generate code that will run on @var{cpu-type}, which is the name of a system |
1fec52be | 10407 | representing a certain processor type. Possible values for |
f13e0d4e UW |
10408 | @var{cpu-type} are @samp{g5}, @samp{g6}, @samp{z900}, and @samp{z990}. |
10409 | When generating code using the instructions available on z/Architecture, | |
10410 | the default is @option{-march=z900}. Otherwise, the default is | |
10411 | @option{-march=g5}. | |
1fec52be | 10412 | |
f13e0d4e | 10413 | @item -mtune=@var{cpu-type} |
35082351 | 10414 | @opindex mtune |
1fec52be | 10415 | Tune to @var{cpu-type} everything applicable about the generated code, |
f13e0d4e UW |
10416 | except for the ABI and the set of available instructions. |
10417 | The list of @var{cpu-type} values is the same as for @option{-march}. | |
10418 | The default is the value used for @option{-march}. | |
1fec52be | 10419 | |
f26c1794 EC |
10420 | @item -mtpf-trace |
10421 | @itemx -mno-tpf-trace | |
10422 | @opindex mtpf-trace | |
10423 | @opindex mno-tpf-trace | |
10424 | Generate code that adds (does not add) in TPF OS specific branches to trace | |
10425 | routines in the operating system. This option is off by default, even | |
10426 | when compiling for the TPF OS. | |
10427 | ||
f2d226e1 AK |
10428 | @item -mfused-madd |
10429 | @itemx -mno-fused-madd | |
10430 | @opindex mfused-madd | |
10431 | @opindex mno-fused-madd | |
10432 | Generate code that uses (does not use) the floating point multiply and | |
10433 | accumulate instructions. These instructions are generated by default if | |
10434 | hardware floating point is used. | |
91abf72d HP |
10435 | @end table |
10436 | ||
39bc1876 NS |
10437 | @node SH Options |
10438 | @subsection SH Options | |
bcf684c7 | 10439 | |
39bc1876 | 10440 | These @samp{-m} options are defined for the SH implementations: |
bcf684c7 | 10441 | |
5d22c1a5 | 10442 | @table @gcctabopt |
39bc1876 NS |
10443 | @item -m1 |
10444 | @opindex m1 | |
10445 | Generate code for the SH1. | |
9f85bca7 | 10446 | |
39bc1876 NS |
10447 | @item -m2 |
10448 | @opindex m2 | |
10449 | Generate code for the SH2. | |
9f85bca7 | 10450 | |
39bc1876 NS |
10451 | @item -m2e |
10452 | Generate code for the SH2e. | |
9f85bca7 | 10453 | |
39bc1876 NS |
10454 | @item -m3 |
10455 | @opindex m3 | |
10456 | Generate code for the SH3. | |
9f85bca7 | 10457 | |
39bc1876 NS |
10458 | @item -m3e |
10459 | @opindex m3e | |
10460 | Generate code for the SH3e. | |
9f85bca7 | 10461 | |
39bc1876 NS |
10462 | @item -m4-nofpu |
10463 | @opindex m4-nofpu | |
10464 | Generate code for the SH4 without a floating-point unit. | |
9f85bca7 | 10465 | |
39bc1876 NS |
10466 | @item -m4-single-only |
10467 | @opindex m4-single-only | |
10468 | Generate code for the SH4 with a floating-point unit that only | |
10469 | supports single-precision arithmetic. | |
9f85bca7 | 10470 | |
39bc1876 NS |
10471 | @item -m4-single |
10472 | @opindex m4-single | |
10473 | Generate code for the SH4 assuming the floating-point unit is in | |
10474 | single-precision mode by default. | |
9f85bca7 | 10475 | |
39bc1876 NS |
10476 | @item -m4 |
10477 | @opindex m4 | |
10478 | Generate code for the SH4. | |
9f85bca7 | 10479 | |
39bc1876 NS |
10480 | @item -mb |
10481 | @opindex mb | |
10482 | Compile code for the processor in big endian mode. | |
9f85bca7 | 10483 | |
39bc1876 NS |
10484 | @item -ml |
10485 | @opindex ml | |
10486 | Compile code for the processor in little endian mode. | |
9f85bca7 | 10487 | |
39bc1876 NS |
10488 | @item -mdalign |
10489 | @opindex mdalign | |
10490 | Align doubles at 64-bit boundaries. Note that this changes the calling | |
10491 | conventions, and thus some functions from the standard C library will | |
10492 | not work unless you recompile it first with @option{-mdalign}. | |
9f85bca7 | 10493 | |
39bc1876 NS |
10494 | @item -mrelax |
10495 | @opindex mrelax | |
10496 | Shorten some address references at link time, when possible; uses the | |
10497 | linker option @option{-relax}. | |
9f85bca7 | 10498 | |
39bc1876 NS |
10499 | @item -mbigtable |
10500 | @opindex mbigtable | |
10501 | Use 32-bit offsets in @code{switch} tables. The default is to use | |
10502 | 16-bit offsets. | |
9f85bca7 | 10503 | |
39bc1876 NS |
10504 | @item -mfmovd |
10505 | @opindex mfmovd | |
10506 | Enable the use of the instruction @code{fmovd}. | |
9f85bca7 | 10507 | |
39bc1876 NS |
10508 | @item -mhitachi |
10509 | @opindex mhitachi | |
10510 | Comply with the calling conventions defined by Renesas. | |
9f85bca7 | 10511 | |
39bc1876 NS |
10512 | @item -mnomacsave |
10513 | @opindex mnomacsave | |
10514 | Mark the @code{MAC} register as call-clobbered, even if | |
10515 | @option{-mhitachi} is given. | |
9f85bca7 | 10516 | |
39bc1876 NS |
10517 | @item -mieee |
10518 | @opindex mieee | |
10519 | Increase IEEE-compliance of floating-point code. | |
9f85bca7 | 10520 | |
39bc1876 NS |
10521 | @item -misize |
10522 | @opindex misize | |
10523 | Dump instruction size and location in the assembly code. | |
9f85bca7 | 10524 | |
39bc1876 NS |
10525 | @item -mpadstruct |
10526 | @opindex mpadstruct | |
10527 | This option is deprecated. It pads structures to multiple of 4 bytes, | |
10528 | which is incompatible with the SH ABI@. | |
9f85bca7 | 10529 | |
39bc1876 NS |
10530 | @item -mspace |
10531 | @opindex mspace | |
10532 | Optimize for space instead of speed. Implied by @option{-Os}. | |
9f85bca7 | 10533 | |
39bc1876 NS |
10534 | @item -mprefergot |
10535 | @opindex mprefergot | |
10536 | When generating position-independent code, emit function calls using | |
10537 | the Global Offset Table instead of the Procedure Linkage Table. | |
9f85bca7 | 10538 | |
39bc1876 NS |
10539 | @item -musermode |
10540 | @opindex musermode | |
10541 | Generate a library function call to invalidate instruction cache | |
10542 | entries, after fixing up a trampoline. This library function call | |
10543 | doesn't assume it can write to the whole memory address space. This | |
10544 | is the default when the target is @code{sh-*-linux*}. | |
9f85bca7 JM |
10545 | @end table |
10546 | ||
39bc1876 NS |
10547 | @node SPARC Options |
10548 | @subsection SPARC Options | |
10549 | @cindex SPARC options | |
69a0611f | 10550 | |
39bc1876 | 10551 | These @samp{-m} options are supported on the SPARC: |
69a0611f GK |
10552 | |
10553 | @table @gcctabopt | |
39bc1876 NS |
10554 | @item -mno-app-regs |
10555 | @itemx -mapp-regs | |
10556 | @opindex mno-app-regs | |
10557 | @opindex mapp-regs | |
10558 | Specify @option{-mapp-regs} to generate output using the global registers | |
10559 | 2 through 4, which the SPARC SVR4 ABI reserves for applications. This | |
10560 | is the default. | |
69a0611f | 10561 | |
39bc1876 NS |
10562 | To be fully SVR4 ABI compliant at the cost of some performance loss, |
10563 | specify @option{-mno-app-regs}. You should compile libraries and system | |
10564 | software with this option. | |
70899148 | 10565 | |
39bc1876 NS |
10566 | @item -mfpu |
10567 | @itemx -mhard-float | |
10568 | @opindex mfpu | |
10569 | @opindex mhard-float | |
10570 | Generate output containing floating point instructions. This is the | |
10571 | default. | |
70899148 | 10572 | |
39bc1876 NS |
10573 | @item -mno-fpu |
10574 | @itemx -msoft-float | |
10575 | @opindex mno-fpu | |
10576 | @opindex msoft-float | |
10577 | Generate output containing library calls for floating point. | |
10578 | @strong{Warning:} the requisite libraries are not available for all SPARC | |
10579 | targets. Normally the facilities of the machine's usual C compiler are | |
10580 | used, but this cannot be done directly in cross-compilation. You must make | |
10581 | your own arrangements to provide suitable library functions for | |
10582 | cross-compilation. The embedded targets @samp{sparc-*-aout} and | |
10583 | @samp{sparclite-*-*} do provide software floating point support. | |
70899148 | 10584 | |
39bc1876 NS |
10585 | @option{-msoft-float} changes the calling convention in the output file; |
10586 | therefore, it is only useful if you compile @emph{all} of a program with | |
10587 | this option. In particular, you need to compile @file{libgcc.a}, the | |
10588 | library that comes with GCC, with @option{-msoft-float} in order for | |
10589 | this to work. | |
70899148 | 10590 | |
39bc1876 NS |
10591 | @item -mhard-quad-float |
10592 | @opindex mhard-quad-float | |
10593 | Generate output containing quad-word (long double) floating point | |
10594 | instructions. | |
70899148 | 10595 | |
39bc1876 NS |
10596 | @item -msoft-quad-float |
10597 | @opindex msoft-quad-float | |
10598 | Generate output containing library calls for quad-word (long double) | |
10599 | floating point instructions. The functions called are those specified | |
10600 | in the SPARC ABI@. This is the default. | |
70899148 | 10601 | |
39bc1876 NS |
10602 | As of this writing, there are no SPARC implementations that have hardware |
10603 | support for the quad-word floating point instructions. They all invoke | |
10604 | a trap handler for one of these instructions, and then the trap handler | |
10605 | emulates the effect of the instruction. Because of the trap handler overhead, | |
10606 | this is much slower than calling the ABI library routines. Thus the | |
10607 | @option{-msoft-quad-float} option is the default. | |
70899148 | 10608 | |
39bc1876 NS |
10609 | @item -mno-unaligned-doubles |
10610 | @itemx -munaligned-doubles | |
10611 | @opindex mno-unaligned-doubles | |
10612 | @opindex munaligned-doubles | |
10613 | Assume that doubles have 8 byte alignment. This is the default. | |
70899148 | 10614 | |
39bc1876 NS |
10615 | With @option{-munaligned-doubles}, GCC assumes that doubles have 8 byte |
10616 | alignment only if they are contained in another type, or if they have an | |
10617 | absolute address. Otherwise, it assumes they have 4 byte alignment. | |
10618 | Specifying this option avoids some rare compatibility problems with code | |
10619 | generated by other compilers. It is not the default because it results | |
10620 | in a performance loss, especially for floating point code. | |
70899148 | 10621 | |
39bc1876 NS |
10622 | @item -mno-faster-structs |
10623 | @itemx -mfaster-structs | |
10624 | @opindex mno-faster-structs | |
10625 | @opindex mfaster-structs | |
10626 | With @option{-mfaster-structs}, the compiler assumes that structures | |
10627 | should have 8 byte alignment. This enables the use of pairs of | |
10628 | @code{ldd} and @code{std} instructions for copies in structure | |
10629 | assignment, in place of twice as many @code{ld} and @code{st} pairs. | |
10630 | However, the use of this changed alignment directly violates the SPARC | |
10631 | ABI@. Thus, it's intended only for use on targets where the developer | |
10632 | acknowledges that their resulting code will not be directly in line with | |
10633 | the rules of the ABI@. | |
70899148 | 10634 | |
39bc1876 NS |
10635 | @item -mimpure-text |
10636 | @opindex mimpure-text | |
10637 | @option{-mimpure-text}, used in addition to @option{-shared}, tells | |
