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@c Copyright (c) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,

@c Copyright (c) 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008,

@c 2010, Free Software Foundation, Inc.

@c 2010, Free Software Foundation, Inc.

@c This is part of the CPP and GCC manuals.

@c This is part of the CPP and GCC manuals.

@c For copying conditions, see the file gcc.texi.

@c For copying conditions, see the file gcc.texi.

@c ---------------------------------------------------------------------

@c ---------------------------------------------------------------------

@c Options affecting the preprocessor

@c Options affecting the preprocessor

@c ---------------------------------------------------------------------

@c ---------------------------------------------------------------------

@c If this file is included with the flag ``cppmanual'' set, it is

@c If this file is included with the flag ``cppmanual'' set, it is

@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.

@c formatted for inclusion in the CPP manual; otherwise the main GCC manual.

@table @gcctabopt

@table @gcctabopt

@item -D @var{name}

@item -D @var{name}

@opindex D

@opindex D

Predefine @var{name} as a macro, with definition @code{1}.

Predefine @var{name} as a macro, with definition @code{1}.

@item -D @var{name}=@var{definition}

@item -D @var{name}=@var{definition}

The contents of @var{definition} are tokenized and processed as if

The contents of @var{definition} are tokenized and processed as if

they appeared during translation phase three in a @samp{#define}

they appeared during translation phase three in a @samp{#define}

directive.  In particular, the definition will be truncated by

directive.  In particular, the definition will be truncated by

embedded newline characters.

embedded newline characters.

If you are invoking the preprocessor from a shell or shell-like

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

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.

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

If you wish to define a function-like macro on the command line, write

its argument list with surrounding parentheses before the equals sign

its argument list with surrounding parentheses before the equals sign

(if any).  Parentheses are meaningful to most shells, so you will need

(if any).  Parentheses are meaningful to most shells, so you will need

to quote the option.  With @command{sh} and @command{csh},

to quote the option.  With @command{sh} and @command{csh},

@option{-D'@var{name}(@var{args@dots{}})=@var{definition}'} works.

@option{-D'@var{name}(@var{args@dots{}})=@var{definition}'} works.

@option{-D} and @option{-U} options are processed in the order they

@option{-D} and @option{-U} options are processed in the order they

are given on the command line.  All @option{-imacros @var{file}} and

are given on the command line.  All @option{-imacros @var{file}} and

@option{-include @var{file}} options are processed after all

@option{-include @var{file}} options are processed after all

@option{-D} and @option{-U} options.

@option{-D} and @option{-U} options.

@item -U @var{name}

@item -U @var{name}

@opindex U

@opindex U

Cancel any previous definition of @var{name}, either built in or

Cancel any previous definition of @var{name}, either built in or

provided with a @option{-D} option.

provided with a @option{-D} option.

@item -undef

@item -undef

@opindex undef

@opindex undef

Do not predefine any system-specific or GCC-specific macros.  The

Do not predefine any system-specific or GCC-specific macros.  The

standard predefined macros remain defined.

standard predefined macros remain defined.

@ifset cppmanual

@ifset cppmanual

@xref{Standard Predefined Macros}.

@xref{Standard Predefined Macros}.

@end ifset

@end ifset

@item -I @var{dir}

@item -I @var{dir}

@opindex I

@opindex I

Add the directory @var{dir} to the list of directories to be searched

Add the directory @var{dir} to the list of directories to be searched

for header files.

for header files.

@ifset cppmanual

@ifset cppmanual

@xref{Search Path}.

@xref{Search Path}.

@end ifset

@end ifset

Directories named by @option{-I} are searched before the standard

Directories named by @option{-I} are searched before the standard

system include directories.  If the directory @var{dir} is a standard

system include directories.  If the directory @var{dir} is a standard

system include directory, the option is ignored to ensure that the

system include directory, the option is ignored to ensure that the

default search order for system directories and the special treatment

default search order for system directories and the special treatment

of system headers are not defeated

of system headers are not defeated

@ifset cppmanual

@ifset cppmanual

(@pxref{System Headers})

(@pxref{System Headers})

@end ifset

@end ifset

.

.

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

@item -o @var{file}

@item -o @var{file}

@opindex o

@opindex o

Write output to @var{file}.  This is the same as specifying @var{file}

Write output to @var{file}.  This is the same as specifying @var{file}

as the second non-option argument to @command{cpp}.  @command{gcc} has a

as the second non-option argument to @command{cpp}.  @command{gcc} has a

different interpretation of a second non-option argument, so you must

different interpretation of a second non-option argument, so you must

use @option{-o} to specify the output file.

use @option{-o} to specify the output file.

@item -Wall

@item -Wall

@opindex Wall

@opindex Wall

Turns on all optional warnings which are desirable for normal code.

Turns on all optional warnings which are desirable for normal code.

At present this is @option{-Wcomment}, @option{-Wtrigraphs},

At present this is @option{-Wcomment}, @option{-Wtrigraphs},

@option{-Wmultichar} and a warning about integer promotion causing a

@option{-Wmultichar} and a warning about integer promotion causing a

change of sign in @code{#if} expressions.  Note that many of the

change of sign in @code{#if} expressions.  Note that many of the

preprocessor's warnings are on by default and have no options to

preprocessor's warnings are on by default and have no options to

control them.

control them.

@item -Wcomment

@item -Wcomment

@itemx -Wcomments

@itemx -Wcomments

@opindex Wcomment

@opindex Wcomment

@opindex Wcomments

@opindex Wcomments

Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*}

Warn whenever a comment-start sequence @samp{/*} appears in a @samp{/*}

comment, or whenever a backslash-newline appears in a @samp{//} comment.

comment, or whenever a backslash-newline appears in a @samp{//} comment.

(Both forms have the same effect.)

(Both forms have the same effect.)

@item -Wtrigraphs

@item -Wtrigraphs

@opindex Wtrigraphs

@opindex Wtrigraphs

@anchor{Wtrigraphs}

@anchor{Wtrigraphs}

Most trigraphs in comments cannot affect the meaning of the program.

Most trigraphs in comments cannot affect the meaning of the program.

However, a trigraph that would form an escaped newline (@samp{??/} at

However, a trigraph that would form an escaped newline (@samp{??/} at

the end of a line) can, by changing where the comment begins or ends.

the end of a line) can, by changing where the comment begins or ends.

Therefore, only trigraphs that would form escaped newlines produce

Therefore, only trigraphs that would form escaped newlines produce

warnings inside a comment.

warnings inside a comment.

This option is implied by @option{-Wall}.  If @option{-Wall} is not

This option is implied by @option{-Wall}.  If @option{-Wall} is not

given, this option is still enabled unless trigraphs are enabled.  To

given, this option is still enabled unless trigraphs are enabled.  To

get trigraph conversion without warnings, but get the other

get trigraph conversion without warnings, but get the other

@option{-Wall} warnings, use @samp{-trigraphs -Wall -Wno-trigraphs}.

