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CPP(1)				      GNU				CPP(1)



NAME
       cpp - The C Preprocessor

SYNOPSIS
       cpp [-Dmacro[=defn]...] [-Umacro]
	   [-Idir...] [-iquotedir...]
	   [-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
       remainder.

DESCRIPTION
       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
       Objective-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
       (Pascal, 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
       conditional 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=c90, -std=c99 or -std=c11 options, depending on
       which version of the standard you want.	To get all the mandatory
       diagnostics, you must also use -pedantic.

       This manual describes the behavior of the ISO preprocessor.  To
       minimize 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.

OPTIONS
       The C preprocessor expects two file names as arguments, infile and
       outfile.	 The preprocessor reads infile together with any other files
       it specifies with #include.  All the output generated by the combined
       input 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
	   The contents of definition are tokenized and processed as if they
	   appeared during translation phase three in a #define directive.  In
	   particular, the definition will be truncated by embedded newline
	   characters.

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

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

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

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

       -undef
	   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
	   include directories.	 If the directory dir is a standard system
	   include 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 .  If dir begins with "=", then the
	   "=" will be replaced by the sysroot prefix; see --sysroot and
	   -isysroot.

       -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
	   interpretation of a second non-option argument, so you must use -o
	   to specify the output file.

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

       -Wcomment
       -Wcomments
	   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.)

       -Wtrigraphs
	   Most trigraphs in comments cannot affect the meaning of the
	   program.  However, a trigraph that would form an escaped 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
	   option is still enabled unless trigraphs are enabled.  To get
	   trigraph conversion without warnings, but get the other -Wall
	   warnings, use -trigraphs -Wall -Wno-trigraphs.

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

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

       -Wunused-macros
	   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
	   defined in include files are not warned about.

	   Note: If a macro is actually used, but only used in skipped
	   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 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
		   #endif

       -Wendif-labels
	   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.

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

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

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

       -pedantic
	   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.

       -pedantic-errors
	   Issue all the mandatory diagnostics, and make all mandatory
	   diagnostics 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 name of the source file with any suffix replaced
	   with object file suffix and with any leading directory parts
	   removed.  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.
	   Debug output will still be sent to the regular output stream as
	   normal.

	   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
	   dependencies 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
	   generation, -MG assumes missing header files are generated files
	   and adds them to the dependency list without raising an error.  The
	   dependency filename is taken directly from the "#include" directive
	   without prepending any path.	 -MG also suppresses preprocessed
	   output, 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

		   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, deletes any
	   directory components and any file suffix such as .c, and appends
	   the platform'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 takes the name of the input file, removes any
	   directory components and suffix, and applies a .d suffix.

	   If -MD is used in conjunction with -E, any -o switch is understood
	   to specify the dependency output file, 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.

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

       -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
	   recognize 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
	   selected both the language and the standards conformance level.
	   This option has been removed, because it conflicts with the -l
	   option.

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

	   standard may be one of:

	   "c90"
	   "c89"
	   "iso9899:1990"
	       The ISO C standard from 1990.  c90 is the customary shorthand
	       for this version of the standard.

	       The -ansi option is equivalent to -std=c90.

	   "iso9899:199409"
	       The 1990 C standard, as amended in 1994.

	   "iso9899:1999"
	   "c99"
	   "iso9899:199x"
	   "c9x"
	       The revised ISO C standard, published in December 1999.	Before
	       publication, this was known as C9X.

	   "iso9899:2011"
	   "c11"
	   "c1x"
	       The revised ISO C standard, published in December 2011.	Before
	       publication, this was known as C1X.

	   "gnu90"
	   "gnu89"
	       The 1990 C standard plus GNU extensions.	 This is the default.

	   "gnu99"
	   "gnu9x"
	       The 1999 C standard plus GNU extensions.

	   "gnu11"
	   "gnu1x"
	       The 2011 C standard plus GNU extensions.

	   "c++98"
	       The 1998 ISO C++ standard plus amendments.

	   "gnu++98"
	       The same as -std=c++98 plus GNU extensions.  This is the
	       default for C++ code.

       -I- Split the include path.  Any directories specified with -I options
	   before -I- are searched only for headers requested with
	   "#include "file""; they are not searched for "#include <file>".  If
	   additional 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"".

	   This option has been deprecated.

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

       -nostdinc++
	   Do not search for header files in the C++-specific standard
	   directories, 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
	   directory 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
	   allows you to acquire all the macros from a header without also
	   processing 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
	   specified with -I and the standard system directories have been
	   exhausted.  dir is treated as a system include directory.  If dir
	   begins with "=", then the "=" will be replaced by the sysroot
	   prefix; see --sysroot and -isysroot.

       -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.
	   -iwithprefixbefore puts it in the same place -I would; -iwithprefix
	   puts it where -idirafter would.

       -isysroot dir
	   This option is like the --sysroot option, but applies only to
	   header files (except for Darwin targets, where it applies to both
	   header files and libraries).	 See the --sysroot option for more
	   information.

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

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

	   If dir begins with "=", then the "=" will be replaced by the
	   sysroot prefix; see --sysroot and -isysroot.

       -iquote dir
	   Search dir only for header files requested with "#include "file"";
	   they are not searched for "#include <file>", before all directories
	   specified by -I and before the standard system directories.

	   If dir begins with "=", then the "=" will be replaced by the
	   sysroot prefix; see --sysroot and -isysroot.

       -fdirectives-only
	   When preprocessing, handle directives, but do not expand macros.

	   The option's behavior depends on the -E and -fpreprocessed options.

	   With -E, preprocessing is limited to the handling of directives
	   such as "#define", "#ifdef", and "#error".  Other preprocessor
	   operations, such as macro expansion and trigraph conversion are not
	   performed.  In addition, the -dD option is implicitly enabled.

