invoke.texi

理解和实践操作系统的一本好书

@c Copyright (C) 2004, 2005, 2006, 2007
@c Free Software Foundation, Inc.
@c This is part of the GNU Fortran manual.   
@c For copying conditions, see the file gfortran.texi.

@ignore
@c man begin COPYRIGHT
Copyright @copyright{} 2004, 2005, 2006, 2007
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 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{@value{BUGURL}}.
@c man end
@c man begin AUTHOR
See the Info entry for @command{gfortran} for contributors to GCC and
GNU Fortran.
@c man end
@end ignore

@node Invoking GNU Fortran
@chapter GNU Fortran Command Options
@cindex GNU Fortran command options
@cindex command options
@cindex options, @command{gfortran} command

@c man begin DESCRIPTION

The @command{gfortran} command supports all the options supported by the
@command{gcc} command.  Only options specific to GNU Fortran 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
All GCC and GNU Fortran 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 GNU Fortran to the GCC distribution
enables acceptance of GNU Fortran 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.
* Error and Warning Options::     How picky should the compiler be?
* Debugging Options::   Symbol tables, measurements, and debugging dumps.
* Directory Options::   Where to find module files
* Link Options ::       Influencing the linking step
* Runtime Options::     Influencing runtime behavior
* Code Gen Options::    Specifying conventions for function calls, data layout
                        and register usage.
* Environment Variables:: Environment variables that affect @command{gfortran}.
@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{-fall-intrinsics  -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  -fopenmp  -fno-range-check -fbackslash -fmodule-private}

@item Error and Warning Options
@xref{Error and Warning Options,,Options to request or suppress errors
and warnings}.
@gccoptlist{-fmax-errors=@var{n} @gol
-fsyntax-only  -pedantic  -pedantic-errors @gol
-Wall  -Waliasing  -Wampersand  -Wcharacter-truncation  -Wconversion @gol
-Wimplicit-interface  -Wline-truncation  -Wnonstd-intrinsics  -Wsurprising @gol
-Wno-tabs  -Wunderflow -Wunused-parameter}

@item Debugging Options
@xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
@gccoptlist{-fdump-parse-tree  -ffpe-trap=@var{list} @gol
-fdump-core -fbacktrace}

@item Directory Options
@xref{Directory Options,,Options for directory search}.
@gccoptlist{-I@var{dir}  -J@var{dir}  -M@var{dir}  -fintrinsic-modules-path @var{dir}}

@item Link Options
@xref{Link Options,,Options for influencing the linking step}.
@gccoptlist{-static-libgfortran}

@item Runtime Options
@xref{Runtime Options,,Options for influencing runtime behavior}.
@gccoptlist{-fconvert=@var{conversion}  -frecord-marker=@var{length} @gol
-fmax-subrecord-length=@var{length}  -fsign-zero}

@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
-fpack-derived  -frepack-arrays  -fshort-enums  -fexternal-blas @gol
-fblas-matmul-limit=@var{n} -frecursive -finit-local-zero @gol
-finit-integer=@var{n} -finit-real=@var{<zero|inf|-inf|nan>} @gol
-finit-logical=@var{<true|false>} -finit-character=@var{n}}
@end table

@menu
* Fortran Dialect Options::  Controlling the variant of Fortran language
                             compiled.
* Error and Warning Options::     How picky should the compiler be?
* Debugging Options::   Symbol tables, measurements, and debugging dumps.
* Directory Options::   Where to find module files
* Link Options ::       Influencing the linking step
* 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 details of the Fortran dialect
accepted by the compiler:

@table @gcctabopt
@item -ffree-form
@item -ffixed-form
@opindex @code{ffree-form}
@opindex @code{fno-fixed-form}
@cindex options, fortran dialect
@cindex file format, free
@cindex file format, fixed
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.  When neither option is specified, the source
form is determined by the file extension.

@item -fall-intrinsics
@opindex @code{fall-intrinsics}
Accept all of the intrinsic procedures provided in libgfortran 
without regard to the setting of @option{-std}.  In particular, 
this option can be quite useful with @option{-std=f95}.  Additionally,
@command{gfortran} will ignore @option{-Wnonstd-intrinsics}.

@item -fd-lines-as-code
@item -fd-lines-as-comments
@opindex @code{fd-lines-as-code}
@opindex @code{fd-lines-as-comments}
Enable special treatment for lines beginning with @code{d} or @code{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.

