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CPP(1)				      GNU				CPP(1)

       cpp - The C Preprocessor

       cpp [-Dmacro[=defn]...] [-Umacro]
	   [-Idir...] [-Wwarn...]
	   [-M|-MM] [-MG] [-MF filename]
	   [-MP] [-MQ target...]
	   [-MT	target...]
	   [-P]	[-fno-working-directory]
	   [-x language] [-std=standard]
	   infile outfile

       Only the	most useful options are	listed here; see below for the remain-

       The C preprocessor, often known as cpp, is a macro processor that is
       used automatically by the C compiler to transform your program before
       compilation.  It	is called a macro processor because it allows you to
       define macros, which are	brief abbreviations for	longer constructs.

       The C preprocessor is intended to be used only with C, C++, and Objec-
       tive-C source code.  In the past, it has	been abused as a general text
       processor.  It will choke on input which	does not obey C's lexical
       rules.  For example, apostrophes	will be	interpreted as the beginning
       of character constants, and cause errors.  Also,	you cannot rely	on it
       preserving characteristics of the input which are not significant to
       C-family	languages.  If a Makefile is preprocessed, all the hard	tabs
       will be removed,	and the	Makefile will not work.

       Having said that, you can often get away	with using cpp on things which
       are not C.  Other Algol-ish programming languages are often safe	(Pas-
       cal, Ada, etc.) So is assembly, with caution.  -traditional-cpp mode
       preserves more white space, and is otherwise more permissive.  Many of
       the problems can	be avoided by writing C	or C++ style comments instead
       of native language comments, and	keeping	macros simple.

       Wherever	possible, you should use a preprocessor	geared to the language
       you are writing in.  Modern versions of the GNU assembler have macro
       facilities.  Most high level programming	languages have their own con-
       ditional	compilation and	inclusion mechanism.  If all else fails, try a
       true general text processor, such as GNU	M4.

       C preprocessors vary in some details.  This manual discusses the	GNU C
       preprocessor, which provides a small superset of	the features of	ISO
       Standard	C.  In its default mode, the GNU C preprocessor	does not do a
       few things required by the standard.  These are features	which are
       rarely, if ever,	used, and may cause surprising changes to the meaning
       of a program which does not expect them.	 To get	strict ISO Standard C,
       you should use the -std=c89 or -std=c99 options,	depending on which
       version of the standard you want.  To get all the mandatory diagnos-
       tics, you must also use -pedantic.

       This manual describes the behavior of the ISO preprocessor.  To mini-
       mize gratuitous differences, where the ISO preprocessor's behavior does
       not conflict with traditional semantics,	the traditional	preprocessor
       should behave the same way.  The	various	differences that do exist are
       detailed	in the section Traditional Mode.

       For clarity, unless noted otherwise, references to CPP in this manual
       refer to	GNU CPP.

       The C preprocessor expects two file names as arguments, infile and out-
       file.  The preprocessor reads infile together with any other files it
       specifies with #include.	 All the output	generated by the combined in-
       put files is written in outfile.

       Either infile or	outfile	may be -, which	as infile means	to read	from
       standard	input and as outfile means to write to standard	output.	 Also,
       if either file is omitted, it means the same as if - had	been specified
       for that	file.

       Unless otherwise	noted, or the option ends in =,	all options which take
       an argument may have that argument appear either	immediately after the
       option, or with a space between option and argument: -Ifoo and -I foo
       have the	same effect.

       Many options have multi-letter names; therefore multiple	single-letter
       options may not be grouped: -dM is very different from -d -M.

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

       -D name=definition
	   Predefine name as a macro, with definition definition.  The con-
	   tents of definition are tokenized and processed as if they appeared
	   during translation phase three in a #define directive.  In particu-
	   lar,	the definition will be truncated by embedded newline charac-

	   If you are invoking the preprocessor	from a shell or	shell-like
	   program you may need	to use the shell's quoting syntax to protect
	   characters such as spaces that have a meaning in the	shell syntax.

	   If you wish to define a function-like macro on the command line,
	   write its argument list with	surrounding parentheses	before the
	   equals sign (if any).  Parentheses are meaningful to	most shells,
	   so you will need to quote the option.  With sh and csh,
	   -D'name(args...)=definition'	works.

	   -D and -U options are processed in the order	they are given on the
	   command line.  All -imacros file and	-include file options are pro-
	   cessed after	all -D and -U options.

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

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

       -I dir
	   Add the directory dir to the	list of	directories to be searched for
	   header files.

