-@c Copyright (C) 2004, 2005, 2006
+@c Copyright (C) 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
@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
+Copyright @copyright{} 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
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
+under the terms of the GNU Free Documentation License, Version 1.3 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.
-
+Invariant Sections being ``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
[@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{-m}@var{machine-option}@dots{}]
[@option{-o} @var{outfile}] @var{infile}@dots{}
Only the most useful options are listed here; see below for the
@c man end
@c man begin BUGS
For instructions on reporting bugs, see
-@w{@uref{http://gcc.gnu.org/bugs.html}}.
+@w{@value{BUGURL}}.
@c man end
@c man begin AUTHOR
See the Info entry for @command{gfortran} for contributors to GCC and
therefore, the @command{gfortran} command).
@cindex options, negative forms
-@cindex negative forms of options
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,
without explanations.
* Fortran Dialect Options:: Controlling the variant of Fortran language
compiled.
-* Warning Options:: How picky should the compiler be?
+* Preprocessing Options:: Enable and customize preprocessing.
+* 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:: Env vars that affect @command{gfortran}.
+* Environment Variables:: Environment variables that affect @command{gfortran}.
@end menu
@node Option Summary
-@section Option Summary
+@section Option summary
@c man begin OPTIONS
@table @emph
@item Fortran Language Options
-@xref{Fortran Dialect Options,,Options Controlling Fortran Dialect}.
-@gccoptlist{
--fall-intrinsics -ffree-form -fno-fixed-form @gol
+@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
+-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 -frange-check }
-
-@item Warning Options
-@xref{Warning Options,,Options to Request or Suppress Warnings}.
-@gccoptlist{
--fsyntax-only -pedantic -pedantic-errors @gol
--w -Wall -Waliasing -Wampersand -Wconversion -Wimplicit-interface @gol
--Wtabs -Wnonstd-intrinsics -Wsurprising -Wunderflow @gol
--Wunused-labels -Wline-truncation -W}
+-fcray-pointer -fopenmp -fno-range-check -fbackslash -fmodule-private}
+
+@item Preprocessing Options
+@xref{Preprocessing Options,,Enable and customize preprocessing}.
+@gccoptlist{-cpp -dD -dI -dM -dN -dU -fworking-directory @gol
+-imultilib @var{dir} -iprefix @var{file} -isysroot @var{dir} @gol
+-iquote -isystem @var{dir} -nocpp -nostdinc -undef @gol
+-A@var{question}=@var{answer} -A-@var{question}@r{[}=@var{answer}@r{]} @gol
+-C -CC -D@var{macro}@r{[}=@var{defn}@r{]} -U@var{macro} -H -P}
+
+@item Error and Warning Options
+@xref{Error and Warning Options,,Options to request or suppress errors
+and warnings}.
+@gccoptlist{-fmax-errors=@var{n}
+-fsyntax-only -pedantic -pedantic-errors -Wall @gol
+-Waliasing -Wampersand -Warray-bounds -Wcharacter-truncation @gol
+-Wconversion -Wimplicit-interface -Wimplicit-procedure -Wline-truncation @gol
+-Wintrinsics-std -Wreal-q-constant -Wsurprising -Wno-tabs -Wunderflow @gol
+-Wunused-parameter -Wintrinsic-shadow -Wno-align-commons @gol
+-Wfunction-elimination}
@item Debugging Options
-@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
-@gccoptlist{
--fdump-parse-tree -ffpe-trap=@var{list}}
+@xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
+@gccoptlist{-fdump-fortran-original -fdump-fortran-optimized @gol
+-ffpe-trap=@var{list} -fbacktrace -fdump-parse-tree}
@item Directory Options
-@xref{Directory Options,,Options for Directory Search}.
-@gccoptlist{
--I@var{dir} -M@var{dir}}
+@xref{Directory Options,,Options for directory search}.
+@gccoptlist{-I@var{dir} -J@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}}
+@gccoptlist{-fconvert=@var{conversion} -fno-range-check
+-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}
+@xref{Code Gen Options,,Options for code generation conventions}.
+@gccoptlist{-fno-automatic -ff2c -fno-underscoring @gol
+-fwhole-file -fsecond-underscore @gol
+-fbounds-check -fcheck-array-temporaries -fmax-array-constructor =@var{n} @gol
+-fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} @gol
+-fcoarray=@var{<none|single|lib>} -fmax-stack-var-size=@var{n} @gol
+-fstack-arrays @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|snan>} @gol
+-finit-logical=@var{<true|false>} -finit-character=@var{n} @gol
+-fno-align-commons -fno-protect-parens -frealloc-lhs @gol
+-faggressive-function-elimination -ffrontend-optimize}
@end table
@menu
* Fortran Dialect Options:: Controlling the variant of Fortran language
compiled.
-* Warning Options:: How picky should the compiler be?
+* Preprocessing Options:: Enable and customize preprocessing.
+* 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
+@section Options controlling Fortran dialect
@cindex dialect options
@cindex language, dialect options
@cindex options, dialect
accepted by the compiler:
@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
+@itemx -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.
-@cindex -fall-intrinsics
@item -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}.
-
-@cindex option, -fd-lines-as-code
-@cindex -fd-lines-as-code, option
-@cindex option, -fd-lines-as-comments
-@cindex -fd-lines-as-comments, option
+@opindex @code{fall-intrinsics}
+This option causes all intrinsic procedures (including the GNU-specific
+extensions) to be accepted. This can be useful with @option{-std=f95} to
+force standard-compliance but get access to the full range of intrinsics
+available with @command{gfortran}. As a consequence, @option{-Wintrinsics-std}
+will be ignored and no user-defined procedure with the same name as any
+intrinsic will be called except when it is explicitly declared @code{EXTERNAL}.
+
@item -fd-lines-as-code
-@item -fd-lines-as-comment
-Enable special treatment for lines beginning with @samp{d} or @samp{D}
+@itemx -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.
-@cindex option, -fdefault-double-8
-@cindex -fdefault-double-8, option
@item -fdefault-double-8
-Set the @code{DOUBLE PRECISION} type to an 8 byte wide type.
+@opindex @code{fdefault-double-8}
+Set the @code{DOUBLE PRECISION} type to an 8 byte wide type. If
+@option{-fdefault-real-8} is given, @code{DOUBLE PRECISION} would
+instead be promoted to 16 bytes if possible, and @option{-fdefault-double-8}
+can be used to prevent this. The kind of real constants like @code{1.d0} will
+not be changed by @option{-fdefault-real-8} though, so also
+@option{-fdefault-double-8} does not affect it.
-@cindex option, -fdefault-integer-8
-@cindex -fdefault-integer-8, option
@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.
