g77.texi

gcc-2.95.3 Linux下最常用的C编译器

@node Invoking G77
@chapter GNU Fortran Command Options
@cindex GNU Fortran command options
@cindex command options
@cindex options, GNU Fortran command

The @code{g77} command supports all the options supported by the
@code{gcc} command.
@xref{Invoking GCC,,GNU CC Command Options,gcc,Using and Porting GNU CC},
for information
on the non-Fortran-specific aspects of the @code{gcc} command (and,
therefore, the @code{g77} command).

@cindex options, negative forms
@cindex negative forms of options
All @code{gcc} and @code{g77} options
are accepted both by @code{g77} and by @code{gcc}
(as well as any other drivers built at the same time,
such as @code{g++}),
since adding @code{g77} to the @code{gcc} distribution
enables acceptance of @code{g77}-specific options
by all of the relevant drivers.

In some cases, options have positive and negative forms;
the negative form of @samp{-ffoo} would be @samp{-fno-foo}.
This manual documents only one of these two forms, whichever
one is not the default.

@menu
* Option Summary::      Brief list of all @code{g77} options,
                        without explanations.
* Overall Options::     Controlling the kind of output:
                        an executable, object files, assembler files,
                        or preprocessed source.
* Shorthand Options::   Options that are shorthand for other options.
* 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.
* Optimize Options::    How much optimization?
* Preprocessor Options:: Controlling header files and macro definitions.
                         Also, getting dependency information for Make.
* Directory Options::   Where to find header files and libraries.
                        Where to find the compiler executable 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

Here is a summary of all the options specific to GNU Fortran, grouped
by type.  Explanations are in the following sections.

@table @emph
@item Overall Options
@xref{Overall Options,,Options Controlling the Kind of Output}.
@smallexample
-fversion  -fset-g77-defaults  -fno-silent
@end smallexample

@item Shorthand Options
@xref{Shorthand Options}.
@smallexample
-ff66  -fno-f66  -ff77  -fno-f77  -fno-ugly
@end smallexample

@item Fortran Language Options
@xref{Fortran Dialect Options,,Options Controlling Fortran Dialect}.
@smallexample
-ffree-form  -fno-fixed-form  -ff90
-fvxt  -fdollar-ok  -fno-backslash
-fno-ugly-args  -fno-ugly-assign  -fno-ugly-assumed
-fugly-comma  -fugly-complex  -fugly-init  -fugly-logint
-fonetrip  -ftypeless-boz
-fintrin-case-initcap  -fintrin-case-upper
-fintrin-case-lower  -fintrin-case-any
-fmatch-case-initcap  -fmatch-case-upper
-fmatch-case-lower  -fmatch-case-any
-fsource-case-upper -fsource-case-lower  -fsource-case-preserve
-fsymbol-case-initcap  -fsymbol-case-upper
-fsymbol-case-lower  -fsymbol-case-any
-fcase-strict-upper  -fcase-strict-lower
-fcase-initcap  -fcase-upper  -fcase-lower  -fcase-preserve
-ff2c-intrinsics-delete  -ff2c-intrinsics-hide
-ff2c-intrinsics-disable  -ff2c-intrinsics-enable
-fbadu77-intrinsics-delete  -fbadu77-intrinsics-hide
-fbadu77-intrinsics-disable  -fbadu77-intrinsics-enable
-ff90-intrinsics-delete  -ff90-intrinsics-hide
-ff90-intrinsics-disable  -ff90-intrinsics-enable
-fgnu-intrinsics-delete  -fgnu-intrinsics-hide
-fgnu-intrinsics-disable  -fgnu-intrinsics-enable
-fmil-intrinsics-delete  -fmil-intrinsics-hide
-fmil-intrinsics-disable  -fmil-intrinsics-enable
-funix-intrinsics-delete  -funix-intrinsics-hide
-funix-intrinsics-disable  -funix-intrinsics-enable
-fvxt-intrinsics-delete  -fvxt-intrinsics-hide
-fvxt-intrinsics-disable  -fvxt-intrinsics-enable
-ffixed-line-length-@var{n}  -ffixed-line-length-none
@end smallexample