	   Directories named by	-I are searched	before the standard system in-
	   clude directories.  If the directory	dir is a standard system in-
	   clude directory, the	option is ignored to ensure that the default
	   search order	for system directories and the special treatment of
	   system headers are not defeated .

       -o file
	   Write output	to file.  This is the same as specifying file as the
	   second non-option argument to cpp.  gcc has a different interpreta-
	   tion	of a second non-option argument, so you	must use -o to specify
	   the output file.

	   Turns on all	optional warnings which	are desirable for normal code.
	   At present this is -Wcomment, -Wtrigraphs, -Wmultichar and a	warn-
	   ing about integer promotion causing a change	of sign	in "#if" ex-
	   pressions.  Note that many of the preprocessor's warnings are on by
	   default and have no options to control them.

	   Warn	whenever a comment-start sequence /* appears in	a /* comment,
	   or whenever a backslash-newline appears in a	// comment.  (Both
	   forms have the same effect.)

	   @anchor{Wtrigraphs} Most trigraphs in comments cannot affect	the
	   meaning of the program.  However, a trigraph	that would form	an es-
	   caped newline (??/ at the end of a line) can, by changing where the
	   comment begins or ends.  Therefore, only trigraphs that would form
	   escaped newlines produce warnings inside a comment.

	   This	option is implied by -Wall.  If	-Wall is not given, this op-
	   tion	is still enabled unless	trigraphs are enabled.	To get tri-
	   graph conversion without warnings, but get the other	-Wall warn-
	   ings, use -trigraphs	-Wall -Wno-trigraphs.

	   Warn	about certain constructs that behave differently in tradi-
	   tional and ISO C.  Also warn	about ISO C constructs that have no
	   traditional C equivalent, and problematic constructs	which should
	   be avoided.

	   Warn	the first time #import is used.

	   Warn	whenever an identifier which is	not a macro is encountered in
	   an #if directive, outside of	defined.  Such identifiers are re-
	   placed with zero.

	   Warn	about macros defined in	the main file that are unused.	A
	   macro is 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 time it is redefined or undefined.

	   Built-in macros, macros defined on the command line,	and macros de-
	   fined in include files are not warned about.

	   Note: If a macro is actually	used, but only used in skipped condi-
	   tional 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
	   definition by, for example, moving it into the first	skipped	block.
	   Alternatively, you could provide a dummy use	with something like:

		   #if defined the_macro_causing_the_warning

	   Warn	whenever an #else or an	#endif are followed by text.  This
	   usually happens in code of the form

		   #if FOO
		   #else FOO
		   #endif FOO

	   The second and third	"FOO" should be	in comments, but often are not
	   in older programs.  This warning is on by default.

	   Make	all warnings into hard errors.	Source code which triggers
	   warnings will be rejected.

	   Issue warnings for code in system headers.  These are normally un-
	   helpful in finding bugs in your own code, therefore suppressed.  If
	   you are responsible for the system library, you may want to see

       -w  Suppress all	warnings, including those which	GNU CPP	issues by de-

	   Issue all the mandatory diagnostics listed in the C standard.  Some
	   of them are left out	by default, since they trigger frequently on
	   harmless code.

	   Issue all the mandatory diagnostics,	and make all mandatory diag-
	   nostics into	errors.	 This includes mandatory diagnostics that GCC
	   issues without -pedantic but	treats as warnings.

       -M  Instead of outputting the result of preprocessing, output a rule
	   suitable for	make describing	the dependencies of the	main source
	   file.  The preprocessor outputs one make rule containing the	object
	   file	name for that source file, a colon, and	the names of all the
	   included files, including those coming from -include	or -imacros
	   command line	options.

	   Unless specified explicitly (with -MT or -MQ), the object file name
	   consists of the basename of the source file with any	suffix re-
	   placed with object file suffix.  If there are many included files
	   then	the rule is split into several lines using \-newline.  The
	   rule	has no commands.

	   This	option does not	suppress the preprocessor's debug output, such
	   as -dM.  To avoid mixing such debug output with the dependency
	   rules you should explicitly specify the dependency output file with
	   -MF,	or use an environment variable like DEPENDENCIES_OUTPUT.  De-
	   bug output will still be sent to the	regular	output stream as nor-

	   Passing -M to the driver implies -E,	and suppresses warnings	with
	   an implicit -w.

       -MM Like	-M but do not mention header files that	are found in system
	   header directories, nor header files	that are included, directly or
	   indirectly, from such a header.

