-@c Copyright (C) 2004, 2005, 2006
+@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
+Copyright @copyright{} 2004, 2005, 2006, 2007
Free Software Foundation, Inc.
Permission is granted to copy, distribute and/or modify this document
without explanations.
* Fortran Dialect Options:: Controlling the variant of Fortran language
compiled.
-* Warning Options:: How picky should the compiler be?
+* 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
* Runtime Options:: Influencing runtime behavior
@table @emph
@item Fortran Language Options
@xref{Fortran Dialect Options,,Options Controlling Fortran Dialect}.
-@gccoptlist{
--fall-intrinsics -ffree-form -fno-fixed-form @gol
+@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 }
+-fcray-pointer -fopenmp -frange-check -fno-backslash }
-@item Warning Options
-@xref{Warning Options,,Options to Request or Suppress Warnings}.
-@gccoptlist{
+@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
--w -Wall -Waliasing -Wampersand -Wconversion -Wimplicit-interface @gol
+-w -Wall -Waliasing -Wampersand -Wconversion -Wimplicit-interface @gol
-Wtabs -Wnonstd-intrinsics -Wsurprising -Wunderflow @gol
-Wline-truncation -W}
@item Debugging Options
@xref{Debugging Options,,Options for Debugging Your Program or GCC}.
-@gccoptlist{
--fdump-parse-tree -ffpe-trap=@var{list}}
+@gccoptlist{-fdump-parse-tree -ffpe-trap=@var{list}
+-fdump-core}
@item Directory Options
@xref{Directory Options,,Options for Directory Search}.
-@gccoptlist{
--I@var{dir} -M@var{dir}}
+@gccoptlist{-I@var{dir} -M@var{dir}}
@item Runtime Options
@xref{Runtime Options,,Options for influencing runtime behavior}.
-@gccoptlist{
--fconvert=@var{conversion} -frecord-marker=@var{length}}
+@gccoptlist{-fconvert=@var{conversion} -frecord-marker=@var{length}}
@item Code Generation Options
@xref{Code Gen Options,,Options for Code Generation Conventions}.
-@gccoptlist{
--fno-automatic -ff2c -fno-underscoring -fsecond-underscore @gol
+@gccoptlist{-fno-automatic -ff2c -fno-underscoring
+-fsecond-underscore @gol
-fbounds-check -fmax-stack-var-size=@var{n} @gol
--fpack-derived -frepack-arrays -fshort-enums}
+-fpack-derived -frepack-arrays -fshort-enums -fexternal-blas @gol
+-fblas-matmul-limit=@var{n}}
@end table
@menu
* Fortran Dialect Options:: Controlling the variant of Fortran language
compiled.
-* Warning Options:: How picky should the compiler be?
+* 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
* Runtime Options:: Influencing runtime behavior
accepted by the compiler:
@table @gcctabopt
-@cindex -ffree-form option
-@cindex options, -ffree-form
-@cindex -fno-fixed-form option
-@cindex options, -fno-fixed-form
+@item -ffree-form
+@item -ffixed-form
+@cindex @code{-ffree-form} option
+@cindex option, @code{-ffree-form}
+@cindex @code{-fno-fixed-form} option
+@cindex option, @code{-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. When neither option is specified, the source
form is determined by the file extension.
-@cindex -fall-intrinsics
@item -fall-intrinsics
+@cindex @code{-fall-intrinsics} option
+@cindex option, @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}.
-@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
-Enable special treatment for lines beginning with @samp{d} or @samp{D}
+@cindex @code{-fd-lines-as-code}, option
+@cindex option, @code{-fd-lines-as-code}
+@cindex @code{-fd-lines-as-comments}, option
+@cindex option, @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
+@cindex @code{-fdefault-double-8}, option
+@cindex option, @code{-fdefault-double-8}
Set the @code{DOUBLE PRECISION} type to an 8 byte wide type.
-@cindex option, -fdefault-integer-8
-@cindex -fdefault-integer-8, option
@item -fdefault-integer-8
+@cindex @code{-fdefault-integer-8}, option
+@cindex option, @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.
-@cindex option, -fdefault-real-8
-@cindex -fdefault-real-8, option
@item -fdefault-real-8
+@cindex @code{-fdefault-real-8}, option
+@cindex option, @code{-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 @code{-fdollar-ok} option
+@cindex option, @code{-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 @code{-fno-backslash} option
+@cindex option, @code{-fno-backslash}
@cindex backslash
@cindex escape characters
Change the interpretation of backslashes in string literals 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 @code{-ffixed-line-length-}@var{n} option
+@cindex option, @code{-ffixed-line-length-}@var{n}
@cindex source file format
@cindex lines, length
@cindex length of source lines
@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 @code{-ffree-line-length-}@var{n} option
+@cindex option, @code{-ffree-line-length-}@var{n}
@cindex source file format
@cindex lines, length
@cindex length of source lines
@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}
+@cindex @code{-fmax-identifier-length=}@var{n} option
+@cindex option @option{-fmax-identifier-length=}@var{n}
Specify the maximum allowed identifier length. Typical values are
31 (Fortran 95) and 63 (Fortran 2003).