10638 | the compiler to not pass @option{-z text} to the linker when linking a | |
10639 | shared object. Using this option, you can link position-dependent | |
10640 | code into a shared object. | |
70899148 | 10641 | |
39bc1876 NS |
10642 | @option{-mimpure-text} suppresses the ``relocations remain against |
10643 | allocatable but non-writable sections'' linker error message. | |
10644 | However, the necessary relocations will trigger copy-on-write, and the | |
10645 | shared object is not actually shared across processes. Instead of | |
10646 | using @option{-mimpure-text}, you should compile all source code with | |
10647 | @option{-fpic} or @option{-fPIC}. | |
10648 | ||
10649 | This option is only available on SunOS and Solaris. | |
10650 | ||
10651 | @item -mcpu=@var{cpu_type} | |
10652 | @opindex mcpu | |
10653 | Set the instruction set, register set, and instruction scheduling parameters | |
10654 | for machine type @var{cpu_type}. Supported values for @var{cpu_type} are | |
10655 | @samp{v7}, @samp{cypress}, @samp{v8}, @samp{supersparc}, @samp{sparclite}, | |
10656 | @samp{f930}, @samp{f934}, @samp{hypersparc}, @samp{sparclite86x}, | |
10657 | @samp{sparclet}, @samp{tsc701}, @samp{v9}, @samp{ultrasparc}, and | |
10658 | @samp{ultrasparc3}. | |
70899148 | 10659 | |
39bc1876 NS |
10660 | Default instruction scheduling parameters are used for values that select |
10661 | an architecture and not an implementation. These are @samp{v7}, @samp{v8}, | |
10662 | @samp{sparclite}, @samp{sparclet}, @samp{v9}. | |
70899148 | 10663 | |
39bc1876 NS |
10664 | Here is a list of each supported architecture and their supported |
10665 | implementations. | |
70899148 | 10666 | |
39bc1876 NS |
10667 | @smallexample |
10668 | v7: cypress | |
10669 | v8: supersparc, hypersparc | |
10670 | sparclite: f930, f934, sparclite86x | |
10671 | sparclet: tsc701 | |
10672 | v9: ultrasparc, ultrasparc3 | |
10673 | @end smallexample | |
70899148 | 10674 | |
39bc1876 NS |
10675 | By default (unless configured otherwise), GCC generates code for the V7 |
10676 | variant of the SPARC architecture. With @option{-mcpu=cypress}, the compiler | |
10677 | additionally optimizes it for the Cypress CY7C602 chip, as used in the | |
10678 | SPARCStation/SPARCServer 3xx series. This is also appropriate for the older | |
10679 | SPARCStation 1, 2, IPX etc. | |
70899148 | 10680 | |
39bc1876 NS |
10681 | With @option{-mcpu=v8}, GCC generates code for the V8 variant of the SPARC |
10682 | architecture. The only difference from V7 code is that the compiler emits | |
10683 | the integer multiply and integer divide instructions which exist in SPARC-V8 | |
10684 | but not in SPARC-V7. With @option{-mcpu=supersparc}, the compiler additionally | |
10685 | optimizes it for the SuperSPARC chip, as used in the SPARCStation 10, 1000 and | |
10686 | 2000 series. | |
70899148 | 10687 | |
39bc1876 NS |
10688 | With @option{-mcpu=sparclite}, GCC generates code for the SPARClite variant of |
10689 | the SPARC architecture. This adds the integer multiply, integer divide step | |
10690 | and scan (@code{ffs}) instructions which exist in SPARClite but not in SPARC-V7. | |
10691 | With @option{-mcpu=f930}, the compiler additionally optimizes it for the | |
10692 | Fujitsu MB86930 chip, which is the original SPARClite, with no FPU. With | |
10693 | @option{-mcpu=f934}, the compiler additionally optimizes it for the Fujitsu | |
10694 | MB86934 chip, which is the more recent SPARClite with FPU. | |
70899148 | 10695 | |
39bc1876 NS |
10696 | With @option{-mcpu=sparclet}, GCC generates code for the SPARClet variant of |
10697 | the SPARC architecture. This adds the integer multiply, multiply/accumulate, | |
10698 | integer divide step and scan (@code{ffs}) instructions which exist in SPARClet | |
10699 | but not in SPARC-V7. With @option{-mcpu=tsc701}, the compiler additionally | |
10700 | optimizes it for the TEMIC SPARClet chip. | |
70899148 | 10701 | |
39bc1876 NS |
10702 | With @option{-mcpu=v9}, GCC generates code for the V9 variant of the SPARC |
10703 | architecture. This adds 64-bit integer and floating-point move instructions, | |
10704 | 3 additional floating-point condition code registers and conditional move | |
10705 | instructions. With @option{-mcpu=ultrasparc}, the compiler additionally | |
10706 | optimizes it for the Sun UltraSPARC I/II chips. With | |
10707 | @option{-mcpu=ultrasparc3}, the compiler additionally optimizes it for the | |
10708 | Sun UltraSPARC III chip. | |
70899148 | 10709 | |
39bc1876 NS |
10710 | @item -mtune=@var{cpu_type} |
10711 | @opindex mtune | |
10712 | Set the instruction scheduling parameters for machine type | |
10713 | @var{cpu_type}, but do not set the instruction set or register set that the | |
10714 | option @option{-mcpu=@var{cpu_type}} would. | |
70899148 | 10715 | |
39bc1876 NS |
10716 | The same values for @option{-mcpu=@var{cpu_type}} can be used for |
10717 | @option{-mtune=@var{cpu_type}}, but the only useful values are those | |
10718 | that select a particular cpu implementation. Those are @samp{cypress}, | |
10719 | @samp{supersparc}, @samp{hypersparc}, @samp{f930}, @samp{f934}, | |
10720 | @samp{sparclite86x}, @samp{tsc701}, @samp{ultrasparc}, and | |
10721 | @samp{ultrasparc3}. | |
70899148 | 10722 | |
39bc1876 NS |
10723 | @item -mv8plus |
10724 | @itemx -mno-v8plus | |
10725 | @opindex mv8plus | |
10726 | @opindex mno-v8plus | |
10727 | With @option{-mv8plus}, GCC generates code for the SPARC-V8+ ABI. The | |
10728 | difference from the V8 ABI is that the global and out registers are | |
10729 | considered 64-bit wide. This is enabled by default on Solaris in 32-bit | |
10730 | mode for all SPARC-V9 processors. | |
70899148 | 10731 | |
39bc1876 NS |
10732 | @item -mvis |
10733 | @itemx -mno-vis | |
10734 | @opindex mvis | |
10735 | @opindex mno-vis | |
10736 | With @option{-mvis}, GCC generates code that takes advantage of the UltraSPARC | |
10737 | Visual Instruction Set extensions. The default is @option{-mno-vis}. | |
10738 | @end table | |
70899148 | 10739 | |
39bc1876 NS |
10740 | These @samp{-m} options are supported in addition to the above |
10741 | on SPARC-V9 processors in 64-bit environments: | |
70899148 | 10742 | |
39bc1876 NS |
10743 | @table @gcctabopt |
10744 | @item -mlittle-endian | |
10745 | @opindex mlittle-endian | |
10746 | Generate code for a processor running in little-endian mode. It is only | |
10747 | available for a few configurations and most notably not on Solaris. | |
70899148 | 10748 | |
39bc1876 NS |
10749 | @item -m32 |
10750 | @itemx -m64 | |
10751 | @opindex m32 | |
10752 | @opindex m64 | |
10753 | Generate code for a 32-bit or 64-bit environment. | |
10754 | The 32-bit environment sets int, long and pointer to 32 bits. | |
10755 | The 64-bit environment sets int to 32 bits and long and pointer | |
10756 | to 64 bits. | |
70899148 | 10757 | |
39bc1876 NS |
10758 | @item -mcmodel=medlow |
10759 | @opindex mcmodel=medlow | |
10760 | Generate code for the Medium/Low code model: 64-bit addresses, programs | |
10761 | must be linked in the low 32 bits of memory. Programs can be statically | |
10762 | or dynamically linked. | |
70899148 | 10763 | |
39bc1876 NS |
10764 | @item -mcmodel=medmid |
10765 | @opindex mcmodel=medmid | |
10766 | Generate code for the Medium/Middle code model: 64-bit addresses, programs | |
10767 | must be linked in the low 44 bits of memory, the text and data segments must | |
10768 | be less than 2GB in size and the data segment must be located within 2GB of | |
10769 | the text segment. | |
70899148 | 10770 | |
39bc1876 NS |
10771 | @item -mcmodel=medany |
10772 | @opindex mcmodel=medany | |
10773 | Generate code for the Medium/Anywhere code model: 64-bit addresses, programs | |
10774 | may be linked anywhere in memory, the text and data segments must be less | |
10775 | than 2GB in size and the data segment must be located within 2GB of the | |
10776 | text segment. | |
70899148 | 10777 | |
39bc1876 NS |
10778 | @item -mcmodel=embmedany |
10779 | @opindex mcmodel=embmedany | |
10780 | Generate code for the Medium/Anywhere code model for embedded systems: | |
10781 | 64-bit addresses, the text and data segments must be less than 2GB in | |
10782 | size, both starting anywhere in memory (determined at link time). The | |
10783 | global register %g4 points to the base of the data segment. Programs | |
10784 | are statically linked and PIC is not supported. | |
70899148 | 10785 | |
39bc1876 NS |
10786 | @item -mstack-bias |
10787 | @itemx -mno-stack-bias | |
10788 | @opindex mstack-bias | |
10789 | @opindex mno-stack-bias | |
10790 | With @option{-mstack-bias}, GCC assumes that the stack pointer, and | |
10791 | frame pointer if present, are offset by @minus{}2047 which must be added back | |
10792 | when making stack frame references. This is the default in 64-bit mode. | |
10793 | Otherwise, assume no such offset is present. | |
10794 | @end table | |
70899148 | 10795 | |
39bc1876 NS |
10796 | @node System V Options |
10797 | @subsection Options for System V | |
70899148 | 10798 | |
39bc1876 NS |
10799 | These additional options are available on System V Release 4 for |
10800 | compatibility with other compilers on those systems: | |
70899148 | 10801 | |
39bc1876 NS |
10802 | @table @gcctabopt |
10803 | @item -G | |
10804 | @opindex G | |
10805 | Create a shared object. | |
10806 | It is recommended that @option{-symbolic} or @option{-shared} be used instead. | |
70899148 | 10807 | |
39bc1876 NS |
10808 | @item -Qy |
10809 | @opindex Qy | |
10810 | Identify the versions of each tool used by the compiler, in a | |
10811 | @code{.ident} assembler directive in the output. | |
70899148 | 10812 | |
39bc1876 NS |
10813 | @item -Qn |
10814 | @opindex Qn | |
10815 | Refrain from adding @code{.ident} directives to the output file (this is | |
10816 | the default). | |
70899148 | 10817 | |
39bc1876 NS |
10818 | @item -YP,@var{dirs} |
10819 | @opindex YP | |
10820 | Search the directories @var{dirs}, and no others, for libraries | |
10821 | specified with @option{-l}. | |
70899148 | 10822 | |
39bc1876 NS |
10823 | @item -Ym,@var{dir} |
10824 | @opindex Ym | |
10825 | Look in the directory @var{dir} to find the M4 preprocessor. | |
10826 | The assembler uses this option. | |
10827 | @c This is supposed to go with a -Yd for predefined M4 macro files, but | |
10828 | @c the generic assembler that comes with Solaris takes just -Ym. | |
10829 | @end table | |
70899148 | 10830 | |
39bc1876 NS |
10831 | @node TMS320C3x/C4x Options |
10832 | @subsection TMS320C3x/C4x Options | |
10833 | @cindex TMS320C3x/C4x Options | |
70899148 | 10834 | |
39bc1876 | 10835 | These @samp{-m} options are defined for TMS320C3x/C4x implementations: |
70899148 | 10836 | |
39bc1876 | 10837 | @table @gcctabopt |
70899148 | 10838 | |
39bc1876 NS |
10839 | @item -mcpu=@var{cpu_type} |
10840 | @opindex mcpu | |
10841 | Set the instruction set, register set, and instruction scheduling | |
10842 | parameters for machine type @var{cpu_type}. Supported values for | |
10843 | @var{cpu_type} are @samp{c30}, @samp{c31}, @samp{c32}, @samp{c40}, and | |