	   This	implies	that the choice	of angle brackets or double quotes in
	   an #include directive does not in itself determine whether that
	   header will appear in -MM dependency	output.	 This is a slight
	   change in semantics from GCC	versions 3.0 and earlier.


       -MF file
	   When	used with -M or	-MM, specifies a file to write the dependen-
	   cies	to.  If	no -MF switch is given the preprocessor	sends the
	   rules to the	same place it would have sent preprocessed output.

	   When	used with the driver options -MD or -MMD, -MF overrides	the
	   default dependency output file.

       -MG In conjunction with an option such as -M requesting dependency gen-
	   eration, -MG	assumes	missing	header files are generated files and
	   adds	them to	the dependency list without raising an error.  The de-
	   pendency filename is	taken directly from the	"#include" directive
	   without prepending any path.	 -MG also suppresses preprocessed out-
	   put,	as a missing header file renders this useless.

	   This	feature	is used	in automatic updating of makefiles.

       -MP This	option instructs CPP to	add a phony target for each dependency
	   other than the main file, causing each to depend on nothing.	 These
	   dummy rules work around errors make gives if	you remove header
	   files without updating the Makefile to match.

	   This	is typical output:

		   test.o: test.c test.h


       -MT target
	   Change the target of	the rule emitted by dependency generation.  By
	   default CPP takes the name of the main input	file, including	any
	   path, deletes any file suffix such as .c, and appends the plat-
	   form's usual	object suffix.	The result is the target.

	   An -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 argument to -MT, or use multiple -MT options.

	   For example,	-MT '$(objpfx)foo.o' might give

		   $(objpfx)foo.o: foo.c

       -MQ target
	   Same	as -MT,	but it quotes any characters which are special to
	   Make.  -MQ '$(objpfx)foo.o' gives

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

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

       -MD -MD is equivalent to	-M -MF file, except that -E is not implied.
	   The driver determines file based on whether an -o option is given.
	   If it is, the driver	uses its argument but with a suffix of .d,
	   otherwise it	take the basename of the input file and	applies	a .d

	   If -MD is used in conjunction with -E, any -o switch	is understood
	   to specify the dependency output file (but @pxref{dashMF,,-MF}),
	   but if used without -E, each	-o is understood to specify a target
	   object file.

	   Since -E is not implied, -MD	can be used to generate	a dependency
	   output file as a side-effect	of the compilation process.

	   Like	-MD except mention only	user header files, not system -header

       -x c
       -x c++
       -x objective-c
       -x assembler-with-cpp
	   Specify the source language:	C, C++,	Objective-C, or	assembly.
	   This	has nothing to do with standards conformance or	extensions; it
	   merely 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: .c,	.cc, .m, or .S.	 Some other common extensions
	   for C++ and assembly	are also recognized.  If cpp does not recog-
	   nize	the extension, it will treat the file as C; this is the	most
	   generic mode.

	   Note: Previous versions of cpp accepted a -lang option which	se-
	   lected both the language and	the standards conformance level.  This
	   option has been removed, because it conflicts with the -l option.

	   Specify the standard	to which the code should conform.  Currently
	   CPP knows about C and C++ standards;	others may be added in the fu-

	   standard may	be one of:

	       The ISO C standard from 1990.  c89 is the customary shorthand
	       for this	version	of the standard.

	       The -ansi option	is equivalent to -std=c89.

	       The 1990	C standard, as amended in 1994.

	       The revised ISO C standard, published in	December 1999.	Before
	       publication, this was known as C9X.

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

	       The 1999	C standard plus	GNU extensions.

	       The 1998	ISO C++	standard plus amendments.

	       The same	as -std=c++98 plus GNU extensions.  This is the	de-
	       fault for C++ code.

       -I- Split the include path.  Any	directories specified with -I options
	   before -I- are searched only	for headers requested with "#in-
	   clude "file""; they are not searched	for "#include <file_".	If ad-
	   ditional directories	are specified with -I options after the	-I-,
	   those directories are searched for all #include directives.

	   In addition,	-I- inhibits the use of	the directory of the current
	   file	directory as the first search directory	for "#include "file"".

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

	   Do not search for header files in the C++-specific standard direc-
	   tories, but do still	search the other standard directories.	(This
	   option is used when building	the C++	library.)

       -include	file
	   Process file	as if "#include	"file""	appeared as the	first line of
	   the primary source file.  However, the first	directory searched for
	   file	is the preprocessor's working directory	instead	of the direc-
	   tory	containing the main source file.  If not found there, it is
	   searched for	in the remainder of the	"#include "..."" search	chain
	   as normal.

