This is the mail archive of the
gcc-patches@gcc.gnu.org
mailing list for the GCC project.
[gfortran] Update documentation.
- From: Paul Brook <paul at codesourcery dot com>
- To: fortran at gcc dot gnu dot org, gcc-patches at gcc dot gnu dot org
- Date: Sun, 11 Apr 2004 12:34:44 +0100
- Subject: [gfortran] Update documentation.
- Organization: CodeSourcery
The attached patch updates the gfortran documentation. I've ripped out some
old bits, made changes so it's more consistent with the website, and added
documentation for the commandline options.
I'm fairly sure there are still names missing from the "Contributors" section,
so if you think you should be listed, please let me know.
Applied to tree-ssa branch.
Paul
2004-04-11 Paul Brook <paul@codesourcery.com>
* Make-lang.in (GFORTRAN_TEXI): Set it.
(fortran/dfortran.dvi): Use it. Add fortran to include paths.
(fortran/gfortran.info): Ditto.
* gfortran.texi: Major update.
* invoke.texi: New file.
Index: Make-lang.in
===================================================================
RCS file: /var/cvsroot/gcc-cvs/gcc/gcc/fortran/Attic/Make-lang.in,v
retrieving revision 1.1.2.15
diff -u -r1.1.2.15 Make-lang.in
--- a/Make-lang.in 19 Feb 2004 08:19:56 -0000 1.1.2.15
+++ b/Make-lang.in 11 Apr 2004 11:22:38 -0000
@@ -150,23 +150,25 @@
lang_checks += check-gfortran
# GFORTRAN documentation.
-fortran/gfortran.info: $(srcdir)/fortran/gfortran.texi \
- $(srcdir)/doc/include/fdl.texi \
- $(srcdir)/doc/include/gpl.texi \
- $(srcdir)/doc/include/funding.texi \
- $(srcdir)/doc/include/gcc-common.texi
+GFORTRAN_TEXI = \
+ $(srcdir)/fortran/gfortran.texi \
+ $(srcdir)/fortran/invoke.texi \
+ $(srcdir)/doc/include/fdl.texi \
+ $(srcdir)/doc/include/gpl.texi \
+ $(srcdir)/doc/include/funding.texi \
+ $(srcdir)/doc/include/gcc-common.texi
+
+fortran/gfortran.info: $(GFORTRAN_TEXI)
if [ x$(BUILD_INFO) = xinfo ]; then \
rm -f fortran/gfortran.info-*; \
- $(MAKEINFO) -I$(srcdir)/doc/include -o fortran/gfortran.info $(srcdir)/fortran/gfortran.texi; \
+ $(MAKEINFO) -I$(srcdir)/doc/include -I$(srcdir)/fortran \
+ -o fortran/gfortran.info $(srcdir)/fortran/gfortran.texi; \
else true; fi
-fortran/gfortran.dvi: $(srcdir)/fortran/gfortran.texi \
- $(srcdir)/doc/include/fdl.texi \
- $(srcdir)/doc/include/gpl.texi \
- $(srcdir)/doc/include/funding.texi \
- $(srcdir)/doc/include/gcc-common.texi
- s=`cd $(srcdir); ${PWD}`; export s; \
- cd fortran && $(TEXI2DVI) -I $$s/doc/include $$s/fortran/gfortran.texi
+fortran/gfortran.dvi: $(GFORTRAN_TEXI)
+ s=`cd $(srcdir); ${PWD}`; export s; \
+ cd fortran && $(TEXI2DVI) -I $$s/doc/include -I $$s/fortran \
+ $$s/fortran/gfortran.texi
#
# Install hooks:
Index: gfortran.texi
===================================================================
RCS file: /var/cvsroot/gcc-cvs/gcc/gcc/fortran/Attic/gfortran.texi,v
retrieving revision 1.1.2.4
diff -u -r1.1.2.4 gfortran.texi
--- a/gfortran.texi 8 Feb 2004 16:38:47 -0000 1.1.2.4
+++ b/gfortran.texi 11 Apr 2004 10:54:06 -0000
@@ -1,8 +1,8 @@
\input texinfo @c -*-texinfo-*-
@c %**start of header
@setfilename gfortran.info
-@set last-update January 06, 2003
-@set copyrights-gfortran 1999-2003
+@set last-update March 10, 2004
+@set copyrights-gfortran 1999-2004
@set version-gfortran 0.235
@include gcc-common.texi
@@ -120,13 +120,9 @@
and how to report bugs.
@ifset DEVELOPMENT
-@emph{Warning:} This document is still under development,
-and might not accurately reflect the status of the
-most recent @command{gfortran}.
-This compiler is still under development,
-and even though efforts are made to keep this document up-to-date,
-for now we will put emphasis on developing the compiler itself
-rather than on writing user documentation.
+@emph{Warning:} This document, and the compiler it describes, are still
+under development. While efforts are made too keep it up-to-date it might
+not accurately reflect the status of the most recent @command{gfortran}.
@end ifset
@menu
@@ -138,7 +134,7 @@
* Getting Started:: What you should know about @command{gfortran}.
* GFORTRAN and GCC:: You can compile Fortran, C, or other programs.
* GFORTRAN and G77:: Why we choose to start from scratch.