10844 | @samp{c44}. The default is @samp{c40} to generate code for the | |
10845 | TMS320C40. | |
70899148 | 10846 | |
39bc1876 NS |
10847 | @item -mbig-memory |
10848 | @itemx -mbig | |
10849 | @itemx -msmall-memory | |
10850 | @itemx -msmall | |
10851 | @opindex mbig-memory | |
10852 | @opindex mbig | |
10853 | @opindex msmall-memory | |
10854 | @opindex msmall | |
10855 | Generates code for the big or small memory model. The small memory | |
10856 | model assumed that all data fits into one 64K word page. At run-time | |
10857 | the data page (DP) register must be set to point to the 64K page | |
10858 | containing the .bss and .data program sections. The big memory model is | |
10859 | the default and requires reloading of the DP register for every direct | |
10860 | memory access. | |
70899148 | 10861 | |
39bc1876 NS |
10862 | @item -mbk |
10863 | @itemx -mno-bk | |
10864 | @opindex mbk | |
10865 | @opindex mno-bk | |
10866 | Allow (disallow) allocation of general integer operands into the block | |
10867 | count register BK@. | |
70899148 | 10868 | |
39bc1876 NS |
10869 | @item -mdb |
10870 | @itemx -mno-db | |
10871 | @opindex mdb | |
10872 | @opindex mno-db | |
10873 | Enable (disable) generation of code using decrement and branch, | |
10874 | DBcond(D), instructions. This is enabled by default for the C4x. To be | |
10875 | on the safe side, this is disabled for the C3x, since the maximum | |
10876 | iteration count on the C3x is @math{2^{23} + 1} (but who iterates loops more than | |
10877 | @math{2^{23}} times on the C3x?). Note that GCC will try to reverse a loop so | |
10878 | that it can utilize the decrement and branch instruction, but will give | |
10879 | up if there is more than one memory reference in the loop. Thus a loop | |
10880 | where the loop counter is decremented can generate slightly more | |
10881 | efficient code, in cases where the RPTB instruction cannot be utilized. | |
70899148 | 10882 | |
39bc1876 NS |
10883 | @item -mdp-isr-reload |
10884 | @itemx -mparanoid | |
10885 | @opindex mdp-isr-reload | |
10886 | @opindex mparanoid | |
10887 | Force the DP register to be saved on entry to an interrupt service | |
10888 | routine (ISR), reloaded to point to the data section, and restored on | |
10889 | exit from the ISR@. This should not be required unless someone has | |
10890 | violated the small memory model by modifying the DP register, say within | |
10891 | an object library. | |
70899148 | 10892 | |
39bc1876 NS |
10893 | @item -mmpyi |
10894 | @itemx -mno-mpyi | |
10895 | @opindex mmpyi | |
10896 | @opindex mno-mpyi | |
10897 | For the C3x use the 24-bit MPYI instruction for integer multiplies | |
10898 | instead of a library call to guarantee 32-bit results. Note that if one | |
10899 | of the operands is a constant, then the multiplication will be performed | |
10900 | using shifts and adds. If the @option{-mmpyi} option is not specified for the C3x, | |
10901 | then squaring operations are performed inline instead of a library call. | |
70899148 | 10902 | |
39bc1876 NS |
10903 | @item -mfast-fix |
10904 | @itemx -mno-fast-fix | |
10905 | @opindex mfast-fix | |
10906 | @opindex mno-fast-fix | |
10907 | The C3x/C4x FIX instruction to convert a floating point value to an | |
10908 | integer value chooses the nearest integer less than or equal to the | |
10909 | floating point value rather than to the nearest integer. Thus if the | |
10910 | floating point number is negative, the result will be incorrectly | |
10911 | truncated an additional code is necessary to detect and correct this | |
10912 | case. This option can be used to disable generation of the additional | |
10913 | code required to correct the result. | |
70899148 | 10914 | |
39bc1876 NS |
10915 | @item -mrptb |
10916 | @itemx -mno-rptb | |
10917 | @opindex mrptb | |
10918 | @opindex mno-rptb | |
10919 | Enable (disable) generation of repeat block sequences using the RPTB | |
10920 | instruction for zero overhead looping. The RPTB construct is only used | |
10921 | for innermost loops that do not call functions or jump across the loop | |
10922 | boundaries. There is no advantage having nested RPTB loops due to the | |
10923 | overhead required to save and restore the RC, RS, and RE registers. | |
10924 | This is enabled by default with @option{-O2}. | |
70899148 | 10925 | |
39bc1876 NS |
10926 | @item -mrpts=@var{count} |
10927 | @itemx -mno-rpts | |
10928 | @opindex mrpts | |
10929 | @opindex mno-rpts | |
10930 | Enable (disable) the use of the single instruction repeat instruction | |
10931 | RPTS@. If a repeat block contains a single instruction, and the loop | |
10932 | count can be guaranteed to be less than the value @var{count}, GCC will | |
10933 | emit a RPTS instruction instead of a RPTB@. If no value is specified, | |
10934 | then a RPTS will be emitted even if the loop count cannot be determined | |
10935 | at compile time. Note that the repeated instruction following RPTS does | |
10936 | not have to be reloaded from memory each iteration, thus freeing up the | |
10937 | CPU buses for operands. However, since interrupts are blocked by this | |
10938 | instruction, it is disabled by default. | |
70899148 | 10939 | |
39bc1876 NS |
10940 | @item -mloop-unsigned |
10941 | @itemx -mno-loop-unsigned | |
10942 | @opindex mloop-unsigned | |
10943 | @opindex mno-loop-unsigned | |
10944 | The maximum iteration count when using RPTS and RPTB (and DB on the C40) | |
10945 | is @math{2^{31} + 1} since these instructions test if the iteration count is | |
10946 | negative to terminate the loop. If the iteration count is unsigned | |
10947 | there is a possibility than the @math{2^{31} + 1} maximum iteration count may be | |
10948 | exceeded. This switch allows an unsigned iteration count. | |
70899148 | 10949 | |
39bc1876 NS |
10950 | @item -mti |
10951 | @opindex mti | |
10952 | Try to emit an assembler syntax that the TI assembler (asm30) is happy | |
10953 | with. This also enforces compatibility with the API employed by the TI | |
10954 | C3x C compiler. For example, long doubles are passed as structures | |
10955 | rather than in floating point registers. | |
70899148 | 10956 | |
39bc1876 NS |
10957 | @item -mregparm |
10958 | @itemx -mmemparm | |
10959 | @opindex mregparm | |
10960 | @opindex mmemparm | |
10961 | Generate code that uses registers (stack) for passing arguments to functions. | |
10962 | By default, arguments are passed in registers where possible rather | |
10963 | than by pushing arguments on to the stack. | |
70899148 | 10964 | |
39bc1876 NS |
10965 | @item -mparallel-insns |
10966 | @itemx -mno-parallel-insns | |
10967 | @opindex mparallel-insns | |
10968 | @opindex mno-parallel-insns | |
10969 | Allow the generation of parallel instructions. This is enabled by | |
10970 | default with @option{-O2}. | |
70899148 | 10971 | |
39bc1876 NS |
10972 | @item -mparallel-mpy |
10973 | @itemx -mno-parallel-mpy | |
10974 | @opindex mparallel-mpy | |
10975 | @opindex mno-parallel-mpy | |
10976 | Allow the generation of MPY||ADD and MPY||SUB parallel instructions, | |
10977 | provided @option{-mparallel-insns} is also specified. These instructions have | |
10978 | tight register constraints which can pessimize the code generation | |
10979 | of large functions. | |
70899148 | 10980 | |
39bc1876 | 10981 | @end table |
70899148 | 10982 | |
39bc1876 NS |
10983 | @node V850 Options |
10984 | @subsection V850 Options | |
10985 | @cindex V850 Options | |
70899148 | 10986 | |
39bc1876 | 10987 | These @samp{-m} options are defined for V850 implementations: |
70899148 | 10988 | |
39bc1876 NS |
10989 | @table @gcctabopt |
10990 | @item -mlong-calls | |
10991 | @itemx -mno-long-calls | |
10992 | @opindex mlong-calls | |
10993 | @opindex mno-long-calls | |
10994 | Treat all calls as being far away (near). If calls are assumed to be | |
10995 | far away, the compiler will always load the functions address up into a | |
10996 | register, and call indirect through the pointer. | |
70899148 | 10997 | |
39bc1876 NS |
10998 | @item -mno-ep |
10999 | @itemx -mep | |
11000 | @opindex mno-ep | |
11001 | @opindex mep | |
11002 | Do not optimize (do optimize) basic blocks that use the same index | |
11003 | pointer 4 or more times to copy pointer into the @code{ep} register, and | |
11004 | use the shorter @code{sld} and @code{sst} instructions. The @option{-mep} | |
11005 | option is on by default if you optimize. | |
70899148 | 11006 | |
39bc1876 NS |
11007 | @item -mno-prolog-function |
11008 | @itemx -mprolog-function | |
11009 | @opindex mno-prolog-function | |
11010 | @opindex mprolog-function | |
11011 | Do not use (do use) external functions to save and restore registers | |
11012 | at the prologue and epilogue of a function. The external functions | |
11013 | are slower, but use less code space if more than one function saves | |
11014 | the same number of registers. The @option{-mprolog-function} option | |
11015 | is on by default if you optimize. | |
70899148 | 11016 | |
39bc1876 NS |
11017 | @item -mspace |
11018 | @opindex mspace | |
11019 | Try to make the code as small as possible. At present, this just turns | |
11020 | on the @option{-mep} and @option{-mprolog-function} options. | |
70899148 | 11021 | |
39bc1876 NS |
11022 | @item -mtda=@var{n} |
11023 | @opindex mtda | |
11024 | Put static or global variables whose size is @var{n} bytes or less into | |
11025 | the tiny data area that register @code{ep} points to. The tiny data | |
11026 | area can hold up to 256 bytes in total (128 bytes for byte references). | |
70899148 | 11027 | |
39bc1876 NS |
11028 | @item -msda=@var{n} |
11029 | @opindex msda | |
11030 | Put static or global variables whose size is @var{n} bytes or less into | |
11031 | the small data area that register @code{gp} points to. The small data | |
11032 | area can hold up to 64 kilobytes. | |
70899148 | 11033 | |
39bc1876 NS |
11034 | @item -mzda=@var{n} |
11035 | @opindex mzda | |
11036 | Put static or global variables whose size is @var{n} bytes or less into | |
11037 | the first 32 kilobytes of memory. | |
70899148 | 11038 | |
39bc1876 NS |
11039 | @item -mv850 |
11040 | @opindex mv850 | |
11041 | Specify that the target processor is the V850. | |
70899148 | 11042 | |
39bc1876 NS |
11043 | @item -mbig-switch |
11044 | @opindex mbig-switch | |
11045 | Generate code suitable for big switch tables. Use this option only if | |
11046 | the assembler/linker complain about out of range branches within a switch | |
11047 | table. | |
70899148 | 11048 | |
39bc1876 NS |
11049 | @item -mapp-regs |
11050 | @opindex mapp-regs | |
11051 | This option will cause r2 and r5 to be used in the code generated by | |
11052 | the compiler. This setting is the default. | |
70899148 | 11053 | |
39bc1876 NS |
11054 | @item -mno-app-regs |
11055 | @opindex mno-app-regs | |
11056 | This option will cause r2 and r5 to be treated as fixed registers. | |
70899148 | 11057 | |
39bc1876 NS |
11058 | @item -mv850e1 |
11059 | @opindex mv850e1 | |