	   If multiple -include	options	are given, the files are included in
	   the order they appear on the	command	line.

       -imacros	file
	   Exactly like	-include, except that any output produced by scanning
	   file	is thrown away.	 Macros	it defines remain defined.  This al-
	   lows	you to acquire all the macros from a header without also pro-
	   cessing its declarations.

	   All files specified by -imacros are processed before	all files
	   specified by	-include.

       -idirafter dir
	   Search dir for header files,	but do it after	all directories	speci-
	   fied	with -I	and the	standard system	directories have been ex-
	   hausted.  dir is treated as a system	include	directory.

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

       -iwithprefix dir
       -iwithprefixbefore dir
	   Append dir to the prefix specified previously with -iprefix,	and
	   add the resulting directory to the include search path.  -iwithpre-
	   fixbefore puts it in	the same place -I would; -iwithprefix puts it
	   where -idirafter would.

       -isystem	dir
	   Search dir for header files,	after all directories specified	by -I
	   but before the standard system directories.	Mark it	as a system
	   directory, so that it gets the same special treatment as is applied
	   to the standard system directories.

	   @anchor{fdollars-in-identifiers} Accept $ in	identifiers.

	   Indicate to the preprocessor	that the input file has	already	been
	   preprocessed.  This suppresses things like macro expansion, tri-
	   graph conversion, escaped newline splicing, and processing of most
	   directives.	The preprocessor still recognizes and removes com-
	   ments, so that you can pass a file preprocessed with	-C to the com-
	   piler without problems.  In this mode the integrated	preprocessor
	   is little more than a tokenizer for the front ends.

	   -fpreprocessed is implicit if the input file	has one	of the exten-
	   sions .i, .ii or .mi.  These	are the	extensions that	GCC uses for
	   preprocessed	files created by -save-temps.

	   Set the distance between tab	stops.	This helps the preprocessor
	   report 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 ignored.	The default is 8.

	   Set the execution character set, used for string and	character con-
	   stants.  The	default	is UTF-8.  charset can be any encoding sup-
	   ported by the system's "iconv" library routine.

	   Set the wide	execution character set, used for wide string and
	   character constants.	 The default is	UTF-32 or UTF-16, whichever
	   corresponds to the width of "wchar_t".  As with -ftarget-charset,
	   charset can be any encoding supported by the	system's "iconv" li-
	   brary routine; however, you will have problems with encodings that
	   do not fit exactly in "wchar_t".

	   Set the input character set,	used for translation from the charac-
	   ter 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, the	default	is UTF-8. This can be overridden by
	   either the locale or	this command line option. Currently the	com-
	   mand	line option takes precedence if	there's	a conflict. charset
	   can be any encoding supported by the	system's "iconv" library rou-

	   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 preproces-
	   sor will emit, after	the initial linemarker,	a second linemarker
	   with	the current working directory followed by two slashes.	GCC
	   will	use this directory, when it's present in the preprocessed in-
	   put,	as the directory emitted as the	current	working	directory in
	   some	debugging information formats.	This option is implicitly en-
	   abled if debugging information is enabled, but this can be inhib-
	   ited	with the negated form -fno-working-directory.  If the -P flag
	   is present in the command line, this	option has no effect, since no
	   "#line" directives are emitted whatsoever.

	   Do not print	column numbers in diagnostics.	This may be necessary
	   if diagnostics are being scanned by a program that does not under-
	   stand the column numbers, such as dejagnu.

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

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

	   CHARS is a sequence of one or more of the following characters, 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 are silently ignored.  If	you specify characters whose behavior
	   conflicts, the result is undefined.

	   M   Instead of the normal output, generate a	list of	#define	direc-
	       tives for all the macros	defined	during the execution of	the
	       preprocessor, including predefined macros.  This	gives you a
	       way of finding out what is predefined in	your version of	the
	       preprocessor.  Assuming you have	no file	foo.h, the command

		       touch foo.h; cpp	-dM foo.h

	       will show all the predefined macros.

	   D   Like M except in	two respects: it does not include the prede-
	       fined macros, and it outputs both the #define directives	and
	       the result of preprocessing.  Both kinds	of output go to	the
	       standard	output file.

	   N   Like D, but emit	only the macro names, not their	expansions.