+Do nothing if this is already the default. This option also affects
+the kind of integer constants like @code{42}.
-@cindex option, -fdefault-real-8
-@cindex -fdefault-real-8, option
@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.
+Do nothing if this is already the default. This option also affects
+the kind of non-double real constants like @code{1.0}, and does promote
+the default width of @code{DOUBLE PRECISION} to 16 bytes if possible, unless
+@code{-fdefault-double-8} is given, too.
-@cindex -fdollar-ok option
-@cindex options, -fdollar-ok
@item -fdollar-ok
-@cindex dollar sign
+@opindex @code{fdollar-ok}
+@cindex @code{$}
@cindex symbol names
@cindex character set
-Allow @samp{$} as a valid character in a symbol name.
+Allow @samp{$} as a valid non-first character in a symbol name. Symbols
+that start with @samp{$} are rejected since it is unclear which rules to
+apply to implicit typing as different vendors implement different rules.
+Using @samp{$} in @code{IMPLICIT} statements is also rejected.
-@cindex -fno-backslash option
-@cindex options, -fno-backslash
-@item -fno-backslash
+@item -fbackslash
+@opindex @code{backslash}
@cindex backslash
@cindex escape characters
-Change the interpretation of backslashes in string literals from
-``C-style'' escape characters to a single backslash character.
+Change the interpretation of backslashes in string literals from a single
+backslash character to ``C-style'' escape characters. The following
+combinations are expanded @code{\a}, @code{\b}, @code{\f}, @code{\n},
+@code{\r}, @code{\t}, @code{\v}, @code{\\}, and @code{\0} to the ASCII
+characters alert, backspace, form feed, newline, carriage return,
+horizontal tab, vertical tab, backslash, and NUL, respectively.
+Additionally, @code{\x}@var{nn}, @code{\u}@var{nnnn} and
+@code{\U}@var{nnnnnnnn} (where each @var{n} is a hexadecimal digit) are
+translated into the Unicode characters corresponding to the specified code
+points. 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}.
-@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
+@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.
-@cindex card image
-@cindex extended-source option
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).
@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
+@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}.
-@cindex -fmax-identifier-length=@var{n} option
-@cindex option -fmax-identifier-length=@var{n}
@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).
+31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008).
-@cindex -fimplicit-none option
-@cindex options, -fimplicit-none
@item -fimplicit-none
+@opindex @code{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.
+@code{IMPLICIT} statements. This is the equivalent of adding
+@code{implicit none} to the start of every procedure.
-@cindex -fcray-pointer option
-@cindex options, -fcray-pointer
@item -fcray-pointer
+@opindex @code{fcray-pointer}
Enable the Cray pointer extension, which provides C-like pointer
functionality.
-@cindex -fopenmp
-@cindex options, -fopenmp
@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.
-
-@cindex -frange-check
-@cindex options, -frange-check
-@item -frange-check
-Enable range checking on results of simplification of constant expressions
-during compilation. For example, by default, GNU Fortran will give
-an overflow error at compile time when simplifying @code{a = EXP(1000)}.
-With @samp{-fno-range-check}, no error will be given and the variable @code{a}
-will be assigned the value @code{+Infinity}. Similarly,
-@code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow on most systems,
-but with @samp{-fno-range-check} the value will ``wrap around'' and @code{i}
-will be initialized to @math{-1} instead.
-
-@cindex -std=@var{std} option
-@cindex option, -std=@var{std}
+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}
-Conform to the specified standard. The default value for @var{std} is
-@samp{gnu}; a superset of the Fortran 95 standard which includes all
-of the GNU extensions recommended for use in new code. The @samp{legacy}
-value also includes obsolete extensions that may be required for old
-non-standard programs. Strict conformance to the Fortran 95 and Fortran 2003
-standards is specified by @samp{f95} and @samp{f2003}, respectively.
+@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{f2008}, @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}, @samp{f2003} and @samp{f2008} values specify strict
+conformance to the Fortran 95, Fortran 2003 and Fortran 2008 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. @samp{-std=f2008tr}
+allows the Fortran 2008 standard including the additions of the
+technical report (TR) 29113.
+
+@end table
+
+@node Preprocessing Options
+@section Enable and customize preprocessing
+@cindex preprocessor
+@cindex options, preprocessor
+@cindex CPP
+
+Preprocessor related options. See section
+@ref{Preprocessing and conditional compilation} for more detailed
+information on preprocessing in @command{gfortran}.
+@table @gcctabopt
+@item -cpp
+@itemx -nocpp
+@opindex @code{cpp}
+@opindex @code{fpp}
+@cindex preprocessor, enable
+@cindex preprocessor, disable
+Enable preprocessing. The preprocessor is automatically invoked if
+the file extension is @file{.fpp}, @file{.FPP}, @file{.F}, @file{.FOR},
+@file{.FTN}, @file{.F90}, @file{.F95}, @file{.F03} or @file{.F08}. Use
+this option to manually enable preprocessing of any kind of Fortran file.
+
+To disable preprocessing of files with any of the above listed extensions,
+use the negative form: @option{-nocpp}.
+
+The preprocessor is run in traditional mode. Any restrictions of the
+file-format, especially the limits on line length, apply for
+preprocessed output as well, so it might be advisable to use the
+@option{-ffree-line-length-none} or @option{-ffixed-line-length-none}
+options.
+
+@item -dM
+@opindex @code{dM}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Instead of the normal output, generate a list of @code{'#define'}
+directives for all the macros defined during the execution of the
+preprocessor, including predefined macros. This gives you a way
+of finding out what is predefined in your version of the preprocessor.
+Assuming you have no file @file{foo.f90}, the command
+@smallexample
+ touch foo.f90; gfortran -cpp -E -dM foo.f90
+@end smallexample
+will show all the predefined macros.
+
+@item -dD
+@opindex @code{dD}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Like @option{-dM} except in two respects: it does not include the
+predefined macros, and it outputs both the @code{#define} directives
+and the result of preprocessing. Both kinds of output go to the
+standard output file.
+
+@item -dN
+@opindex @code{dN}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Like @option{-dD}, but emit only the macro names, not their expansions.
+
+@item -dU
+@opindex @code{dU}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Like @option{dD} except that only macros that are expanded, or whose
+definedness is tested in preprocessor directives, are output; the
+output is delayed until the use or test of the macro; and @code{'#undef'}
+directives are also output for macros tested but undefined at the time.
+
+@item -dI
+@opindex @code{dI}
+@cindex preprocessor, debugging
+@cindex debugging, preprocessor
+Output @code{'#include'} directives in addition to the result
+of preprocessing.