@item -fdefault-double-8
@opindex @code{fdefault-double-8}
Set the @code{DOUBLE PRECISION} type to an 8 byte wide type.

@item -fdefault-integer-8
@opindex @code{fdefault-integer-8}
Set the default integer and logical types to an 8 byte wide type.
Do nothing if this is already the default.

@item -fdefault-real-8
@opindex @code{fdefault-real-8}
Set the default real type to an 8 byte wide type.
Do nothing if this is already the default.

@item -fdollar-ok
@opindex @code{fdollar-ok}
@cindex $
@cindex symbol names
@cindex character set
Allow @samp{$} as a valid character in a symbol name.

@item -fbackslash
@opindex @code{backslash}
@cindex backslash
@cindex escape characters
Change the interpretation of backslashes in string literals
from a single backslash character to ``C-style'' escape characters.
The following combinations are expanded \a, \b, \f, \n, \r, \t,
\v, \\, and \0 to the ASCII characters alert, backspace, form feed,
newline, carriage return, horizontal tab, vertical tab, backslash,
and NUL, respectively.  All other combinations of a character preceded
by \ are unexpanded.

@item -fmodule-private
@opindex @code{fmodule-private}
@cindex module entities
@cindex private
Set the default accessibility of module entities to @code{PRIVATE}.
Use-associated entities will not be accessible unless they are explicitly
declared as @code{PUBLIC}.

@item -ffixed-line-length-@var{n}
@opindex @code{ffixed-line-length-}@var{n}
@cindex file format, fixed
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.

Popular values for @var{n} include 72 (the
standard and the default), 80 (card image), and 132 (corresponding
to ``extended-source'' options in some popular compilers).
@var{n} may also 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}.

@item -ffree-line-length-@var{n}
@opindex @code{ffree-line-length-}@var{n}
@cindex file format, free
Set column after which characters are ignored in typical free-form
lines in the source file. 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}.

@item -fmax-identifier-length=@var{n}
@opindex @code{fmax-identifier-length=}@var{n}
Specify the maximum allowed identifier length. Typical values are
31 (Fortran 95) and 63 (Fortran 2003).

@item -fimplicit-none
@opindex @code{fimplicit-none}
Specify that no implicit typing is allowed, unless overridden by explicit
@code{IMPLICIT} statements.  This is the equivalent of adding
@code{implicit none} to the start of every procedure.

@item -fcray-pointer
@opindex @code{fcray-pointer}
Enable the Cray pointer extension, which provides C-like pointer
functionality.

@item -fopenmp
@opindex @code{fopenmp}
@cindex OpenMP
Enable the OpenMP extensions.  This includes OpenMP @code{!$omp} directives
in free form
and @code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form,
@code{!$} conditional compilation sentinels in free form
and @code{c$}, @code{*$} and @code{!$} sentinels in fixed form, 
and when linking arranges for the OpenMP runtime library to be linked
in.  The option @option{-fopenmp} implies @option{-frecursive}.

@item -fno-range-check
@opindex @code{frange-check}
Disable range checking on results of simplification of constant
expressions during compilation.  For example, GNU Fortran will give
an error at compile time when simplifying @code{a = 1. / 0}.
With this option, no error will be given and @code{a} will be assigned
the value @code{+Infinity}.  If an expression evaluates to a value
outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}],
then the expression will be replaced by @code{-Inf} or @code{+Inf}
as appropriate.
Similarly, @code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow
on most systems, but with @option{-fno-range-check} the value will
``wrap around'' and @code{i} will be initialized to @math{-1} instead.

@item -std=@var{std}
@opindex @code{std=}@var{std} option
Specify the standard to which the program is expected to conform, which
may be one of @samp{f95}, @samp{f2003}, @samp{gnu}, or @samp{legacy}.
The default value for @var{std} is @samp{gnu}, which specifies a
superset of the Fortran 95 standard that includes all of the extensions
supported by GNU Fortran, although warnings will be given for obsolete
extensions not recommended for use in new code.  The @samp{legacy} value
is equivalent but without the warnings for obsolete extensions, and may
be useful for old non-standard programs.  The @samp{f95} and
@samp{f2003} values specify strict conformance to the Fortran 95 and
Fortran 2003 standards, respectively; errors are given for all
extensions beyond the relevant language standard, and warnings are given
for the Fortran 77 features that are permitted but obsolescent in later
standards.