	   I   Output #include directives in addition to the result of prepro-

       -P  Inhibit generation of linemarkers in	the output from	the preproces-
	   sor.	 This might be useful when running the preprocessor on some-
	   thing that is not C code, and will be sent to a program which might
	   be confused by the linemarkers.

       -C  Do not discard comments.  All comments are passed through to	the
	   output file,	except for comments in processed directives, which are
	   deleted along with the directive.

	   You should be prepared for side effects when	using -C; it causes
	   the preprocessor to treat comments as tokens	in their own right.
	   For example,	comments appearing at the start	of what	would be a di-
	   rective line	have the effect	of turning that	line into an ordinary
	   source line,	since the first	token on the line is no	longer a #.

       -CC Do not discard comments, including during macro expansion.  This is
	   like	-C, except that	comments contained within macros are also
	   passed through to the output	file where the macro is	expanded.

	   In addition to the side-effects of the -C option, the -CC option
	   causes all C++-style	comments inside	a macro	to be converted	to
	   C-style comments.  This is to prevent later use of that macro from
	   inadvertently commenting out	the remainder of the source line.

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

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

	   Process trigraph sequences.

	   Enable special code to work around file systems which only permit
	   very	short file names, such as MS-DOS.

	   Print text describing all the command line options instead of pre-
	   processing anything.

       -v  Verbose mode.  Print	out GNU	CPP's version number at	the beginning
	   of execution, and report the	final form of the include path.

       -H  Print the name of each header file used, in addition	to other nor-
	   mal activities.  Each name is indented to show how deep in the #in-
	   clude stack it is.  Precompiled header files	are also printed, even
	   if they are found to	be invalid; an invalid precompiled header file
	   is printed with ...x	and a valid one	with ...! .

	   Print out GNU CPP's version number.	With one dash, proceed to pre-
	   process as normal.  With two	dashes,	exit immediately.

       This section describes the environment variables	that affect how	CPP
       operates.  You can use them to specify directories or prefixes to use
       when searching for include files, or to control dependency output.

       Note that you can also specify places to	search using options such as
       -I, and control dependency output with options like -M.	These take
       precedence over environment variables, which in turn take precedence
       over the	configuration of GCC.

	   Each	variable's value is a list of directories separated by a spe-
	   cial	character, much	like PATH, in which to look for	header files.
	   The special character, "PATH_SEPARATOR", is target-dependent	and
	   determined at GCC build time.  For Microsoft	Windows-based targets
	   it is a semicolon, and for almost all other targets it is a colon.

	   CPATH specifies a list of directories to be searched	as if speci-
	   fied	with -I, but after any paths given with	-I options on the com-
	   mand	line.  This environment	variable is used regardless of which
	   language is being preprocessed.

	   The remaining environment variables apply only when preprocessing
	   the particular language indicated.  Each specifies a	list of	direc-
	   tories to be	searched as if specified with -isystem,	but after any
	   paths given with -isystem options on	the command line.

	   In all these	variables, an empty element instructs the compiler to
	   search its current working directory.  Empty	elements can appear at
	   the beginning or end	of a path.  For	instance, if the value of
	   CPATH is ":/special/include", that has the same effect as
	   -I. -I/special/include.

	   If this variable is set, its	value specifies	how to output depen-
	   dencies for Make based on the non-system header files processed by
	   the compiler.  System header	files are ignored in the dependency

	   The value of	DEPENDENCIES_OUTPUT can	be just	a file name, in	which
	   case	the Make rules are written to that file, guessing the target
	   name	from the source	file name.  Or the value can have the form
	   file	target,	in which case the rules	are written to file file using
	   target as the target	name.

	   In other words, this	environment variable is	equivalent to combin-
	   ing the options -MM and -MF,	with an	optional -MT switch too.

	   This	variable is the	same as	DEPENDENCIES_OUTPUT (see above), ex-
	   cept	that system header files are not ignored, so it	implies	-M
	   rather than -MM.  However, the dependence on	the main input file is

       gpl(7), gfdl(7),	fsf-funding(7),	gcc(1),	as(1), ld(1), and the Info en-
       tries for cpp, gcc, and binutils.

       Copyright (c) 1987, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
       1998, 1999, 2000, 2001, 2002, 2003, 2004	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 1.1 or
       any later version published by the Free Software	Foundation.  A copy of
       the license is included in the man page gfdl(7).	 This manual contains
       no Invariant Sections.  The Front-Cover Texts are (a) (see below), and
       the Back-Cover Texts are	(b) (see below).

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

	    A GNU Manual

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

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

gcc-3.4.6			  2006-03-06				CPP(1)


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