+
+@item -fworking-directory
+@opindex @code{fworking-directory}
+@cindex preprocessor, working directory
+Enable generation of linemarkers in the preprocessor output that will
+let the compiler know the current working directory at the time of
+preprocessing. When this option is enabled, the preprocessor will emit,
+after the initial linemarker, a second linemarker with the current
+working directory followed by two slashes. GCC will use this directory,
+when it's present in the preprocessed input, as the directory emitted
+as the current working directory in some debugging information formats.
+This option is implicitly enabled if debugging information is enabled,
+but this can be inhibited with the negated form
+@option{-fno-working-directory}. If the @option{-P} flag is present
+in the command line, this option has no effect, since no @code{#line}
+directives are emitted whatsoever.
+
+@item -idirafter @var{dir}
+@opindex @code{idirafter @var{dir}}
+@cindex preprocessing, include path
+Search @var{dir} for include files, but do it after all directories
+specified with @option{-I} and the standard system directories have
+been exhausted. @var{dir} is treated as a system include directory.
+If dir begins with @code{=}, then the @code{=} will be replaced by
+the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
+
+@item -imultilib @var{dir}
+@opindex @code{imultilib @var{dir}}
+@cindex preprocessing, include path
+Use @var{dir} as a subdirectory of the directory containing target-specific
+C++ headers.
+
+@item -iprefix @var{prefix}
+@opindex @code{iprefix @var{prefix}}
+@cindex preprocessing, include path
+Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}
+options. If the @var{prefix} represents a directory, you should include
+the final @code{'/'}.
+
+@item -isysroot @var{dir}
+@opindex @code{isysroot @var{dir}}
+@cindex preprocessing, include path
+This option is like the @option{--sysroot} option, but applies only to
+header files. See the @option{--sysroot} option for more information.
+
+@item -iquote @var{dir}
+@opindex @code{iquote @var{dir}}
+@cindex preprocessing, include path
+Search @var{dir} only for header files requested with @code{#include "file"};
+they are not searched for @code{#include <file>}, before all directories
+specified by @option{-I} and before the standard system directories. If
+@var{dir} begins with @code{=}, then the @code{=} will be replaced by the
+sysroot prefix; see @option{--sysroot} and @option{-isysroot}.
+
+@item -isystem @var{dir}
+@opindex @code{isystem @var{dir}}
+@cindex preprocessing, include path
+Search @var{dir} for header files, after all directories specified by
+@option{-I} but before the standard system directories. Mark it as a
+system directory, so that it gets the same special treatment as is
+applied to the standard system directories. If @var{dir} begins with
+@code{=}, then the @code{=} will be replaced by the sysroot prefix;
+see @option{--sysroot} and @option{-isysroot}.
+
+@item -nostdinc
+@opindex @code{nostdinc}
+Do not search the standard system directories for header files. Only
+the directories you have specified with @option{-I} options (and the
+directory of the current file, if appropriate) are searched.
+
+@item -undef
+@opindex @code{undef}
+Do not predefine any system-specific or GCC-specific macros.
+The standard predefined macros remain defined.
+
+@item -A@var{predicate}=@var{answer}
+@opindex @code{A@var{predicate}=@var{answer}}
+@cindex preprocessing, assertion
+Make an assertion with the predicate @var{predicate} and answer @var{answer}.
+This form is preferred to the older form -A predicate(answer), which is still
+supported, because it does not use shell special characters.
+
+@item -A-@var{predicate}=@var{answer}
+@opindex @code{A-@var{predicate}=@var{answer}}
+@cindex preprocessing, assertion
+Cancel an assertion with the predicate @var{predicate} and answer @var{answer}.
+
+@item -C
+@opindex @code{C}
+@cindex preprocessing, keep comments
+Do not discard comments. All comments are passed through to the output
+file, except for comments in processed directives, which are deleted
+along with the directive.
+
+You should be prepared for side effects when using @option{-C}; it causes
+the preprocessor to treat comments as tokens in their own right. For example,
+comments appearing at the start of what would be a directive line have the
+effect of turning that line into an ordinary source line, since the first
+token on the line is no longer a @code{'#'}.
+
+Warning: this currently handles C-Style comments only. The preprocessor
+does not yet recognize Fortran-style comments.
+
+@item -CC
+@opindex @code{CC}
+@cindex preprocessing, keep comments
+Do not discard comments, including during macro expansion. This is like
+@option{-C}, except that comments contained within macros are also passed
+through to the output file where the macro is expanded.
+
+In addition to the side-effects of the @option{-C} option, the @option{-CC}
+option causes all C++-style comments inside a macro to be converted to C-style
+comments. This is to prevent later use of that macro from inadvertently
+commenting out the remainder of the source line. The @option{-CC} option
+is generally used to support lint comments.
+
+Warning: this currently handles C- and C++-Style comments only. The
+preprocessor does not yet recognize Fortran-style comments.
+
+@item -D@var{name}
+@opindex @code{D@var{name}}
+@cindex preprocessing, define macros
+Predefine name as a macro, with definition @code{1}.
+
+@item -D@var{name}=@var{definition}
+@opindex @code{D@var{name}=@var{definition}}
+@cindex preprocessing, define macros
+The contents of @var{definition} are tokenized and processed as if they
+appeared during translation phase three in a @code{'#define'} directive.
+In particular, the definition will be truncated by embedded newline
+characters.
+
+If you are invoking the preprocessor from a shell or shell-like program
+you may need to use the shell's quoting syntax to protect characters such
+as spaces that have a meaning in the shell syntax.
+
+If you wish to define a function-like macro on the command line, write
+its argument list with surrounding parentheses before the equals sign
+(if any). Parentheses are meaningful to most shells, so you will need
+to quote the option. With sh and csh, @code{-D'name(args...)=definition'}
+works.
+
+@option{-D} and @option{-U} options are processed in the order they are
+given on the command line. All -imacros file and -include file options
+are processed after all -D and -U options.
+
+@item -H
+@opindex @code{H}
+Print the name of each header file used, in addition to other normal
+activities. Each name is indented to show how deep in the @code{'#include'}
+stack it is.
+
+@item -P
+@opindex @code{P}
+@cindex preprocessing, no linemarkers
+Inhibit generation of linemarkers in the output from the preprocessor.
+This might be useful when running the preprocessor on something that
+is not C code, and will be sent to a program which might be confused
+by the linemarkers.
+
+@item -U@var{name}
+@opindex @code{U@var{name}}
+@cindex preprocessing, undefine macros
+Cancel any previous definition of @var{name}, either built in or provided
+with a @option{-D} option.