-@c * Invoking GFORTRAN:: Command options supported by @command{gfortran}.
+* Invoking GFORTRAN:: Command options supported by @command{gfortran}.
* Compiling and Testing::
Need-to-knows about compiling and testing.
* Project Status:: Status of GFORTRAN, Roadmap, proposed extensions.
@@ -285,7 +281,7 @@
@command{f951} ``translates'' the source code to
assembler code. You would typically not use this
program directly;
-instead, the @command{gcc} or @command{f951} driver
+instead, the @command{gcc} or @command{gfortran} driver
programs will call it for you.
@end itemize
@@ -334,48 +330,6 @@
GNU Fortran 95 has a strict separation between the
parser and code generator.
-The default installation of the GNU Compiler Collection
-includes a number of fine compiler front ends:
-
-@itemize @bullet
-@item
-A ``C'' front end, compatible with a number of ``C'' dialects,
-including ANSI C99 and good-old K&R ``C'' for some of you
-old-timers out there.
-
-@item
-A C++ front end with a complete implementation of the
-Standard Template Library.
-
-@item
-An Objective-C front end
-(with work in progress on an Obj-C++ front end).
-
-@item
-The GNU Fortran 77 front end @command{g77},
-the compiler that, in a way, saved FORTRAN from an
-early death. See @ref{GFORTRAN and G77}
-
-@item
-The GNAT Ada 95 front end from Ada Core Technologies.
-This is the @emph{de facto} industry standard Ada compiler,
-and it has been integrated in GCC for version 3.1 and up.
-
-@item
-A Java (TM) front end that creates byte code
-or machine code executables.
-
-@item
-An example front end called ``treelang''.
-This front end is not shipped with release versions of GCC,
-but it does install itself if you use a CVS snapshot.
-@end itemize
-
-Many more front ends exist,
-including very serious ones like GNU Pascal,
-but also many toy front ends,
-and front ends used for teaching courses in compiler design.
-
The goal of the gfortran project is to build a new front end for GCC:
A Fortran 95 front end.
In a non-gfortran installation,
@@ -429,6 +383,7 @@
and then build a Fortran 95 compiler out of it.
+@include invoke.texi
@c ---------------------------------------------------------------------
@c Compiling and Testing
@@ -437,46 +392,60 @@
@node Compiling and Testing
@chapter Compiling and Testing
+@command{gfortran} is not yet part of an official GCC release, so it is
+unlikley that OS distributor will provide it.
+
@menu
+* Precompiled Binaries::
* General notes about compiling GFORTRAN::
* Compiling GFORTRAN::
* Testing::
@end menu
+@node Precompiled Binaries
+@section Precompiled Binaries
+
+Precompiled binaries for i686-linux in rpm format are available from
+@uref{http://people.redhat.com/dnovillo/pub/tree-ssa/snapshot/}
+
@node General notes about compiling GFORTRAN
@section General notes about compiling GFORTRAN
@cindex GMP
-@cindex Multiple Precision
+@cindex Multiple Precision Library
Compiling gfortran requires the presence of GMP,
the GNU Multiple Precision library version 4.0
or better in order to do its arithmetic.
Download @code{gmp} from your favorite GNU mirror,
-configure and compile it. Your mileage may vary.
+configure and compile it. If your OS distributor provides prepackaged
+GMP libraries, you may also need the developent pacakges.
+If you do not have GMP installed in a standard system location, you may
+need to configure GCC with @option{--with-gmp} or @option{--with-gmp-dir}.
+
+Note: GMP is only required for the compiler itself. Compiled fortran programs
+do not depend on the GMP library.
@node Compiling GFORTRAN
@section Compiling GFORTRAN
@cindex Make-lang.in
-To build gfortran,
-you first need to get a copy of the GCC source tree.
+To build gfortran, you first need to get a copy of the GCC source tree.
gfortran uses the new @dfn{GENERIC} intermediate representation
to communicate with the back end.
This new IR has not been merged yet with the GCC mainline,
so you'll need to get a snapshot of the
@emph{tree-ssa-20020619-branch} from the GCC CVS repository.
+This branch also contains the latest version
You can check out this branch from the GNU Subversions server:
@example
-$ cvs -d :pserver:anoncvs@@subversions.gnu.org:/cvsroot/gcc login
-(press enter if asked for a password)
-$ cvs -z9 -d :pserver:anoncvs@@subversions.gnu.org:/cvsroot/gcc co -r tree-ssa-20020619-branch gcc
+$ export CVS_RSH=ssh
+$ cvs -z9 -d :ext:anoncvs@@subversions.gnu.org:/cvsroot/gcc co -r tree-ssa-20020619-branch gcc
@end example
You can now build GCC following the instructions on the
@uref{htpp://gcc.gnu.org/,GCC homepage},
-but with the f95 front end enabled
(configure with @option{--enable-languages=f95}).
@@ -493,17 +462,9 @@
In this way, we can be assured that once your fix has been made,
the problem isn't re-introduced at some later time.
-The suites are located on Sourceforge in the directory
-@file{/home/groups/g/g9/g95/htdocs/test_suite/}.
-To get it, just use @command{sftp} to login to your Sourceforge account.
-If you don't have a Sourceforge account,
-you can get a tar-gzipped copy of the suites by pointing
-your browser to @uref{http://g95.sourceforge.net/cgi-bin/send_suite}.