@option{-Wall} warnings, use @samp{-trigraphs -Wall -Wno-trigraphs}.

@item -Wtraditional

@item -Wtraditional

@opindex Wtraditional

@opindex Wtraditional

Warn about certain constructs that behave differently in traditional and

Warn about certain constructs that behave differently in traditional and

ISO C@.  Also warn about ISO C constructs that have no traditional C

ISO C@.  Also warn about ISO C constructs that have no traditional C

equivalent, and problematic constructs which should be avoided.

equivalent, and problematic constructs which should be avoided.

@ifset cppmanual

@ifset cppmanual

@xref{Traditional Mode}.

@xref{Traditional Mode}.

@end ifset

@end ifset

@item -Wundef

@item -Wundef

@opindex Wundef

@opindex Wundef

Warn whenever an identifier which is not a macro is encountered in an

Warn whenever an identifier which is not a macro is encountered in an

@samp{#if} directive, outside of @samp{defined}.  Such identifiers are

@samp{#if} directive, outside of @samp{defined}.  Such identifiers are

replaced with zero.

replaced with zero.

@item -Wunused-macros

@item -Wunused-macros

@opindex Wunused-macros

@opindex Wunused-macros

Warn about macros defined in the main file that are unused.  A macro

Warn about macros defined in the main file that are unused.  A macro

is @dfn{used} if it is expanded or tested for existence at least once.

is @dfn{used} if it is expanded or tested for existence at least once.

The preprocessor will also warn if the macro has not been used at the

The preprocessor will also warn if the macro has not been used at the

time it is redefined or undefined.

time it is redefined or undefined.

Built-in macros, macros defined on the command line, and macros

Built-in macros, macros defined on the command line, and macros

defined in include files are not warned about.

defined in include files are not warned about.

@emph{Note:} If a macro is actually used, but only used in skipped

@emph{Note:} If a macro is actually used, but only used in skipped

conditional blocks, then CPP will report it as unused.  To avoid the

conditional blocks, then CPP will report it as unused.  To avoid the

warning in such a case, you might improve the scope of the macro's

warning in such a case, you might improve the scope of the macro's

definition by, for example, moving it into the first skipped block.

definition by, for example, moving it into the first skipped block.

Alternatively, you could provide a dummy use with something like:

Alternatively, you could provide a dummy use with something like:

@smallexample

@smallexample

#if defined the_macro_causing_the_warning

#if defined the_macro_causing_the_warning

#endif

#endif

@end smallexample

@end smallexample

@item -Wendif-labels

@item -Wendif-labels

@opindex Wendif-labels

@opindex Wendif-labels

Warn whenever an @samp{#else} or an @samp{#endif} are followed by text.

Warn whenever an @samp{#else} or an @samp{#endif} are followed by text.

This usually happens in code of the form

This usually happens in code of the form

@smallexample

@smallexample

#if FOO

#if FOO

@dots{}

@dots{}

#else FOO

#else FOO

@dots{}

@dots{}

#endif FOO

#endif FOO

@end smallexample

@end smallexample

@noindent

@noindent

The second and third @code{FOO} should be in comments, but often are not

The second and third @code{FOO} should be in comments, but often are not

in older programs.  This warning is on by default.

in older programs.  This warning is on by default.

@item -Werror

@item -Werror

@opindex Werror

@opindex Werror

Make all warnings into hard errors.  Source code which triggers warnings

Make all warnings into hard errors.  Source code which triggers warnings

will be rejected.

will be rejected.

@item -Wsystem-headers

@item -Wsystem-headers

@opindex Wsystem-headers

@opindex Wsystem-headers

Issue warnings for code in system headers.  These are normally unhelpful

Issue warnings for code in system headers.  These are normally unhelpful

in finding bugs in your own code, therefore suppressed.  If you are

in finding bugs in your own code, therefore suppressed.  If you are

responsible for the system library, you may want to see them.

responsible for the system library, you may want to see them.

@item -w

@item -w

@opindex w

@opindex w

Suppress all warnings, including those which GNU CPP issues by default.

Suppress all warnings, including those which GNU CPP issues by default.

@item -pedantic

@item -pedantic

@opindex pedantic

@opindex pedantic

Issue all the mandatory diagnostics listed in the C standard.  Some of

Issue all the mandatory diagnostics listed in the C standard.  Some of

them are left out by default, since they trigger frequently on harmless

them are left out by default, since they trigger frequently on harmless

code.

code.

@item -pedantic-errors

@item -pedantic-errors

@opindex pedantic-errors

@opindex pedantic-errors

Issue all the mandatory diagnostics, and make all mandatory diagnostics

Issue all the mandatory diagnostics, and make all mandatory diagnostics

into errors.  This includes mandatory diagnostics that GCC issues

into errors.  This includes mandatory diagnostics that GCC issues

without @samp{-pedantic} but treats as warnings.

without @samp{-pedantic} but treats as warnings.

@item -M

@item -M

@opindex M

@opindex M

@cindex @command{make}

@cindex @command{make}

@cindex dependencies, @command{make}

@cindex dependencies, @command{make}

Instead of outputting the result of preprocessing, output a rule

Instead of outputting the result of preprocessing, output a rule

suitable for @command{make} describing the dependencies of the main

suitable for @command{make} describing the dependencies of the main

source file.  The preprocessor outputs one @command{make} rule containing

source file.  The preprocessor outputs one @command{make} rule containing

the object file name for that source file, a colon, and the names of all

the object file name for that source file, a colon, and the names of all

the included files, including those coming from @option{-include} or

the included files, including those coming from @option{-include} or

@option{-imacros} command line options.

@option{-imacros} command line options.

Unless specified explicitly (with @option{-MT} or @option{-MQ}), the

Unless specified explicitly (with @option{-MT} or @option{-MQ}), the

object file name consists of the name of the source file with any

object file name consists of the name of the source file with any

suffix replaced with object file suffix and with any leading directory

suffix replaced with object file suffix and with any leading directory

parts removed.  If there are many included files then the rule is

parts removed.  If there are many included files then the rule is

split into several lines using @samp{\}-newline.  The rule has no

split into several lines using @samp{\}-newline.  The rule has no

commands.

commands.

This option does not suppress the preprocessor's debug output, such as

This option does not suppress the preprocessor's debug output, such as

@option{-dM}.  To avoid mixing such debug output with the dependency

@option{-dM}.  To avoid mixing such debug output with the dependency

rules you should explicitly specify the dependency output file with

rules you should explicitly specify the dependency output file with

@option{-MF}, or use an environment variable like

@option{-MF}, or use an environment variable like

@env{DEPENDENCIES_OUTPUT} (@pxref{Environment Variables}).  Debug output

@env{DEPENDENCIES_OUTPUT} (@pxref{Environment Variables}).  Debug output

will still be sent to the regular output stream as normal.

will still be sent to the regular output stream as normal.