@end table
-@node Warning Options
-@section Options to Request or Suppress Warnings
+
+@node Error and Warning Options
+@section Options to request or suppress errors and warnings
@cindex options, warnings
+@cindex options, errors
@cindex warnings, suppressing
+@cindex messages, error
@cindex messages, warning
@cindex suppressing warnings
+Errors are diagnostic messages that report that the GNU Fortran compiler
+cannot compile the relevant piece of source code. The compiler will
+continue to process the program in an attempt to report further errors
+to aid in debugging, but will not produce any compiled output.
+
Warnings are diagnostic messages that report constructions which
-are not inherently erroneous but which are risky or suggest there
-might have been an error.
+are not inherently erroneous but which are risky or suggest there is
+likely to be a bug in the program. Unless @option{-Werror} is specified,
+they do not prevent compilation of the program.
You can request many specific warnings with options beginning @option{-W},
for example @option{-Wimplicit} to request warnings on implicit
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:
+These options control the amount and kinds of errors and warnings produced
+by GNU Fortran:
@table @gcctabopt
-@cindex syntax checking
-@cindex -fsyntax-only option
-@cindex options, -fsyntax-only
+@item -fmax-errors=@var{n}
+@opindex @code{fmax-errors=}@var{n}
+@cindex errors, limiting
+Limits the maximum number of error messages to @var{n}, at which point
+GNU Fortran bails out rather than attempting to continue processing the
+source code. If @var{n} is 0, there is no limit on the number of error
+messages produced.
+
@item -fsyntax-only
-Check the code for syntax errors, but don't do anything beyond that.
+@opindex @code{fsyntax-only}
+@cindex syntax checking
+Check the code for syntax errors, but don't actually compile it. This
+will generate module files for each module present in the code, but no
+other output file.
-@cindex -pedantic option
-@cindex options, -pedantic
@item -pedantic
+@opindex @code{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}.
+character constant within a directive like @code{#include}.
Valid Fortran 95 programs should compile properly with or without
this option.
nonstandard practices, but not all.
However, improvements to GNU Fortran in this area are welcome.
-This should be used in conjunction with -std=@var{std}.
+This should be used in conjunction with @option{-std=f95},
+@option{-std=f2003} or @option{-std=f2008}.
-@cindex -pedantic-errors option
-@cindex options, -pedantic-errors
@item -pedantic-errors
+@opindex @code{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
+@opindex @code{Wall}
@cindex all warnings
@cindex warnings, all
Enables commonly used warning options pertaining to usage that
we recommend avoiding and that we believe are easy to avoid.
-This currently includes @option{-Wunused-labels}, @option{-Waliasing},
-@option{-Wampersand}, @option{-Wsurprising}, @option{-Wnonstd-intrinsic},
-@option{-Wno-tabs}, and @option{-Wline-truncation}.
-
+This currently includes @option{-Waliasing}, @option{-Wampersand},
+@option{-Wconversion}, @option{-Wsurprising}, @option{-Wintrinsics-std},
+@option{-Wno-tabs}, @option{-Wintrinsic-shadow}, @option{-Wline-truncation},
+@option{-Wreal-q-constant} and @option{-Wunused}.
-@cindex -Waliasing option
-@cindex options, -Waliasing
@item -Waliasing
+@opindex @code{Waliasing}
@cindex aliasing
+@cindex warnings, 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
+@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.
call bar(a,a)
@end smallexample
-
-@cindex -Wampersand option
-@cindex options, -Wampersand
@item -Wampersand
-@cindex ampersand
+@opindex @code{Wampersand}
+@cindex warnings, ampersand
+@cindex @code{&}
Warn about missing ampersand in continued character constants. The warning is
-given with @option{-Wampersand}, @option{-pedantic}, @option{-std=f95}, and
-@option{-std=f2003}. Note: With no ampersand given in a continued character
-constant, GNU Fortran assumes continuation at the first non-comment,
-non-whitespace character after the ampersand that initiated the continuation.
+given with @option{-Wampersand}, @option{-pedantic}, @option{-std=f95},
+@option{-std=f2003} and @option{-std=f2008}. Note: With no ampersand
+given in a continued character constant, GNU Fortran assumes continuation
+at the first non-comment, non-whitespace character after the ampersand
+that initiated the continuation.
+
+@item -Warray-temporaries
+@opindex @code{Warray-temporaries}
+@cindex warnings, array temporaries
+Warn about array temporaries generated by the compiler. The information
+generated by this warning is sometimes useful in optimization, in order to
+avoid such temporaries.
+
+@item -Wcharacter-truncation
+@opindex @code{Wcharacter-truncation}
+@cindex warnings, character truncation
+Warn when a character assignment will truncate the assigned string.
+
+@item -Wline-truncation
+@opindex @code{Wline-truncation}
+@cindex warnings, line truncation
+Warn when a source code line will be truncated.
-
-@cindex -Wconversion option
-@cindex options, -Wconversion
@item -Wconversion
+@opindex @code{Wconversion}
+@cindex warnings, conversion
@cindex conversion
-Warn about implicit conversions between different types.
+Warn about implicit conversions that are likely to change the value of
+the expression after conversion. Implied by @option{-Wall}.
+@item -Wconversion-extra
+@opindex @code{Wconversion-extra}
+@cindex warnings, conversion
+@cindex conversion
+Warn about implicit conversions between different types and kinds.
-@cindex -Wimplicit-interface option
-@cindex options, -Wimplicit-interface
@item -Wimplicit-interface
-Warn about when procedure are called without an explicit interface.
+@opindex @code{Wimplicit-interface}
+@cindex warnings, implicit interface
+Warn if a procedure is 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.
+@item -Wimplicit-procedure
+@opindex @code{Wimplicit-procedure}
+@cindex warnings, implicit procedure
+Warn if a procedure is called that has neither an explicit interface
+nor has been declared as @code{EXTERNAL}.
+
+@item -Wintrinsics-std
+@opindex @code{Wintrinsics-std}
+@cindex warnings, non-standard intrinsics
+@cindex warnings, intrinsics of other standards
+Warn if @command{gfortran} finds a procedure named like an intrinsic not
+available in the currently selected standard (with @option{-std}) and treats
+it as @code{EXTERNAL} procedure because of this. @option{-fall-intrinsics} can
+be used to never trigger this behavior and always link to the intrinsic
+regardless of the selected standard.
+
+@item -Wreal-q-constant
+@opindex @code{Wreal-q-constant}
+@cindex warnings, @code{q} exponent-letter
+Produce a warning if a real-literal-constant contains a @code{q}
+exponent-letter.
