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GFORTRAN(1)				       GNU				      GFORTRAN(1)

NAME
       gfortran - GNU Fortran compiler

SYNOPSIS
       gfortran [-c|-S|-E]
		[-g] [-pg] [-Olevel]
		[-Wwarn...] [-pedantic]
		[-Idir...] [-Ldir...]
		[-Dmacro[=defn]...] [-Umacro]
		[-foption...]
		[-mmachine-option...]
		[-o outfile] infile...

       Only the most useful options are listed here; see below for the remainder.

DESCRIPTION
       The gfortran command supports all the options supported by the gcc command.  Only options
       specific to GNU Fortran are documented here.

       All GCC and GNU Fortran options are accepted both by gfortran and by gcc (as well as any
       other drivers built at the same time, such as g++), since adding GNU Fortran to the GCC
       distribution enables acceptance of GNU Fortran options by all of the relevant drivers.

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

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

       Fortran Language Options
	   -fall-intrinsics  -ffree-form  -fno-fixed-form -fdollar-ok  -fimplicit-none
	   -fmax-identifier-length -std=std -fd-lines-as-code  -fd-lines-as-comments
	   -ffixed-line-length-n  -ffixed-line-length-none -ffree-line-length-n
	   -ffree-line-length-none -fdefault-double-8  -fdefault-integer-8  -fdefault-real-8
	   -fcray-pointer  -fopenmp  -fno-range-check -fbackslash -fmodule-private

       Preprocessing Options
	   -cpp -dD -dI -dM -dN -dU -fworking-directory -imultilib dir -iprefix file -isysroot
	   dir -iquote -isystem dir -nocpp -nostdinc -undef -Aquestion=answer
	   -A-question[=answer] -C -CC -Dmacro[=defn] -Umacro -H -P

       Error and Warning Options
	   -fmax-errors=n -fsyntax-only  -pedantic  -pedantic-errors -Wall  -Waliasing
	   -Wampersand	-Warray-bounds -Wcharacter-truncation -Wconversion -Wimplicit-interface
	   -Wline-truncation  -Wintrinsics-std -Wsurprising -Wno-tabs  -Wunderflow
	   -Wunused-parameter -Wintrinsics-shadow -Wno-align-commons

       Debugging Options
	   -fdump-parse-tree  -ffpe-trap=list -fdump-core -fbacktrace

       Directory Options
	   -Idir  -Jdir -fintrinsic-modules-path dir

       Link Options
	   -static-libgfortran

       Runtime Options
	   -fconvert=conversion  -fno-range-check -frecord-marker=length
	   -fmax-subrecord-length=length -fsign-zero

       Code Generation Options
	   -fno-automatic  -ff2c  -fno-underscoring -fsecond-underscore -fbounds-check
	   -fcheck-array-temporaries  -fmax-array-constructor =n -fmax-stack-var-size=n
	   -fpack-derived  -frepack-arrays  -fshort-enums  -fexternal-blas -fblas-matmul-limit=n
	   -frecursive -finit-local-zero -finit-integer=n -finit-real=<zero|inf|-inf|nan>
	   -finit-logical=<true|false> -finit-character=n -fno-align-commons

   Options controlling Fortran dialect
       The following options control the details of the Fortran dialect accepted by the compiler:

       -ffree-form
       -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.

       -fall-intrinsics
	   This option causes all intrinsic procedures (including the GNU-specific extensions) to
	   be accepted.  This can be useful with -std=f95 to force standard-compliance but get
	   access to the full range of intrinsics available with gfortran.  As a consequence,
	   -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 "EXTERNAL".

       -fd-lines-as-code
       -fd-lines-as-comments
	   Enable special treatment for lines beginning with "d" or "D" in fixed form sources.
	   If the -fd-lines-as-code option is given they are treated as if the first column
	   contained a blank.  If the -fd-lines-as-comments option is given, they are treated as
	   comment lines.

       -fdefault-double-8
	   Set the "DOUBLE PRECISION" type to an 8 byte wide type.  If -fdefault-real-8 is given,
	   "DOUBLE PRECISION" would instead be promoted to 16 bytes if possible, and
	   -fdefault-double-8 can be used to prevent this.  The kind of real constants like
	   "1.d0" will not be changed by -fdefault-real-8 though, so also -fdefault-double-8 does
	   not affect it.

