CbC/CbC_gcc: gcc/fortran/invoke.texi comparison

comparison gcc/fortran/invoke.texi @ 111:04ced10e8804

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author	kono
date	Fri, 27 Oct 2017 22:46:09 +0900
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children	84e7813d76e9

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+@c Copyright (C) 2004-2017 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{} 2004-2017 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 1.3 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.
+@c man end
+@c Set file name and title for the man page.
+@setfilename gfortran
+@settitle GNU Fortran compiler.
+@c man begin SYNOPSIS
+gfortran [@option{-c}|@option{-S}|@option{-E}]
+[@option{-g}] [@option{-pg}] [@option{-O}@var{level}]
+[@option{-W}@var{warn}@dots{}] [@option{-pedantic}]
+[@option{-I}@var{dir}@dots{}] [@option{-L}@var{dir}@dots{}]
+[@option{-D}@var{macro}[=@var{defn}]@dots{}] [@option{-U}@var{macro}]
+[@option{-f}@var{option}@dots{}]
+[@option{-m}@var{machine-option}@dots{}]
+[@option{-o} @var{outfile}] @var{infile}@dots{}
+Only the most useful options are listed here; see below for the
+remainder.
+@c man end
+@c man begin SEEALSO
+gpl(7), gfdl(7), fsf-funding(7),
+cpp(1), gcov(1), gcc(1), as(1), ld(1), gdb(1), adb(1), dbx(1), sdb(1)
+and the Info entries for @file{gcc}, @file{cpp}, @file{gfortran}, @file{as},
+@file{ld}, @file{binutils} and @file{gdb}.
+@c man end
+@c man begin BUGS
+For instructions on reporting bugs, see
+@w{@value{BUGURL}}.
+@c man end
+@c man begin AUTHOR
+See the Info entry for @command{gfortran} for contributors to GCC and
+GNU Fortran.
+@c man end
+@end ignore
+@node Invoking GNU Fortran
+@chapter GNU Fortran Command Options
+@cindex GNU Fortran command options
+@cindex command options
+@cindex options, @command{gfortran} command
+@c man begin DESCRIPTION
+The @command{gfortran} command supports all the options supported by the
+@command{gcc} command.  Only options specific to GNU Fortran are documented
+here.
+@xref{Invoking GCC,,GCC Command Options,gcc,Using the GNU Compiler
+Collection (GCC)}, for information
+on the non-Fortran-specific aspects of the @command{gcc} command (and,
+therefore, the @command{gfortran} command).
+@cindex options, negative forms
+All GCC and GNU Fortran options
+are accepted both by @command{gfortran} and by @command{gcc}
+(as well as any other drivers built at the same time,
+such as @command{g++}),
+since adding GNU Fortran to the GCC distribution
+enables acceptance of GNU Fortran options
+by all of the relevant drivers.
+In some cases, options have positive and negative forms;
+the negative form of @option{-ffoo} would be @option{-fno-foo}.
+This manual documents only one of these two forms, whichever
+one is not the default.
+@c man end
+@menu
+* Option Summary::      Brief list of all @command{gfortran} options,
+without explanations.
+* Fortran Dialect Options::  Controlling the variant of Fortran language
+compiled.
+* 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.
+* Interoperability Options::  Options for interoperability with other
+languages.
+* Environment Variables:: Environment variables that affect @command{gfortran}.
+@end menu
+@node Option Summary
+@section Option summary
+@c man begin OPTIONS
+Here is a summary of all the options specific to GNU Fortran, grouped
+by type.  Explanations are in the following sections.
+@table @emph
+@item Fortran Language Options
+@xref{Fortran Dialect Options,,Options controlling Fortran dialect}.
+@gccoptlist{-fall-intrinsics -fbackslash -fcray-pointer -fd-lines-as-code @gol
+-fd-lines-as-comments @gol
+-fdec -fdec-structure -fdec-intrinsic-ints -fdec-static -fdec-math @gol
+-fdefault-double-8 -fdefault-integer-8 -fdefault-real-8 @gol
+-fdefault-real-10 -fdefault-real-16 -fdollar-ok -ffixed-line-length-@var{n} @gol
+-ffixed-line-length-none -ffree-form -ffree-line-length-@var{n} @gol
+-ffree-line-length-none -fimplicit-none -finteger-4-integer-8 @gol
+-fmax-identifier-length -fmodule-private -ffixed-form -fno-range-check @gol
+-fopenacc -fopenmp -freal-4-real-10 -freal-4-real-16 -freal-4-real-8 @gol
+-freal-8-real-10 -freal-8-real-16 -freal-8-real-4 -std=@var{std}
+-ftest-forall-temp
+}
+@item Preprocessing Options
+@xref{Preprocessing Options,,Enable and customize preprocessing}.