-@cindex -Wnonstd-intrinsic option
-@cindex options, -Wnonstd-intrinsic
-@item -Wnonstd-intrinsic
-Warn if the user tries to use an intrinsic that does not belong to the
-standard the user has chosen via the -std option.
-
-
-@cindex -Wsurprising
-@cindex options, -Wsurprising
@item -Wsurprising
-@cindex Suspicious
+@opindex @code{Wsurprising}
+@cindex warnings, suspicious code
Produce a warning when ``suspicious'' code constructs are encountered.
While technically legal these usually indicate that an error has been made.
@item
A LOGICAL SELECT construct has three CASE statements.
-@end itemize
+@item
+A TRANSFER specifies a source that is shorter than the destination.
+
+@item
+The type of a function result is declared more than once with the same type. If
+@option{-pedantic} or standard-conforming mode is enabled, this is an error.
+
+@item
+A @code{CHARACTER} variable is declared with negative length.
+@end itemize
-@cindex -Wtabs
-@cindex options, -Wtabs
@item -Wtabs
-@cindex Tabs
+@opindex @code{Wtabs}
+@cindex warnings, tabs
+@cindex tabulators
By default, tabs are accepted as whitespace, but tabs are not members
-of the Fortran Character Set. @option{-Wno-tabs} will cause a warning
-to be issued if a tab is encountered. Note, @option{-Wno-tabs} is active
-for @option{-pedantic}, @option{-std=f95}, and @option{-Wall}.
+of the Fortran Character Set. For continuation lines, a tab followed
+by a digit between 1 and 9 is supported. @option{-Wno-tabs} will cause
+a warning to be issued if a tab is encountered. Note, @option{-Wno-tabs}
+is active for @option{-pedantic}, @option{-std=f95}, @option{-std=f2003},
+@option{-std=f2008} and @option{-Wall}.
-
-@cindex -Wunderflow
-@cindex options, -Wunderflow
@item -Wunderflow
-@cindex UNDERFLOW
+@opindex @code{Wunderflow}
+@cindex warnings, underflow
+@cindex underflow
Produce a warning when numerical constant expressions are
encountered, which yield an UNDERFLOW during compilation.
-
-@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.
+@item -Wintrinsic-shadow
+@opindex @code{Wintrinsic-shadow}
+@cindex warnings, intrinsic
+@cindex intrinsic
+Warn if a user-defined procedure or module procedure has the same name as an
+intrinsic; in this case, an explicit interface or @code{EXTERNAL} or
+@code{INTRINSIC} declaration might be needed to get calls later resolved to
+the desired intrinsic/procedure.
+
+@item -Wunused-dummy-argument
+@opindex @code{Wunused-dummy-argument}
+@cindex warnings, unused dummy argument
+@cindex unused dummy argument
+@cindex dummy argument, unused
+Warn about unused dummy arguments. This option is implied by @option{-Wall}.
+
+@item -Wunused-parameter
+@opindex @code{Wunused-parameter}
+@cindex warnings, unused parameter
+@cindex unused parameter
+Contrary to @command{gcc}'s meaning of @option{-Wunused-parameter},
+@command{gfortran}'s implementation of this option does not warn
+about unused dummy arguments (see @option{-Wunused-dummy-argument}),
+but about unused @code{PARAMETER} values. @option{-Wunused-parameter}
+is not included in @option{-Wall} but is implied by @option{-Wall -Wextra}.
+
+@item -Walign-commons
+@opindex @code{Walign-commons}
+@cindex warnings, alignment of @code{COMMON} blocks
+@cindex alignment of @code{COMMON} blocks
+By default, @command{gfortran} warns about any occasion of variables being
+padded for proper alignment inside a @code{COMMON} block. This warning can be turned
+off via @option{-Wno-align-commons}. See also @option{-falign-commons}.
+
+@item -Wfunction-elimination
+@opindex @code{Wfunction-elimination}
+@cindex function elimination
+@cindex warnings, function elimination
+Warn if any calls to functions are eliminated by the optimizations
+enabled by the @option{-ffrontend-optimize} option.
-@cindex -Werror
-@cindex options, -Werror
@item -Werror
+@opindex @code{Werror}
+@cindex warnings, to errors
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 GNU Fortran.)
@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.
+@xref{Warning Options,,Options to Request or Suppress Errors and
+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
+@section Options for debugging your program or GNU Fortran
@cindex options, debugging
@cindex debugging information options
either your program or the GNU Fortran compiler.
@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 useful for debugging the GNU Fortran compiler itself.
-@end table
+@item -fdump-fortran-original
+@opindex @code{fdump-fortran-original}
+Output the internal parse tree after translating the source program
+into internal representation. Only really useful for debugging the
+GNU Fortran compiler itself.
+
+@item -fdump-optimized-tree
+@opindex @code{fdump-fortran-optimized}
+Output the parse tree after front-end optimization. Only really
+useful for debugging the GNU Fortran compiler itself.
+
+@opindex @code{fdump-parse-tree}
+Output the internal parse tree after translating the source program
+into internal representation. Only really useful for debugging the
+GNU Fortran compiler itself. This option is deprecated; use
+@code{-fdump-fortran-original} instead.
-@table @gcctabopt
-@cindex -ffpe-trap=@var{list} option
-@cindex option, -ffpe-trap=@var{list}
@item -ffpe-trap=@var{list}
+@opindex @code{ffpe-trap=}@var{list}
Specify a list of IEEE exceptions when a Floating Point Exception
(FPE) should be raised. On most systems, this will result in a SIGFPE
signal being sent and the program being interrupted, producing a core
file useful for debugging. @var{list} is a (possibly empty) comma-separated
list of the following IEEE exceptions: @samp{invalid} (invalid floating
-point operation, such as @code{sqrt(-1.0)}), @samp{zero} (division by
+point operation, such as @code{SQRT(-1.0)}), @samp{zero} (division by
zero), @samp{overflow} (overflow in a floating point operation),
@samp{underflow} (underflow in a floating point operation),
@samp{precision} (loss of precision during operation) and @samp{denormal}
-(operation produced a denormal denormal value).
+(operation produced a denormal value).
+
+Some of the routines in the Fortran runtime library, like
+@samp{CPU_TIME}, are likely to trigger floating point exceptions when
+@code{ffpe-trap=precision} is used. For this reason, the use of
+@code{ffpe-trap=precision} is not recommended.
+
+@item -fno-backtrace
+@opindex @code{fno-backtrace}
+@cindex backtrace
+@cindex trace
+When a serious runtime error is encountered or a deadly signal is
+emitted (segmentation fault, illegal instruction, bus error,
+floating-point exception, and the other POSIX signals that have the
+action @samp{core}), the Fortran runtime library tries to output a
+backtrace of the error. @code{-fno-backtrace} disables the backtrace
+generation. This option only has influence for compilation of the
+Fortran main program.