       -fdefault-integer-8
	   Set the default integer and logical types to an 8 byte wide type.  Do nothing if this
	   is already the default.  This option also affects the kind of integer constants like
	   42.

       -fdefault-real-8
	   Set the default real type to an 8 byte wide type.  Do nothing if this is already the
	   default.  This option also affects the kind of non-double real constants like 1.0, and
	   does promote the default width of "DOUBLE PRECISION" to 16 bytes if possible, unless
	   "-fdefault-double-8" is given, too.

       -fdollar-ok
	   Allow $ as a valid character in a symbol name.

       -fbackslash
	   Change the interpretation of backslashes in string literals from a single backslash
	   character to "C-style" escape characters. The following combinations are expanded
	   "\a", "\b", "\f", "\n", "\r", "\t", "\v", "\\", and "\0" to the ASCII characters
	   alert, backspace, form feed, newline, carriage return, horizontal tab, vertical tab,
	   backslash, and NUL, respectively.  Additionally, "\x"nn, "\u"nnnn and "\U"nnnnnnnn
	   (where each 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.

       -fmodule-private
	   Set the default accessibility of module entities to "PRIVATE".  Use-associated
	   entities will not be accessible unless they are explicitly declared as "PUBLIC".

       -ffixed-line-length-n
	   Set column after which characters are ignored in typical fixed-form lines in the
	   source file, and through which spaces are assumed (as if padded to that length) after
	   the ends of short fixed-form lines.

	   Popular values for n include 72 (the standard and the default), 80 (card image), and
	   132 (corresponding to "extended-source" options in some popular compilers).	n may
	   also be none, meaning that the entire line is meaningful and that continued character
	   constants never have implicit spaces appended to them to fill out the line.
	   -ffixed-line-length-0 means the same thing as -ffixed-line-length-none.

       -ffree-line-length-n
	   Set column after which characters are ignored in typical free-form lines in the source
	   file. The default value is 132.  n may be none, meaning that the entire line is
	   meaningful.	-ffree-line-length-0 means the same thing as -ffree-line-length-none.

       -fmax-identifier-length=n
	   Specify the maximum allowed identifier length. Typical values are 31 (Fortran 95) and
	   63 (Fortran 2003 and Fortran 2008).

       -fimplicit-none
	   Specify that no implicit typing is allowed, unless overridden by explicit "IMPLICIT"
	   statements.	This is the equivalent of adding "implicit none" to the start of every
	   procedure.

       -fcray-pointer
	   Enable the Cray pointer extension, which provides C-like pointer functionality.

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

       -fno-range-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 "a = 1. / 0".  With this option, no error will be given and "a" will be
	   assigned the value "+Infinity".  If an expression evaluates to a value outside of the
	   relevant range of ["-HUGE()":"HUGE()"], then the expression will be replaced by "-Inf"
	   or "+Inf" as appropriate.  Similarly, "DATA i/Z'FFFFFFFF'/" will result in an integer
	   overflow on most systems, but with -fno-range-check the value will "wrap around" and
	   "i" will be initialized to -1 instead.

       -std=std
	   Specify the standard to which the program is expected to conform, which may be one of
	   f95, f2003, f2008, gnu, or legacy.  The default value for std is 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 legacy value is equivalent but without the warnings for
	   obsolete extensions, and may be useful for old non-standard programs.  The f95, f2003
	   and 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.

   Enable and customize preprocessing
       Preprocessor related options. See section Preprocessing and conditional compilation for
       more detailed information on preprocessing in gfortran.

       -cpp
       -nocpp
	   Enable preprocessing. The preprocessor is automatically invoked if the file extension
	   is .fpp, .FPP,  .F, .FOR, .FTN, .F90, .F95, .F03 or .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: -nocpp.

	   The preprocessor is run in traditional mode, be aware that any restrictions of the
	   file-format, e.g. fixed-form line width, apply for preprocessed output as well.

       -dM Instead of the normal output, generate a list of '#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 foo.f90, the command

		     touch foo.f90; gfortran -cpp -dM foo.f90

	   will show all the predefined macros.

