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cpp(1)                             GNU Tools                            cpp(1)

NAME
       cpp - The GNU C-Compatible Compiler Preprocessor.

SYNOPSIS
       cpp    [-$] [-Apredicate[(value)]] [-C] [-Dname[=definition]] [-dD]
              [-dM] [-I directory] [-H] [-I-] [-imacros file] [-include file]
              [-idirafter dir] [-iprefix prefix] [-iwithprefix dir] [-lang-c]
              [-lang-c++] [-lang-objc] [-lang-objc++] [-lint] [-M [-MG]]
              [-MM [-MG]] [-MD file ] [-MMD file ] [-nostdinc] [-nostdinc++]
              [-P] [-pedantic] [-pedantic-errors] [-traditional] [-trigraphs]
              [-Uname] [-undef] [-Wtrigraphs] [-Wcomment] [-Wall]
              [-Wtraditional]
              [infile|-] [outfile|-]

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

       The C preprocessor provides four separate facilities that you can use
       as you see fit:

       o      Inclusion of header files.  These are files of declarations that
              can be substituted into your program.

       o      Macro expansion.  You can define macros, which are abbreviations
              for arbitrary fragments of C code, and then the C preprocessor
              will replace the macros with their definitions throughout the
              program.

       o      Conditional compilation.  Using special preprocessing
              directives, you can include or exclude parts of the program
              according to various conditions.

       o      Line control.  If you use a program to combine or rearrange
              source files into an intermediate file which is then compiled,
              you can use line control to inform the compiler of where each
              source line originally came from.

       C preprocessors vary in some details.  For a full explanation of the
       GNU C preprocessor, see the info file `cpp.info', or the manual The C
       Preprocessor.  Both of these are built from the same documentation
       source file, `cpp.texinfo'.  The GNU C preprocessor provides a superset
       of the features of ANSI Standard C.

       ANSI Standard C requires the rejection of many harmless constructs
       commonly used by today's C programs.  Such incompatibility would be
       inconvenient for users, so the GNU C preprocessor is configured to
       accept these constructs by default.  Strictly speaking, to get ANSI
       Standard C, you must use the options `-trigraphs', `-undef' and
       `-pedantic', but in practice the consequences of having strict ANSI
       Standard C make it undesirable to do this.

       Most often when you use the C preprocessor you will not have to invoke
       it explicitly: the C compiler will do so automatically.  However, the
       preprocessor is sometimes useful individually.

       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 outfile or both file names are omitted, the standard output and
       standard input are used for the omitted file names.

OPTIONS
       Here is a table of command options accepted by the C preprocessor.
       These options can also be given when compiling a C program; they are
       passed along automatically to the preprocessor when it is invoked by
       the compiler.

       -P     Inhibit generation of `#'-lines with line-number information 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
              `#'-lines.

       -C     Do not discard comments: pass them through to the output file.
              Comments appearing in arguments of a macro call will be copied
              to the output before the expansion of the macro call.

       -traditional
              Try to imitate the behavior of old-fashioned C, as opposed to
              ANSI C.

       -trigraphs
              Process ANSI standard trigraph sequences.  These are three-
              character sequences, all starting with `??', that are defined by
              ANSI C to stand for single characters.  For example, `??/'
              stands for `\', so `'??/n'' is a character constant for a
              newline.  Strictly speaking, the GNU C preprocessor does not
              support all programs in ANSI Standard C unless `-trigraphs' is
              used, but if you ever notice the difference it will be with
              relief.

              You don't want to know any more about trigraphs.

       -pedantic
              Issue warnings required by the ANSI C standard in certain cases
              such as when text other than a comment follows `#else' or
              `#endif'.

       -pedantic-errors
              Like `-pedantic', except that errors are produced rather than
              warnings.

       -Wtrigraphs
              Warn if any trigraphs are encountered (assuming they are
              enabled).

       -Wcomment

       -Wcomments
              Warn whenever a comment-start sequence `/*' appears in a
              comment.  (Both forms have the same effect).

       -Wall  Requests both `-Wtrigraphs' and `-Wcomment' (but not
              `-Wtraditional').

       -Wtraditional
              Warn about certain constructs that behave differently in
              traditional and ANSI C.

       -I directory
               Add the directory directory to the end of the list of
              directories to be searched for header files.  This can be used
              to override a system header file, substituting your own version,
              since these directories are searched before the system header
              file directories.  If you use more than one `-I' option, the
              directories are scanned in left-to-right order; the standard
              system directories come after.

       -I-    Any directories specified with `-I' options before the `-I-'
              option are searched only for the case of `#include file"'; they
              are not searched for `#include <file>'.

              If additional directories are specified with `-I' options after
              the `-I-', these directories are searched for all `#include'
              directives.