+
@end table
@xref{Debugging Options,,Options for Debugging Your Program or GCC,
debugging options.
@node Directory Options
-@section Options for Directory Search
+@section Options for directory search
@cindex directory, options
@cindex options, directory search
@cindex search path
-
-@cindex INCLUDE directive
-@cindex directive, INCLUDE
+@cindex @code{INCLUDE} directive
+@cindex directive, @code{INCLUDE}
These options affect how GNU Fortran searches
for files specified by the @code{INCLUDE} directive and where it searches
for previously compiled modules.
Fortran source.
@table @gcctabopt
-@cindex -Idir option
-@cindex options, -Idir
@item -I@var{dir}
+@opindex @code{I}@var{dir}
@cindex directory, search paths for inclusion
@cindex inclusion, directory search paths for
@cindex search paths, for included files
@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
+This path is also used to search for @file{.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 modules.
+@opindex @code{J}@var{dir}
+@opindex @code{M}@var{dir}
+@cindex paths, search
+@cindex module search path
+This option specifies where to put @file{.mod} files for compiled modules.
It is also added to the list of directories to searched 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.
+@item -fintrinsic-modules-path @var{dir}
+@opindex @code{fintrinsic-modules-path} @var{dir}
+@cindex paths, search
+@cindex module search path
+This option specifies the location of pre-compiled intrinsic modules, if
+they are not in the default location expected by the compiler.
+@end table
+
+@node Link Options
+@section Influencing the linking step
+@cindex options, linking
+@cindex linking, static
+
+These options come into play when the compiler links object files into an
+executable output file. They are meaningless if the compiler is not doing
+a link step.
+
+@table @gcctabopt
+@item -static-libgfortran
+@opindex @code{static-libgfortran}
+On systems that provide @file{libgfortran} as a shared and a static
+library, this option forces the use of the static version. If no
+shared version of @file{libgfortran} was built when the compiler was
+configured, this option has no effect.
@end table
+
@node Runtime Options
@section Influencing runtime behavior
-@cindex runtime, options
+@cindex options, runtime
These options affect the runtime behavior of programs compiled with GNU Fortran.
+
@table @gcctabopt
-@cindex -fconvert=@var{conversion} option
@item -fconvert=@var{conversion}
+@opindex @code{fconvert=}@var{conversion}
Specify the representation of data for unformatted files. Valid
values for conversion are: @samp{native}, the default; @samp{swap},
swap between big- and little-endian; @samp{big-endian}, use big-endian
@emph{This option has an effect only when used in the main program.
The @code{CONVERT} specifier and the GFORTRAN_CONVERT_UNIT environment
-variable override the default specified by -fconvert.}
+variable override the default specified by @option{-fconvert}.}
+
+
+@item -fno-range-check
+@opindex @code{fno-range-check}
+Disable range checking of input values during integer @code{READ} operations.
+For example, GNU Fortran will give an error if an input value is
+outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}]. In other words,
+with @code{INTEGER (kind=4) :: i} , attempting to read @math{-2147483648} will
+give an error unless @option{-fno-range-check} is given.
+
-@cindex -frecord-marker=@var{length}
@item -frecord-marker=@var{length}
+@opindex @code{frecord-marker=}@var{length}
Specify the length of record markers for unformatted files.
-Valid values for @var{length} are 4 and 8. Default is whatever
-@code{off_t} is specified to be on that particular system.
-Note that specifying @var{length} as 4 limits the record
-length of unformatted files to 2 GB. This option does not
-extend the maximum possible record length on systems where
-@code{off_t} is a four_byte quantity.
-
+Valid values for @var{length} are 4 and 8. Default is 4.
+@emph{This is different from previous versions of @command{gfortran}},
+which specified a default record marker length of 8 on most
+systems. If you want to read or write files compatible
+with earlier versions of @command{gfortran}, use @option{-frecord-marker=8}.
+
+@item -fmax-subrecord-length=@var{length}
+@opindex @code{fmax-subrecord-length=}@var{length}
+Specify the maximum length for a subrecord. The maximum permitted
+value for length is 2147483639, which is also the default. Only
+really useful for use by the gfortran testsuite.
+
+@item -fsign-zero
+@opindex @code{fsign-zero}
+When enabled, floating point numbers of value zero with the sign bit set
+are written as negative number in formatted output and treated as
+negative in the @code{SIGN} intrinsic. @code{fno-sign-zero} does not
+print the negative sign of zero values and regards zero as positive
+number in the @code{SIGN} intrinsic for compatibility with F77.
+Default behavior is to show the negative sign.
@end table
@node Code Gen Options
-@section Options for Code Generation Conventions
+@section Options for code generation conventions
@cindex code generation, conventions
@cindex options, code generation
-@cindex run-time, options
+@cindex options, run-time
These machine-independent options control the interface conventions
used in code generation.
it.
@table @gcctabopt
-@cindex @option{-fno-automatic} option
-@cindex options, @option{-fno-automatic}
@item -fno-automatic
-@cindex SAVE statement
-@cindex statements, SAVE
-Treat each program unit as if the @code{SAVE} statement was specified for
-every local variable and array referenced in it. Does not affect common
-blocks. (Some Fortran compilers provide this option under the name
-@option{-static}.)
-
-@cindex @option{-ff2c} option
-@cindex options, @option{-ff2c}
+@opindex @code{fno-automatic}
+@cindex @code{SAVE} statement
+@cindex statement, @code{SAVE}
+Treat each program unit (except those marked as RECURSIVE) as if the
+@code{SAVE} statement were specified for every local variable and array
+referenced in it. Does not affect common blocks. (Some Fortran compilers
+provide this option under the name @option{-static} or @option{-save}.)
+The default, which is @option{-fautomatic}, uses the stack for local
+variables smaller than the value given by @option{-fmax-stack-var-size}.
+Use the option @option{-frecursive} to use no static memory.
+
@item -ff2c
+@opindex ff2c
@cindex calling convention
@cindex @command{f2c} calling convention
@cindex @command{g77} calling convention
This does not affect the generation of code that interfaces with
the @command{libgfortran} library.
-@emph{Caution:} It is not a good idea to mix Fortran code compiled
-with @code{-ff2c} with code compiled with the default @code{-fno-f2c}
+@emph{Caution:} It is not a good idea to mix Fortran code compiled with
+@option{-ff2c} with code compiled with the default @option{-fno-f2c}
calling conventions as, calling @code{COMPLEX} or default @code{REAL}
functions between program parts which were compiled with different
calling conventions will break at execution time.