+@gccoptlist{-A-@var{question}@r{[}=@var{answer}@r{]}
+-A@var{question}=@var{answer} -C -CC -D@var{macro}@r{[}=@var{defn}@r{]}
+-H -P @gol
+-U@var{macro} -cpp -dD -dI -dM -dN -dU -fworking-directory
+-imultilib @var{dir} @gol
+-iprefix @var{file} -iquote -isysroot @var{dir} -isystem @var{dir} -nocpp
+-nostdinc @gol
+-undef
+}
+@item Error and Warning Options
+@xref{Error and Warning Options,,Options to request or suppress errors
+and warnings}.
+@gccoptlist{-Waliasing -Wall -Wampersand -Wargument-mismatch -Warray-bounds
+-Wc-binding-type -Wcharacter-truncation -Wconversion @gol
+-Wdo-subscript -Wfunction-elimination -Wimplicit-interface @gol
+-Wimplicit-procedure -Wintrinsic-shadow -Wuse-without-only -Wintrinsics-std @gol
+-Wline-truncation -Wno-align-commons -Wno-tabs -Wreal-q-constant @gol
+-Wsurprising -Wunderflow -Wunused-parameter -Wrealloc-lhs -Wrealloc-lhs-all @gol
+-Wtarget-lifetime -fmax-errors=@var{n} -fsyntax-only -pedantic -pedantic-errors
+}
+@item Debugging Options
+@xref{Debugging Options,,Options for debugging your program or GNU Fortran}.
+@gccoptlist{-fbacktrace -fdump-fortran-optimized -fdump-fortran-original @gol
+-fdump-parse-tree -ffpe-trap=@var{list} -ffpe-summary=@var{list}
+}
+@item Directory Options
+@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} -fmax-subrecord-length=@var{length} @gol
+-frecord-marker=@var{length} -fsign-zero
+}
+@item Interoperability Options
+@xref{Interoperability Options,,Options for interoperability}.
+@gccoptlist{-fc-prototypes}
+@item Code Generation Options
+@xref{Code Gen Options,,Options for code generation conventions}.
+@gccoptlist{-faggressive-function-elimination -fblas-matmul-limit=@var{n} @gol
+-fbounds-check -fcheck-array-temporaries @gol
+-fcheck=@var{<all|array-temps|bounds|do|mem|pointer|recursion>} @gol
+-fcoarray=@var{<none|single|lib>} -fexternal-blas -ff2c
+-ffrontend-optimize @gol
+-finit-character=@var{n} -finit-integer=@var{n} -finit-local-zero @gol
+-finit-derived @gol
+-finit-logical=@var{<true|false>}
+-finit-real=@var{<zero|inf|-inf|nan|snan>} @gol
+-finline-matmul-limit=@var{n} @gol
+-fmax-array-constructor=@var{n} -fmax-stack-var-size=@var{n}
+-fno-align-commons @gol
+-fno-automatic -fno-protect-parens -fno-underscoring @gol
+-fsecond-underscore -fpack-derived -frealloc-lhs -frecursive @gol
+-frepack-arrays -fshort-enums -fstack-arrays
+}
+@end table
+@node Fortran Dialect Options
+@section Options controlling Fortran dialect
+@cindex dialect options
+@cindex language, dialect options
+@cindex options, dialect
+The following options control the details of the Fortran dialect
+accepted by the compiler:
+@table @gcctabopt
+@item -ffree-form
+@itemx -ffixed-form
+@opindex @code{ffree-form}
+@opindex @code{ffixed-form}
+@cindex options, Fortran dialect
+@cindex file format, free
+@cindex file format, fixed
+Specify the layout used by the source file.  The free form layout
+was introduced in Fortran 90.  Fixed form was traditionally used in
+older Fortran programs.  When neither option is specified, the source
+form is determined by the file extension.
+@item -fall-intrinsics
+@opindex @code{fall-intrinsics}
+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
+@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.
+@item -fdec
+@opindex @code{fdec}
+DEC compatibility mode. Enables extensions and other features that mimic
+the default behavior of older compilers (such as DEC).
+These features are non-standard and should be avoided at all costs.
+For details on GNU Fortran's implementation of these extensions see the
+full documentation.
