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=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.
 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 .
 -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.
 -Wimport
 Warn the first time #import is used.
 -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 basename of the source file with any suffix
 replaced 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.
 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.
 -dependency-file
 Like -MF. (APPLE ONLY)
 -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, including any
 path, deletes 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 take the basename of the input file 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 objective-c++
 -x assembler-with-cpp
 Specify the source language: C, C++, Objective-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, .mm, 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:
 "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.
 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.
 -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 Apple's version of GCC, where it applies
 to both header files and libraries and effectively replaces the
 --sysroot option. 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.
 -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.
 -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.
 -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.
 -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, 1989, 1991, 1992, 1993, 1994, 1995, 1996, 1997,
 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005 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-4.2.1 2012年06月15日 cpp(1)