@emph{Caution:} This will break code which passes intrinsic functions
of type default @code{REAL} or @code{COMPLEX} as actual arguments, as
-the library implementations use the @command{-fno-f2c} calling conventions.
+the library implementations use the @option{-fno-f2c} calling conventions.
-@cindex @option{-fno-underscoring option}
-@cindex options, @option{-fno-underscoring}
@item -fno-underscoring
+@opindex @code{fno-underscoring}
@cindex underscore
@cindex symbol names, underscores
@cindex transforming symbol names
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).
+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,
+@option{-fcase-lower} and that @code{j()} and @code{max_count()} are
+external functions while @code{my_var} and @code{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
prevent accidental linking between procedures with incompatible
interfaces.
-@cindex @option{-fsecond-underscore option}
-@cindex options, @option{-fsecond-underscore}
+@item -fwhole-file
+@opindex @code{fwhole-file}
+By default, GNU Fortran parses, resolves and translates each procedure
+in a file separately. Using this option modifies this such that the
+whole file is parsed and placed in a single front-end tree. During
+resolution, in addition to all the usual checks and fixups, references
+to external procedures that are in the same file effect resolution of
+that procedure, if not already done, and a check of the interfaces. The
+dependences are resolved by changing the order in which the file is
+translated into the backend tree. Thus, a procedure that is referenced
+is translated before the reference and the duplication of backend tree
+declarations eliminated.
+
@item -fsecond-underscore
+@opindex @code{fsecond-underscore}
@cindex underscore
@cindex symbol names, underscores
@cindex transforming symbol names
This option has no effect if @option{-fno-underscoring} is
in effect. It is implied by the @option{-ff2c} option.
-Otherwise, with this option, an external name such as @samp{MAX_COUNT}
+Otherwise, with this option, an external name such as @code{MAX_COUNT}
is implemented as a reference to the link-time external symbol
-@samp{max_count__}, instead of @samp{max_count_}. This is required
+@code{max_count__}, instead of @code{max_count_}. This is required
for compatibility with @command{g77} and @command{f2c}, and is implied
by use of the @option{-ff2c} option.
+@item -fcoarray=@var{<keyword>}
+@opindex @code{fcoarray}
+@cindex coarrays
-@cindex -fbounds-check option
-@cindex -ffortran-bounds-check option
-@item -fbounds-check
+@table @asis
+@item @samp{none}
+Disable coarray support; using coarray declarations and image-control
+statements will produce a compile-time error. (Default)
+
+@item @samp{single}
+Single-image mode, i.e. @code{num_images()} is always one.
+
+@item @samp{lib}
+Library-based coarray parallelization; a suitable GNU Fortran coarray
+library needs to be linked.
+@end table
+
+
+@item -fcheck=@var{<keyword>}
+@opindex @code{fcheck}
+@cindex array, bounds checking
@cindex bounds checking
+@cindex pointer checking
+@cindex memory checking
@cindex range checking
-@cindex array bounds checking
@cindex subscript checking
@cindex checking subscripts
+@cindex run-time checking
+@cindex checking array temporaries
+
+Enable the generation of run-time checks; the argument shall be
+a comma-delimited list of the following keywords.
+
+@table @asis
+@item @samp{all}
+Enable all run-time test of @option{-fcheck}.
+
+@item @samp{array-temps}
+Warns at run time when for passing an actual argument a temporary array
+had to be generated. The information generated by this warning is
+sometimes useful in optimization, in order to avoid such temporaries.
+
+Note: The warning is only printed once per location.
+
+@item @samp{bounds}
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.
+shape arrays against the actual allocated bounds and ensures that all string
+lengths are equal for character array constructors without an explicit
+typespec.
+
+Some checks require that @option{-fcheck=bounds} is set for
+the compilation of the main program.
+
+Note: In the future this may also include other forms of checking, e.g.,
+checking substring references.
+
+@item @samp{do}
+Enable generation of run-time checks for invalid modification of loop
+iteration variables.
+
+@item @samp{mem}
+Enable generation of run-time checks for memory allocation.
+Note: This option does not affect explicit allocations using the
+@code{ALLOCATE} statement, which will be always checked.
+
+@item @samp{pointer}
+Enable generation of run-time checks for pointers and allocatables.
+
+@item @samp{recursion}
+Enable generation of run-time checks for recursively called subroutines and
+functions which are not marked as recursive. See also @option{-frecursive}.
+Note: This check does not work for OpenMP programs and is disabled if used
+together with @option{-frecursive} and @option{-fopenmp}.
+@end table
+
+
+@item -fbounds-check
+@opindex @code{fbounds-check}
+@c Note: This option is also referred in gcc's manpage
+Deprecated alias for @option{-fcheck=bounds}.
-In the future this may also include other forms of checking, eg. checking
-substring references.
+@item -fcheck-array-temporaries
+@opindex @code{fcheck-array-temporaries}
+Deprecated alias for @option{-fcheck=array-temps}.
+
+@item -fmax-array-constructor=@var{n}
+@opindex @code{fmax-array-constructor}
+This option can be used to increase the upper limit permitted in
+array constructors. The code below requires this option to expand
+the array at compile time.
+
+@smallexample
+program test
+implicit none
+integer j
+integer, parameter :: n = 100000
+integer, parameter :: i(n) = (/ (2*j, j = 1, n) /)
+print '(10(I0,1X))', i
+end program test
+@end smallexample
+
+@emph{Caution: This option can lead to long compile times and excessively
+large object files.}
+
+The default value for @var{n} is 65535.
-@cindex -fmax-stack-var-size option
@item -fmax-stack-var-size=@var{n}
+@opindex @code{fmax-stack-var-size}
This option specifies the size in bytes of the largest array that will be put
-on the stack.
+on the stack; if the size is exceeded static memory is used (except in
+procedures marked as RECURSIVE). Use the option @option{-frecursive} to
+allow for recursive procedures which do not have a RECURSIVE attribute or
+for parallel programs. Use @option{-fno-automatic} to never use the stack.
This option currently only affects local arrays declared with constant
bounds, and may not apply to all character variables.
The default value for @var{n} is 32768.
-@cindex -fpack-derived
+@item -fstack-arrays
+@opindex @code{fstack-arrays}
+Adding this option will make the fortran compiler put all local arrays,
+even those of unknown size onto stack memory. If your program uses very
+large local arrays it's possible that you'll have to extend your runtime
+limits for stack memory on some operating systems.