Passing @option{-M} to the driver implies @option{-E}, and suppresses

Passing @option{-M} to the driver implies @option{-E}, and suppresses

warnings with an implicit @option{-w}.

warnings with an implicit @option{-w}.

@item -MM

@item -MM

@opindex MM

@opindex MM

Like @option{-M} but do not mention header files that are found in

Like @option{-M} but do not mention header files that are found in

system header directories, nor header files that are included,

system header directories, nor header files that are included,

directly or indirectly, from such a header.

directly or indirectly, from such a header.

This implies that the choice of angle brackets or double quotes in an

This implies that the choice of angle brackets or double quotes in an

@samp{#include} directive does not in itself determine whether that

@samp{#include} directive does not in itself determine whether that

header will appear in @option{-MM} dependency output.  This is a

header will appear in @option{-MM} dependency output.  This is a

slight change in semantics from GCC versions 3.0 and earlier.

slight change in semantics from GCC versions 3.0 and earlier.

@anchor{dashMF}

@anchor{dashMF}

@item -MF @var{file}

@item -MF @var{file}

@opindex MF

@opindex MF

When used with @option{-M} or @option{-MM}, specifies a

When used with @option{-M} or @option{-MM}, specifies a

file to write the dependencies to.  If no @option{-MF} switch is given

file to write the dependencies to.  If no @option{-MF} switch is given

the preprocessor sends the rules to the same place it would have sent

the preprocessor sends the rules to the same place it would have sent

preprocessed output.

preprocessed output.

When used with the driver options @option{-MD} or @option{-MMD},

When used with the driver options @option{-MD} or @option{-MMD},

@option{-MF} overrides the default dependency output file.

@option{-MF} overrides the default dependency output file.

@item -MG

@item -MG

@opindex MG

@opindex MG

In conjunction with an option such as @option{-M} requesting

In conjunction with an option such as @option{-M} requesting

dependency generation, @option{-MG} assumes missing header files are

dependency generation, @option{-MG} assumes missing header files are

generated files and adds them to the dependency list without raising

generated files and adds them to the dependency list without raising

an error.  The dependency filename is taken directly from the

an error.  The dependency filename is taken directly from the

@code{#include} directive without prepending any path.  @option{-MG}

@code{#include} directive without prepending any path.  @option{-MG}

also suppresses preprocessed output, as a missing header file renders

also suppresses preprocessed output, as a missing header file renders

this useless.

this useless.

This feature is used in automatic updating of makefiles.

This feature is used in automatic updating of makefiles.

@item -MP

@item -MP

@opindex MP

@opindex MP

This option instructs CPP to add a phony target for each dependency

This option instructs CPP to add a phony target for each dependency

other than the main file, causing each to depend on nothing.  These

other than the main file, causing each to depend on nothing.  These

dummy rules work around errors @command{make} gives if you remove header

dummy rules work around errors @command{make} gives if you remove header

files without updating the @file{Makefile} to match.

files without updating the @file{Makefile} to match.

This is typical output:

This is typical output:

@smallexample

@smallexample

test.o: test.c test.h

test.o: test.c test.h

test.h:

test.h:

@end smallexample

@end smallexample

@item -MT @var{target}

@item -MT @var{target}

@opindex MT

@opindex MT

Change the target of the rule emitted by dependency generation.  By

Change the target of the rule emitted by dependency generation.  By

default CPP takes the name of the main input file, deletes any

default CPP takes the name of the main input file, deletes any

directory components and any file suffix such as @samp{.c}, and

directory components and any file suffix such as @samp{.c}, and

appends the platform's usual object suffix.  The result is the target.

appends the platform's usual object suffix.  The result is the target.

An @option{-MT} option will set the target to be exactly the string you

An @option{-MT} option will set the target to be exactly the string you

specify.  If you want multiple targets, you can specify them as a single

specify.  If you want multiple targets, you can specify them as a single

argument to @option{-MT}, or use multiple @option{-MT} options.

argument to @option{-MT}, or use multiple @option{-MT} options.

For example, @option{@w{-MT '$(objpfx)foo.o'}} might give

For example, @option{@w{-MT '$(objpfx)foo.o'}} might give

@smallexample

@smallexample

$(objpfx)foo.o: foo.c

$(objpfx)foo.o: foo.c

@end smallexample

@end smallexample

@item -MQ @var{target}

@item -MQ @var{target}

@opindex MQ

@opindex MQ

Same as @option{-MT}, but it quotes any characters which are special to

Same as @option{-MT}, but it quotes any characters which are special to

Make.  @option{@w{-MQ '$(objpfx)foo.o'}} gives

Make.  @option{@w{-MQ '$(objpfx)foo.o'}} gives

@smallexample

@smallexample

$$(objpfx)foo.o: foo.c

$$(objpfx)foo.o: foo.c

@end smallexample

@end smallexample

The default target is automatically quoted, as if it were given with

The default target is automatically quoted, as if it were given with

@option{-MQ}.

@option{-MQ}.

@item -MD

@item -MD

@opindex MD

@opindex MD

@option{-MD} is equivalent to @option{-M -MF @var{file}}, except that

@option{-MD} is equivalent to @option{-M -MF @var{file}}, except that

@option{-E} is not implied.  The driver determines @var{file} based on

@option{-E} is not implied.  The driver determines @var{file} based on

whether an @option{-o} option is given.  If it is, the driver uses its

whether an @option{-o} option is given.  If it is, the driver uses its

argument but with a suffix of @file{.d}, otherwise it takes the name

argument but with a suffix of @file{.d}, otherwise it takes the name

of the input file, removes any directory components and suffix, and

of the input file, removes any directory components and suffix, and

applies a @file{.d} suffix.

applies a @file{.d} suffix.

If @option{-MD} is used in conjunction with @option{-E}, any

If @option{-MD} is used in conjunction with @option{-E}, any

@option{-o} switch is understood to specify the dependency output file

@option{-o} switch is understood to specify the dependency output file

(@pxref{dashMF,,-MF}), but if used without @option{-E}, each @option{-o}

(@pxref{dashMF,,-MF}), but if used without @option{-E}, each @option{-o}

is understood to specify a target object file.

is understood to specify a target object file.

Since @option{-E} is not implied, @option{-MD} can be used to generate

Since @option{-E} is not implied, @option{-MD} can be used to generate

a dependency output file as a side-effect of the compilation process.

a dependency output file as a side-effect of the compilation process.

@item -MMD

@item -MMD

@opindex MMD

@opindex MMD

Like @option{-MD} except mention only user header files, not system

Like @option{-MD} except mention only user header files, not system

header files.

header files.