@item Warning Options
@xref{Warning Options,,Options to Request or Suppress Warnings}.
@smallexample
-fsyntax-only  -pedantic  -pedantic-errors  -fpedantic
-w  -Wno-globals  -Wimplicit -Wunused  -Wuninitialized
-Wall  -Wsurprising
-Werror  -W
@end smallexample

@item Debugging Options
@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
@smallexample
-g
@end smallexample

@item Optimization Options
@xref{Optimize Options,,Options that Control Optimization}.
@smallexample
-malign-double
-ffloat-store  -fforce-mem  -fforce-addr  -fno-inline
-ffast-math  -fstrength-reduce  -frerun-cse-after-loop
-fexpensive-optimizations  -fdelayed-branch
-fschedule-insns  -fschedule-insn2  -fcaller-saves
-funroll-loops  -funroll-all-loops
-fno-move-all-movables  -fno-reduce-all-givs
-fno-rerun-loop-opt
@end smallexample

@item Directory Options
@xref{Directory Options,,Options for Directory Search}.
@smallexample
-I@var{dir}  -I-
@end smallexample

@item Code Generation Options
@xref{Code Gen Options,,Options for Code Generation Conventions}.
@smallexample
-fno-automatic  -finit-local-zero  -fno-f2c
-ff2c-library  -fno-underscoring  -fno-ident
-fpcc-struct-return  -freg-struct-return
-fshort-double  -fno-common  -fpack-struct
-fzeros  -fno-second-underscore
-fdebug-kludge  -femulate-complex
-falias-check  -fargument-alias
-fargument-noalias  -fno-argument-noalias-global
-fno-globals  -fflatten-arrays
-fbounds-check  -ffortran-bounds-check
@end smallexample
@end table

@menu
* Overall Options::     Controlling the kind of output:
                        an executable, object files, assembler files,
                        or preprocessed source.
* Shorthand Options::   Options that are shorthand for other options.
* 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.
* Optimize Options::    How much optimization?
* Preprocessor Options:: Controlling header files and macro definitions.
                         Also, getting dependency information for Make.
* Directory Options::   Where to find header files and libraries.
                        Where to find the compiler executable files.
* Code Gen Options::    Specifying conventions for function calls, data layout
                        and register usage.
@end menu

@node Overall Options
@section Options Controlling the Kind of Output
@cindex overall options
@cindex options, overall

Compilation can involve as many as four stages: preprocessing, code
generation (often what is really meant by the term ``compilation''),
assembly, and linking, always in that order.  The first three
stages apply to an individual source file, and end by producing an
object file; linking combines all the object files (those newly
compiled, and those specified as input) into an executable file.

@cindex file name suffix
@cindex suffixes, file name
@cindex file name extension
@cindex extensions, file name
@cindex file type
@cindex types, file
For any given input file, the file name suffix determines what kind of
program is contained in the file---that is, the language in which the
program is written is generally indicated by the suffix.
Suffixes specific to GNU Fortran are listed below.
@xref{Overall Options,,gcc,Using and Porting GNU CC}, for
information on suffixes recognized by GNU CC.

@table @code
@cindex .f filename suffix
@cindex .for filename suffix
@cindex .FOR filename suffix
@item @var{file}.f
@item @var{file}.for
@item @var{file}.FOR
Fortran source code that should not be preprocessed.

Such source code cannot contain any preprocessor directives, such
as @code{#include}, @code{#define}, @code{#if}, and so on.

You can force @samp{.f} files to be preprocessed by @code{cpp} by using
@samp{-x f77-cpp-input}.
@xref{LEX}.

@cindex preprocessor
@cindex C preprocessor
@cindex cpp preprocessor
@cindex Fortran preprocessor
@cindex cpp program
@cindex programs, cpp
@cindex .F filename suffix
@cindex .fpp filename suffix
@cindex .FPP filename suffix
@item @var{file}.F
@item @var{file}.fpp
@item @var{file}.FPP
Fortran source code that must be preprocessed (by the C preprocessor
@code{cpp}, which is part of GNU CC).