-
-If you wish to add test code,
-mail your test code to the gcc-g95 mailing list,
-or to one of the individual developers if your test
-code is really large.
+The gfortran test suite is included in the gcc source distribution.
+
+We also encourage you to test gfortran on your own Fortran codes.
@c ---------------------------------------------------------------------
@c Project Status
@@ -527,149 +488,93 @@
the GCC homepage in March 18, 2000
(even though Andy had already been working on it for a while,
or course).
-What is the current status of gfortran?
+
+Gfortran is currently reaching the stage where is is able to compile real
+world programs. However it is still under development and has many rough
+edges.
@menu
* Compiler Status::
-* Milestones::
+* Library Status::
* Proposed Extensions::
@end menu
@node Compiler Status
@section Compiler Status
-The Fortran 95 parser is as good as finished,
-and most of the type and name resolution phase has been
-implemented as well.
-This means that @command{gfortran} correctly generates complete syntax
-trees from the source files it gets thrown at.
-@command{gfortran} does @emph{not} produce executables for the full
-Fortran 95 language at this stage,
-but we @emph{can} generate code for most statements and expressions.
-We are aiming for feature-completeness before GCC 3.5
-(probably around Q2 2004).
-
-The compiler can also produces modules (a @code{.mod}-file).
-The @code{.mod}-files do not contain object code,
-but they do contain information needed for compiling,
-@emph{not linking!},
-program units which @code{USE} the module,
-i.e. public interfaces, constants, etc.
-Those @code{.mod}-files are generated during the parsing stage.
-Most commercial compilers generate a @code{.mod}-file for
-every module they encounter, and an @code{.o}-file
-for every source file.
-We plan to do the same.
-
-After the type resolution phase is finished,
-the @code{gfc_code} trees are translated to @command{gcc}'s
-GENERIC intermediate representation.
-The back end then generates first RTL, and later assembly and
-object-code from this representation.
-The resulting object code will have to be linked against a
-library which contains Fortran's intrinsics, I/O-code, etc.
-Once all this is finished, you have a working Fortran 95 executable.
-
-Very different parts of a complete Fortran development
-framework are missing:
-
-@enumerate
-@item Parser
-Mostly finished, but some parts are still missing.
-Writing the parser is tedious work,
-since it is very bug-prone on both the language-side
-(understand the standard correctly)
-and on the implementation side (build data structures that
-contain the actual program's information -- and represent in
-a way that is well suited to manipulation of GNU back
-end subroutines and macros that generate the back-end
-@code{tree} structures).
-We would also like to add support for the F programming
-language, which is essentially a subset of Fortran 90.
-See @ref{Projects}.
-
-@item Back end interface
-Work on this interface has only started recently.
-The interface translates gfortran's syntax tree to a
-data structure from which the back end can generate code.
-
-This is supposedly an easier part of the work.
-It implies agreeing on the data layout
-(where we can take examples from other compilers),
-building the AST and making all this work together.
-
-GCC is moving to a new,
-high level intermediate representation
-(``GENERIC'', essentially a subset three-code variant of C).
-There's some unfinished but good documentation
-on @code{tree} structures in the GCC manual,
-but these documents appear to be more useful for
-architecture hackers than for front end people.
-
-@item The runtime library
-This is a large chunk of work,
-but big chunks of it can actually be implemented in Fortran,
-thus allowing the target audience to contribute
-(which supposedly is much more Fortran-savvy than C-savvy),
-and allowing greater parallelism in getting this work done;
-this also allows for saving us work by taking parts of
-SGI's Pro64 Fortran 90 library, under certain circumstances.
-@end enumerate
+@itemize @emph
+@item Front end
+This is the part of gfortran which parses a source file, verifies that it
+is valid Fortran 95, performs compile time replacement of constants
+(PARAMETER variables) and reads and generate module files. This is
+almost complete. Every Fortran 95 source should be accepted, and most
+none-Fortran 95 source should be rejected. If you find a source file where
+this is not true, please tell us. You can use the -fsyntax-only switch to
+make gfortran quit after running the front end, effectively reducing it to
+a syntax checker.
+
+@item Middle end interface
+These are the parts of gfortran that take the parse tree generated by the
+front end and translate it to the GENERIC form required by the GCC back
+end. Work is ongoing in these parts of gfortran, but a large part has
+already been completed.
+@end itemize
+@node Library Status
+@section Library Status
-@node Milestones
-@section Milestones
+Some intrinsic functions map directly to library functions, and in most
+cases the name of the library function used depends on the type of the
+arguments. For some intrinsics we generate inline code, and for others,
+such as sin, cos and sqrt, we rely on the backend to use special
+instructions in the floating point unit of the CPU if available, or to
+fall back to a call to libm if these are not available.
+
+Implementation of some non-elemental intrinsic functions (eg. DOT_PRODUCT,
+AVERAGE) is not yet optimal. This is hard because we have to make decisions
+whether to use inline code (good for small arrays as no function call
+overhead occurs) or generate function calls (good for large arrays as it
+allows use of hand-optimized assembly routines, SIMD instructions, etc.)