@ifclear cppmanual

@ifclear cppmanual

@item -fpch-deps

@item -fpch-deps

@opindex fpch-deps

@opindex fpch-deps

When using precompiled headers (@pxref{Precompiled Headers}), this flag

When using precompiled headers (@pxref{Precompiled Headers}), this flag

will cause the dependency-output flags to also list the files from the

will cause the dependency-output flags to also list the files from the

precompiled header's dependencies.  If not specified only the

precompiled header's dependencies.  If not specified only the

precompiled header would be listed and not the files that were used to

precompiled header would be listed and not the files that were used to

create it because those files are not consulted when a precompiled

create it because those files are not consulted when a precompiled

header is used.

header is used.

@item -fpch-preprocess

@item -fpch-preprocess

@opindex fpch-preprocess

@opindex fpch-preprocess

This option allows use of a precompiled header (@pxref{Precompiled

This option allows use of a precompiled header (@pxref{Precompiled

Headers}) together with @option{-E}.  It inserts a special @code{#pragma},

Headers}) together with @option{-E}.  It inserts a special @code{#pragma},

@code{#pragma GCC pch_preprocess "@var{filename}"} in the output to mark

@code{#pragma GCC pch_preprocess "@var{filename}"} in the output to mark

the place where the precompiled header was found, and its @var{filename}.

the place where the precompiled header was found, and its @var{filename}.

When @option{-fpreprocessed} is in use, GCC recognizes this @code{#pragma}

When @option{-fpreprocessed} is in use, GCC recognizes this @code{#pragma}

and loads the PCH@.

and loads the PCH@.

This option is off by default, because the resulting preprocessed output

This option is off by default, because the resulting preprocessed output

is only really suitable as input to GCC@.  It is switched on by

is only really suitable as input to GCC@.  It is switched on by

@option{-save-temps}.

@option{-save-temps}.

You should not write this @code{#pragma} in your own code, but it is

You should not write this @code{#pragma} in your own code, but it is

safe to edit the filename if the PCH file is available in a different

safe to edit the filename if the PCH file is available in a different

location.  The filename may be absolute or it may be relative to GCC's

location.  The filename may be absolute or it may be relative to GCC's

current directory.

current directory.

@end ifclear

@end ifclear

@item -x c

@item -x c

@itemx -x c++

@itemx -x c++

@itemx -x objective-c

@itemx -x objective-c

@itemx -x assembler-with-cpp

@itemx -x assembler-with-cpp

@opindex x

@opindex x

Specify the source language: C, C++, Objective-C, or assembly.  This has

Specify the source language: C, C++, Objective-C, or assembly.  This has

nothing to do with standards conformance or extensions; it merely

nothing to do with standards conformance or extensions; it merely

selects which base syntax to expect.  If you give none of these options,

selects which base syntax to expect.  If you give none of these options,

cpp will deduce the language from the extension of the source file:

cpp will deduce the language from the extension of the source file:

@samp{.c}, @samp{.cc}, @samp{.m}, or @samp{.S}.  Some other common

@samp{.c}, @samp{.cc}, @samp{.m}, or @samp{.S}.  Some other common

extensions for C++ and assembly are also recognized.  If cpp does not

extensions for C++ and assembly are also recognized.  If cpp does not

recognize the extension, it will treat the file as C; this is the most

recognize the extension, it will treat the file as C; this is the most

generic mode.

generic mode.

@emph{Note:} Previous versions of cpp accepted a @option{-lang} option

@emph{Note:} Previous versions of cpp accepted a @option{-lang} option

which selected both the language and the standards conformance level.

which selected both the language and the standards conformance level.

This option has been removed, because it conflicts with the @option{-l}

This option has been removed, because it conflicts with the @option{-l}

option.

option.

@item -std=@var{standard}

@item -std=@var{standard}

@itemx -ansi

@itemx -ansi

@opindex ansi

@opindex ansi

@opindex std=

@opindex std=

Specify the standard to which the code should conform.  Currently CPP

Specify the standard to which the code should conform.  Currently CPP

knows about C and C++ standards; others may be added in the future.

knows about C and C++ standards; others may be added in the future.

@var{standard}

@var{standard}

may be one of:

may be one of:

@table @code

@table @code

@item c90

@item c90

@itemx c89

@itemx c89

@itemx iso9899:1990

@itemx iso9899:1990

The ISO C standard from 1990.  @samp{c90} is the customary shorthand for

The ISO C standard from 1990.  @samp{c90} is the customary shorthand for

this version of the standard.

this version of the standard.

The @option{-ansi} option is equivalent to @option{-std=c90}.

The @option{-ansi} option is equivalent to @option{-std=c90}.

@item iso9899:199409

@item iso9899:199409

The 1990 C standard, as amended in 1994.

The 1990 C standard, as amended in 1994.

@item iso9899:1999

@item iso9899:1999

@itemx c99

@itemx c99

@itemx iso9899:199x

@itemx iso9899:199x

@itemx c9x

@itemx c9x

The revised ISO C standard, published in December 1999.  Before

The revised ISO C standard, published in December 1999.  Before

publication, this was known as C9X@.

publication, this was known as C9X@.

@item iso9899:2011

@item iso9899:2011

@itemx c11

@itemx c11

@itemx c1x

@itemx c1x

The revised ISO C standard, published in December 2011.  Before

The revised ISO C standard, published in December 2011.  Before

publication, this was known as C1X@.

publication, this was known as C1X@.

@item gnu90

@item gnu90

@itemx gnu89

@itemx gnu89

The 1990 C standard plus GNU extensions.  This is the default.

The 1990 C standard plus GNU extensions.  This is the default.

@item gnu99

@item gnu99

@itemx gnu9x

@itemx gnu9x

The 1999 C standard plus GNU extensions.

The 1999 C standard plus GNU extensions.

@item gnu11

@item gnu11

@itemx gnu1x

@itemx gnu1x

The 2011 C standard plus GNU extensions.

The 2011 C standard plus GNU extensions.

@item c++98

@item c++98

The 1998 ISO C++ standard plus amendments.

The 1998 ISO C++ standard plus amendments.

@item gnu++98

@item gnu++98

The same as @option{-std=c++98} plus GNU extensions.  This is the

The same as @option{-std=c++98} plus GNU extensions.  This is the

default for C++ code.

default for C++ code.

@end table

@end table

@item -I-

@item -I-

@opindex I-

@opindex I-

Split the include path.  Any directories specified with @option{-I}

Split the include path.  Any directories specified with @option{-I}

options before @option{-I-} are searched only for headers requested with

options before @option{-I-} are searched only for headers requested with

@code{@w{#include "@var{file}"}}; they are not searched for

@code{@w{#include "@var{file}"}}; they are not searched for

@code{@w{#include <@var{file}>}}.  If additional directories are

@code{@w{#include <@var{file}>}}.  If additional directories are

specified with @option{-I} options after the @option{-I-}, those

specified with @option{-I} options after the @option{-I-}, those

directories are searched for all @samp{#include} directives.

directories are searched for all @samp{#include} directives.

In addition, @option{-I-} inhibits the use of the directory of the current

In addition, @option{-I-} inhibits the use of the directory of the current

file directory as the first search directory for @code{@w{#include

file directory as the first search directory for @code{@w{#include

"@var{file}"}}.