Note that preprocessing is not extended to the contents of
files included by the @code{INCLUDE} directive---the @code{#include}
preprocessor directive must be used instead.

@cindex Ratfor preprocessor
@cindex programs, @code{ratfor}
@cindex @samp{.r} filename suffix
@cindex @code{ratfor}
@item @var{file}.r
Ratfor source code, which must be preprocessed by the @code{ratfor}
command, which is available separately (as it is not yet part of the GNU
Fortran distribution).
One version in Fortran, adapted for use with @code{g77}, is at
@uref{ftp://members.aol.com/n8tm/rat7.uue} (of uncertain copyright
status).  Another, public domain version in C is at
@uref{http://sepwww.stanford.edu/sep/prof/ratfor.shar.2}.
@end table

UNIX users typically use the @file{@var{file}.f} and @file{@var{file}.F}
nomenclature.
Users of other operating systems, especially those that cannot
distinguish upper-case
letters from lower-case letters in their file names, typically use
the @file{@var{file}.for} and @file{@var{file}.fpp} nomenclature.

@cindex #define
@cindex #include
@cindex #if
Use of the preprocessor @code{cpp} allows use of C-like
constructs such as @code{#define} and @code{#include}, but can
lead to unexpected, even mistaken, results due to Fortran's source file
format.
It is recommended that use of the C preprocessor
be limited to @code{#include} and, in
conjunction with @code{#define}, only @code{#if} and related directives,
thus avoiding in-line macro expansion entirely.
This recommendation applies especially
when using the traditional fixed source form.
With free source form,
fewer unexpected transformations are likely to happen, but use of
constructs such as Hollerith and character constants can nevertheless
present problems, especially when these are continued across multiple
source lines.
These problems result, primarily, from differences between the way
such constants are interpreted by the C preprocessor and by a Fortran
compiler.

Another example of a problem that results from using the C preprocessor
is that a Fortran comment line that happens to contain any
characters ``interesting'' to the C preprocessor,
such as a backslash at the end of the line,
is not recognized by the preprocessor as a comment line,
so instead of being passed through ``raw'',
the line is edited according to the rules for the preprocessor.
For example, the backslash at the end of the line is removed,
along with the subsequent newline, resulting in the next
line being effectively commented out---unfortunate if that
line is a non-comment line of important code!

@emph{Note:} The @samp{-traditional} and @samp{-undef} flags are supplied
to @code{cpp} by default, to help avoid unpleasant surprises.
@xref{Preprocessor Options,,Options Controlling the Preprocessor,
gcc,Using and Porting GNU CC}.
This means that ANSI C preprocessor features (such as the @samp{#}
operator) aren't available, and only variables in the C reserved
namespace (generally, names with a leading underscore) are liable to
substitution by C predefines.
Thus, if you want to do system-specific
tests, use, for example, @samp{#ifdef __linux__} rather than @samp{#ifdef linux}.
Use the @samp{-v} option to see exactly how the preprocessor is invoked.

@cindex /*
Unfortunately, the @samp{-traditional} flag will not avoid an error from
anything that @code{cpp} sees as an unterminated C comment, such as:
@smallexample
C Some Fortran compilers accept /* as starting
C an inline comment.
@end smallexample
@xref{Trailing Comment}.

The following options that affect overall processing are recognized
by the @code{g77} and @code{gcc} commands in a GNU Fortran installation:

@table @code
@cindex -fversion option
@cindex options, -fversion
@cindex printing version information
@cindex version information, printing
@cindex consistency checks
@cindex internal consistency checks
@cindex checks, of internal consistency
@item -fversion
Ensure that the @code{g77}-specific version of the compiler phase is reported,
if run,
and, starting in @code{egcs} version 1.1,
that internal consistency checks in the @file{f771} program are run.

This option is supplied automatically when @samp{-v} or @samp{--verbose}
is specified as a command-line option for @code{g77} or @code{gcc}
and when the resulting commands compile Fortran source files.

@cindex -fset-g77-defaults option
@cindex options, -fset-g77-defaults
@it