-``Mainstream'' projects:
+The IO library is still under development. The following features should be
+usable for real programs:
-@itemize @bullet
-@item
-Figure out what remaining test suite parse failures are due to bad
-Fortran code (@emph{ongoing}, but more people needed. Any volunteers?).
-
-@item
-Implement error printing for diagnostics within simplification
-functions.
-
-@item
-Implement section 14.1.2 Procedure type resolution
-rules (@emph{ongoing}).
+@itemize @minus
+@item List directed
+@item Unformatted sequential
+@end itemize
-@item
-Reduce the resolution phase error percentage (@emph{ongoing}).
+Usable with bugs:
-@item
-Finish interfacing with GCC (@emph{ongoing}).
+@itemize @minus
+@item Formatted sequential ('T' edit descriptor, and others)
+@item Namelist (can read a namelist that it writes, but not free-form)
+@end itemize
-@item
-Start interfacing with runtime libraries
- -- I/O, math and unix (@emph{ongoing}).
+Not recommended:
-@item
-Start work on producing what the I/O libraries lack.
+@itemize @minus
+@item Unformatted direct access
+@item Formatted direct access
@end itemize
+Many Fortran programs only use a small subset of the available IO
+capabilities, so your milage may vary.
@node Proposed Extensions
@section Proposed Extensions
-Here's a list of proposed extensions for @command{gfortran}.
-Most of these are necessary to be fully compatible with
-existing Fortran compilers,
-but they are not part of the official J3 Fortran 95 standard.
+Here's a list of proposed extensions for @command{gfortran}, in no particular
+order. Most of these are necessary to be fully compatible with
+existing Fortran compilers, but they are not part of the official
+J3 Fortran 95 standard.
@subsection Compiler extensions:
@itemize @bullet
@item
-Flag for suppressing warning messages.
-
-@item
Flag for defining the kind number for default logicals.
@item
--r8 and -i8 options to define default real and integer kinds.
-
-@item
User-specified alignment rules for structures.
@item
Flag to generate a @code{Makefile} info.
@@ -680,10 +585,6 @@
@item
Cray pointers (this was high on the @command{g77} wishlist).
-@item
-Compile flag to generate code for array bounds checking (similar to
-@command{g77}'s -fbounds-check).
-
@item
Compile code that conserves memory by dynamically allocating common and
module storage either on stack or heap.
@@ -700,9 +601,6 @@
Compile flag to generate code for array conformance checking (suggest -CC).
@item
-Support conditional compilation (i.e. through a preprocessor).
-
-@item
User control of symbol names (underscores, etc).
@item
@@ -733,11 +631,17 @@
Allow setting default unit number.
@item
-Flag to cause compiler to dump the parse tree in ASCII form.
-
-@item
Option to initialize of otherwise uninitialized integer and floating
point variables.
+
+@item
+Support for OpenMP directives. This also requires support from the runtime
+library and the rest of the compiler.
+
+@item
+Support for Fortran 200x. This includes several new features including
+floating point exceptions, extended use of allocatable arrays, C
+interoperability, Parameterizer data types and function pointers.
@end itemize
@@ -850,6 +754,8 @@
@item Niels Kristian Bech Jensen
@item Steven Johnson
@item Paul Brook
+@item Feng Wang
+@item Bud Davis
@end itemize
The following people have contributed bug reports,
@@ -868,8 +774,7 @@
and we welcome you to do the same!
If you already have done so,
and you would like to see your name listed in the
-list above, please feel free to mail the project maintainer.
-@c TODO: fill in maintainer email
+list above, please contact us.
@node Projects
@@ -890,7 +795,7 @@
@item Smaller projects (``bug'' fixes):
@itemize @minus
@item Allow init exprs to be numbers raised to integer powers.
- @item Implement correct rounding
+ @item Implement correct rounding.
@item Implement F restrictions on Fortran 95 syntax.
@item See about making Emacs-parsable error messages.
@end itemize
Index: invoke.texi
===================================================================
RCS file: invoke.texi
diff -N invoke.texi
--- /dev/null 1 Jan 1970 00:00:00 -0000
+++ b/invoke.texi 11 Apr 2004 11:11:29 -0000
@@ -0,0 +1,656 @@
+@c Copyright (C) 2004
+@c Free Software Foundation, Inc.
+@c This is part of the GFORTRAN manual.
+@c For copying conditions, see the file gfortran.texi.
+
+@ignore
+@c man begin COPYRIGHT
+Copyright @copyright{} 2004
+Free Software Foundation, Inc.
+
+Permission is granted to copy, distribute and/or modify this document
+under the terms of the GNU Free Documentation License, Version 1.2 or
+any later version published by the Free Software Foundation; with the
+Invariant Sections being ``GNU General Public License'' and ``Funding
+Free Software'', the Front-Cover texts being (a) (see below), and with
+the Back-Cover Texts being (b) (see below). A copy of the license is
+included in the gfdl(7) man page.
+
+(a) The FSF's Front-Cover Text is:
+
+ A GNU Manual
+
+(b) The FSF's Back-Cover Text is:
+
+ You have freedom to copy and modify this GNU Manual, like GNU
+ software. Copies published by the Free Software Foundation raise
+ funds for GNU development.
+@c man end
+@c Set file name and title for the man page.
+@setfilename gfortran
+@settitle GNU Fortran 95 compiler.