+Other flags enabled by this switch are:
+@option{-fdollar-ok} @option{-fcray-pointer} @option{-fdec-structure}
+@option{-fdec-intrinsic-ints} @option{-fdec-static} @option{-fdec-math}
+If @option{-fd-lines-as-code}/@option{-fd-lines-as-comments} are unset, then
+@option{-fdec} also sets @option{-fd-lines-as-comments}.
+@item -fdec-structure
+@opindex @code{fdec-structure}
+Enable DEC @code{STRUCTURE} and @code{RECORD} as well as @code{UNION},
+@code{MAP}, and dot ('.') as a member separator (in addition to '%'). This is
+provided for compatibility only; Fortran 90 derived types should be used
+instead where possible.
+@item -fdec-intrinsic-ints
+@opindex @code{fdec-intrinsic-ints}
+Enable B/I/J/K kind variants of existing integer functions (e.g. BIAND, IIAND,
+JIAND, etc...). For a complete list of intrinsics see the full documentation.
+@item -fdec-math
+@opindex @code{fdec-math}
+Enable legacy math intrinsics such as COTAN and degree-valued trigonometric
+functions (e.g. TAND, ATAND, etc...) for compatability with older code.
+@item -fdec-static
+@opindex @code{fdec-static}
+Enable DEC-style STATIC and AUTOMATIC attributes to explicitly specify
+the storage of variables and other objects.
+@item -fdollar-ok
+@opindex @code{fdollar-ok}
+@cindex @code{$}
+@cindex symbol names
+@cindex character set
+Allow @samp{$} 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.
+@item -fbackslash
+@opindex @code{backslash}
+@cindex backslash
+@cindex escape characters
+Change the interpretation of backslashes in string literals from a single
+backslash character to ``C-style'' escape characters. The following
+combinations are expanded @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}.
+@item -ffixed-line-length-@var{n}
+@opindex @code{ffixed-line-length-}@var{n}
+@cindex file format, fixed
+Set column after which characters are ignored in typical fixed-form
+lines in the source file, and through which spaces are assumed (as
+if padded to that length) after the ends of short fixed-form lines.
+Popular values for @var{n} include 72 (the
+standard and the default), 80 (card image), and 132 (corresponding
+to ``extended-source'' options in some popular compilers).
+@var{n} may also be @samp{none}, meaning that the entire line is meaningful
+and that continued character constants never have implicit spaces appended
+to them to fill out the line.
+@option{-ffixed-line-length-0} means the same thing as
+@option{-ffixed-line-length-none}.
+@item -ffree-line-length-@var{n}
+@opindex @code{ffree-line-length-}@var{n}
+@cindex file format, free
+Set column after which characters are ignored in typical free-form
+lines in the source file. The default value is 132.
+@var{n} may be @samp{none}, meaning that the entire line is meaningful.
+@option{-ffree-line-length-0} means the same thing as
+@option{-ffree-line-length-none}.
+@item -fmax-identifier-length=@var{n}
+@opindex @code{fmax-identifier-length=}@var{n}
+Specify the maximum allowed identifier length. Typical values are
+31 (Fortran 95) and 63 (Fortran 2003 and Fortran 2008).
+@item -fimplicit-none
+@opindex @code{fimplicit-none}
+Specify that no implicit typing is allowed, unless overridden by explicit
+@code{IMPLICIT} statements.  This is the equivalent of adding
+@code{implicit none} to the start of every procedure.
+@item -fcray-pointer
+@opindex @code{fcray-pointer}
+Enable the Cray pointer extension, which provides C-like pointer
+functionality.
+@item -fopenacc
+@opindex @code{fopenacc}
+@cindex OpenACC
+Enable the OpenACC extensions.  This includes OpenACC @code{!$acc}
+directives in free form and @code{c$acc}, @code{*$acc} and
+@code{!$acc} 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
+OpenACC runtime library to be linked in.
+Note that this is an experimental feature, incomplete, and subject to
+change in future versions of GCC.  See
+@w{@uref{https://gcc.gnu.org/wiki/OpenACC}} for more information.
+@item -fopenmp
+@opindex @code{fopenmp}
+@cindex OpenMP
+Enable the OpenMP extensions.  This includes OpenMP @code{!$omp} directives
+in free form
+and @code{c$omp}, @code{*$omp} and @code{!$omp} directives in fixed form,
+@code{!$} conditional compilation sentinels in free form
+and @code{c$}, @code{*$} and @code{!$} sentinels in fixed form,
+and when linking arranges for the OpenMP runtime library to be linked
+in.  The option @option{-fopenmp} implies @option{-frecursive}.