       -dD Like -dM except in two respects: it does not include the predefined macros, and it
	   outputs both the "#define" directives and the result of preprocessing. Both kinds of
	   output go to the standard output file.

       -dN Like -dD, but emit only the macro names, not their expansions.

       -dU Like 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 '#undef' directives are also output for macros tested but undefined at
	   the time.

       -dI Output '#include' directives in addition to the result of preprocessing.

       -fworking-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 -fno-working-directory. If the -P flag is present in the command
	   line, this option has no effect, since no "#line" directives are emitted whatsoever.

       -idirafter dir
	   Search dir for include files, but do it after all directories specified with -I and
	   the standard system directories have been exhausted. dir is treated as a system
	   include directory.  If dir begins with "=", then the "=" will be replaced by the
	   sysroot prefix; see --sysroot and -isysroot.

       -imultilib dir
	   Use dir as a subdirectory of the directory containing target-specific C++ headers.

       -iprefix prefix
	   Specify prefix as the prefix for subsequent -iwithprefix options. If the prefix
	   represents a directory, you should include the final '/'.

       -isysroot dir
	   This option is like the --sysroot option, but applies only to header files. See the
	   --sysroot option for more information.

       -iquote dir
	   Search dir only for header files requested with "#include "file""; they are not
	   searched for "#include <file>", before all directories specified by -I and before the
	   standard system directories. If dir begins with "=", then the "=" will be replaced by
	   the sysroot prefix; see --sysroot and -isysroot.

       -isystem dir
	   Search dir for header files, after all directories specified by -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 dir begins with
	   "=", then the "=" will be replaced by the sysroot prefix; see --sysroot and -isysroot.

       -nostdinc
	   Do not search the standard system directories for header files. Only the directories
	   you have specified with -I options (and the directory of the current file, if
	   appropriate) are searched.

       -undef
	   Do not predefine any system-specific or GCC-specific macros.  The standard predefined
	   macros remain defined.

       -Apredicate=answer
	   Make an assertion with the predicate predicate and answer answer.  This form is
	   preferred to the older form -A predicate(answer), which is still supported, because it
	   does not use shell special characters.

       -A-predicate=answer
	   Cancel an assertion with the predicate predicate and answer answer.

       -C  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 -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 '#'.

	   Warning: this currently handles C-Style comments only. The preprocessor does not yet
	   recognize Fortran-style comments.

       -CC Do not discard comments, including during macro expansion. This is like -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 -C option, the -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 -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.

       -Dname
	   Predefine name as a macro, with definition 1.

       -Dname=definition
	   The contents of definition are tokenized and processed as if they appeared during
	   translation phase three in a '#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,
	   "-D'name(args...)=definition'" works.

	   -D and -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.

       -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 '#include' stack it is.

       -P  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.

       -Uname
	   Cancel any previous definition of name, either built in or provided with a -D option.

   Options to request or suppress errors and 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 is likely to be a bug in the program.
       Unless -Werror is specified, they do not prevent compilation of the program.

       You can request many specific warnings with options beginning -W, for example -Wimplicit
       to request warnings on implicit declarations.  Each of these specific warning options also
       has a negative form beginning -Wno- to turn off warnings; for example, -Wno-implicit.
       This manual lists only one of the two forms, whichever is not the default.

       These options control the amount and kinds of errors and warnings produced by GNU Fortran:

       -fmax-errors=n
	   Limits the maximum number of error messages to n, at which point GNU Fortran bails out
	   rather than attempting to continue processing the source code.  If n is 0, there is no
	   limit on the number of error messages produced.

       -fsyntax-only
	   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.

       -pedantic
	   Issue warnings for uses of extensions to Fortran 95.  -pedantic also applies to
	   C-language constructs where they occur in GNU Fortran source files, such as use of \e
	   in a character constant within a directive like "#include".

	   Valid Fortran 95 programs should compile properly with or without this option.
	   However, without this option, certain GNU extensions and traditional Fortran features
	   are supported as well.  With this option, many of them are rejected.

	   Some users try to use -pedantic to check programs for conformance.  They soon find
	   that it does not do quite what they want---it finds some nonstandard practices, but
	   not all.  However, improvements to GNU Fortran in this area are welcome.