11060 | Specify that the target processor is the V850E1. The preprocessor | |
11061 | constants @samp{__v850e1__} and @samp{__v850e__} will be defined if | |
11062 | this option is used. | |
70899148 | 11063 | |
39bc1876 NS |
11064 | @item -mv850e |
11065 | @opindex mv850e | |
11066 | Specify that the target processor is the V850E. The preprocessor | |
11067 | constant @samp{__v850e__} will be defined if this option is used. | |
70899148 | 11068 | |
39bc1876 NS |
11069 | If neither @option{-mv850} nor @option{-mv850e} nor @option{-mv850e1} |
11070 | are defined then a default target processor will be chosen and the | |
11071 | relevant @samp{__v850*__} preprocessor constant will be defined. | |
70899148 | 11072 | |
39bc1876 NS |
11073 | The preprocessor constants @samp{__v850} and @samp{__v851__} are always |
11074 | defined, regardless of which processor variant is the target. | |
70899148 | 11075 | |
39bc1876 NS |
11076 | @item -mdisable-callt |
11077 | @opindex mdisable-callt | |
11078 | This option will suppress generation of the CALLT instruction for the | |
11079 | v850e and v850e1 flavors of the v850 architecture. The default is | |
11080 | @option{-mno-disable-callt} which allows the CALLT instruction to be used. | |
70899148 | 11081 | |
39bc1876 | 11082 | @end table |
70899148 | 11083 | |
39bc1876 NS |
11084 | @node VAX Options |
11085 | @subsection VAX Options | |
11086 | @cindex VAX options | |
70899148 | 11087 | |
39bc1876 | 11088 | These @samp{-m} options are defined for the VAX: |
70899148 | 11089 | |
39bc1876 NS |
11090 | @table @gcctabopt |
11091 | @item -munix | |
11092 | @opindex munix | |
11093 | Do not output certain jump instructions (@code{aobleq} and so on) | |
11094 | that the Unix assembler for the VAX cannot handle across long | |
11095 | ranges. | |
70899148 | 11096 | |
39bc1876 NS |
11097 | @item -mgnu |
11098 | @opindex mgnu | |
11099 | Do output those jump instructions, on the assumption that you | |
11100 | will assemble with the GNU assembler. | |
70899148 | 11101 | |
39bc1876 NS |
11102 | @item -mg |
11103 | @opindex mg | |
11104 | Output code for g-format floating point numbers instead of d-format. | |
11105 | @end table | |
70899148 | 11106 | |
39bc1876 NS |
11107 | @node x86-64 Options |
11108 | @subsection x86-64 Options | |
11109 | @cindex x86-64 options | |
70899148 | 11110 | |
39bc1876 | 11111 | These are listed under @xref{i386 and x86-64 Options}. |
70899148 | 11112 | |
39bc1876 NS |
11113 | @node Xstormy16 Options |
11114 | @subsection Xstormy16 Options | |
11115 | @cindex Xstormy16 Options | |
70899148 | 11116 | |
39bc1876 | 11117 | These options are defined for Xstormy16: |
70899148 | 11118 | |
39bc1876 NS |
11119 | @table @gcctabopt |
11120 | @item -msim | |
11121 | @opindex msim | |
11122 | Choose startup files and linker script suitable for the simulator. | |
70899148 BS |
11123 | @end table |
11124 | ||
03984308 BW |
11125 | @node Xtensa Options |
11126 | @subsection Xtensa Options | |
11127 | @cindex Xtensa Options | |
11128 | ||
6cedbe44 | 11129 | These options are supported for Xtensa targets: |
03984308 BW |
11130 | |
11131 | @table @gcctabopt | |
f42f5a1b BW |
11132 | @item -mconst16 |
11133 | @itemx -mno-const16 | |
11134 | @opindex mconst16 | |
11135 | @opindex mno-const16 | |
6c2e8d1c BW |
11136 | Enable or disable use of @code{CONST16} instructions for loading |
11137 | constant values. The @code{CONST16} instruction is currently not a | |
11138 | standard option from Tensilica. When enabled, @code{CONST16} | |
11139 | instructions are always used in place of the standard @code{L32R} | |
11140 | instructions. The use of @code{CONST16} is enabled by default only if | |
11141 | the @code{L32R} instruction is not available. | |
11142 | ||
03984308 BW |
11143 | @item -mfused-madd |
11144 | @itemx -mno-fused-madd | |
11145 | @opindex mfused-madd | |
11146 | @opindex mno-fused-madd | |
11147 | Enable or disable use of fused multiply/add and multiply/subtract | |
11148 | instructions in the floating-point option. This has no effect if the | |
11149 | floating-point option is not also enabled. Disabling fused multiply/add | |
11150 | and multiply/subtract instructions forces the compiler to use separate | |
11151 | instructions for the multiply and add/subtract operations. This may be | |
11152 | desirable in some cases where strict IEEE 754-compliant results are | |
11153 | required: the fused multiply add/subtract instructions do not round the | |
11154 | intermediate result, thereby producing results with @emph{more} bits of | |
11155 | precision than specified by the IEEE standard. Disabling fused multiply | |
11156 | add/subtract instructions also ensures that the program output is not | |
11157 | sensitive to the compiler's ability to combine multiply and add/subtract | |
11158 | operations. | |
11159 | ||
03984308 BW |
11160 | @item -mtext-section-literals |
11161 | @itemx -mno-text-section-literals | |
11162 | @opindex mtext-section-literals | |
11163 | @opindex mno-text-section-literals | |
11164 | Control the treatment of literal pools. The default is | |
11165 | @option{-mno-text-section-literals}, which places literals in a separate | |
11166 | section in the output file. This allows the literal pool to be placed | |
11167 | in a data RAM/ROM, and it also allows the linker to combine literal | |
11168 | pools from separate object files to remove redundant literals and | |
11169 | improve code size. With @option{-mtext-section-literals}, the literals | |
11170 | are interspersed in the text section in order to keep them as close as | |
11171 | possible to their references. This may be necessary for large assembly | |
11172 | files. | |
11173 | ||
11174 | @item -mtarget-align | |
11175 | @itemx -mno-target-align | |
11176 | @opindex mtarget-align | |
11177 | @opindex mno-target-align | |
11178 | When this option is enabled, GCC instructs the assembler to | |
11179 | automatically align instructions to reduce branch penalties at the | |
11180 | expense of some code density. The assembler attempts to widen density | |
11181 | instructions to align branch targets and the instructions following call | |
11182 | instructions. If there are not enough preceding safe density | |
11183 | instructions to align a target, no widening will be performed. The | |
11184 | default is @option{-mtarget-align}. These options do not affect the | |
11185 | treatment of auto-aligned instructions like @code{LOOP}, which the | |
11186 | assembler will always align, either by widening density instructions or | |
11187 | by inserting no-op instructions. | |
11188 | ||
11189 | @item -mlongcalls | |
11190 | @itemx -mno-longcalls | |
11191 | @opindex mlongcalls | |
11192 | @opindex mno-longcalls | |
11193 | When this option is enabled, GCC instructs the assembler to translate | |
11194 | direct calls to indirect calls unless it can determine that the target | |
11195 | of a direct call is in the range allowed by the call instruction. This | |
11196 | translation typically occurs for calls to functions in other source | |
11197 | files. Specifically, the assembler translates a direct @code{CALL} | |
11198 | instruction into an @code{L32R} followed by a @code{CALLX} instruction. | |
11199 | The default is @option{-mno-longcalls}. This option should be used in | |
11200 | programs where the call target can potentially be out of range. This | |
11201 | option is implemented in the assembler, not the compiler, so the | |
11202 | assembly code generated by GCC will still show direct call | |
11203 | instructions---look at the disassembled object code to see the actual | |
11204 | instructions. Note that the assembler will use an indirect call for | |
11205 | every cross-file call, not just those that really will be out of range. | |
11206 | @end table | |
11207 | ||
39bc1876 NS |
11208 | @node zSeries Options |
11209 | @subsection zSeries Options | |
11210 | @cindex zSeries options | |
11211 | ||
11212 | These are listed under @xref{S/390 and zSeries Options}. | |
11213 | ||
74291a4b MM |
11214 | @node Code Gen Options |
11215 | @section Options for Code Generation Conventions | |
11216 | @cindex code generation conventions | |
11217 | @cindex options, code generation | |
11218 | @cindex run-time options | |
11219 | ||
11220 | These machine-independent options control the interface conventions | |
11221 | used in code generation. | |
11222 | ||
11223 | Most of them have both positive and negative forms; the negative form | |
630d3d5a | 11224 | of @option{-ffoo} would be @option{-fno-foo}. In the table below, only |
74291a4b MM |
11225 | one of the forms is listed---the one which is not the default. You |
11226 | can figure out the other form by either removing @samp{no-} or adding | |
11227 | it. | |
11228 | ||
2642624b | 11229 | @table @gcctabopt |
d4463dfc JQ |
11230 | @item -fbounds-check |
11231 | @opindex fbounds-check | |
11232 | For front-ends that support it, generate additional code to check that | |
11233 | indices used to access arrays are within the declared range. This is | |
11234 | currently only supported by the Java and Fortran 77 front-ends, where | |
11235 | this option defaults to true and false respectively. | |
11236 | ||
11237 | @item -ftrapv | |
11238 | @opindex ftrapv | |
11239 | This option generates traps for signed overflow on addition, subtraction, | |
11240 | multiplication operations. | |
11241 | ||
4fa26a60 RS |
11242 | @item -fwrapv |
11243 | @opindex fwrapv | |
11244 | This option instructs the compiler to assume that signed arithmetic | |
11245 | overflow of addition, subtraction and multiplication wraps around | |
c0cbdbd9 | 11246 | using twos-complement representation. This flag enables some optimizations |
4fa26a60 RS |
11247 | and disables other. This option is enabled by default for the Java |
11248 | front-end, as required by the Java language specification. | |
11249 | ||
956d6950 | 11250 | @item -fexceptions |
cd3bb277 | 11251 | @opindex fexceptions |
767094dd | 11252 | Enable exception handling. Generates extra code needed to propagate |
f0523f02 | 11253 | exceptions. For some targets, this implies GCC will generate frame |
c5c76735 JL |
11254 | unwind information for all functions, which can produce significant data |
11255 | size overhead, although it does not affect execution. If you do not | |
f0523f02 | 11256 | specify this option, GCC will enable it by default for languages like |
90ecce3e | 11257 | C++ which normally require exception handling, and disable it for |
c5c76735 JL |
11258 | languages like C that do not normally require it. However, you may need |
11259 | to enable this option when compiling C code that needs to interoperate | |
11260 | properly with exception handlers written in C++. You may also wish to | |
11261 | disable this option if you are compiling older C++ programs that don't | |
11262 | use exception handling. | |
956d6950 | 11263 | |
6cfc0341 RH |
11264 | @item -fnon-call-exceptions |
11265 | @opindex fnon-call-exceptions | |
11266 | Generate code that allows trapping instructions to throw exceptions. | |