+@item -fno-range-check
+@opindex @code{frange-check}
+Disable range checking on results of simplification of constant
+expressions during compilation.  For example, GNU Fortran will give
+an error at compile time when simplifying @code{a = 1. / 0}.
+With this option, no error will be given and @code{a} will be assigned
+the value @code{+Infinity}.  If an expression evaluates to a value
+outside of the relevant range of [@code{-HUGE()}:@code{HUGE()}],
+then the expression will be replaced by @code{-Inf} or @code{+Inf}
+as appropriate.
+Similarly, @code{DATA i/Z'FFFFFFFF'/} will result in an integer overflow
+on most systems, but with @option{-fno-range-check} the value will
+``wrap around'' and @code{i} will be initialized to @math{-1} instead.
+@item -fdefault-integer-8
+@opindex @code{fdefault-integer-8}
+Set the default integer and logical types to an 8 byte wide type.  This option
+also affects the kind of integer constants like @code{42}. Unlike
+@option{-finteger-4-integer-8}, it does not promote variables with explicit
+kind declaration.
+@item -fdefault-real-8
+@opindex @code{fdefault-real-8}
+Set the default real type to an 8 byte wide type. 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. Unlike @option{-freal-4-real-8},
+it does not promote variables with explicit kind declaration.
+@item -fdefault-real-10
+@opindex @code{fdefault-real-10}
+Set the default real type to a 10 byte wide type. 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. Unlike @option{-freal-4-real-10},
+it does not promote variables with explicit kind declaration.
+@item -fdefault-real-16
+@opindex @code{fdefault-real-16}
+Set the default real type to a 16 byte wide type. 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. Unlike @option{-freal-4-real-16},
+it does not promote variables with explicit kind declaration.
+@item -fdefault-double-8
+@opindex @code{fdefault-double-8}
+Set the @code{DOUBLE PRECISION} type to an 8 byte wide type.  Do nothing if this
+is already the default.  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.
+@item -finteger-4-integer-8
+@opindex @code{finteger-4-integer-8}
+Promote all @code{INTEGER(KIND=4)} entities to an @code{INTEGER(KIND=8)}
+entities.  If @code{KIND=8} is unavailable, then an error will be issued.
+This option should be used with care and may not be suitable for your codes.
+Areas of possible concern include calls to external procedures,
+alignment in @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
+BOZ literal constant conversion, and I/O.  Inspection of the intermediate
+representation of the translated Fortran code, produced by
+@option{-fdump-tree-original}, is suggested.
+@item  -freal-4-real-8
+@itemx -freal-4-real-10
+@itemx -freal-4-real-16
+@itemx -freal-8-real-4
+@itemx -freal-8-real-10
+@itemx -freal-8-real-16
+@opindex @code{freal-4-real-8}
+@opindex @code{freal-4-real-10}
+@opindex @code{freal-4-real-16}
+@opindex @code{freal-8-real-4}
+@opindex @code{freal-8-real-10}
+@opindex @code{freal-8-real-16}
+@cindex options, real kind type promotion
+Promote all @code{REAL(KIND=M)} entities to @code{REAL(KIND=N)} entities.
+If @code{REAL(KIND=N)} is unavailable, then an error will be issued.
+All other real kind types are unaffected by this option.
+These options should be used with care and may not be suitable for your
+codes.  Areas of possible concern include calls to external procedures,
+alignment in @code{EQUIVALENCE} and/or @code{COMMON}, generic interfaces,
+BOZ literal constant conversion, and I/O.  Inspection of the intermediate
+representation of the translated Fortran code, produced by
+@option{-fdump-tree-original}, is suggested.
+@item -std=@var{std}
+@opindex @code{std=}@var{std} option
+Specify the standard to which the program is expected to conform, which
+may be one of @samp{f95}, @samp{f2003}, @samp{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=f2008ts}
+allows the Fortran 2008 standard including the additions of the
+Technical Specification (TS) 29113 on Further Interoperability of Fortran
+with C and TS 18508 on Additional Parallel Features in Fortran.
+@item -ftest-forall-temp
+@opindex @code{ftest-forall-temp}
+Enhance test coverage by forcing most forall assignments to use temporary.
+@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 is 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 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 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
+declarations.  Each of these specific warning options also has a
+negative form beginning @option{-Wno-} to turn off warnings;
+for example, @option{-Wno-implicit}.  This manual lists only one of the
+two forms, whichever is not the default.