	   This should be used in conjunction with -std=f95, -std=f2003 or -std=f2008.

       -pedantic-errors
	   Like -pedantic, except that errors are produced rather than warnings.

       -Wall
	   Enables commonly used warning options pertaining to usage that we recommend avoiding
	   and that we believe are easy to avoid.  This currently includes -Waliasing,
	   -Wampersand, -Wsurprising, -Wintrinsics-std, -Wno-tabs, -Wintrinsic-shadow and
	   -Wline-truncation.

       -Waliasing
	   Warn about possible aliasing of dummy arguments. Specifically, it warns if the same
	   actual argument is associated with a dummy argument with "INTENT(IN)" and a dummy
	   argument with "INTENT(OUT)" in a call with an explicit interface.

	   The following example will trigger the warning.

		     interface
		       subroutine bar(a,b)
			 integer, intent(in) :: a
			 integer, intent(out) :: b
		       end subroutine
		     end interface
		     integer :: a

		     call bar(a,a)

       -Wampersand
	   Warn about missing ampersand in continued character constants. The warning is given
	   with -Wampersand, -pedantic, -std=f95, -std=f2003 and -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.

       -Warray-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.

       -Wcharacter-truncation
	   Warn when a character assignment will truncate the assigned string.

       -Wline-truncation
	   Warn when a source code line will be truncated.

       -Wconversion
	   Warn about implicit conversions between different types.

       -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.

       -Wintrinsics-std
	   Warn if gfortran finds a procedure named like an intrinsic not available in the
	   currently selected standard (with -std) and treats it as "EXTERNAL" procedure because
	   of this.  -fall-intrinsics can be used to never trigger this behaviour and always link
	   to the intrinsic regardless of the selected standard.

       -Wsurprising
	   Produce a warning when "suspicious" code constructs are encountered.  While
	   technically legal these usually indicate that an error has been made.

	   This currently produces a warning under the following circumstances:

	   o   An INTEGER SELECT construct has a CASE that can never be matched as its lower
	       value is greater than its upper value.

	   o   A LOGICAL SELECT construct has three CASE statements.

	   o   A TRANSFER specifies a source that is shorter than the destination.

	   o   The type of a function result is declared more than once with the same type.  If
	       -pedantic or standard-conforming mode is enabled, this is an error.

       -Wtabs
	   By default, tabs are accepted as whitespace, but tabs are not members of the Fortran
	   Character Set.  For continuation lines, a tab followed by a digit between 1 and 9 is
	   supported.  -Wno-tabs will cause a warning to be issued if a tab is encountered. Note,
	   -Wno-tabs is active for -pedantic, -std=f95, -std=f2003, -std=f2008 and -Wall.

       -Wunderflow
	   Produce a warning when numerical constant expressions are encountered, which yield an
	   UNDERFLOW during compilation.

       -Wintrinsic-shadow
	   Warn if a user-defined procedure or module procedure has the same name as an
	   intrinsic; in this case, an explicit interface or "EXTERNAL" or "INTRINSIC"
	   declaration might be needed to get calls later resolved to the desired
	   intrinsic/procedure.

       -Wunused-parameter
	   Contrary to gcc's meaning of -Wunused-parameter, gfortran's implementation of this
	   option does not warn about unused dummy arguments, but about unused "PARAMETER"
	   values.  -Wunused-parameter is not included in -Wall but is implied by -Wall -Wextra.

       -Walign-commons
	   By default, gfortran warns about any occasion of variables being padded for proper
	   alignment inside a COMMON block. This warning can be turned off via
	   -Wno-align-commons. See also -falign-commons.

       -Werror
	   Turns all warnings into errors.

       Some of these have no effect when compiling programs written in Fortran.

   Options for debugging your program or GNU Fortran
       GNU Fortran has various special options that are used for debugging either your program or
       the GNU Fortran compiler.

       -fdump-parse-tree
	   Output the internal parse tree before starting code generation.  Only really useful
	   for debugging the GNU Fortran compiler itself.