11267 | Note that this requires platform-specific runtime support that does | |
11268 | not exist everywhere. Moreover, it only allows @emph{trapping} | |
e979f9e8 | 11269 | instructions to throw exceptions, i.e.@: memory references or floating |
6cfc0341 RH |
11270 | point instructions. It does not allow exceptions to be thrown from |
11271 | arbitrary signal handlers such as @code{SIGALRM}. | |
11272 | ||
14a774a9 | 11273 | @item -funwind-tables |
cd3bb277 | 11274 | @opindex funwind-tables |
bedc7537 | 11275 | Similar to @option{-fexceptions}, except that it will just generate any needed |
14a774a9 RK |
11276 | static data, but will not affect the generated code in any other way. |
11277 | You will normally not enable this option; instead, a language processor | |
11278 | that needs this handling would enable it on your behalf. | |
11279 | ||
b932f770 JH |
11280 | @item -fasynchronous-unwind-tables |
11281 | @opindex funwind-tables | |
11282 | Generate unwind table in dwarf2 format, if supported by target machine. The | |
11283 | table is exact at each instruction boundary, so it can be used for stack | |
11284 | unwinding from asynchronous events (such as debugger or garbage collector). | |
11285 | ||
74291a4b | 11286 | @item -fpcc-struct-return |
cd3bb277 | 11287 | @opindex fpcc-struct-return |
74291a4b MM |
11288 | Return ``short'' @code{struct} and @code{union} values in memory like |
11289 | longer ones, rather than in registers. This convention is less | |
11290 | efficient, but it has the advantage of allowing intercallability between | |
a9c60612 JJ |
11291 | GCC-compiled files and files compiled with other compilers, particularly |
11292 | the Portable C Compiler (pcc). | |
74291a4b MM |
11293 | |
11294 | The precise convention for returning structures in memory depends | |
11295 | on the target configuration macros. | |
11296 | ||
11297 | Short structures and unions are those whose size and alignment match | |
11298 | that of some integer type. | |
11299 | ||
a9c60612 JJ |
11300 | @strong{Warning:} code compiled with the @option{-fpcc-struct-return} |
11301 | switch is not binary compatible with code compiled with the | |
11302 | @option{-freg-struct-return} switch. | |
11303 | Use it to conform to a non-default application binary interface. | |
11304 | ||
74291a4b | 11305 | @item -freg-struct-return |
cd3bb277 | 11306 | @opindex freg-struct-return |
9c34dbbf ZW |
11307 | Return @code{struct} and @code{union} values in registers when possible. |
11308 | This is more efficient for small structures than | |
11309 | @option{-fpcc-struct-return}. | |
74291a4b | 11310 | |
9c34dbbf | 11311 | If you specify neither @option{-fpcc-struct-return} nor |
630d3d5a | 11312 | @option{-freg-struct-return}, GCC defaults to whichever convention is |
0c2d1a2a | 11313 | standard for the target. If there is no standard convention, GCC |
9c34dbbf ZW |
11314 | defaults to @option{-fpcc-struct-return}, except on targets where GCC is |
11315 | the principal compiler. In those cases, we can choose the standard, and | |
11316 | we chose the more efficient register return alternative. | |
74291a4b | 11317 | |
a9c60612 JJ |
11318 | @strong{Warning:} code compiled with the @option{-freg-struct-return} |
11319 | switch is not binary compatible with code compiled with the | |
11320 | @option{-fpcc-struct-return} switch. | |
11321 | Use it to conform to a non-default application binary interface. | |
11322 | ||
74291a4b | 11323 | @item -fshort-enums |
cd3bb277 | 11324 | @opindex fshort-enums |
74291a4b MM |
11325 | Allocate to an @code{enum} type only as many bytes as it needs for the |
11326 | declared range of possible values. Specifically, the @code{enum} type | |
11327 | will be equivalent to the smallest integer type which has enough room. | |
11328 | ||
a9c60612 JJ |
11329 | @strong{Warning:} the @option{-fshort-enums} switch causes GCC to generate |
11330 | code that is not binary compatible with code generated without that switch. | |
11331 | Use it to conform to a non-default application binary interface. | |
11332 | ||
74291a4b | 11333 | @item -fshort-double |
cd3bb277 | 11334 | @opindex fshort-double |
74291a4b MM |
11335 | Use the same size for @code{double} as for @code{float}. |
11336 | ||
a9c60612 JJ |
11337 | @strong{Warning:} the @option{-fshort-double} switch causes GCC to generate |
11338 | code that is not binary compatible with code generated without that switch. | |
11339 | Use it to conform to a non-default application binary interface. | |
11340 | ||
11341 | @item -fshort-wchar | |
11342 | @opindex fshort-wchar | |
11343 | Override the underlying type for @samp{wchar_t} to be @samp{short | |
11344 | unsigned int} instead of the default for the target. This option is | |
11345 | useful for building programs to run under WINE@. | |
11346 | ||
11347 | @strong{Warning:} the @option{-fshort-wchar} switch causes GCC to generate | |
11348 | code that is not binary compatible with code generated without that switch. | |
11349 | Use it to conform to a non-default application binary interface. | |
11350 | ||
74291a4b | 11351 | @item -fshared-data |
cd3bb277 | 11352 | @opindex fshared-data |
74291a4b MM |
11353 | Requests that the data and non-@code{const} variables of this |
11354 | compilation be shared data rather than private data. The distinction | |
11355 | makes sense only on certain operating systems, where shared data is | |
11356 | shared between processes running the same program, while private data | |
11357 | exists in one copy per process. | |
11358 | ||
11359 | @item -fno-common | |
cd3bb277 | 11360 | @opindex fno-common |
90ecce3e | 11361 | In C, allocate even uninitialized global variables in the data section of the |
74291a4b MM |
11362 | object file, rather than generating them as common blocks. This has the |
11363 | effect that if the same variable is declared (without @code{extern}) in | |
11364 | two different compilations, you will get an error when you link them. | |
11365 | The only reason this might be useful is if you wish to verify that the | |
11366 | program will work on other systems which always work this way. | |
11367 | ||
11368 | @item -fno-ident | |
cd3bb277 | 11369 | @opindex fno-ident |
74291a4b MM |
11370 | Ignore the @samp{#ident} directive. |
11371 | ||
74291a4b | 11372 | @item -finhibit-size-directive |
cd3bb277 | 11373 | @opindex finhibit-size-directive |
74291a4b MM |
11374 | Don't output a @code{.size} assembler directive, or anything else that |
11375 | would cause trouble if the function is split in the middle, and the | |
11376 | two halves are placed at locations far apart in memory. This option is | |
11377 | used when compiling @file{crtstuff.c}; you should not need to use it | |
11378 | for anything else. | |
11379 | ||
11380 | @item -fverbose-asm | |
cd3bb277 | 11381 | @opindex fverbose-asm |
74291a4b MM |
11382 | Put extra commentary information in the generated assembly code to |
11383 | make it more readable. This option is generally only of use to those | |
11384 | who actually need to read the generated assembly code (perhaps while | |
11385 | debugging the compiler itself). | |
11386 | ||
630d3d5a | 11387 | @option{-fno-verbose-asm}, the default, causes the |
74291a4b MM |
11388 | extra information to be omitted and is useful when comparing two assembler |
11389 | files. | |
11390 | ||
74291a4b | 11391 | @item -fpic |
cd3bb277 | 11392 | @opindex fpic |
74291a4b MM |
11393 | @cindex global offset table |
11394 | @cindex PIC | |
11395 | Generate position-independent code (PIC) suitable for use in a shared | |
11396 | library, if supported for the target machine. Such code accesses all | |
161d7b59 | 11397 | constant addresses through a global offset table (GOT)@. The dynamic |
861bb6c1 | 11398 | loader resolves the GOT entries when the program starts (the dynamic |
0c2d1a2a | 11399 | loader is not part of GCC; it is part of the operating system). If |
861bb6c1 JL |
11400 | the GOT size for the linked executable exceeds a machine-specific |
11401 | maximum size, you get an error message from the linker indicating that | |
630d3d5a | 11402 | @option{-fpic} does not work; in that case, recompile with @option{-fPIC} |
b6e69d94 | 11403 | instead. (These maximums are 8k on the SPARC and 32k |
861bb6c1 | 11404 | on the m68k and RS/6000. The 386 has no such limit.) |
74291a4b MM |
11405 | |
11406 | Position-independent code requires special support, and therefore works | |
0c2d1a2a | 11407 | only on certain machines. For the 386, GCC supports PIC for System V |
74291a4b MM |
11408 | but not for the Sun 386i. Code generated for the IBM RS/6000 is always |
11409 | position-independent. | |
11410 | ||
74291a4b | 11411 | @item -fPIC |
cd3bb277 | 11412 | @opindex fPIC |
74291a4b MM |
11413 | If supported for the target machine, emit position-independent code, |
11414 | suitable for dynamic linking and avoiding any limit on the size of the | |
b6e69d94 | 11415 | global offset table. This option makes a difference on the m68k |
981f6289 | 11416 | and the SPARC. |
74291a4b MM |
11417 | |
11418 | Position-independent code requires special support, and therefore works | |
11419 | only on certain machines. | |
11420 | ||
24a4dd31 JJ |
11421 | @item -fpie |
11422 | @itemx -fPIE | |
11423 | @opindex fpie | |
11424 | @opindex fPIE | |
11425 | These options are similar to @option{-fpic} and @option{-fPIC}, but | |
11426 | generated position independent code can be only linked into executables. | |
11427 | Usually these options are used when @option{-pie} GCC option will be | |
11428 | used during linking. | |
11429 | ||
74291a4b | 11430 | @item -ffixed-@var{reg} |
cd3bb277 | 11431 | @opindex ffixed |
74291a4b MM |
11432 | Treat the register named @var{reg} as a fixed register; generated code |
11433 | should never refer to it (except perhaps as a stack pointer, frame | |
11434 | pointer or in some other fixed role). | |
11435 | ||
11436 | @var{reg} must be the name of a register. The register names accepted | |
11437 | are machine-specific and are defined in the @code{REGISTER_NAMES} | |
11438 | macro in the machine description macro file. | |
11439 | ||
11440 | This flag does not have a negative form, because it specifies a | |
11441 | three-way choice. | |
11442 | ||
11443 | @item -fcall-used-@var{reg} | |
cd3bb277 | 11444 | @opindex fcall-used |
956d6950 | 11445 | Treat the register named @var{reg} as an allocable register that is |
74291a4b MM |
11446 | clobbered by function calls. It may be allocated for temporaries or |
11447 | variables that do not live across a call. Functions compiled this way | |
11448 | will not save and restore the register @var{reg}. | |
11449 | ||
cb2fdc84 GRK |
11450 | It is an error to used this flag with the frame pointer or stack pointer. |
11451 | Use of this flag for other registers that have fixed pervasive roles in | |
11452 | the machine's execution model will produce disastrous results. | |
74291a4b MM |
11453 | |
11454 | This flag does not have a negative form, because it specifies a | |
11455 | three-way choice. | |
11456 | ||