+@c man begin SYNOPSIS
+gfortran [@option{-c}|@option{-S}|@option{-E}]
+ [@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
+ [@option{-W}@var{warn}@dots{}] [@option{-pedantic}]
+ [@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
+ [@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
+ [@option{-f}@var{option}@dots{}]
+ [@option{-m}@var{machine-option}@dots{}]
+ [@option{-o} @var{outfile}] @var{infile}@dots{}
+
+Only the most useful options are listed here; see below for the
+remainder.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7),
+cpp(1), gcov(1), gcc(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1)
+and the Info entries for @file{gcc}, @file{cpp}, @file{gfortran}, @file{as},
+@file{ld}, @file{binutils} and @file{gdb}.
+@c man end
+@c man begin BUGS
+For instructions on reporting bugs, see
+@w{@uref{http://gcc.gnu.org/bugs.html}}.
+@c man end
+@c man begin AUTHOR
+See the Info entry for @command{gfortran} for contributors to GCC and
+GFORTRAN@.
+@c man end
+@end ignore
+
+@node Invoking GFORTRAN
+@chapter GNU Fortran 95 Command Options
+@cindex GNU Fortran 95 command options
+@cindex command options
+@cindex options, GNU Fortran 95 command
+
+@c man begin DESCRIPTION
+
+The @command{gfortran} command supports all the options supported by the
+@command{gcc} command. Only options specific to gfortran are documented here.
+
+@xref{Invoking GCC,,GCC Command Options,gcc,Using the GNU Compiler
+Collection (GCC)}, for information
+on the non-Fortran-specific aspects of the @command{gcc} command (and,
+therefore, the @command{gfortran} command).
+
+@cindex options, negative forms
+@cindex negative forms of options
+All @command{gcc} and @command{gfortran} options
+are accepted both by @command{gfortran} and by @command{gcc}
+(as well as any other drivers built at the same time,
+such as @command{g++}),
+since adding @command{gfortran} to the @command{gcc} distribution
+enables acceptance of @command{gfortran} options
+by all of the relevant drivers.
+
+In some cases, options have positive and negative forms;
+the negative form of @option{-ffoo} would be @option{-fno-foo}.
+This manual documents only one of these two forms, whichever
+one is not the default.
+@c man end
+
+@menu
+* Option Summary:: Brief list of all @command{gfortran} options,
+ without explanations.
+* Fortran Dialect Options:: Controlling the variant of Fortran language
+ compiled.
+* Warning Options:: How picky should the compiler be?
+* Debugging Options:: Symbol tables, measurements, and debugging dumps.
+* Directory Options:: Where to find module files
+* Code Gen Options:: Specifying conventions for function calls, data layout
+ and register usage.
+* Environment Variables:: Env vars that affect GNU Fortran.
+@end menu
+
+@node Option Summary
+@section Option Summary
+
+@c man begin OPTIONS
+
+Here is a summary of all the options specific to GNU Fortran, grouped
+by type. Explanations are in the following sections.
+
+@table @emph
+@item Fortran Language Options
+@xref{Fortran Dialect Options,,Options Controlling Fortran Dialect}.
+@gccoptlist{
+-ffree-form -fno-fixed-form @gol
+-fdollar-ok -fimplicit-none -fmax-identifier-length @gol
+-std=@var{std}
+-ffixed-line-length-@var{n} -ffixed-line-length-none @gol
+-i8 -r8 -d8}
+
+@item Warning Options
+@xref{Warning Options,,Options to Request or Suppress Warnings}.
+@gccoptlist{
+-fsyntax-only -pedantic -pedantic-errors @gol
+-w -Wall -Waliasing -Wconversion @gol
+-Wimplicit-interface -Wsurprising -Wunused-labels @gol
+-Wline-truncation @gol
+-Werror -W}
+
+@item Debugging Options
+@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
+@gccoptlist{
+-fdump-parse-tree}
+
+@item Directory Options
+@xref{Directory Options,,Options for Directory Search}.
+@gccoptlist{
+-I@var{dir} -M@var{dir}}
+
+@item Code Generation Options
+@xref{Code Gen Options,,Options for Code Generation Conventions}.
+@gccoptlist{
+-fno-underscoring -fno-second-underscore @gol
+-fbounds-check -fmax-stack-var-size=@var{n} @gol
+-fpackderived -frepack-arrays}
+@end table
+
+@c man end
+
+@menu
+* Fortran Dialect Options:: Controlling the variant of Fortran language
+ compiled.
+* Warning Options:: How picky should the compiler be?
+* Debugging Options:: Symbol tables, measurements, and debugging dumps.
+* Directory Options:: Where to find module files
+* Code Gen Options:: Specifying conventions for function calls, data layout
+ and register usage.
+@end menu
+
+@node Fortran Dialect Options
+@section Options Controlling Fortran Dialect
+@cindex dialect options
+@cindex language, dialect options
+@cindex options, dialect
+
+The following options control the dialect of Fortran
+that the compiler accepts:
+
+@table @gcctabopt
+@cindex -ffree-form option
+@cindex options, -ffree-form
+@cindex -fno-fixed-form option
+@cindex options, -fno-fixed-form
+@cindex source file format
+@cindex free form
+@cindex fixed form
+@cindex Source Form
+@cindex Fortran 90, features
+@item -ffree-form
+@item -ffixed-form
+Specify the layout used by the the source file. The tree form layout
+was introduced in Fortran 90. Fixed form was traditionally used in
+older Fortran programs.