       -ffpe-trap=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.  list is a
	   (possibly empty) comma-separated list of the following IEEE exceptions: invalid
	   (invalid floating point operation, such as "SQRT(-1.0)"), zero (division by zero),
	   overflow (overflow in a floating point operation), underflow (underflow in a floating
	   point operation), precision (loss of precision during operation) and denormal
	   (operation produced a denormal value).

	   Some of the routines in the Fortran runtime library, like CPU_TIME, are likely to
	   trigger floating point exceptions when "ffpe-trap=precision" is used. For this reason,
	   the use of "ffpe-trap=precision" is not recommended.

       -fbacktrace
	   Specify that, when a runtime error is encountered or a deadly signal is emitted
	   (segmentation fault, illegal instruction, bus error or floating-point exception), the
	   Fortran runtime library should output a backtrace of the error.  This option only has
	   influence for compilation of the Fortran main program.

       -fdump-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.

   Options for directory search
       These options affect how GNU Fortran searches for files specified by the "INCLUDE"
       directive and where it searches for previously compiled modules.

       It also affects the search paths used by cpp when used to preprocess Fortran source.

       -Idir
	   These affect interpretation of the "INCLUDE" directive (as well as of the "#include"
	   directive of the cpp preprocessor).

	   Also note that the general behavior of -I and "INCLUDE" is pretty much the same as of
	   -I with "#include" in the cpp preprocessor, with regard to looking for header.gcc
	   files and other such things.

	   This path is also used to search for .mod files when previously compiled modules are
	   required by a "USE" statement.

       -Jdir
	   This option specifies where to put .mod files for compiled modules.	It is also added
	   to the list of directories to searched by an "USE" statement.

	   The default is the current directory.

       -fintrinsic-modules-path dir
	   This option specifies the location of pre-compiled intrinsic modules, if they are not
	   in the default location expected by the compiler.

   Influencing the linking step
       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.

       -static-libgfortran
	   On systems that provide libgfortran as a shared and a static library, this option
	   forces the use of the static version. If no shared version of libgfortran was built
	   when the compiler was configured, this option has no effect.

   Influencing runtime behavior
       These options affect the runtime behavior of programs compiled with GNU Fortran.

       -fconvert=conversion
	   Specify the representation of data for unformatted files.  Valid values for conversion
	   are: native, the default; swap, swap between big- and little-endian; big-endian, use
	   big-endian representation for unformatted files; little-endian, use little-endian
	   representation for unformatted files.

	   This option has an effect only when used in the main program.  The "CONVERT" specifier
	   and the GFORTRAN_CONVERT_UNIT environment variable override the default specified by
	   -fconvert.

       -fno-range-check
	   Disable range checking of input values during integer "READ" operations.  For example,
	   GNU Fortran will give an error if an input value is outside of the relevant range of
	   ["-HUGE()":"HUGE()"]. In other words, with "INTEGER (kind=4) :: i" , attempting to
	   read -2147483648 will give an error unless -fno-range-check is given.

       -frecord-marker=length
	   Specify the length of record markers for unformatted files.	Valid values for length
	   are 4 and 8.  Default is 4.	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
	   -frecord-marker=8.

       -fmax-subrecord-length=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.

       -fsign-zero
	   When writing zero values, show the negative sign if the sign bit is set.
	   "fno-sign-zero" does not print the negative sign of zero values for compatibility with
	   F77.  Default behavior is to show the negative sign.

   Options for code generation conventions
       These machine-independent options control the interface conventions used in code
       generation.

       Most of them have both positive and negative forms; the negative form of -ffoo would be
       -fno-foo.  In the table below, only one of the forms is listed---the one which is not the
       default.  You can figure out the other form by either removing no- or adding it.

       -fno-automatic
	   Treat each program unit (except those marked as RECURSIVE) as if the "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 -static or
	   -save.)  The default, which is -fautomatic, uses the stack for local variables smaller
	   than the value given by -fmax-stack-var-size.  Use the option -frecursive to use no
	   static memory.

       -ff2c
	   Generate code designed to be compatible with code generated by g77 and f2c.

