invoke.texi

gcc-fortran,linux使用fortran的编译软件。很好用的。

@c Copyright (C) 2004, 2005
@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, 2005
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
* Runtime Options::     Influencing runtime behavior
* 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} -fd-lines-as-code -fd-lines-as-comments @gol
-ffixed-line-length-@var{n}  -ffixed-line-length-none @gol
-ffree-line-length-@var{n}  -ffree-line-length-none @gol
-fdefault-double-8  -fdefault-integer-8  -fdefault-real-8 @gol
-fcray-pointer }

@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  -Wnonstd-intrinsics  -Wsurprising  -Wunderflow @gol
-Wunused-labels -Wline-truncation -W}

@item Debugging Options
@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
@gccoptlist{
-fdump-parse-tree -ffpe-trap=@var{list}}

@item Directory Options
@xref{Directory Options,,Options for Directory Search}.
@gccoptlist{
-I@var{dir}  -M@var{dir}}

@item Runtime Options
@xref{Runtime Options,,Options for influencing runtime behavior}.
@gccoptlist{
-fconvert=@var{conversion}}

@item Code Generation Options
@xref{Code Gen Options,,Options for Code Generation Conventions}.
@gccoptlist{
-fno-automatic -ff2c -fno-underscoring  -fsecond-underscore @gol
-fbounds-check  -fmax-stack-var-size=@var{n} @gol
-fpackderived  -frepack-arrays  -fshort-enums}
@end table

@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
* Runtime Options::     Influencing runtime behavior
* 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 source file.  The free form layout
was introduced in Fortran 90.  Fixed form was traditionally used in
older Fortran programs.

@cindex option, -fd-lines-as-code
@cindex -fd-lines-as-code, option
@cindex option, -fd-lines-as-comments
@cindex -fd-lines-as-comments, option
@item -fd-lines-as-code
@item -fd-lines-as-comment
Enables special treating for lines with @samp{d} or @samp{D} in fixed
form sources.  If the @option{-fd-lines-as-code} option is given
they are treated as if the first column contained a blank.  If the
@option{-fd-lines-as-comments} option is given, they are treated as
comment lines.

@cindex option, -fdefault-double-8
@cindex -fdefault-double-8, option
@item -fdefault-double-8
Set the "DOUBLE PRECISION" type to an 8 byte wide.

@cindex option, -fdefault-integer-8
@cindex -fdefault-integer-8, option
@item -fdefault-integer-8
Set the default integer and logical types to an 8 byte wide type.
Do nothing if this is already the default.

@cindex option, -fdefault-real-8
@cindex -fdefault-real-8, option
@item -fdefault-real-8
Set the default real type to an 8 byte wide type.
Do nothing if this is already the default.

@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 -fno-backslash option
@cindex options, -fno-backslash
@item -fno-backslash
@cindex backslash
@cindex escape characters
Compile switch to change the interpretation of a backslash from
``C''-style escape characters to a single backslash character.

@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 -ffree-line-length-@var{n} option
@cindex options, -ffree-line-length-@var{n}
@item -ffree-line-length-@var{n}
@cindex source file format
@cindex lines, length
@cindex length of source lines
@cindex free form
@cindex limits, lengths of source lines
Set column after which characters are ignored in typical free-form
lines in the source file. For free-form, the default value is 132.
@var{n} may be @samp{none}, meaning that the entire line is meaningful.
@option{-ffree-line-length-0} means the same thing as
@option{-ffree-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 -fimplicit-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 -fcray-pointer option
@cindex options, -fcray-pointer
@item -fcray-pointer
Enables the Cray pointer extension, which provides a C-like pointer.

@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}, @samp{f2003} and @samp{legacy}.

@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 currently includes @option{-Wunused-labels}, @option{-Waliasing},
@option{-Wsurprising}, @option{-Wnonstd-intrinsic} and
@option{-Wline-truncation}.


@cindex -Waliasing option
@cindex options, -Waliasing
@item -Waliasing
@cindex aliasing
Warn about possible aliasing of dummy arguments. Specifically, it warns
if the same actual argument is associated with a dummy argument with
@code{intent(in)} and a dummy argument with @code{intent(out)} in a call
with an explicit interface.

The following example will trigger the warning.
@smallexample
  interface
    subroutine bar(a,b)
      integer, intent(in) :: a
      integer, intent(out) :: b
    end subroutine
  end interface
  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 -Wnonstd-intrinsic option
@cindex options, -Wnonstd-intrinsic