+
+@cindex -fdollar-ok option
+@cindex options, -fdollar-ok
+@item -fdollar-ok
+@cindex dollar sign
+@cindex symbol names
+@cindex character set
+Allow @samp{$} as a valid character in a symbol name.
+
+@cindex -ffixed-line-length-@var{n} option
+@cindex options, -ffixed-line-length-@var{n}
+@item -ffixed-line-length-@var{n}
+@cindex source file format
+@cindex lines, length
+@cindex length of source lines
+@cindex fixed form
+@cindex limits, lengths of source lines
+Set column after which characters are ignored in typical fixed-form
+lines in the source file, and through which spaces are assumed (as
+if padded to that length) after the ends of short fixed-form lines.
+
+@cindex card image
+@cindex extended-source option
+Popular values for @var{n} include 72 (the
+standard and the default), 80 (card image), and 132 (corresponds
+to ``extended-source'' options in some popular compilers).
+@var{n} may be @samp{none}, meaning that the entire line is meaningful
+and that continued character constants never have implicit spaces appended
+to them to fill out the line.
+@option{-ffixed-line-length-0} means the same thing as
+@option{-ffixed-line-length-none}.
+
+@cindex -fmax-identifier-length=@var{n} option
+@cindex option -fmax-identifier-length=@var{n}
+@item -fmax-identifier-length=@var{n}
+Specify the maximum allowed identifier length. Typical values are
+31 (Fortran 95) and 63 (Fortran 200x).
+
+@cindex -fimpicit-none option
+@cindex options, -fimplicit-none
+@item -fimplicit-none
+Specify that no implicit typing is allowed, unless overridden by explicit
+@samp{IMPLICIT} statements. This is the equivalent of adding
+@samp{implicit none} to the start of every procedure.
+
+@cindex -std=@var{std} option
+@cindex option, -std=@var{std}
+@item -std=@var{std}
+Conform to the specified standard. Allowed values for @var{std} are
+@samp{gnu}, @samp{f95} and @samp{f90}.
+
+@cindex option, -i8
+@cindex -i8, option
+@cindex option, -r8
+@cindex -r8, option
+@cindex option, -d8
+@cindex -d8, option
+@item -i8
+@item -r8
+@item -d8
+The @option{-i8} and @option{-j8} options set the default INTEGER and REAL
+kinds to KIND=8. The @option{-d8} option is equivalent to specifying
+both @option{-i8} and @option{-r8}.
+
+@end table
+
+@node Warning Options
+@section Options to Request or Suppress Warnings
+@cindex options, warnings
+@cindex warnings, suppressing
+@cindex messages, warning
+@cindex suppressing warnings
+
+Warnings are diagnostic messages that report constructions which
+are not inherently erroneous but which are risky or suggest there
+might have been an error.
+
+You can request many specific warnings with options beginning @option{-W},
+for example @option{-Wimplicit} to request warnings on implicit
+declarations. Each of these specific warning options also has a
+negative form beginning @option{-Wno-} to turn off warnings;
+for example, @option{-Wno-implicit}. This manual lists only one of the
+two forms, whichever is not the default.
+
+These options control the amount and kinds of warnings produced by GNU
+Fortran:
+
+@table @gcctabopt
+@cindex syntax checking
+@cindex -fsyntax-only option
+@cindex options, -fsyntax-only
+@item -fsyntax-only
+Check the code for syntax errors, but don't do anything beyond that.
+
+@cindex -pedantic option
+@cindex options, -pedantic
+@item -pedantic
+Issue warnings for uses of extensions to FORTRAN 95.
+@option{-pedantic} also applies to C-language constructs where they
+occur in GNU Fortran source files, such as use of @samp{\e} in a
+character constant within a directive like @samp{#include}.
+
+Valid FORTRAN 95 programs should compile properly with or without
+this option.
+However, without this option, certain GNU extensions and traditional
+Fortran features are supported as well.
+With this option, many of them are rejected.
+
+Some users try to use @option{-pedantic} to check programs for conformance.
+They soon find that it does not do quite what they want---it finds some
+nonstandard practices, but not all.
+However, improvements to @command{gfortran} in this area are welcome.
+
+This should be used in conjunction with -std=@var{std}.
+
+@cindex -pedantic-errors option
+@cindex options, -pedantic-errors
+@item -pedantic-errors
+Like @option{-pedantic}, except that errors are produced rather than
+warnings.
+
+@cindex -w option
+@cindex options, -w
+@item -w
+Inhibit all warning messages.
+
+
+@cindex -Wall option
+@cindex options, -Wall
+@item -Wall
+@cindex all warnings
+@cindex warnings, all
+Enables commonly used warning options that which pertain to usage that
+we recommend avoiding and that we believe is easy to avoid.
+This currenly includes @option{-Wunused-labels}, @option{-Waliasing},
+@option{-Wsurprising} and @option{-Wline-truncation}.
+
+
+@cindex -Waliasing option
+@cindex options, -Waliasing
+@item -Waliasing
+@cindex aliasing
+Warn about possible aliasing of dummy arguments. The following example
+witll trigger teh warhing as it would be illegal to @code{bar} to
+modify either parameter.