+These options control the amount and kinds of errors and warnings produced
+by GNU Fortran:
+@table @gcctabopt
+@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
+@opindex @code{fsyntax-only}
+@cindex syntax checking
+Check the code for syntax errors, but do not actually compile it.  This
+will generate module files for each module present in the code, but no
+other output file.
+@item -Wpedantic
+@itemx -pedantic
+@opindex @code{pedantic}
+@opindex @code{Wpedantic}
+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 @code{#include}.
+Valid Fortran 95 programs should compile properly with or without
+this option.
+However, without this option, certain GNU extensions and traditional
+Fortran features are supported as well.
+With this option, many of them are rejected.
+Some users try to use @option{-pedantic} to check programs for conformance.
+They soon find that it does not do quite what they want---it finds some
+nonstandard practices, but not all.
+However, improvements to GNU Fortran in this area are welcome.
+This should be used in conjunction with @option{-std=f95},
+@option{-std=f2003} or @option{-std=f2008}.
+@item -pedantic-errors
+@opindex @code{pedantic-errors}
+Like @option{-pedantic}, except that errors are produced rather than
+warnings.
+@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{-Waliasing}, @option{-Wampersand},
+@option{-Wconversion}, @option{-Wsurprising}, @option{-Wc-binding-type},
+@option{-Wintrinsics-std}, @option{-Wtabs}, @option{-Wintrinsic-shadow},
+@option{-Wline-truncation}, @option{-Wtarget-lifetime},
+@option{-Winteger-division}, @option{-Wreal-q-constant}, @option{-Wunused}
+and @option{-Wundefined-do-loop}.
+@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
+with an explicit interface.
+The following example will trigger the warning.
+@smallexample
+interface
+subroutine bar(a,b)
+integer, intent(in) :: a
+integer, intent(out) :: b
+end subroutine
+end interface
+integer :: a
+call bar(a,a)
+@end smallexample
+@item -Wampersand
+@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},
+@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 -Wargument-mismatch
+@opindex @code{Wargument-mismatch}
+@cindex warnings, argument mismatch
+@cindex warnings, parameter mismatch
+@cindex warnings, interface mismatch
+Warn about type, rank, and other mismatches between formal parameters and actual
+arguments to functions and subroutines.  These warnings are recommended and
+thus enabled by default.
+@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 -Wc-binding-type
+@opindex @code{Wc-binding-type}
+@cindex warning, C binding type
+Warn if the a variable might not be C interoperable.  In particular, warn if
+the variable has been declared using an intrinsic type with default kind
+instead of using a kind parameter defined for C interoperability in the
+intrinsic @code{ISO_C_Binding} module.  This option is implied by
+@option{-Wall}.
+@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.  This option is
+implied by @option{-Wall}.  For free-form source code, the default is
+@option{-Werror=line-truncation} such that truncations are reported as
+error.
+@item -Wconversion
+@opindex @code{Wconversion}
+@cindex warnings, conversion
+@cindex conversion
+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. This
+option does @emph{not} imply @option{-Wconversion}.
+@item -Wextra
+@opindex @code{Wextra}
+@cindex extra warnings
+@cindex warnings, extra
+Enables some warning options for usages of language features which
+may be problematic. This currently includes @option{-Wcompare-reals},
+@option{-Wunused-parameter} and @option{-Wdo-subscript}.
+@item -Wimplicit-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 -Winteger-division
+@opindex @code{Winteger-division}
+@cindex warnings, integer division
+@cindex warnings, division of integers
+Warn if a constant integer division truncates it result.
+As an example, 3/5 evaluates to 0.
+@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.
+@item -Wsurprising
+@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.
+This currently produces a warning under the following circumstances:
+@itemize @bullet
+@item
+An INTEGER SELECT construct has a CASE that can never be matched as its
+lower value is greater than its upper value.
+@item
+A LOGICAL SELECT construct has three CASE statements.
+@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
+@item -Wtabs
+@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.  For continuation lines, a tab followed
+by a digit between 1 and 9 is supported.  @option{-Wtabs} will cause
+a warning to be issued if a tab is encountered. Note, @option{-Wtabs}
+is active for @option{-pedantic}, @option{-std=f95}, @option{-std=f2003},
+@option{-std=f2008}, @option{-std=f2008ts} and @option{-Wall}.
+@item -Wundefined-do-loop
+@opindex @code{Wundefined-do-loop}
+@cindex warnings, undefined do loop
+Warn if a DO loop with step either 1 or -1 yields an underflow or an overflow
+during iteration of an induction variable of the loop.
+This option is implied by @option{-Wall}.