"@var{file}"}}.

@ifset cppmanual

@ifset cppmanual

@xref{Search Path}.

@xref{Search Path}.

@end ifset

@end ifset

This option has been deprecated.

This option has been deprecated.

@item -nostdinc

@item -nostdinc

@opindex nostdinc

@opindex nostdinc

Do not search the standard system directories for header files.

Do not search the standard system directories for header files.

Only the directories you have specified with @option{-I} options

Only the directories you have specified with @option{-I} options

(and the directory of the current file, if appropriate) are searched.

(and the directory of the current file, if appropriate) are searched.

@item -nostdinc++

@item -nostdinc++

@opindex nostdinc++

@opindex nostdinc++

Do not search for header files in the C++-specific standard directories,

Do not search for header files in the C++-specific standard directories,

but do still search the other standard directories.  (This option is

but do still search the other standard directories.  (This option is

used when building the C++ library.)

used when building the C++ library.)

@item -include @var{file}

@item -include @var{file}

@opindex include

@opindex include

Process @var{file} as if @code{#include "file"} appeared as the first

Process @var{file} as if @code{#include "file"} appeared as the first

line of the primary source file.  However, the first directory searched

line of the primary source file.  However, the first directory searched

for @var{file} is the preprocessor's working directory @emph{instead of}

for @var{file} is the preprocessor's working directory @emph{instead of}

the directory containing the main source file.  If not found there, it

the directory containing the main source file.  If not found there, it

is searched for in the remainder of the @code{#include "@dots{}"} search

is searched for in the remainder of the @code{#include "@dots{}"} search

chain as normal.

chain as normal.

If multiple @option{-include} options are given, the files are included

If multiple @option{-include} options are given, the files are included

in the order they appear on the command line.

in the order they appear on the command line.

@item -imacros @var{file}

@item -imacros @var{file}

@opindex imacros

@opindex imacros

Exactly like @option{-include}, except that any output produced by

Exactly like @option{-include}, except that any output produced by

scanning @var{file} is thrown away.  Macros it defines remain defined.

scanning @var{file} is thrown away.  Macros it defines remain defined.

This allows you to acquire all the macros from a header without also

This allows you to acquire all the macros from a header without also

processing its declarations.

processing its declarations.

All files specified by @option{-imacros} are processed before all files

All files specified by @option{-imacros} are processed before all files

specified by @option{-include}.

specified by @option{-include}.

@item -idirafter @var{dir}

@item -idirafter @var{dir}

@opindex idirafter

@opindex idirafter

Search @var{dir} for header files, but do it @emph{after} all

Search @var{dir} for header files, but do it @emph{after} all

directories specified with @option{-I} and the standard system directories

directories specified with @option{-I} and the standard system directories

have been exhausted.  @var{dir} is treated as a system include directory.

have been exhausted.  @var{dir} is treated as a system include directory.

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

@item -iprefix @var{prefix}

@item -iprefix @var{prefix}

@opindex iprefix

@opindex iprefix

Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}

Specify @var{prefix} as the prefix for subsequent @option{-iwithprefix}

options.  If the prefix represents a directory, you should include the

options.  If the prefix represents a directory, you should include the

final @samp{/}.

final @samp{/}.

@item -iwithprefix @var{dir}

@item -iwithprefix @var{dir}

@itemx -iwithprefixbefore @var{dir}

@itemx -iwithprefixbefore @var{dir}

@opindex iwithprefix

@opindex iwithprefix

@opindex iwithprefixbefore

@opindex iwithprefixbefore

Append @var{dir} to the prefix specified previously with

Append @var{dir} to the prefix specified previously with

@option{-iprefix}, and add the resulting directory to the include search

@option{-iprefix}, and add the resulting directory to the include search

path.  @option{-iwithprefixbefore} puts it in the same place @option{-I}

path.  @option{-iwithprefixbefore} puts it in the same place @option{-I}

would; @option{-iwithprefix} puts it where @option{-idirafter} would.

would; @option{-iwithprefix} puts it where @option{-idirafter} would.

@item -isysroot @var{dir}

@item -isysroot @var{dir}

@opindex isysroot

@opindex isysroot

This option is like the @option{--sysroot} option, but applies only to

This option is like the @option{--sysroot} option, but applies only to

header files (except for Darwin targets, where it applies to both header

header files (except for Darwin targets, where it applies to both header

files and libraries).  See the @option{--sysroot} option for more

files and libraries).  See the @option{--sysroot} option for more

information.

information.

@item -imultilib @var{dir}

@item -imultilib @var{dir}

@opindex imultilib

@opindex imultilib

Use @var{dir} as a subdirectory of the directory containing

Use @var{dir} as a subdirectory of the directory containing

target-specific C++ headers.

target-specific C++ headers.

@item -isystem @var{dir}

@item -isystem @var{dir}

@opindex isystem

@opindex isystem

Search @var{dir} for header files, after all directories specified by

Search @var{dir} for header files, after all directories specified by

@option{-I} but before the standard system directories.  Mark it

@option{-I} but before the standard system directories.  Mark it

as a system directory, so that it gets the same special treatment as

as a system directory, so that it gets the same special treatment as

is applied to the standard system directories.

is applied to the standard system directories.

@ifset cppmanual

@ifset cppmanual

@xref{System Headers}.

@xref{System Headers}.

@end ifset

@end ifset

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

@item -iquote @var{dir}

@item -iquote @var{dir}

@opindex iquote

@opindex iquote

Search @var{dir} only for header files requested with

Search @var{dir} only for header files requested with

@code{@w{#include "@var{file}"}}; they are not searched for

@code{@w{#include "@var{file}"}}; they are not searched for

@code{@w{#include <@var{file}>}}, before all directories specified by

@code{@w{#include <@var{file}>}}, before all directories specified by

@option{-I} and before the standard system directories.

@option{-I} and before the standard system directories.

@ifset cppmanual

@ifset cppmanual

@xref{Search Path}.

@xref{Search Path}.

@end ifset

@end ifset

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

If @var{dir} begins with @code{=}, then the @code{=} will be replaced

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

by the sysroot prefix; see @option{--sysroot} and @option{-isysroot}.

@item -fdirectives-only

@item -fdirectives-only

@opindex fdirectives-only

@opindex fdirectives-only

When preprocessing, handle directives, but do not expand macros.

When preprocessing, handle directives, but do not expand macros.

The option's behavior depends on the @option{-E} and @option{-fpreprocessed}

The option's behavior depends on the @option{-E} and @option{-fpreprocessed}

options.

options.