11457 | @item -fcall-saved-@var{reg} | |
cd3bb277 | 11458 | @opindex fcall-saved |
956d6950 | 11459 | Treat the register named @var{reg} as an allocable register saved by |
74291a4b MM |
11460 | functions. It may be allocated even for temporaries or variables that |
11461 | live across a call. Functions compiled this way will save and restore | |
11462 | the register @var{reg} if they use it. | |
11463 | ||
cb2fdc84 GRK |
11464 | It is an error to used this flag with the frame pointer or stack pointer. |
11465 | Use of this flag for other registers that have fixed pervasive roles in | |
11466 | the machine's execution model will produce disastrous results. | |
74291a4b MM |
11467 | |
11468 | A different sort of disaster will result from the use of this flag for | |
11469 | a register in which function values may be returned. | |
11470 | ||
11471 | This flag does not have a negative form, because it specifies a | |
11472 | three-way choice. | |
11473 | ||
11474 | @item -fpack-struct | |
cd3bb277 | 11475 | @opindex fpack-struct |
a9c60612 JJ |
11476 | Pack all structure members together without holes. |
11477 | ||
11478 | @strong{Warning:} the @option{-fpack-struct} switch causes GCC to generate | |
11479 | code that is not binary compatible with code generated without that switch. | |
3364c33b | 11480 | Additionally, it makes the code suboptimal. |
a9c60612 | 11481 | Use it to conform to a non-default application binary interface. |
74291a4b | 11482 | |
07417085 | 11483 | @item -finstrument-functions |
cd3bb277 | 11484 | @opindex finstrument-functions |
07417085 KR |
11485 | Generate instrumentation calls for entry and exit to functions. Just |
11486 | after function entry and just before function exit, the following | |
11487 | profiling functions will be called with the address of the current | |
11488 | function and its call site. (On some platforms, | |
11489 | @code{__builtin_return_address} does not work beyond the current | |
11490 | function, so the call site information may not be available to the | |
11491 | profiling functions otherwise.) | |
11492 | ||
3ab51846 | 11493 | @smallexample |
310668e8 JM |
11494 | void __cyg_profile_func_enter (void *this_fn, |
11495 | void *call_site); | |
11496 | void __cyg_profile_func_exit (void *this_fn, | |
11497 | void *call_site); | |
3ab51846 | 11498 | @end smallexample |
07417085 KR |
11499 | |
11500 | The first argument is the address of the start of the current function, | |
11501 | which may be looked up exactly in the symbol table. | |
11502 | ||
11503 | This instrumentation is also done for functions expanded inline in other | |
11504 | functions. The profiling calls will indicate where, conceptually, the | |
11505 | inline function is entered and exited. This means that addressable | |
11506 | versions of such functions must be available. If all your uses of a | |
11507 | function are expanded inline, this may mean an additional expansion of | |
11508 | code size. If you use @samp{extern inline} in your C code, an | |
11509 | addressable version of such functions must be provided. (This is | |
11510 | normally the case anyways, but if you get lucky and the optimizer always | |
11511 | expands the functions inline, you might have gotten away without | |
11512 | providing static copies.) | |
11513 | ||
11514 | A function may be given the attribute @code{no_instrument_function}, in | |
11515 | which case this instrumentation will not be done. This can be used, for | |
11516 | example, for the profiling functions listed above, high-priority | |
11517 | interrupt routines, and any functions from which the profiling functions | |
11518 | cannot safely be called (perhaps signal handlers, if the profiling | |
11519 | routines generate output or allocate memory). | |
11520 | ||
861bb6c1 | 11521 | @item -fstack-check |
cd3bb277 | 11522 | @opindex fstack-check |
861bb6c1 JL |
11523 | Generate code to verify that you do not go beyond the boundary of the |
11524 | stack. You should specify this flag if you are running in an | |
11525 | environment with multiple threads, but only rarely need to specify it in | |
11526 | a single-threaded environment since stack overflow is automatically | |
11527 | detected on nearly all systems if there is only one stack. | |
11528 | ||
a157febd GK |
11529 | Note that this switch does not actually cause checking to be done; the |
11530 | operating system must do that. The switch causes generation of code | |
11531 | to ensure that the operating system sees the stack being extended. | |
11532 | ||
11533 | @item -fstack-limit-register=@var{reg} | |
11534 | @itemx -fstack-limit-symbol=@var{sym} | |
11535 | @itemx -fno-stack-limit | |
cd3bb277 JM |
11536 | @opindex fstack-limit-register |
11537 | @opindex fstack-limit-symbol | |
11538 | @opindex fno-stack-limit | |
a157febd GK |
11539 | Generate code to ensure that the stack does not grow beyond a certain value, |
11540 | either the value of a register or the address of a symbol. If the stack | |
11541 | would grow beyond the value, a signal is raised. For most targets, | |
11542 | the signal is raised before the stack overruns the boundary, so | |
11543 | it is possible to catch the signal without taking special precautions. | |
11544 | ||
9c34dbbf ZW |
11545 | For instance, if the stack starts at absolute address @samp{0x80000000} |
11546 | and grows downwards, you can use the flags | |
11547 | @option{-fstack-limit-symbol=__stack_limit} and | |
11548 | @option{-Wl,--defsym,__stack_limit=0x7ffe0000} to enforce a stack limit | |
11549 | of 128KB@. Note that this may only work with the GNU linker. | |
a157febd | 11550 | |
e5eb27e5 JL |
11551 | @cindex aliasing of parameters |
11552 | @cindex parameters, aliased | |
11553 | @item -fargument-alias | |
04afd9d6 JL |
11554 | @itemx -fargument-noalias |
11555 | @itemx -fargument-noalias-global | |
cd3bb277 JM |
11556 | @opindex fargument-alias |
11557 | @opindex fargument-noalias | |
11558 | @opindex fargument-noalias-global | |
e5eb27e5 JL |
11559 | Specify the possible relationships among parameters and between |
11560 | parameters and global data. | |
11561 | ||
630d3d5a | 11562 | @option{-fargument-alias} specifies that arguments (parameters) may |
9c34dbbf | 11563 | alias each other and may alias global storage.@* |
630d3d5a | 11564 | @option{-fargument-noalias} specifies that arguments do not alias |
9c34dbbf | 11565 | each other, but may alias global storage.@* |
630d3d5a | 11566 | @option{-fargument-noalias-global} specifies that arguments do not |
e5eb27e5 JL |
11567 | alias each other and do not alias global storage. |
11568 | ||
11569 | Each language will automatically use whatever option is required by | |
11570 | the language standard. You should not need to use these options yourself. | |
19283265 RH |
11571 | |
11572 | @item -fleading-underscore | |
cd3bb277 | 11573 | @opindex fleading-underscore |
695ac33f | 11574 | This option and its counterpart, @option{-fno-leading-underscore}, forcibly |
19283265 RH |
11575 | change the way C symbols are represented in the object file. One use |
11576 | is to help link with legacy assembly code. | |
11577 | ||
a9c60612 JJ |
11578 | @strong{Warning:} the @option{-fleading-underscore} switch causes GCC to |
11579 | generate code that is not binary compatible with code generated without that | |
11580 | switch. Use it to conform to a non-default application binary interface. | |
11581 | Not all targets provide complete support for this switch. | |
3d78f2e9 RH |
11582 | |
11583 | @item -ftls-model=@var{model} | |
11584 | Alter the thread-local storage model to be used (@pxref{Thread-Local}). | |
11585 | The @var{model} argument should be one of @code{global-dynamic}, | |
11586 | @code{local-dynamic}, @code{initial-exec} or @code{local-exec}. | |
11587 | ||
11588 | The default without @option{-fpic} is @code{initial-exec}; with | |
11589 | @option{-fpic} the default is @code{global-dynamic}. | |
74291a4b MM |
11590 | @end table |
11591 | ||
ee457005 JM |
11592 | @c man end |
11593 | ||
74291a4b | 11594 | @node Environment Variables |
0c2d1a2a | 11595 | @section Environment Variables Affecting GCC |
74291a4b MM |
11596 | @cindex environment variables |
11597 | ||
ee457005 | 11598 | @c man begin ENVIRONMENT |
0c2d1a2a JB |
11599 | This section describes several environment variables that affect how GCC |
11600 | operates. Some of them work by specifying directories or prefixes to use | |
767094dd | 11601 | when searching for various kinds of files. Some are used to specify other |
46103ab4 | 11602 | aspects of the compilation environment. |
74291a4b | 11603 | |
74291a4b | 11604 | Note that you can also specify places to search using options such as |
630d3d5a | 11605 | @option{-B}, @option{-I} and @option{-L} (@pxref{Directory Options}). These |
74291a4b | 11606 | take precedence over places specified using environment variables, which |
161d7b59 | 11607 | in turn take precedence over those specified by the configuration of GCC@. |
b11cc610 JM |
11608 | @xref{Driver,, Controlling the Compilation Driver @file{gcc}, gccint, |
11609 | GNU Compiler Collection (GCC) Internals}. | |
74291a4b | 11610 | |
bedc7537 | 11611 | @table @env |
ab87f8c8 JL |
11612 | @item LANG |
11613 | @itemx LC_CTYPE | |
11614 | @c @itemx LC_COLLATE | |
11615 | @itemx LC_MESSAGES | |
11616 | @c @itemx LC_MONETARY | |
11617 | @c @itemx LC_NUMERIC | |
11618 | @c @itemx LC_TIME | |
11619 | @itemx LC_ALL | |
11620 | @findex LANG | |
11621 | @findex LC_CTYPE | |
11622 | @c @findex LC_COLLATE | |
11623 | @findex LC_MESSAGES | |
11624 | @c @findex LC_MONETARY | |
11625 | @c @findex LC_NUMERIC | |
11626 | @c @findex LC_TIME | |
11627 | @findex LC_ALL | |
11628 | @cindex locale | |
0c2d1a2a JB |
11629 | These environment variables control the way that GCC uses |
11630 | localization information that allow GCC to work with different | |
11631 | national conventions. GCC inspects the locale categories | |
bedc7537 | 11632 | @env{LC_CTYPE} and @env{LC_MESSAGES} if it has been configured to do |
ab87f8c8 JL |
11633 | so. These locale categories can be set to any value supported by your |
11634 | installation. A typical value is @samp{en_UK} for English in the United | |
11635 | Kingdom. | |
11636 | ||
bedc7537 | 11637 | The @env{LC_CTYPE} environment variable specifies character |
0c2d1a2a | 11638 | classification. GCC uses it to determine the character boundaries in |
ab87f8c8 JL |
11639 | a string; this is needed for some multibyte encodings that contain quote |
11640 | and escape characters that would otherwise be interpreted as a string | |
11641 | end or escape. | |
11642 | ||
bedc7537 | 11643 | The @env{LC_MESSAGES} environment variable specifies the language to |
ab87f8c8 JL |
11644 | use in diagnostic messages. |
11645 | ||
bedc7537 NC |
11646 | If the @env{LC_ALL} environment variable is set, it overrides the value |
11647 | of @env{LC_CTYPE} and @env{LC_MESSAGES}; otherwise, @env{LC_CTYPE} | |
11648 | and @env{LC_MESSAGES} default to the value of the @env{LANG} | |
0c2d1a2a | 11649 | environment variable. If none of these variables are set, GCC |