+@item -Wunderflow
+@opindex @code{Wunderflow}
+@cindex warnings, underflow
+@cindex underflow
+Produce a warning when numerical constant expressions are
+encountered, which yield an UNDERFLOW during compilation. Enabled by default.
+@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.  This option is implied by @option{-Wall}.
+@item -Wuse-without-only
+@opindex @code{Wuse-without-only}
+@cindex warnings, use statements
+@cindex intrinsic
+Warn if a @code{USE} statement has no @code{ONLY} qualifier and
+thus implicitly imports all public entities of the used module.
+@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 implied by @option{-Wextra} if also @option{-Wunused} or
+@option{-Wall} is used.
+@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.
+@item -Wrealloc-lhs
+@opindex @code{Wrealloc-lhs}
+@cindex Reallocate the LHS in assignments, notification
+Warn when the compiler might insert code to for allocation or reallocation of
+an allocatable array variable of intrinsic type in intrinsic assignments.  In
+hot loops, the Fortran 2003 reallocation feature may reduce the performance.
+If the array is already allocated with the correct shape, consider using a
+whole-array array-spec (e.g. @code{(:,:,:)}) for the variable on the left-hand
+side to prevent the reallocation check. Note that in some cases the warning
+is shown, even if the compiler will optimize reallocation checks away.  For
+instance, when the right-hand side contains the same variable multiplied by
+a scalar.  See also @option{-frealloc-lhs}.
+@item -Wrealloc-lhs-all
+@opindex @code{Wrealloc-lhs-all}
+Warn when the compiler inserts code to for allocation or reallocation of an
+allocatable variable; this includes scalars and derived types.
+@item -Wcompare-reals
+@opindex @code{Wcompare-reals}
+Warn when comparing real or complex types for equality or inequality.
+This option is implied by @option{-Wextra}.
+@item -Wtarget-lifetime
+@opindex @code{Wtargt-lifetime}
+Warn if the pointer in a pointer assignment might be longer than the its
+target. This option is implied by @option{-Wall}.
+@item -Wzerotrip
+@opindex @code{Wzerotrip}
+Warn if a @code{DO} loop is known to execute zero times at compile
+time.  This option is implied by @option{-Wall}.
+@item -Wdo-subscript
+@opindex @code{Wdo-subscript}
+Warn if an array subscript inside a DO loop could lead to an
+out-of-bounds access even if the compiler can not prove that the
+statement is actually executed, in cases like
+@smallexample
+real a(3)
+do i=1,4
+if (condition(i)) then
+a(i) = 1.2
+end if
+end do
+@end smallexample
+This option is implied by @option{-Wextra}.
+@item -Werror
+@opindex @code{Werror}
+@cindex warnings, to errors
+Turns all warnings into errors.
+@end table
+@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
+@cindex options, debugging
+@cindex debugging information options
+GNU Fortran has various special options that are used for debugging
+either your program or the GNU Fortran compiler.
+@table @gcctabopt
+@item -fdump-fortran-original
+@opindex @code{fdump-fortran-original}
+Output the internal parse tree after translating the source program
+into internal representation.  This option is mostly useful for
+debugging the GNU Fortran compiler itself. The output generated by
+this option might change between releases. This option may also
+generate internal compiler errors for features which have only
+recently been added.
+@item -fdump-fortran-optimized
+@opindex @code{fdump-fortran-optimized}
+Output the parse tree after front-end optimization.  Mostly useful for
+debugging the GNU Fortran compiler itself. The output generated by
+this option might change between releases.  This option may also
+generate internal compiler errors for features which have only
+recently been added.
+@item -fdump-parse-tree
+@opindex @code{fdump-parse-tree}
+Output the internal parse tree after translating the source program
+into internal representation.  Mostly useful for debugging the GNU
+Fortran compiler itself. The output generated by this option might
+change between releases. This option may also generate internal
+compiler errors for features which have only recently been added. This
+option is deprecated; use @code{-fdump-fortran-original} instead.
+@item -ffpe-trap=@var{list}
+@opindex @code{ffpe-trap=}@var{list}
+Specify a list of floating point exception traps to enable.  On most
+systems, if a floating point exception occurs and the trap for that
+exception is enabled, a SIGFPE signal will be sent and the program
+being aborted, producing a core file useful for debugging.  @var{list}
+is a (possibly empty) comma-separated list of the following
+exceptions: @samp{invalid} (invalid floating 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{inexact} (loss of precision
+during operation), and @samp{denormal} (operation performed on a
+denormal value).  The first five exceptions correspond to the five
+IEEE 754 exceptions, whereas the last one (@samp{denormal}) is not
+part of the IEEE 754 standard but is available on some common
+architectures such as x86.