	   The calling conventions used by g77 (originally implemented in f2c) require functions
	   that return type default "REAL" to actually return the C type "double", and functions
	   that return type "COMPLEX" to return the values via an extra argument in the calling
	   sequence that points to where to store the return value.  Under the default GNU
	   calling conventions, such functions simply return their results as they would in GNU
	   C---default "REAL" functions return the C type "float", and "COMPLEX" functions return
	   the GNU C type "complex".  Additionally, this option implies the -fsecond-underscore
	   option, unless -fno-second-underscore is explicitly requested.

	   This does not affect the generation of code that interfaces with the libgfortran
	   library.

	   Caution: It is not a good idea to mix Fortran code compiled with -ff2c with code
	   compiled with the default -fno-f2c calling conventions as, calling "COMPLEX" or
	   default "REAL" functions between program parts which were compiled with different
	   calling conventions will break at execution time.

	   Caution: This will break code which passes intrinsic functions of type default "REAL"
	   or "COMPLEX" as actual arguments, as the library implementations use the -fno-f2c
	   calling conventions.

       -fno-underscoring
	   Do not transform names of entities specified in the Fortran source file by appending
	   underscores to them.

	   With -funderscoring in effect, GNU Fortran appends one underscore to external names
	   with no underscores.  This is done to ensure compatibility with code produced by many
	   UNIX Fortran compilers.

	   Caution: The default behavior of GNU Fortran is incompatible with f2c and g77, please
	   use the -ff2c option if you want object files compiled with GNU Fortran to be
	   compatible with object code created with these tools.

	   Use of -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).

	   For example, with -funderscoring, and assuming other defaults like -fcase-lower and
	   that "j()" and "max_count()" are external functions while "my_var" and "lvar" are
	   local variables, a statement like

		   I = J() + MAX_COUNT (MY_VAR, LVAR)

	   is implemented as something akin to:

		   i = j_() + max_count__(&my_var__, &lvar);

	   With -fno-underscoring, the same statement is implemented as:

		   i = j() + max_count(&my_var, &lvar);

	   Use of -fno-underscoring allows direct specification of user-defined names while
	   debugging and when interfacing GNU Fortran code with other languages.

	   Note that just because the names match does not mean that the interface implemented by
	   GNU Fortran for an external name matches the interface implemented by some other
	   language for that same name.  That is, getting code produced by GNU Fortran to link to
	   code produced by some other compiler using this or any other method can be only a
	   small part of the overall solution---getting the code generated by both compilers to
	   agree on issues other than naming can require significant effort, and, unlike naming
	   disagreements, linkers normally cannot detect disagreements in these other areas.

	   Also, note that with -fno-underscoring, the lack of appended underscores introduces
	   the very real possibility that a user-defined external name will conflict with a name
	   in a system library, which could make finding unresolved-reference bugs quite
	   difficult in some cases---they might occur at program run time, and show up only as
	   buggy behavior at run time.

	   In future versions of GNU Fortran we hope to improve naming and linking issues so that
	   debugging always involves using the names as they appear in the source, even if the
	   names as seen by the linker are mangled to prevent accidental linking between
	   procedures with incompatible interfaces.

       -fsecond-underscore
	   By default, GNU Fortran appends an underscore to external names.  If this option is
	   used GNU Fortran appends two underscores to names with underscores and one underscore
	   to external names with no underscores.  GNU Fortran also appends two underscores to
	   internal names with underscores to avoid naming collisions with external names.

	   This option has no effect if -fno-underscoring is in effect.  It is implied by the
	   -ff2c option.

	   Otherwise, with this option, an external name such as "MAX_COUNT" is implemented as a
	   reference to the link-time external symbol "max_count__", instead of "max_count_".
	   This is required for compatibility with g77 and f2c, and is implied by use of the
	   -ff2c option.

       -fbounds-check
	   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 and ensures that all string lengths
	   are equal for character array constructors without an explicit typespec.

	   Some checks require that -fbounds-check 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.

       fcheck-array-temporaries
	   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.

       -fmax-array-constructor=n
	   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.

		   C<program test>
		   C<implicit none>
		   C<integer j>
		   C<integer, parameter :: n = 100000>
		   C<integer, parameter :: i(n) = (/ (2*j, j = 1, n) /)>
		   C<print '(10(I0,1X))', i>
		   C<end program test>

	   Caution:  This option can lead to long compile times and excessively large object
	   files.