ab87f8c8 JL |
11650 | defaults to traditional C English behavior. |
11651 | ||
74291a4b MM |
11652 | @item TMPDIR |
11653 | @findex TMPDIR | |
bedc7537 | 11654 | If @env{TMPDIR} is set, it specifies the directory to use for temporary |
0c2d1a2a | 11655 | files. GCC uses temporary files to hold the output of one stage of |
74291a4b MM |
11656 | compilation which is to be used as input to the next stage: for example, |
11657 | the output of the preprocessor, which is the input to the compiler | |
11658 | proper. | |
11659 | ||
11660 | @item GCC_EXEC_PREFIX | |
11661 | @findex GCC_EXEC_PREFIX | |
bedc7537 | 11662 | If @env{GCC_EXEC_PREFIX} is set, it specifies a prefix to use in the |
74291a4b MM |
11663 | names of the subprograms executed by the compiler. No slash is added |
11664 | when this prefix is combined with the name of a subprogram, but you can | |
11665 | specify a prefix that ends with a slash if you wish. | |
11666 | ||
f0523f02 | 11667 | If @env{GCC_EXEC_PREFIX} is not set, GCC will attempt to figure out |
0deb20df TT |
11668 | an appropriate prefix to use based on the pathname it was invoked with. |
11669 | ||
0c2d1a2a | 11670 | If GCC cannot find the subprogram using the specified prefix, it |
74291a4b MM |
11671 | tries looking in the usual places for the subprogram. |
11672 | ||
bedc7537 | 11673 | The default value of @env{GCC_EXEC_PREFIX} is |
8e5f33ff | 11674 | @file{@var{prefix}/lib/gcc/} where @var{prefix} is the value |
74291a4b MM |
11675 | of @code{prefix} when you ran the @file{configure} script. |
11676 | ||
630d3d5a | 11677 | Other prefixes specified with @option{-B} take precedence over this prefix. |
74291a4b MM |
11678 | |
11679 | This prefix is also used for finding files such as @file{crt0.o} that are | |
11680 | used for linking. | |
11681 | ||
11682 | In addition, the prefix is used in an unusual way in finding the | |
11683 | directories to search for header files. For each of the standard | |
8e5f33ff | 11684 | directories whose name normally begins with @samp{/usr/local/lib/gcc} |
bedc7537 | 11685 | (more precisely, with the value of @env{GCC_INCLUDE_DIR}), GCC tries |
74291a4b | 11686 | replacing that beginning with the specified prefix to produce an |
630d3d5a | 11687 | alternate directory name. Thus, with @option{-Bfoo/}, GCC will search |
74291a4b MM |
11688 | @file{foo/bar} where it would normally search @file{/usr/local/lib/bar}. |
11689 | These alternate directories are searched first; the standard directories | |
11690 | come next. | |
11691 | ||
11692 | @item COMPILER_PATH | |
11693 | @findex COMPILER_PATH | |
bedc7537 NC |
11694 | The value of @env{COMPILER_PATH} is a colon-separated list of |
11695 | directories, much like @env{PATH}. GCC tries the directories thus | |
74291a4b | 11696 | specified when searching for subprograms, if it can't find the |
bedc7537 | 11697 | subprograms using @env{GCC_EXEC_PREFIX}. |
74291a4b MM |
11698 | |
11699 | @item LIBRARY_PATH | |
11700 | @findex LIBRARY_PATH | |
bedc7537 NC |
11701 | The value of @env{LIBRARY_PATH} is a colon-separated list of |
11702 | directories, much like @env{PATH}. When configured as a native compiler, | |
0c2d1a2a | 11703 | GCC tries the directories thus specified when searching for special |
bedc7537 | 11704 | linker files, if it can't find them using @env{GCC_EXEC_PREFIX}. Linking |
0c2d1a2a | 11705 | using GCC also uses these directories when searching for ordinary |
630d3d5a JM |
11706 | libraries for the @option{-l} option (but directories specified with |
11707 | @option{-L} come first). | |
74291a4b | 11708 | |
56f48ce9 DB |
11709 | @item LANG |
11710 | @findex LANG | |
11711 | @cindex locale definition | |
767094dd | 11712 | This variable is used to pass locale information to the compiler. One way in |
56f48ce9 DB |
11713 | which this information is used is to determine the character set to be used |
11714 | when character literals, string literals and comments are parsed in C and C++. | |
11715 | When the compiler is configured to allow multibyte characters, | |
bedc7537 | 11716 | the following values for @env{LANG} are recognized: |
56f48ce9 | 11717 | |
2642624b | 11718 | @table @samp |
56f48ce9 DB |
11719 | @item C-JIS |
11720 | Recognize JIS characters. | |
11721 | @item C-SJIS | |
11722 | Recognize SJIS characters. | |
11723 | @item C-EUCJP | |
11724 | Recognize EUCJP characters. | |
11725 | @end table | |
11726 | ||
bedc7537 | 11727 | If @env{LANG} is not defined, or if it has some other value, then the |
56f48ce9 DB |
11728 | compiler will use mblen and mbtowc as defined by the default locale to |
11729 | recognize and translate multibyte characters. | |
74291a4b MM |
11730 | @end table |
11731 | ||
40adaa27 NB |
11732 | @noindent |
11733 | Some additional environments variables affect the behavior of the | |
11734 | preprocessor. | |
11735 | ||
11736 | @include cppenv.texi | |
11737 | ||
9d86bffc JM |
11738 | @c man end |
11739 | ||
17211ab5 GK |
11740 | @node Precompiled Headers |
11741 | @section Using Precompiled Headers | |
11742 | @cindex precompiled headers | |
11743 | @cindex speed of compilation | |
11744 | ||
11745 | Often large projects have many header files that are included in every | |
11746 | source file. The time the compiler takes to process these header files | |
11747 | over and over again can account for nearly all of the time required to | |
11748 | build the project. To make builds faster, GCC allows users to | |
11749 | `precompile' a header file; then, if builds can use the precompiled | |
11750 | header file they will be much faster. | |
11751 | ||
f7b6f250 MM |
11752 | @strong{Caution:} There are a few known situations where GCC will |
11753 | crash when trying to use a precompiled header. If you have trouble | |
11754 | with a precompiled header, you should remove the precompiled header | |
11755 | and compile without it. In addition, please use GCC's on-line | |
11756 | defect-tracking system to report any problems you encounter with | |
11757 | precompiled headers. @xref{Bugs}. | |
11758 | ||
17211ab5 GK |
11759 | To create a precompiled header file, simply compile it as you would any |
11760 | other file, if necessary using the @option{-x} option to make the driver | |
11761 | treat it as a C or C++ header file. You will probably want to use a | |
11762 | tool like @command{make} to keep the precompiled header up-to-date when | |
11763 | the headers it contains change. | |
11764 | ||
11765 | A precompiled header file will be searched for when @code{#include} is | |
11766 | seen in the compilation. As it searches for the included file | |
24726b96 | 11767 | (@pxref{Search Path,,Search Path,cpp,The C Preprocessor}) the |
17211ab5 GK |
11768 | compiler looks for a precompiled header in each directory just before it |
11769 | looks for the include file in that directory. The name searched for is | |
d8fad4ea | 11770 | the name specified in the @code{#include} with @samp{.gch} appended. If |
17211ab5 GK |
11771 | the precompiled header file can't be used, it is ignored. |
11772 | ||
11773 | For instance, if you have @code{#include "all.h"}, and you have | |
d8fad4ea | 11774 | @file{all.h.gch} in the same directory as @file{all.h}, then the |
17211ab5 GK |
11775 | precompiled header file will be used if possible, and the original |
11776 | header will be used otherwise. | |
11777 | ||
11778 | Alternatively, you might decide to put the precompiled header file in a | |
11779 | directory and use @option{-I} to ensure that directory is searched | |
11780 | before (or instead of) the directory containing the original header. | |
11781 | Then, if you want to check that the precompiled header file is always | |
11782 | used, you can put a file of the same name as the original header in this | |
11783 | directory containing an @code{#error} command. | |
11784 | ||
11785 | This also works with @option{-include}. So yet another way to use | |
11786 | precompiled headers, good for projects not designed with precompiled | |
11787 | header files in mind, is to simply take most of the header files used by | |
11788 | a project, include them from another header file, precompile that header | |
11789 | file, and @option{-include} the precompiled header. If the header files | |
11790 | have guards against multiple inclusion, they will be skipped because | |
11791 | they've already been included (in the precompiled header). | |
11792 | ||
11793 | If you need to precompile the same header file for different | |
11794 | languages, targets, or compiler options, you can instead make a | |
d8fad4ea | 11795 | @emph{directory} named like @file{all.h.gch}, and put each precompiled |
54e109ed GK |
11796 | header in the directory, perhaps using @option{-o}. It doesn't matter |
11797 | what you call the files in the directory, every precompiled header in | |
11798 | the directory will be considered. The first precompiled header | |
11799 | encountered in the directory that is valid for this compilation will | |
11800 | be used; they're searched in no particular order. | |
17211ab5 GK |
11801 | |
11802 | There are many other possibilities, limited only by your imagination, | |
11803 | good sense, and the constraints of your build system. | |
11804 | ||
11805 | A precompiled header file can be used only when these conditions apply: | |
11806 | ||
11807 | @itemize | |
11808 | @item | |
11809 | Only one precompiled header can be used in a particular compilation. | |
54e109ed | 11810 | |
17211ab5 GK |
11811 | @item |
11812 | A precompiled header can't be used once the first C token is seen. You | |
11813 | can have preprocessor directives before a precompiled header; you can | |
11814 | even include a precompiled header from inside another header, so long as | |
11815 | there are no C tokens before the @code{#include}. | |
54e109ed | 11816 | |
17211ab5 GK |
11817 | @item |
11818 | The precompiled header file must be produced for the same language as | |
11819 | the current compilation. You can't use a C precompiled header for a C++ | |
11820 | compilation. | |
54e109ed | 11821 | |
17211ab5 GK |
11822 | @item |
11823 | The precompiled header file must be produced by the same compiler | |
11824 | version and configuration as the current compilation is using. | |
11825 | The easiest way to guarantee this is to use the same compiler binary | |
11826 | for creating and using precompiled headers. | |
54e109ed | 11827 | |
17211ab5 | 11828 | @item |
54e109ed GK |
11829 | Any macros defined before the precompiled header is included must |
11830 | either be defined in the same way as when the precompiled header was | |
11831 | generated, or must not affect the precompiled header, which usually | |
11832 | means that the they don't appear in the precompiled header at all. | |
11833 | ||
11834 | The @option{-D} option is one way to define a macro before a | |
11835 | precompiled header is included; using a @code{#define} can also do it. | |
11836 | There are also some options that define macros implicitly, like | |
11837 | @option{-O} and @option{-Wdeprecated}; the same rule applies to macros | |