              In addition, the `-I-' option inhibits the use of the current
              directory as the first search directory for `#include file"'.
              Therefore, the current directory is searched only if it is
              requested explicitly with `-I.'.  Specifying both `-I-' and
              `-I.' allows you to control precisely which directories are
              searched before the current one and which are searched after.

       -nostdinc
              Do not search the standard system directories for header files.
              Only the directories you have specified with `-I' options (and
              the current directory, 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 libg++.)

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

       -D name=definition
               Predefine name as a macro, with definition definition.  There
              are no restrictions on the contents of definition, but 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 use more than one `-D' for the same name, the
              rightmost definition takes effect.

       -U name
               Do not predefine name.  If both `-U' and `-D' are specified for
              one name, the `-U' beats the `-D' and the name is not
              predefined.

       -undef Do not predefine any nonstandard macros.

       -A name(value)
              Assert (in the same way as the #assert directive) the predicate
              name with tokenlist value.  Remember to escape or quote the
              parentheses on shell command lines.

              You can use `-A-' to disable all predefined assertions; it also
              undefines all predefined macros.

       -dM    Instead of outputting the result of preprocessing, output 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 the values of any predefined macros.

       -dD    Like `-dM' 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.

       -M [-MG]
              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.  If there are many included files then
              the rule is split into several lines using `\'-newline.

              `-MG' says to treat missing header files as generated files and
              assume they live in the same directory as the source file.  It
              must be specified in addition to `-M'.

              This feature is used in automatic updating of makefiles.

       -MM [-MG]
              Like `-M' but mention only the files included with `#include
              "file"'.  System header files included with `#include <file>'
              are omitted.

       -MD file
              Like `-M' but the dependency information is written to `file'.
              This is in addition to compiling the file as specified--`-MD'
              does not inhibit ordinary compilation the way `-M' does.

              When invoking gcc, do not specify the `file' argument.  Gcc will
              create file names made by replacing `.c' with `.d' at the end of
              the input file names.

              In Mach, you can use the utility md to merge multiple files into
              a single dependency file suitable for using with the `make'
              command.

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

       -H     Print the name of each header file used, in addition to other
              normal activities.

       -imacros file
               Process file as input, discarding the resulting output, before
              processing the regular input file.  Because the output generated
              from file is discarded, the only effect of `-imacros file' is to
              make the macros defined in file available for use in the main
              input.  The preprocessor evaluates any `-D' and `-U' options on
              the command line before processing `-imacros file' .

       -include file
              Process file as input, and include all the resulting output,
              before processing the regular input file.

       -idirafter dir
               Add the directory dir to the second include path.  The
              directories on the second include path are searched when a
              header file is not found in any of the directories in the main
              include path (the one that `-I' adds to).

       -iprefix prefix
               Specify prefix as the prefix for subsequent `-iwithprefix'
              options.

       -iwithprefix dir
               Add a directory to the second include path.  The directory's
              name is made by concatenating prefix and dir, where prefix was
              specified previously with `-iprefix'.

       -lang-c

       -lang-c++

       -lang-objc

       -lang-objc++
              Specify the source language.  `-lang-c++' makes the preprocessor
              handle C++ comment syntax, and includes extra default include
              directories for C++, and `-lang-objc' enables the Objective C
              `#import' directive.  `-lang-c' explicitly turns off both of
              these extensions, and `-lang-objc++' enables both.

              These options are generated by the compiler driver gcc, but not
              passed from the `gcc' command line.

       -lint  Look for commands to the program checker lint embedded in
              comments, and emit them preceded by `#pragma lint'.  For
              example, the comment `/* NOTREACHED */' becomes `#pragma lint
              NOTREACHED'.

              This option is available only when you call cpp directly; gcc
              will not pass it from its command line.

       -$     Forbid the use of `$' in identifiers.  This was formerly
              required for strict conformance to the C Standard before the
              standard was corrected.

              This option is available only when you call cpp directly; gcc
              will not pass it from its command line.

SEE ALSO
       `Cpp' entry in info; The C Preprocessor, Richard M. Stallman.
       gcc(1); `Gcc' entry in info; Using and Porting GNU CC (for version
       2.0), Richard M. Stallman.

COPYING
       Copyright (c) 1991, 1992, 1993 Free Software Foundation, Inc.

       Permission is granted to make and distribute verbatim copies of this
       manual provided the copyright notice and this permission notice are
       preserved on all copies.

       Permission is granted to copy and distribute modified versions of this
       manual under the conditions for verbatim copying, provided that the
       entire resulting derived work is distributed under the terms of a
       permission notice identical to this one.

       Permission is granted to copy and distribute translations of this
       manual into another language, under the above conditions for modified
       versions, except that this permission notice may be included in
       translations approved by the Free Software Foundation instead of in the
       original English.

FreeBSD                         April 30, 1993                          cpp(1)

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | SEE ALSO | COPYING

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