-@cindex -fimplicit-none option
-@cindex options, -fimplicit-none
@item -fimplicit-none
+@cindex @code{-fimplicit-none} option
+@cindex option, @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
+@cindex @code{-fcray-pointer} option
+@cindex option, @code{-fcray-pointer}
Enable the Cray pointer extension, which provides C-like pointer
functionality.
-@cindex -fopenmp
-@cindex options, -fopenmp
@item -fopenmp
+@cindex @code{-fopenmp} option
+@cindex option, @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,
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}
+@cindex @code{-frange-check} option
+@cindex option, @code{-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 @option{-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 @option{-fno-range-check} the value will
+``wrap around'' and @code{i} will be initialized to @math{-1} instead.
+
@item -std=@var{std}
+@cindex @code{-std=}@var{std} option
+@cindex option, @code{-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}
@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}
+@cindex @code{-fmax-errors-}@var{n} option
+@cindex option, @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
+@cindex @code{-fsyntax-only} option
+@cindex option, @code{-fsyntax-only}
+@cindex syntax checking
Check the code for syntax errors, but don't do anything beyond that.
-@cindex -pedantic option
-@cindex options, -pedantic
@item -pedantic
+@cindex @code{-pedantic} option
+@cindex option, @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} or
+@option{-std=f2003}.
-@cindex -pedantic-errors option
-@cindex options, -pedantic-errors
@item -pedantic-errors
+@cindex @code{-pedantic-errors} option
+@cindex option, @code{-pedantic-errors}
Like @option{-pedantic}, except that errors are produced rather than
warnings.
-@cindex -w option
-@cindex options, -w
@item -w
+@cindex @code{-w} option
+@cindex option, @code{-w}
Inhibit all warning messages.
-
-@cindex -Wall option
-@cindex options, -Wall
@item -Wall
+@cindex @code{-Wall} option
+@cindex option, @code{-Wall}
@cindex all warnings
@cindex warnings, all
Enables commonly used warning options pertaining to usage that
@option{-Wampersand}, @option{-Wsurprising}, @option{-Wnonstd-intrinsic},
@option{-Wno-tabs}, and @option{-Wline-truncation}.
-
-@cindex -Waliasing option
-@cindex options, -Waliasing
@item -Waliasing
+@cindex @code{-Waliasing} option
+@cindex option, @code{-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
+@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 @code{-Wampersand} option
+@cindex option, @code{-Wampersand}
@cindex ampersand
Warn about missing ampersand in continued character constants. The warning is
given with @option{-Wampersand}, @option{-pedantic}, @option{-std=f95}, and
constant, GNU Fortran assumes continuation at the first non-comment,
non-whitespace character after the ampersand that initiated the continuation.
-
-@cindex -Wconversion option
-@cindex options, -Wconversion
@item -Wconversion
+@cindex @code{-Wconversion} option
+@cindex option, @code{-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.
+@cindex @code{-Wimplicit-interface} option
+@cindex option, @code{-Wimplicit-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.
-
-@cindex -Wnonstd-intrinsic option
-@cindex options, -Wnonstd-intrinsic
@item -Wnonstd-intrinsic
+@cindex @code{-Wnonstd-intrinsic} option
+@cindex option, @code{-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
+@cindex @code{-Wsurprising} option
+@cindex option, @code{-Wsurprising}
+@cindex Suspicious code
Produce a warning when ``suspicious'' code constructs are encountered.
While technically legal these usually indicate that an error has been made.
A LOGICAL SELECT construct has three CASE statements.
@end itemize
-
-@cindex -Wtabs
-@cindex options, -Wtabs
@item -Wtabs
+@cindex @code{-Wtabs} option
+@cindex option, @code{-Wtabs}
@cindex Tabs
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}.
-
-@cindex -Wunderflow
-@cindex options, -Wunderflow
@item -Wunderflow
+@cindex @code{-Wunderflow} option
+@cindex option, @code{-Wunderflow}
@cindex UNDERFLOW
Produce a warning when numerical constant expressions are
encountered, which yield an UNDERFLOW during compilation.
-
-@cindex -Werror
-@cindex options, -Werror
@item -Werror
+@cindex @code{-Werror} option
+@cindex option, @code{-Werror}
Turns all warnings into errors.
-
-@cindex -W option
-@cindex options, -W
@item -W
+@cindex @code{-W} option
+@cindex option, @code{-W}
@cindex extra warnings
@cindex warnings, extra
Turns on ``extra warnings'' and, if optimization is specified
(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{Error and 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.
either your program or the GNU Fortran compiler.