11838 | defined this way. | |
11839 | ||
11840 | @item If debugging information is output when using the precompiled | |
11841 | header, using @option{-g} or similar, the same kind of debugging information | |
11842 | must have been output when building the precompiled header. However, | |
11843 | a precompiled header built using @option{-g} can be used in a compilation | |
11844 | when no debugging information is being output. | |
11845 | ||
11846 | @item The same @option{-m} options must generally be used when building | |
11847 | and using the precompiled header. @xref{Submodel Options}, | |
11848 | for any cases where this rule is relaxed. | |
11849 | ||
11850 | @item Each of the following options must be the same when building and using | |
11851 | the precompiled header: | |
11852 | ||
11853 | @gccoptlist{-fexceptions -funit-at-a-time} | |
11854 | ||
17211ab5 | 11855 | @item |
54e109ed GK |
11856 | Some other command-line options starting with @option{-f}, |
11857 | @option{-p}, or @option{-O} must be defined in the same way as when | |
11858 | the precompiled header was generated. At present, it's not clear | |
11859 | which options are safe to change and which are not; the safest choice | |
11860 | is to use exactly the same options when generating and using the | |
11861 | precompiled header. The following are known to be safe: | |
11862 | ||
c0d578e6 | 11863 | @gccoptlist{-fpreprocessed -pedantic-errors} |
54e109ed | 11864 | |
17211ab5 GK |
11865 | @end itemize |
11866 | ||
54e109ed GK |
11867 | For all of these except the last, the compiler will automatically |
11868 | ignore the precompiled header if the conditions aren't met. If you | |
11869 | find an option combination that doesn't work and doesn't cause the | |
11870 | precompiled header to be ignored, please consider filing a bug report, | |
11871 | see @ref{Bugs}. | |
17211ab5 | 11872 | |
c0d578e6 GK |
11873 | If you do use differing options when generating and using the |
11874 | precompiled header, the actual behaviour will be a mixture of the | |
11875 | behaviour for the options. For instance, if you use @option{-g} to | |
11876 | generate the precompiled header but not when using it, you may or may | |
11877 | not get debugging information for routines in the precompiled header. | |
11878 | ||
74291a4b MM |
11879 | @node Running Protoize |
11880 | @section Running Protoize | |
11881 | ||
161d7b59 | 11882 | The program @code{protoize} is an optional part of GCC@. You can use |
c1030c7c | 11883 | it to add prototypes to a program, thus converting the program to ISO |
74291a4b MM |
11884 | C in one respect. The companion program @code{unprotoize} does the |
11885 | reverse: it removes argument types from any prototypes that are found. | |
11886 | ||
11887 | When you run these programs, you must specify a set of source files as | |
11888 | command line arguments. The conversion programs start out by compiling | |
11889 | these files to see what functions they define. The information gathered | |
11890 | about a file @var{foo} is saved in a file named @file{@var{foo}.X}. | |
11891 | ||
11892 | After scanning comes actual conversion. The specified files are all | |
11893 | eligible to be converted; any files they include (whether sources or | |
11894 | just headers) are eligible as well. | |
11895 | ||
11896 | But not all the eligible files are converted. By default, | |
11897 | @code{protoize} and @code{unprotoize} convert only source and header | |
11898 | files in the current directory. You can specify additional directories | |
630d3d5a | 11899 | whose files should be converted with the @option{-d @var{directory}} |
74291a4b | 11900 | option. You can also specify particular files to exclude with the |
630d3d5a | 11901 | @option{-x @var{file}} option. A file is converted if it is eligible, its |
74291a4b MM |
11902 | directory name matches one of the specified directory names, and its |
11903 | name within the directory has not been excluded. | |
11904 | ||
11905 | Basic conversion with @code{protoize} consists of rewriting most | |
11906 | function definitions and function declarations to specify the types of | |
11907 | the arguments. The only ones not rewritten are those for varargs | |
11908 | functions. | |
11909 | ||
11910 | @code{protoize} optionally inserts prototype declarations at the | |
11911 | beginning of the source file, to make them available for any calls that | |
11912 | precede the function's definition. Or it can insert prototype | |
11913 | declarations with block scope in the blocks where undeclared functions | |
11914 | are called. | |
11915 | ||
11916 | Basic conversion with @code{unprotoize} consists of rewriting most | |
11917 | function declarations to remove any argument types, and rewriting | |
c1030c7c | 11918 | function definitions to the old-style pre-ISO form. |
74291a4b MM |
11919 | |
11920 | Both conversion programs print a warning for any function declaration or | |
11921 | definition that they can't convert. You can suppress these warnings | |
630d3d5a | 11922 | with @option{-q}. |
74291a4b MM |
11923 | |
11924 | The output from @code{protoize} or @code{unprotoize} replaces the | |
11925 | original source file. The original file is renamed to a name ending | |
02f52e19 | 11926 | with @samp{.save} (for DOS, the saved filename ends in @samp{.sav} |
a7db8bbb MK |
11927 | without the original @samp{.c} suffix). If the @samp{.save} (@samp{.sav} |
11928 | for DOS) file already exists, then the source file is simply discarded. | |
74291a4b | 11929 | |
0c2d1a2a | 11930 | @code{protoize} and @code{unprotoize} both depend on GCC itself to |
74291a4b | 11931 | scan the program and collect information about the functions it uses. |
0c2d1a2a | 11932 | So neither of these programs will work until GCC is installed. |
74291a4b MM |
11933 | |
11934 | Here is a table of the options you can use with @code{protoize} and | |
11935 | @code{unprotoize}. Each option works with both programs unless | |
11936 | otherwise stated. | |
11937 | ||
11938 | @table @code | |
11939 | @item -B @var{directory} | |
11940 | Look for the file @file{SYSCALLS.c.X} in @var{directory}, instead of the | |
11941 | usual directory (normally @file{/usr/local/lib}). This file contains | |
11942 | prototype information about standard system functions. This option | |
11943 | applies only to @code{protoize}. | |
11944 | ||
11945 | @item -c @var{compilation-options} | |
05739753 | 11946 | Use @var{compilation-options} as the options when running @command{gcc} to |
630d3d5a | 11947 | produce the @samp{.X} files. The special option @option{-aux-info} is |
05739753 | 11948 | always passed in addition, to tell @command{gcc} to write a @samp{.X} file. |
74291a4b MM |
11949 | |
11950 | Note that the compilation options must be given as a single argument to | |
11951 | @code{protoize} or @code{unprotoize}. If you want to specify several | |
05739753 | 11952 | @command{gcc} options, you must quote the entire set of compilation options |
74291a4b MM |
11953 | to make them a single word in the shell. |
11954 | ||
05739753 | 11955 | There are certain @command{gcc} arguments that you cannot use, because they |
630d3d5a JM |
11956 | would produce the wrong kind of output. These include @option{-g}, |
11957 | @option{-O}, @option{-c}, @option{-S}, and @option{-o} If you include these in | |
74291a4b MM |
11958 | the @var{compilation-options}, they are ignored. |
11959 | ||
11960 | @item -C | |
a7db8bbb | 11961 | Rename files to end in @samp{.C} (@samp{.cc} for DOS-based file |
02f52e19 | 11962 | systems) instead of @samp{.c}. This is convenient if you are converting |
ee77eda5 | 11963 | a C program to C++. This option applies only to @code{protoize}. |
74291a4b MM |
11964 | |
11965 | @item -g | |
11966 | Add explicit global declarations. This means inserting explicit | |
11967 | declarations at the beginning of each source file for each function | |
11968 | that is called in the file and was not declared. These declarations | |
11969 | precede the first function definition that contains a call to an | |
11970 | undeclared function. This option applies only to @code{protoize}. | |
11971 | ||
11972 | @item -i @var{string} | |
11973 | Indent old-style parameter declarations with the string @var{string}. | |
11974 | This option applies only to @code{protoize}. | |
11975 | ||
11976 | @code{unprotoize} converts prototyped function definitions to old-style | |
11977 | function definitions, where the arguments are declared between the | |
11978 | argument list and the initial @samp{@{}. By default, @code{unprotoize} | |
11979 | uses five spaces as the indentation. If you want to indent with just | |
630d3d5a | 11980 | one space instead, use @option{-i " "}. |
74291a4b MM |
11981 | |
11982 | @item -k | |
11983 | Keep the @samp{.X} files. Normally, they are deleted after conversion | |
11984 | is finished. | |
11985 | ||
11986 | @item -l | |
630d3d5a | 11987 | Add explicit local declarations. @code{protoize} with @option{-l} inserts |
74291a4b MM |
11988 | a prototype declaration for each function in each block which calls the |
11989 | function without any declaration. This option applies only to | |
11990 | @code{protoize}. | |
11991 | ||
11992 | @item -n | |
11993 | Make no real changes. This mode just prints information about the conversions | |
630d3d5a | 11994 | that would have been done without @option{-n}. |
74291a4b MM |
11995 | |
11996 | @item -N | |
11997 | Make no @samp{.save} files. The original files are simply deleted. | |
11998 | Use this option with caution. | |
11999 | ||
12000 | @item -p @var{program} | |
12001 | Use the program @var{program} as the compiler. Normally, the name | |
12002 | @file{gcc} is used. | |
12003 | ||
12004 | @item -q | |
12005 | Work quietly. Most warnings are suppressed. | |
12006 | ||
12007 | @item -v | |
05739753 | 12008 | Print the version number, just like @option{-v} for @command{gcc}. |
74291a4b MM |
12009 | @end table |
12010 | ||
12011 | If you need special compiler options to compile one of your program's | |
12012 | source files, then you should generate that file's @samp{.X} file | |
05739753 | 12013 | specially, by running @command{gcc} on that source file with the |
630d3d5a | 12014 | appropriate options and the option @option{-aux-info}. Then run |
74291a4b MM |
12015 | @code{protoize} on the entire set of files. @code{protoize} will use |
12016 | the existing @samp{.X} file because it is newer than the source file. | |
12017 | For example: | |
12018 | ||
3ab51846 | 12019 | @smallexample |
b1018de6 | 12020 | gcc -Dfoo=bar file1.c -aux-info file1.X |
74291a4b | 12021 | protoize *.c |
3ab51846 | 12022 | @end smallexample |
74291a4b MM |
12023 | |
12024 | @noindent | |
12025 | You need to include the special files along with the rest in the | |
12026 | @code{protoize} command, even though their @samp{.X} files already | |
12027 | exist, because otherwise they won't get converted. | |
12028 | ||
12029 | @xref{Protoize Caveats}, for more information on how to use | |
12030 | @code{protoize} successfully. |