+
@item -fpack-derived
-@cindex Structure packing
+@opindex @code{fpack-derived}
+@cindex structure packing
This option tells GNU Fortran to pack derived type members as closely as
possible. Code compiled with this option is likely to be incompatible
with code compiled without this option, and may execute slower.
-@cindex -frepack-arrays option
@item -frepack-arrays
-@cindex Repacking arrays
+@opindex @code{frepack-arrays}
+@cindex repacking arrays
In some circumstances GNU Fortran may pass assumed shape array
-sections via a descriptor describing a discontiguous area of memory.
+sections via a descriptor describing a noncontiguous 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.
+is noncontiguous.
-@cindex -fshort-enums
@item -fshort-enums
+@opindex @code{fshort-enums}
This option is provided for interoperability with C code that was
-compiled with the @command{-fshort-enums} option. It will make
+compiled with the @option{-fshort-enums} option. It will make
GNU Fortran choose the smallest @code{INTEGER} kind a given
enumerator set will fit in, and give all its enumerators this kind.
+
+@item -fexternal-blas
+@opindex @code{fexternal-blas}
+This option will make @command{gfortran} generate calls to BLAS functions
+for some matrix operations like @code{MATMUL}, instead of using our own
+algorithms, if the size of the matrices involved is larger than a given
+limit (see @option{-fblas-matmul-limit}). This may be profitable if an
+optimized vendor BLAS library is available. The BLAS library will have
+to be specified at link time.
+
+@item -fblas-matmul-limit=@var{n}
+@opindex @code{fblas-matmul-limit}
+Only significant when @option{-fexternal-blas} is in effect.
+Matrix multiplication of matrices with size larger than (or equal to) @var{n}
+will be performed by calls to BLAS functions, while others will be
+handled by @command{gfortran} internal algorithms. If the matrices
+involved are not square, the size comparison is performed using the
+geometric mean of the dimensions of the argument and result matrices.
+
+The default value for @var{n} is 30.
+
+@item -frecursive
+@opindex @code{frecursive}
+Allow indirect recursion by forcing all local arrays to be allocated
+on the stack. This flag cannot be used together with
+@option{-fmax-stack-var-size=} or @option{-fno-automatic}.
+
+@item -finit-local-zero
+@itemx -finit-integer=@var{n}
+@itemx -finit-real=@var{<zero|inf|-inf|nan|snan>}
+@itemx -finit-logical=@var{<true|false>}
+@itemx -finit-character=@var{n}
+@opindex @code{finit-local-zero}
+@opindex @code{finit-integer}
+@opindex @code{finit-real}
+@opindex @code{finit-logical}
+@opindex @code{finit-character}
+The @option{-finit-local-zero} option instructs the compiler to
+initialize local @code{INTEGER}, @code{REAL}, and @code{COMPLEX}
+variables to zero, @code{LOGICAL} variables to false, and
+@code{CHARACTER} variables to a string of null bytes. Finer-grained
+initialization options are provided by the
+@option{-finit-integer=@var{n}},
+@option{-finit-real=@var{<zero|inf|-inf|nan|snan>}} (which also initializes
+the real and imaginary parts of local @code{COMPLEX} variables),
+@option{-finit-logical=@var{<true|false>}}, and
+@option{-finit-character=@var{n}} (where @var{n} is an ASCII character
+value) options. These options do not initialize components of derived
+type variables, nor do they initialize variables that appear in an
+@code{EQUIVALENCE} statement. (This limitation may be removed in
+future releases).
+
+Note that the @option{-finit-real=nan} option initializes @code{REAL}
+and @code{COMPLEX} variables with a quiet NaN. For a signalling NaN
+use @option{-finit-real=snan}; note, however, that compile-time
+optimizations may convert them into quiet NaN and that trapping
+needs to be enabled (e.g. via @option{-ffpe-trap}).
+
+@item -falign-commons
+@opindex @code{falign-commons}
+@cindex alignment of @code{COMMON} blocks
+By default, @command{gfortran} enforces proper alignment of all variables in a
+@code{COMMON} block by padding them as needed. On certain platforms this is mandatory,
+on others it increases performance. If a @code{COMMON} block is not declared with
+consistent data types everywhere, this padding can cause trouble, and
+@option{-fno-align-commons} can be used to disable automatic alignment. The
+same form of this option should be used for all files that share a @code{COMMON} block.
+To avoid potential alignment issues in @code{COMMON} blocks, it is recommended to order
+objects from largest to smallest.
+
+@item -fno-protect-parens
+@opindex @code{fno-protect-parens}
+@cindex re-association of parenthesized expressions
+By default the parentheses in expression are honored for all optimization
+levels such that the compiler does not do any re-association. Using
+@option{-fno-protect-parens} allows the compiler to reorder @code{REAL} and
+@code{COMPLEX} expressions to produce faster code. Note that for the re-association
+optimization @option{-fno-signed-zeros} and @option{-fno-trapping-math}
+need to be in effect. The parentheses protection is enabled by default, unless
+@option{-Ofast} is given.
+
+@item -frealloc-lhs
+@opindex @code{frealloc-lhs}
+@cindex Reallocate the LHS in assignments
+An allocatable left-hand side of an intrinsic assignment is automatically
+(re)allocated if it is either unallocated or has a different shape. The
+option is enabled by default except when @option{-std=f95} is given.
+
+@item -faggressive-function-elimination
+@opindex @code{faggressive-function-elimination}
+@cindex Elimination of functions with identical argument lists
+Functions with identical argument lists are eliminated within
+statements, regardless of whether these functions are marked
+@code{PURE} or not. For example, in
+@smallexample
+ a = f(b,c) + f(b,c)
+@end smallexample
+there will only be a single call to @code{f}. This option only works
+if @option{-ffrontend-optimize} is in effect.
+
+@item -ffrontend-optimize
+@opindex @code{frontend-optimize}
+@cindex Front-end optimization
+This option performs front-end optimization, based on manipulating
+parts the Fortran parse tree. Enabled by default by any @option{-O}
+option. Optimizations enabled by this option include elimination of
+identical function calls within expressions, removing unnecessary
+calls to @code{TRIM} in comparisons and assignments and replacing
+@code{TRIM(a)} with @code{a(1:LEN_TRIM(a))}.
+It can be deselected by specifying @option{-fno-frontend-optimize}.
@end table
@xref{Code Gen Options,,Options for Code Generation Conventions,
offered by the GBE
shared by @command{gfortran}, @command{gcc}, and other GNU compilers.
-
@c man end
@node Environment Variables
-@section Environment Variables Affecting @command{gfortran}
-@cindex environment variables
+@section Environment variables affecting @command{gfortran}
+@cindex environment variable
@c man begin ENVIRONMENT
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