+The first three exceptions (@samp{invalid}, @samp{zero}, and
+@samp{overflow}) often indicate serious errors, and unless the program
+has provisions for dealing with these exceptions, enabling traps for
+these three exceptions is probably a good idea.
+Many, if not most, floating point operations incur loss of precision
+due to rounding, and hence the @code{ffpe-trap=inexact} is likely to
+be uninteresting in practice.
+By default no exception traps are enabled.
+@item -ffpe-summary=@var{list}
+@opindex @code{ffpe-summary=}@var{list}
+Specify a list of floating-point exceptions, whose flag status is printed
+to @code{ERROR_UNIT} when invoking @code{STOP} and @code{ERROR STOP}.
+@var{list} can be either @samp{none}, @samp{all} or a comma-separated list
+of the following exceptions: @samp{invalid}, @samp{zero}, @samp{overflow},
+@samp{underflow}, @samp{inexact} and @samp{denormal}. (See
+@option{-ffpe-trap} for a description of the exceptions.)
+By default, a summary for all exceptions but @samp{inexact} is shown.
+@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,
+gcc,Using the GNU Compiler Collection (GCC)}, for more information on
+debugging options.
+@node Directory Options
+@section Options for directory search
+@cindex directory, options
+@cindex options, directory search
+@cindex search path
+@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.
+It also affects the search paths used by @command{cpp} when used to preprocess
+Fortran source.
+@table @gcctabopt
+@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
+@cindex paths, search
+@cindex module search path
+These affect interpretation of the @code{INCLUDE} directive
+(as well as of the @code{#include} directive of the @command{cpp}
+preprocessor).
+Also note that the general behavior of @option{-I} and
+@code{INCLUDE} is pretty much the same as of @option{-I} with
+@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 @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.
+@item -J@var{dir}
+@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.
+@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 options, runtime
+These options affect the runtime behavior of programs compiled with GNU Fortran.
+@table @gcctabopt
+@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
+representation for unformatted files; @samp{little-endian}, use little-endian
+representation for unformatted files.
+@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 @option{-fconvert}.}
+@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 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.  @option{-fno-sign-zero} does not
+print the negative sign of zero values (or values rounded to zero for I/O)
+and regards zero as positive number in the @code{SIGN} intrinsic for
+compatibility with Fortran 77. The default is @option{-fsign-zero}.
+@end table
+@node Code Gen Options
+@section Options for code generation conventions
+@cindex code generation, conventions
+@cindex options, code generation
+@cindex options, run-time
+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 @option{-ffoo} would be @option{-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 @option{no-} or adding
+it.
+@table @gcctabopt
+@item -fno-automatic
+@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
+@cindex libf2c calling convention
+Generate code designed to be compatible with code generated
+by @command{g77} and @command{f2c}.
+The calling conventions used by @command{g77} (originally implemented
+in @command{f2c}) require functions that return type
+default @code{REAL} to actually return the C type @code{double}, and
+functions that return type @code{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 @code{REAL} functions return the C type @code{float}, and
+@code{COMPLEX} functions return the GNU C type @code{complex}.
+Additionally, this option implies the @option{-fsecond-underscore}
+option, unless @option{-fno-second-underscore} is explicitly requested.
+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
+@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 @option{-fno-f2c} calling conventions.
+@item -fno-underscoring
+@opindex @code{fno-underscoring}
+@cindex underscore
+@cindex symbol names, underscores
+@cindex transforming symbol names
+@cindex symbol names, transforming
+Do not transform names of entities specified in the Fortran
+source file by appending underscores to them.
+With @option{-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.
+@emph{Caution}: The default behavior of GNU Fortran is
+incompatible with @command{f2c} and @command{g77}, please use the
+@option{-ff2c} option if you want object files compiled with
+GNU Fortran to be compatible with object code created with these
+tools.
+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).
+For example, with @option{-funderscoring}, and assuming 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
+With @option{-fno-underscoring}, the same statement is implemented as:
+@smallexample
+i = j() + max_count(&my_var, &lvar);
+@end smallexample
+Use of @option{-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 @emph{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 @option{-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.
+@item -fsecond-underscore
+@opindex @code{fsecond-underscore}
+@cindex underscore
+@cindex symbol names, underscores
+@cindex transforming symbol names
+@cindex symbol names, transforming
+@cindex @command{f2c} calling convention
+@cindex @command{g77} calling convention
+@cindex libf2c calling convention
+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 @option{-fno-underscoring} is
+in effect.  It is implied by the @option{-ff2c} option.