	   The default value for n is 65535.

       -fmax-stack-var-size=n
	   This option specifies the size in bytes of the largest array that will be put on the
	   stack; if the size is exceeded static memory is used (except in procedures marked as
	   RECURSIVE). Use the option -frecursive to allow for recursive procedures which do not
	   have a RECURSIVE attribute or for parallel programs. Use -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.  Future versions of GNU Fortran may improve this
	   behavior.

	   The default value for n is 32768.

       -fpack-derived
	   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.

       -frepack-arrays
	   In some circumstances GNU Fortran may pass assumed shape array 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
	   noncontiguous.

       -fshort-enums
	   This option is provided for interoperability with C code that was compiled with the
	   -fshort-enums option.  It will make GNU Fortran choose the smallest "INTEGER" kind a
	   given enumerator set will fit in, and give all its enumerators this kind.

       -fexternal-blas
	   This option will make gfortran generate calls to BLAS functions for some matrix
	   operations like "MATMUL", instead of using our own algorithms, if the size of the
	   matrices involved is larger than a given limit (see -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.

       -fblas-matmul-limit=n
	   Only significant when -fexternal-blas is in effect.	Matrix multiplication of matrices
	   with size larger than (or equal to) n will be performed by calls to BLAS functions,
	   while others will be handled by 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 n is 30.

       -frecursive
	   Allow indirect recursion by forcing all local arrays to be allocated on the stack.
	   This flag cannot be used together with -fmax-stack-var-size= or -fno-automatic.

       -finit-local-zero
       -finit-integer=n
       -finit-real=<zero|inf|-inf|nan>
       -finit-logical=<true|false>
       -finit-character=n
	   The -finit-local-zero option instructs the compiler to initialize local "INTEGER",
	   "REAL", and "COMPLEX" variables to zero, "LOGICAL" variables to false, and "CHARACTER"
	   variables to a string of null bytes.  Finer-grained initialization options are
	   provided by the -finit-integer=n, -finit-real=<zero|inf|-inf|nan> (which also
	   initializes the real and imaginary parts of local "COMPLEX" variables),
	   -finit-logical=<true|false>, and -finit-character=n (where 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 "EQUIVALENCE" statement.	(This
	   limitation may be removed in future releases).

	   Note that the -finit-real=nan option initializes "REAL" and "COMPLEX" variables with a
	   quiet NaN.

       -falign-commons
	   By default, gfortran enforces proper alignment of all variables in a COMMON block by
	   padding them as needed. On certain platforms this is mandatory, on others it increases
	   performance. If a COMMON block is not declared with consistent data types everywhere,
	   this padding can cause trouble, and -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 COMMON block.  To avoid potential alignment issues in COMMON blocks, it is
	   recommended to order objects from largests to smallest.

ENVIRONMENT
       The gfortran compiler currently does not make use of any environment variables to control
       its operation above and beyond those that affect the operation of gcc.

BUGS
       For instructions on reporting bugs, see <http://bugzilla.redhat.com/bugzilla>.

SEE ALSO
       gpl(7), gfdl(7), fsf-funding(7), cpp(1), gcov(1), gcc(1), as(1), ld(1), gdb(1), adb(1),
       dbx(1), sdb(1) and the Info entries for gcc, cpp, gfortran, as, ld, binutils and gdb.

AUTHOR
       See the Info entry for gfortran for contributors to GCC and GNU Fortran.

COPYRIGHT
       Copyright (c) 2004, 2005, 2006, 2007, 2008 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document under the terms of
       the GNU Free Documentation License, Version 1.2 or any later version published by the Free
       Software Foundation; with the Invariant Sections being "Funding Free Software", the Front-
       Cover Texts being (a) (see below), and with the Back-Cover Texts being (b) (see below).	A
       copy of the license is included in the gfdl(7) man page.

       (a) The FSF's Front-Cover Text is:

	    A GNU Manual

       (b) The FSF's Back-Cover Text is:

	    You have freedom to copy and modify this GNU Manual, like GNU
	    software.  Copies published by the Free Software Foundation raise
	    funds for GNU development.

gcc-4.4.7				    2012-03-13				      GFORTRAN(1)
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