	   With -fpreprocessed, predefinition of command line and most builtin
	   macros is disabled.	Macros such as "__LINE__", which are
	   contextually dependent, are handled normally.  This enables
	   compilation of files previously preprocessed with "-E
	   -fdirectives-only".

	   With both -E and -fpreprocessed, the rules for -fpreprocessed take
	   precedence.	This enables full preprocessing of files previously
	   preprocessed with "-E -fdirectives-only".

       -fdollars-in-identifiers
	   Accept $ in identifiers.

       -fextended-identifiers
	   Accept universal character names in identifiers.  This option is
	   experimental; in a future version of GCC, it will be enabled by
	   default for C99 and C++.

       -fno-canonical-system-headers
	   When preprocessing, do not shorten system header paths with
	   canonicalization.

       -fpreprocessed
	   Indicate to the preprocessor that the input file has already been
	   preprocessed.  This suppresses things like macro expansion,
	   trigraph conversion, escaped newline splicing, and processing of
	   most directives.  The preprocessor still recognizes and removes
	   comments, so that you can pass a file preprocessed with -C to the
	   compiler 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
	   extensions .i, .ii or .mi.  These are the extensions that GCC uses
	   for preprocessed files created by -save-temps.

       -ftabstop=width
	   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.

       -fdebug-cpp
	   This option is only useful for debugging GCC.  When used with -E,
	   dumps debugging information about location maps.  Every 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 be:

		   {"P":F</file/path>;"F":F</includer/path>;"L":<line_num>;"C":<col_num>;"S":<system_header_p>;"M":<map_address>;"E":<macro_expansion_p>,"loc":<location>}

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

       -ftrack-macro-expansion[=level]
	   Track locations of tokens across macro expansions. This allows the
	   compiler to emit diagnostic about the current macro expansion stack
	   when a compilation error occurs in a macro expansion. Using this
	   option makes the preprocessor and the compiler consume more memory.
	   The level parameter can be used to choose the level of precision of
	   token location tracking thus decreasing the memory consumption if
	   necessary. Value 0 of level de-activates this option just as if no
	   -ftrack-macro-expansion was present on the command line. Value 1
	   tracks tokens locations in a degraded mode for the sake of minimal
	   memory overhead. In this mode all tokens resulting from the
	   expansion of an argument of a function-like macro have the same
	   location. Value 2 tracks tokens locations completely. This value is
	   the most memory hungry.  When this option is given no argument, the
	   default parameter value is 2.

	   Note that -ftrack-macro-expansion=2 is activated by default.

       -fexec-charset=charset
	   Set the execution character set, used for string and character
	   constants.  The default is UTF-8.  charset can be any encoding
	   supported by the system's "iconv" library routine.

       -fwide-exec-charset=charset
	   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 -fexec-charset,
	   charset can be any encoding supported by the system's "iconv"
	   library routine; however, you will have problems with encodings
	   that do not fit exactly in "wchar_t".

       -finput-charset=charset
	   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 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 command line option takes precedence if there's a
	   conflict.  charset can be any encoding supported by the system's
	   "iconv" library routine.

       -fworking-directory
	   Enable generation of linemarkers in the preprocessor output that
	   will let the compiler know the current working directory at the
	   time of preprocessing.  When this option is enabled, the
	   preprocessor will emit, after the initial linemarker, a second
	   linemarker with the current working directory followed by two
	   slashes.  GCC will use this directory, when it's present in the
	   preprocessed input, as the directory emitted as the current working
	   directory in some debugging information formats.  This option is
	   implicitly enabled if debugging information is enabled, but this
	   can be inhibited with the negated form -fno-working-directory.  If
	   the -P flag is present in the command line, this option has no
	   effect, since no "#line" directives are emitted whatsoever.

       -fno-show-column
	   Do not print column numbers in diagnostics.	This may be necessary
	   if diagnostics are being scanned by a program that does not
	   understand 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
	   characters.

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

       -dCHARS
	   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
	       directives for all the macros defined during the execution of
	       the preprocessor, including predefined macros.  This gives you
	       a way of finding out what is predefined in your version of the
	       preprocessor.  Assuming you have no file foo.h, the command

		       touch foo.h; cpp -dM foo.h

	       will show all the predefined macros.

	       If you use -dM without the -E option, -dM is interpreted as a
	       synonym for -fdump-rtl-mach.

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

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

	   I   Output #include directives in addition to the result of
	       preprocessing.

	   U   Like D except that only macros that are expanded, or whose
	       definedness is tested in preprocessor directives, are output;
	       the output is delayed until the use or test of the macro; and
	       #undef directives are also output for macros tested but
	       undefined at the time.

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

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

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

       -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.

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

       -trigraphs
	   Process trigraph sequences.

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

       --help
       --target-help
	   Print text describing all the command line options instead of
	   preprocessing 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
	   normal activities.  Each name is indented to show how deep in the
	   #include 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 ...! .

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

ENVIRONMENT
       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.

       CPATH
       C_INCLUDE_PATH
       CPLUS_INCLUDE_PATH
       OBJC_INCLUDE_PATH
	   Each variable's value is a list of directories separated by a
	   special 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
	   specified with -I, but after any paths given with -I options on the
	   command 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
	   directories 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.

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

	   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
	   combining the options -MM and -MF, with an optional -MT switch too.

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

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

COPYRIGHT
       Copyright (c) 1987-2015 Free Software Foundation, Inc.

       Permission is granted to copy, distribute and/or modify this document
       under the terms of the GNU Free Documentation License, Version 1.3 or
       any later version published by the Free Software Foundation.  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-4.8.5			  2015-06-23				CPP(1)