+Otherwise, with this option, an external name such as @code{MAX_COUNT}
+is implemented as a reference to the link-time external symbol
+@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
+@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 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.  Prefixing a check with
+@option{no-} disables it if it was activated by a previous specification.
+@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 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
+Example: Assuming you have a file @file{foo.f90}, the command
+@smallexample
+gfortran -fcheck=all,no-array-temps foo.f90
+@end smallexample
+will compile the file with all checks enabled as specified above except
+warnings for generated array temporaries.
+@item -fbounds-check
+@opindex @code{fbounds-check}
+@c Note: This option is also referred in gcc's manpage
+Deprecated alias for @option{-fcheck=bounds}.
+@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.
+@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; 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.
+Future versions of GNU Fortran may improve this behavior.
+The default value for @var{n} is 32768.
+@item -fstack-arrays
+@opindex @code{fstack-arrays}
+Adding this option will make the Fortran compiler put all arrays of
+unknown size and array temporaries onto stack memory.  If your program uses very
+large local arrays it is possible that you will have to extend your runtime
+limits for stack memory on some operating systems. This flag is enabled
+by default at optimization level @option{-Ofast} unless
+@option{-fmax-stack-var-size} is specified.
+@item -fpack-derived
+@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.
+@item -frepack-arrays
+@opindex @code{frepack-arrays}
+@cindex repacking 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.
+@item -fshort-enums
+@opindex @code{fshort-enums}
+This option is provided for interoperability with C code that was
+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 -finline-matmul-limit=@var{n}
+@opindex @code{finline-matmul-limit}
+When front-end optimiztion is active, some calls to the @code{MATMUL}
+intrinsic function will be inlined.  This may result in code size
+increase if the size of the matrix cannot be determined at compile
+time, as code for both cases is generated.  Setting
+@code{-finline-matmul-limit=0} will disable inlining in all cases.
+Setting this option with a value of @var{n} will produce inline code
+for matrices with size up to @var{n}. 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.  The @code{-fblas-matmul-limit}
+can be used to change this value.
+@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-derived
+@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-derived}
+@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.  Components of derived type variables will be initialized
+according to these flags only with @option{-finit-derived}.  These options do
+not initialize
+@itemize @bullet
+@item
+objects with the POINTER attribute
+@item
+allocatable arrays
+@item
+variables that appear in an @code{EQUIVALENCE} statement.
+@end itemize
+(These limitations 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}).
+Finally, note that enabling any of the @option{-finit-*} options will
+silence warnings that would have been emitted by @option{-Wuninitialized}
+for the affected local variables.
+@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. See
+also @option{-Wrealloc-lhs}.
+@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 inlining calls
+to @code{MATMUL}, 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,
+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.
+@c man end
+@node Interoperability Options
+@section Options for interoperability with other languages
+@table @asis
+@item -fc-prototypes
+@opindex @code{c-prototypes}
+@cindex Generating C prototypes from Fortran source code
+This option will generate C prototypes from @code{BIND(C)} variable
+declarations, types and procedure interfaces and writes them to
+standard output.  @code{ENUM} is not yet supported.
+The generated prototypes may need inclusion of an appropriate header,
+such as @code{<stdint.h>} or @code{<stdlib.h>}.  For types which are
+not specified using the appropriate kind from the @code{iso_c_binding}
+module, a warning is added as a comment to the code.
+For function pointers, a pointer to a function returning @code{int}
+without an explicit argument list is generated.
+Example of use:
+@smallexample
+$ gfortran -fc-prototypes -fsyntax-only foo.f90 > foo.h
+@end smallexample
+where the C code intended for interoperating with the Fortran code
+then  uses @code{#include "foo.h"}.
+@end table
+@node Environment Variables
+@section Environment variables affecting @command{gfortran}
+@cindex environment variable
+@c man begin ENVIRONMENT
+The @command{gfortran} compiler currently does not make use of any environment
+variables to control its operation above and beyond those
+that affect the operation of @command{gcc}.
+@xref{Environment Variables,,Environment Variables Affecting GCC,
+gcc,Using the GNU Compiler Collection (GCC)}, for information on environment
+variables.
+@xref{Runtime}, for environment variables that affect the
+run-time behavior of programs compiled with GNU Fortran.
+@c man end

Mercurial > hg > CbC > CbC_gcc

comparison gcc/fortran/invoke.texi @ 111:04ced10e8804