+@smallexample
+ INTEGER A
+ CALL BAR(A,A)
+@end smallexample
+
+
+@cindex -Wconversion option
+@cindex options, -Wconversion
+@item -Wconversion
+@cindex conversion
+Warn about implicit conversions between different types.
+
+
+@cindex -Wimplicit-interface option
+@cindex options, -Wimplicit-interface
+@item -Wimplicit-interface
+Warn about when procedure are called without an explicit interface.
+Note this only checks that an explicit interface is present. It does not
+check that the declared interfaces are consistent across program units.
+
+
+@cindex -Wsurprising
+@cindex options, -Wsurprising
+@item -Wsurprising
+@cindex Suspicious
+Produce a warning when ``suspicous'' code constructs are encountered.
+While techically legal these usually indicate that an error has been made.
+
+This currently produces a warning under the following circumstances:
+
+@itemize @bullet
+@item
+An INTEGER SELECT construct has a CASE the can never be matched as it's
+lower value that is greater than its upper value.
+
+@item
+A LOGICAL SELECT construct has three CASE statements.
+@end itemize
+
+@cindex -Wunused-labels option
+@cindex options, -Wunused-labels
+@item -Wunused-labels
+@cindex unused labels
+@cindex labels, unused
+Warn whenever a label is defined but never referenced.
+
+
+@cindex -Werror
+@cindex options, -Werror
+@item -Werror
+Turns all warnings into errors.
+
+
+@cindex -W option
+@cindex options, -W
+@item -W
+@cindex extra warnings
+@cindex warnings, extra
+Turns on ``extra warnings'' and, if optimization is specified
+via @option{-O}, the @option{-Wuninitialized} option.
+(This might change in future versions of @command{gfortran}
+@end table
+
+@xref{Warning Options,,Options to Request or Suppress Warnings,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on more
+options offered by the GBE shared by @command{gfortran}, @command{gcc} and
+other GNU compilers.
+
+Some of these have no effect when compiling programs written in Fortran.
+
+@node Debugging Options
+@section Options for Debugging Your Program or GNU Fortran
+@cindex options, debugging
+@cindex debugging information options
+
+GNU Fortran has various special options that are used for debugging
+either your program or @command{gfortran}
+
+@table @gcctabopt
+@cindex -fdump-parse-tree option
+@cindex option, -fdump-parse-tree
+@item -fdump-parse-tree
+Output the internal parse tree before starting code generation. Only
+really usedful for debugging gfortran itself.
+@end table
+
+@xref{Debugging Options,,Options for Debugging Your Program or GCC,
+gcc,Using the GNU Compiler Collection (GCC)}, for more information on
+debugging options.
+
+@node Directory Options
+@section Options for Directory Search
+@cindex directory, options
+@cindex options, directory search
+@cindex search path
+
+@cindex INCLUDE directive
+@cindex directive, INCLUDE
+There options affect how affect how @command{gfortran} searches
+for files specified via the @code{INCLUDE} directive, and where it searches
+for previously compiled modules.
+
+It also affects the search paths used by @command{cpp} when used to preprocess
+fortran source.
+
+@table @gcctabopt
+@cindex -Idir option
+@cindex options, -Idir
+@item -I@var{dir}
+@cindex directory, search paths for inclusion
+@cindex inclusion, directory search paths for
+@cindex search paths, for included files
+@cindex paths, search
+@cindex module search path
+These affect interpretation of the @code{INCLUDE} directive
+(as well as of the @code{#include} directive of the @command{cpp}
+preprocessor).
+
+Also note that the general behavior of @option{-I} and
+@code{INCLUDE} is pretty much the same as of @option{-I} with
+@code{#include} in the @command{cpp} preprocessor, with regard to
+looking for @file{header.gcc} files and other such things.
+
+This path is also used to search for @samp{.mod} files when previously
+compiled modules are required by a @code{USE} statement.
+
+@xref{Directory Options,,Options for Directory Search,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on the
+@option{-I} option.
+
+@cindex -Mdir option
+@cindex option, -Mdir
+@item -M@var{dir}
+@item -J@var{dir}
+This option specifies where to put @samp{.mod} files for compiled modiles.
+It is also added to the list of directories to searhed by an @code{USE}
+statement.
+
+The default is the current directory.
+
+@option{-J} is an alias for @option{-M} to avoid conflicts with existing
+GCC options.
+@end table
+
+@node Code Gen Options
+@section Options for Code Generation Conventions
+@cindex code generation, conventions
+@cindex options, code generation
+@cindex run-time, options
+
+These machine-independent options control the interface conventions
+used in code generation.
+
+Most of them have both positive and negative forms; the negative form
+of @option{-ffoo} would be @option{-fno-foo}. In the table below, only
+one of the forms is listed---the one which is not the default. You
+can figure out the other form by either removing @option{no-} or adding
+it.
+
+
+@table @gcctabopt
+@cindex -fno-underscoring option
+@cindex options, -fno-underscoring
+@item -fno-underscoring
+@cindex underscore
+@cindex symbol names, underscores
+@cindex transforming symbol names
+@cindex symbol names, transforming
+Do not transform names of entities specified in the Fortran
+source file by appending underscores to them.