With @option{-E}, preprocessing is limited to the handling of directives

With @option{-E}, preprocessing is limited to the handling of directives

such as @code{#define}, @code{#ifdef}, and @code{#error}.  Other

such as @code{#define}, @code{#ifdef}, and @code{#error}.  Other

preprocessor operations, such as macro expansion and trigraph

preprocessor operations, such as macro expansion and trigraph

conversion are not performed.  In addition, the @option{-dD} option is

conversion are not performed.  In addition, the @option{-dD} option is

implicitly enabled.

implicitly enabled.

With @option{-fpreprocessed}, predefinition of command line and most

With @option{-fpreprocessed}, predefinition of command line and most

builtin macros is disabled.  Macros such as @code{__LINE__}, which are

builtin macros is disabled.  Macros such as @code{__LINE__}, which are

contextually dependent, are handled normally.  This enables compilation of

contextually dependent, are handled normally.  This enables compilation of

files previously preprocessed with @code{-E -fdirectives-only}.

files previously preprocessed with @code{-E -fdirectives-only}.

With both @option{-E} and @option{-fpreprocessed}, the rules for

With both @option{-E} and @option{-fpreprocessed}, the rules for

@option{-fpreprocessed} take precedence.  This enables full preprocessing of

@option{-fpreprocessed} take precedence.  This enables full preprocessing of

files previously preprocessed with @code{-E -fdirectives-only}.

files previously preprocessed with @code{-E -fdirectives-only}.

@item -fdollars-in-identifiers

@item -fdollars-in-identifiers

@opindex fdollars-in-identifiers

@opindex fdollars-in-identifiers

@anchor{fdollars-in-identifiers}

@anchor{fdollars-in-identifiers}

Accept @samp{$} in identifiers.

Accept @samp{$} in identifiers.

@ifset cppmanual

@ifset cppmanual

@xref{Identifier characters}.

@xref{Identifier characters}.

@end ifset

@end ifset

@item -fextended-identifiers

@item -fextended-identifiers

@opindex fextended-identifiers

@opindex fextended-identifiers

Accept universal character names in identifiers.  This option is

Accept universal character names in identifiers.  This option is

experimental; in a future version of GCC, it will be enabled by

experimental; in a future version of GCC, it will be enabled by

default for C99 and C++.

default for C99 and C++.

@item -fpreprocessed

@item -fpreprocessed

@opindex fpreprocessed

@opindex fpreprocessed

Indicate to the preprocessor that the input file has already been

Indicate to the preprocessor that the input file has already been

preprocessed.  This suppresses things like macro expansion, trigraph

preprocessed.  This suppresses things like macro expansion, trigraph

conversion, escaped newline splicing, and processing of most directives.

conversion, escaped newline splicing, and processing of most directives.

The preprocessor still recognizes and removes comments, so that you can

The preprocessor still recognizes and removes comments, so that you can

pass a file preprocessed with @option{-C} to the compiler without

pass a file preprocessed with @option{-C} to the compiler without

problems.  In this mode the integrated preprocessor is little more than

problems.  In this mode the integrated preprocessor is little more than

a tokenizer for the front ends.

a tokenizer for the front ends.

@option{-fpreprocessed} is implicit if the input file has one of the

@option{-fpreprocessed} is implicit if the input file has one of the

extensions @samp{.i}, @samp{.ii} or @samp{.mi}.  These are the

extensions @samp{.i}, @samp{.ii} or @samp{.mi}.  These are the

extensions that GCC uses for preprocessed files created by

extensions that GCC uses for preprocessed files created by

@option{-save-temps}.

@option{-save-temps}.

@item -ftabstop=@var{width}

@item -ftabstop=@var{width}

@opindex ftabstop

@opindex ftabstop

Set the distance between tab stops.  This helps the preprocessor report

Set the distance between tab stops.  This helps the preprocessor report

correct column numbers in warnings or errors, even if tabs appear on the

correct column numbers in warnings or errors, even if tabs appear on the

line.  If the value is less than 1 or greater than 100, the option is

line.  If the value is less than 1 or greater than 100, the option is

ignored.  The default is 8.

ignored.  The default is 8.

@item -fdebug-cpp

@item -fdebug-cpp

@opindex fdebug-cpp

@opindex fdebug-cpp

This option is only useful for debugging GCC.  When used with

This option is only useful for debugging GCC.  When used with

@option{-E}, dumps debugging information about location maps.  Every

@option{-E}, dumps debugging information about location maps.  Every

token in the output is preceded by the dump of the map its location

token in the output is preceded by the dump of the map its location

belongs to.  The dump of the map holding the location of a token would

belongs to.  The dump of the map holding the location of a token would

be:

be:

@smallexample

@smallexample

@{@samp{P}:@file{/file/path};@samp{F}:@file{/includer/path};@samp{L}:@var{line_num};@samp{C}:@var{col_num};@samp{S}:@var{system_header_p};@samp{M}:@var{map_address};@samp{E}:@var{macro_expansion_p},@samp{loc}:@var{location}@}

@{@samp{P}:@file{/file/path};@samp{F}:@file{/includer/path};@samp{L}:@var{line_num};@samp{C}:@var{col_num};@samp{S}:@var{system_header_p};@samp{M}:@var{map_address};@samp{E}:@var{macro_expansion_p},@samp{loc}:@var{location}@}

@end smallexample

@end smallexample

When used without @option{-E}, this option has no effect.

When used without @option{-E}, this option has no effect.

@item -ftrack-macro-expansion@r{[}=@var{level}@r{]}

@item -ftrack-macro-expansion@r{[}=@var{level}@r{]}

@opindex ftrack-macro-expansion

@opindex ftrack-macro-expansion

Track locations of tokens across macro expansions. This allows the

Track locations of tokens across macro expansions. This allows the

compiler to emit diagnostic about the current macro expansion stack

compiler to emit diagnostic about the current macro expansion stack

when a compilation error occurs in a macro expansion. Using this

when a compilation error occurs in a macro expansion. Using this

option makes the preprocessor and the compiler consume more

option makes the preprocessor and the compiler consume more

memory. The @var{level} parameter can be used to choose the level of

memory. The @var{level} parameter can be used to choose the level of

precision of token location tracking thus decreasing the memory

precision of token location tracking thus decreasing the memory

consumption if necessary. Value @samp{0} of @var{level} de-activates

consumption if necessary. Value @samp{0} of @var{level} de-activates

this option just as if no @option{-ftrack-macro-expansion} was present

this option just as if no @option{-ftrack-macro-expansion} was present

on the command line. Value @samp{1} tracks tokens locations in a

on the command line. Value @samp{1} tracks tokens locations in a

degraded mode for the sake of minimal memory overhead. In this mode

degraded mode for the sake of minimal memory overhead. In this mode

all tokens resulting from the expansion of an argument of a

all tokens resulting from the expansion of an argument of a

function-like macro have the same location. Value @samp{2} tracks

function-like macro have the same location. Value @samp{2} tracks

tokens locations completely. This value is the most memory hungry.

tokens locations completely. This value is the most memory hungry.

When this option is given no argument, the default parameter value is

When this option is given no argument, the default parameter value is

@samp{2}.