@table @gcctabopt
-@cindex -fdump-parse-tree option
-@cindex option, -fdump-parse-tree
@item -fdump-parse-tree
+@cindex @code{-fdump-parse-tree} option
+@cindex option, @code{-fdump-parse-tree}
Output the internal parse tree before starting code generation. Only
really useful for debugging the GNU Fortran compiler itself.
-@end table
-@table @gcctabopt
-@cindex -ffpe-trap=@var{list} option
-@cindex option, -ffpe-trap=@var{list}
@item -ffpe-trap=@var{list}
+@cindex @code{-ffpe-trap=}@var{list} option
+@cindex option, @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).
+
+@cindex -fdump-core option
+@cindex options, -fdump-core
+@item -fdump-core
+@cindex core
+Request that a core-dump file is written to disk when a runtime error
+is encountered on systems that support core dumps. This option is
+only effective for the compilation of the Fortran main program.
+
@end table
@xref{Debugging Options,,Options for Debugging Your Program or GCC,
@cindex directory, options
@cindex options, directory search
@cindex search path
-
@cindex INCLUDE directive
@cindex directive, INCLUDE
These options affect how GNU Fortran searches
Fortran source.
@table @gcctabopt
-@cindex -Idir option
-@cindex options, -Idir
@item -I@var{dir}
+@cindex @code{-I}@var{dir} option
+@cindex option, @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.
+@cindex @code{-M}@var{dir} option
+@cindex option, -@code{-M}@var{dir}
+@cindex @code{-J}@var{dir} option
+@cindex option, -@code{-J}@var{dir}
+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.
These options affect the runtime behavior of programs compiled with GNU Fortran.
@table @gcctabopt
-@cindex -fconvert=@var{conversion} option
@item -fconvert=@var{conversion}
+@cindex @code{-fconvert=}@var{conversion} option
+@cindex option, @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}.}
-@cindex -frecord-marker=@var{length}
@item -frecord-marker=@var{length}
+@cindex @code{-frecord-marker=}@var{length} option
+@cindex option, @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 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 gfortran, use @option{-frecord-marker=8}.
+
+@item -fmax-subrecord-length=@var{length}
+@cindex @code{-fmax-subrecord-length=}@var{length} option
+@cindex option, @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.
@end table
@node Code Gen Options
it.
@table @gcctabopt
-@cindex @option{-fno-automatic} option
-@cindex options, @option{-fno-automatic}
@item -fno-automatic
+@cindex @code{-fno-automatic} option
+@cindex option, @code{-fno-automatic}
@cindex SAVE statement
@cindex statements, SAVE
Treat each program unit as if the @code{SAVE} statement was specified for
blocks. (Some Fortran compilers provide this option under the name
@option{-static}.)
-@cindex @option{-ff2c} option
-@cindex options, @option{-ff2c}
@item -ff2c
+@cindex @code{-ff2c} option
+@cindex option, @code{-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
+@cindex @code{-fno-underscoring option}
+@cindex option, @code{-fno-underscoring}
@cindex underscore
@cindex symbol names, underscores
@cindex transforming symbol names
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 -fsecond-underscore
+@cindex @code{-fsecond-underscore option}
+@cindex option, @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.
-
-@cindex -fbounds-check option
-@cindex -ffortran-bounds-check option
@item -fbounds-check
+@cindex @code{-fbounds-check} option
+@cindex option, @code{-fbounds-check}
@cindex bounds checking
@cindex range checking
@cindex array bounds checking
checks array indices for assumed and deferred
shape arrays against the actual allocated bounds.
-In the future this may also include other forms of checking, eg. checking
+In the future this may also include other forms of checking, e.g., checking
substring references.
-
-@cindex -fmax-stack-var-size option
@item -fmax-stack-var-size=@var{n}
+@cindex @code{-fmax-stack-var-size} option
+@cindex option, @code{-fmax-stack-var-size}
This option specifies the size in bytes of the largest array that will be put
on the stack.
The default value for @var{n} is 32768.
-@cindex -fpack-derived
@item -fpack-derived
+@cindex @code{-fpack-derived} option
+@cindex option, @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 @code{-frepack-arrays} option
+@cindex option, @code{-frepack-arrays}
@cindex Repacking arrays
In some circumstances GNU Fortran may pass assumed shape array
-sections via a descriptor describing a discontinuous 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 discontinuous.
+is noncontiguous.
-@cindex -fshort-enums
@item -fshort-enums
+@cindex @code{-fshort-enums} option
+@cindex option, @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
+@cindex @code{-fexternal-blas} option
+@cindex option, @code{-fexternal-blas}
+This option will make 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}
+@cindex @code{-fblas-matmul-limit} option
+@cindex option, @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.
+
@end table
@xref{Code Gen Options,,Options for Code Generation Conventions,
OSDN Git Service
