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    The following form allows you to view linux man pages.

    Command:

    cpp

    
    
    

    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=c89 or -std=c99 options, depending on which
           version of the standard you want.  To get all the mandatory
           diagnostics, you must also use -pedantic.
    
    
           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
               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
    
               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
               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.
    
               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:
    
               "iso9899:1990"
               "c89"
                   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.
    
               "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.
    
               "gnu89"
                   The 1990 C standard plus GNU extensions.  This is the default.
    
               "gnu99"
               "gnu9x"
                   The 1999 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.
               (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.  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
    
           -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++.
    
           -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.
    
           -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.
    
               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.
    
                   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
    
           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

    
           (a) The FSF's Front-Cover Text is:
    
                A GNU Manual
    
           (b) The FSF's Back-Cover Text is:
    
                You have freedom to copy and modify this GNU Manual, like GNU
                software.  Copies published by the Free Software Foundation raise
                funds for GNU development.
    
    
    

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

    
    
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