@samp{2}.

@item -fexec-charset=@var{charset}

@item -fexec-charset=@var{charset}

@opindex fexec-charset

@opindex fexec-charset

@cindex character set, execution

@cindex character set, execution

Set the execution character set, used for string and character

Set the execution character set, used for string and character

constants.  The default is UTF-8.  @var{charset} can be any encoding

constants.  The default is UTF-8.  @var{charset} can be any encoding

supported by the system's @code{iconv} library routine.

supported by the system's @code{iconv} library routine.

@item -fwide-exec-charset=@var{charset}

@item -fwide-exec-charset=@var{charset}

@opindex fwide-exec-charset

@opindex fwide-exec-charset

@cindex character set, wide execution

@cindex character set, wide execution

Set the wide execution character set, used for wide string and

Set the wide execution character set, used for wide string and

character constants.  The default is UTF-32 or UTF-16, whichever

character constants.  The default is UTF-32 or UTF-16, whichever

corresponds to the width of @code{wchar_t}.  As with

corresponds to the width of @code{wchar_t}.  As with

@option{-fexec-charset}, @var{charset} can be any encoding supported

@option{-fexec-charset}, @var{charset} can be any encoding supported

by the system's @code{iconv} library routine; however, you will have

by the system's @code{iconv} library routine; however, you will have

problems with encodings that do not fit exactly in @code{wchar_t}.

problems with encodings that do not fit exactly in @code{wchar_t}.

@item -finput-charset=@var{charset}

@item -finput-charset=@var{charset}

@opindex finput-charset

@opindex finput-charset

@cindex character set, input

@cindex character set, input

Set the input character set, used for translation from the character

Set the input character set, used for translation from the character

set of the input file to the source character set used by GCC@.  If the

set of the input file to the source character set used by GCC@.  If the

locale does not specify, or GCC cannot get this information from the

locale does not specify, or GCC cannot get this information from the

locale, the default is UTF-8.  This can be overridden by either the locale

locale, the default is UTF-8.  This can be overridden by either the locale

or this command line option.  Currently the command line option takes

or this command line option.  Currently the command line option takes

precedence if there's a conflict.  @var{charset} can be any encoding

precedence if there's a conflict.  @var{charset} can be any encoding

supported by the system's @code{iconv} library routine.

supported by the system's @code{iconv} library routine.

@item -fworking-directory

@item -fworking-directory

@opindex fworking-directory

@opindex fworking-directory

@opindex fno-working-directory

@opindex fno-working-directory

Enable generation of linemarkers in the preprocessor output that will

Enable generation of linemarkers in the preprocessor output that will

let the compiler know the current working directory at the time of

let the compiler know the current working directory at the time of

preprocessing.  When this option is enabled, the preprocessor will

preprocessing.  When this option is enabled, the preprocessor will

emit, after the initial linemarker, a second linemarker with the

emit, after the initial linemarker, a second linemarker with the

current working directory followed by two slashes.  GCC will use this

current working directory followed by two slashes.  GCC will use this

directory, when it's present in the preprocessed input, as the

directory, when it's present in the preprocessed input, as the

directory emitted as the current working directory in some debugging

directory emitted as the current working directory in some debugging

information formats.  This option is implicitly enabled if debugging

information formats.  This option is implicitly enabled if debugging

information is enabled, but this can be inhibited with the negated

information is enabled, but this can be inhibited with the negated

form @option{-fno-working-directory}.  If the @option{-P} flag is

form @option{-fno-working-directory}.  If the @option{-P} flag is

present in the command line, this option has no effect, since no

present in the command line, this option has no effect, since no

@code{#line} directives are emitted whatsoever.

@code{#line} directives are emitted whatsoever.

@item -fno-show-column

@item -fno-show-column

@opindex fno-show-column

@opindex fno-show-column

Do not print column numbers in diagnostics.  This may be necessary if

Do not print column numbers in diagnostics.  This may be necessary if

diagnostics are being scanned by a program that does not understand the

diagnostics are being scanned by a program that does not understand the

column numbers, such as @command{dejagnu}.

column numbers, such as @command{dejagnu}.

@item -A @var{predicate}=@var{answer}

@item -A @var{predicate}=@var{answer}

@opindex A

@opindex A

Make an assertion with the predicate @var{predicate} and answer

Make an assertion with the predicate @var{predicate} and answer

@var{answer}.  This form is preferred to the older form @option{-A

@var{answer}.  This form is preferred to the older form @option{-A

@var{predicate}(@var{answer})}, which is still supported, because

@var{predicate}(@var{answer})}, which is still supported, because

it does not use shell special characters.

it does not use shell special characters.

@ifset cppmanual

@ifset cppmanual

@xref{Obsolete Features}.

@xref{Obsolete Features}.

@end ifset

@end ifset

@item -A -@var{predicate}=@var{answer}

@item -A -@var{predicate}=@var{answer}

Cancel an assertion with the predicate @var{predicate} and answer

Cancel an assertion with the predicate @var{predicate} and answer

@var{answer}.

@var{answer}.

@item -dCHARS

@item -dCHARS

@var{CHARS} is a sequence of one or more of the following characters,

@var{CHARS} is a sequence of one or more of the following characters,

and must not be preceded by a space.  Other characters are interpreted

and must not be preceded by a space.  Other characters are interpreted

by the compiler proper, or reserved for future versions of GCC, and so

by the compiler proper, or reserved for future versions of GCC, and so

are silently ignored.  If you specify characters whose behavior

are silently ignored.  If you specify characters whose behavior

conflicts, the result is undefined.

conflicts, the result is undefined.

@table @samp

@table @samp

@item M

@item M

@opindex dM

@opindex dM

Instead of the normal output, generate a list of @samp{#define}

Instead of the normal output, generate a list of @samp{#define}

directives for all the macros defined during the execution of the

directives for all the macros defined during the execution of the

preprocessor, including predefined macros.  This gives you a way of

preprocessor, including predefined macros.  This gives you a way of

finding out what is predefined in your version of the preprocessor.

finding out what is predefined in your version of the preprocessor.

Assuming you have no file @file{foo.h}, the command

Assuming you have no file @file{foo.h}, the command

@smallexample

@smallexample

touch foo.h; cpp -dM foo.h

touch foo.h; cpp -dM foo.h

@end smallexample

@end smallexample

@noindent

@noindent

will show all the predefined macros.

will show all the predefined macros.

If you use @option{-dM} without the @option{-E} option, @option{-dM} is

If you use @option{-dM} without the @option{-E} option, @option{-dM} is

interpreted as a synonym for @option{-fdump-rtl-mach}.

interpreted as a synonym for @option{-fdump-rtl-mach}.

@xref{Debugging Options, , ,gcc}.

@xref{Debugging Options, , ,gcc}.