+
+With @option{-funderscoring} in effect, @command{gfortran} appends two
+underscores to names with underscores and one underscore to external names
+with no underscores. (@command{gfortran} also appends two underscores to
+internal names with underscores to avoid naming collisions with external
+names. The @option{-fno-second-underscore} option disables appending of the
+second underscore in all cases.)
+
+This is done to ensure compatibility with code produced by many
+UNIX Fortran compilers, including @command{f2c} which perform the
+same transformations.
+
+Use of @option{-fno-underscoring} is not recommended unless you are
+experimenting with issues such as integration of (GNU) Fortran into
+existing system environments (vis-a-vis existing libraries, tools, and
+so on).
+
+For example, with @option{-funderscoring}, and assuming other defaults like
+@option{-fcase-lower} and that @samp{j()} and @samp{max_count()} are
+external functions while @samp{my_var} and @samp{lvar} are local variables,
+a statement like
+
+@smallexample
+I = J() + MAX_COUNT (MY_VAR, LVAR)
+@end smallexample
+
+@noindent
+is implemented as something akin to:
+
+@smallexample
+i = j_() + max_count__(&my_var__, &lvar);
+@end smallexample
+
+With @option{-fno-underscoring}, the same statement is implemented as:
+
+@smallexample
+i = j() + max_count(&my_var, &lvar);
+@end smallexample
+
+Use of @option{-fno-underscoring} allows direct specification of
+user-defined names while debugging and when interfacing @command{gfortran}
+code with other languages.
+
+Note that just because the names match does @emph{not} mean that the
+interface implemented by @command{gfortran} for an external name matches the
+interface implemented by some other language for that same name.
+That is, getting code produced by @command{gfortran} to link to code produced
+by some other compiler using this or any other method can be only a
+small part of the overall solution---getting the code generated by
+both compilers to agree on issues other than naming can require
+significant effort, and, unlike naming disagreements, linkers normally
+cannot detect disagreements in these other areas.
+
+Also, note that with @option{-fno-underscoring}, the lack of appended
+underscores introduces the very real possibility that a user-defined
+external name will conflict with a name in a system library, which
+could make finding unresolved-reference bugs quite difficult in some
+cases---they might occur at program run time, and show up only as
+buggy behavior at run time.
+
+In future versions of @command{gfortran} we hope to improve naming and linking
+issues so that debugging always involves using the names as they appear
+in the source, even if the names as seen by the linker are mangled to
+prevent accidental linking between procedures with incompatible
+interfaces.
+
+@cindex -fno-second-underscore option
+@cindex options, -fno-second-underscore
+@item -fno-second-underscore
+@cindex underscore
+@cindex symbol names, underscores
+@cindex transforming symbol names
+@cindex symbol names, transforming
+Do not append a second underscore to names of entities specified
+in the Fortran source file.
+
+This option has no effect if @option{-fno-underscoring} is
+in effect.
+
+Otherwise, with this option, an external name such as @samp{MAX_COUNT}
+is implemented as a reference to the link-time external symbol
+@samp{max_count_}, instead of @samp{max_count__}.
+
+
+@cindex -fbounds-check option
+@cindex -ffortran-bounds-check option
+@item -fbounds-check
+@cindex bounds checking
+@cindex range checking
+@cindex array bounds checking
+@cindex subscript checking
+@cindex checking subscripts
+Enable generation of run-time checks for array subscripts
+and against the declared minimum and maximum values. It also
+checks array indices for assumed and deferred
+shape arrays against the actual allocated bounds.
+
+In the future this may also include other forms of checking, eg. checing
+substring references.
+
+
+@cindex -fmax-stack-var-size option
+@item -fmax-stack-var-size=@var{n}
+This option specifies the size in bytes of the largest array that will be put
+on the stack.
+
+This option currently only affects local arrays declared with constant
+bounds, and may not apply to all character variables.
+Future versions of @command{gfortran} may improve this behavior.
+
+The default value for @var{n} is 32768.
+
+@cindex -fpackderived
+@item -fpackderived
+@cindex Structure packing
+This option tells gfortran to pack derived type members as closely as
+possible. Code compiled with this option is likley to be incompatible
+with code compiled without this option, and may execute slower.
+
+@cindex -frepack-arrays option
+@item -frepack-arrays
+@cindex Repacking arrays
+In some circumstances @command{gfortran} may pass assumed shape array
+sections via a descriptor describing a discontiguous area of memory.
+This option adds code to the function prologue to repack the data into
+a contiguous block at runtime.
+
+This should result in faster accesses to the array. However it can introduce
+significant overhead to the function call, especially when the passed data
+is discontiguous.
+@end table
+
+@xref{Code Gen Options,,Options for Code Generation Conventions,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on more options
+offered by the GBE
+shared by @command{gfortran} @command{gcc} and other GNU compilers.
+
+
+@c man end
+
+@node Environment Variables
+@section Environment Variables Affecting GNU Fortran
+@cindex environment variables
+
+@c man begin ENVIRONMENT
+
+GNU Fortran 95 currently does not make use of any environment
+variables to control its operation above and beyond those
+that affect the operation of @command{gcc}.
+
+@xref{Environment Variables,,Environment Variables Affecting GCC,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on environment
+variables.
+
+@c man end