@item D

@item D

@opindex dD

@opindex dD

Like @samp{M} except in two respects: it does @emph{not} include the

Like @samp{M} except in two respects: it does @emph{not} include the

predefined macros, and it outputs @emph{both} the @samp{#define}

predefined macros, and it outputs @emph{both} the @samp{#define}

directives and the result of preprocessing.  Both kinds of output go to

directives and the result of preprocessing.  Both kinds of output go to

the standard output file.

the standard output file.

@item N

@item N

@opindex dN

@opindex dN

Like @samp{D}, but emit only the macro names, not their expansions.

Like @samp{D}, but emit only the macro names, not their expansions.

@item I

@item I

@opindex dI

@opindex dI

Output @samp{#include} directives in addition to the result of

Output @samp{#include} directives in addition to the result of

preprocessing.

preprocessing.

@item U

@item U

@opindex dU

@opindex dU

Like @samp{D} except that only macros that are expanded, or whose

Like @samp{D} except that only macros that are expanded, or whose

definedness is tested in preprocessor directives, are output; the

definedness is tested in preprocessor directives, are output; the

output is delayed until the use or test of the macro; and

output is delayed until the use or test of the macro; and

@samp{#undef} directives are also output for macros tested but

@samp{#undef} directives are also output for macros tested but

undefined at the time.

undefined at the time.

@end table

@end table

@item -P

@item -P

@opindex P

@opindex P

Inhibit generation of linemarkers in the output from the preprocessor.

Inhibit generation of linemarkers in the output from the preprocessor.

This might be useful when running the preprocessor on something that is

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

not C code, and will be sent to a program which might be confused by the

linemarkers.

linemarkers.

@ifset cppmanual

@ifset cppmanual

@xref{Preprocessor Output}.

@xref{Preprocessor Output}.

@end ifset

@end ifset

@item -C

@item -C

@opindex C

@opindex C

Do not discard comments.  All comments are passed through to the output

Do not discard comments.  All comments are passed through to the output

file, except for comments in processed directives, which are deleted

file, except for comments in processed directives, which are deleted

along with the directive.

along with the directive.

You should be prepared for side effects when using @option{-C}; it

You should be prepared for side effects when using @option{-C}; it

causes the preprocessor to treat comments as tokens in their own right.

causes the preprocessor to treat comments as tokens in their own right.

For example, comments appearing at the start of what would be a

For example, comments appearing at the start of what would be a

directive line have the effect of turning that line into an ordinary

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 @samp{#}.

source line, since the first token on the line is no longer a @samp{#}.

@item -CC

@item -CC

Do not discard comments, including during macro expansion.  This is

Do not discard comments, including during macro expansion.  This is

like @option{-C}, except that comments contained within macros are

like @option{-C}, except that comments contained within macros are

also passed through to the output file where the macro is expanded.

also passed through to the output file where the macro is expanded.

In addition to the side-effects of the @option{-C} option, the

In addition to the side-effects of the @option{-C} option, the

@option{-CC} option causes all C++-style comments inside a macro

@option{-CC} option causes all C++-style comments inside a macro

to be converted to C-style comments.  This is to prevent later use

to be converted to C-style comments.  This is to prevent later use

of that macro from inadvertently commenting out the remainder of

of that macro from inadvertently commenting out the remainder of

the source line.

the source line.

The @option{-CC} option is generally used to support lint comments.

The @option{-CC} option is generally used to support lint comments.

@item -traditional-cpp

@item -traditional-cpp

@opindex traditional-cpp

@opindex traditional-cpp

Try to imitate the behavior of old-fashioned C preprocessors, as

Try to imitate the behavior of old-fashioned C preprocessors, as

opposed to ISO C preprocessors.

opposed to ISO C preprocessors.

@ifset cppmanual

@ifset cppmanual

@xref{Traditional Mode}.

@xref{Traditional Mode}.

@end ifset

@end ifset

@item -trigraphs

@item -trigraphs

@opindex trigraphs

@opindex trigraphs

Process trigraph sequences.

Process trigraph sequences.

@ifset cppmanual

@ifset cppmanual

@xref{Initial processing}.

@xref{Initial processing}.

@end ifset

@end ifset

@ifclear cppmanual

@ifclear cppmanual

These are three-character sequences, all starting with @samp{??}, that

These are three-character sequences, all starting with @samp{??}, that

are defined by ISO C to stand for single characters.  For example,

are defined by ISO C to stand for single characters.  For example,

@samp{??/} stands for @samp{\}, so @samp{'??/n'} is a character

@samp{??/} stands for @samp{\}, so @samp{'??/n'} is a character

constant for a newline.  By default, GCC ignores trigraphs, but in

constant for a newline.  By default, GCC ignores trigraphs, but in

standard-conforming modes it converts them.  See the @option{-std} and

standard-conforming modes it converts them.  See the @option{-std} and

@option{-ansi} options.

@option{-ansi} options.

The nine trigraphs and their replacements are

The nine trigraphs and their replacements are

@smallexample

@smallexample

Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-

Trigraph:       ??(  ??)  ??<  ??>  ??=  ??/  ??'  ??!  ??-

Replacement:      [    ]    @{    @}    #    \    ^    |    ~

Replacement:      [    ]    @{    @}    #    \    ^    |    ~

@end smallexample

@end smallexample

@end ifclear

@end ifclear

@item -remap

@item -remap

@opindex remap

@opindex remap

Enable special code to work around file systems which only permit very

Enable special code to work around file systems which only permit very

short file names, such as MS-DOS@.

short file names, such as MS-DOS@.

@itemx --help

@itemx --help

@itemx --target-help

@itemx --target-help

@opindex help

@opindex help

@opindex target-help

@opindex target-help

Print text describing all the command line options instead of

Print text describing all the command line options instead of

preprocessing anything.

preprocessing anything.

@item -v

@item -v

@opindex v

@opindex v

Verbose mode.  Print out GNU CPP's version number at the beginning of

Verbose mode.  Print out GNU CPP's version number at the beginning of

execution, and report the final form of the include path.

execution, and report the final form of the include path.

@item -H

@item -H

@opindex H

@opindex H

Print the name of each header file used, in addition to other normal

Print the name of each header file used, in addition to other normal

activities.  Each name is indented to show how deep in the

activities.  Each name is indented to show how deep in the

@samp{#include} stack it is.  Precompiled header files are also

@samp{#include} stack it is.  Precompiled header files are also

printed, even if they are found to be invalid; an invalid precompiled

printed, even if they are found to be invalid; an invalid precompiled

header file is printed with @samp{...x} and a valid one with @samp{...!} .

header file is printed with @samp{...x} and a valid one with @samp{...!} .

@item -version

@item -version

@itemx --version

@itemx --version

@opindex version

@opindex version

Print out GNU CPP's version number.  With one dash, proceed to

Print out GNU CPP's version number.  With one dash, proceed to

preprocess as normal.  With two dashes, exit immediately.

preprocess as normal.  With two dashes, exit immediately.

@end table

@end table