cpp(1)                      GNU Tools                      cpp(1)


NAME
       cccp, cpp - The GNU C-Compatible Compiler Preprocessor.



SYNOPSIS
       cccp   [-$] [-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 auto-
       matically  by the C compiler to transform your program be-
       fore 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:

       -      Inclusion of header files.  These are files of dec-
              larations that can be substituted  into  your  pro-
              gram.

       -      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.

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

       -      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 orig-
              inally came from.

       C preprocessors vary in some details.  For a full explana-
       tion  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  in-



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       compatibility  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.

       When  you  call the preprocessor individually, either name
       (cpp or cccp) will do--they are completely synonymous.

       The C preprocessor expects two file  names  as  arguments,
       infile and outfile.  The preprocessor reads infile togeth-
       er with any other files it specifies with `#include'.  All
       the  output generated by the combined input files is writ-
       ten 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  pre-
       processor.  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  sin-
              gle characters.  For example, `??/' stands for `\',
              so `'??/n'' is a character constant for a  newline.



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              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 com-
              ment 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  differ-
              ently 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 directo-
              ries are searched before the system header file di-
              rectories.  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  `#in-
              clude <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



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              for  `#include  file"'.  Therefore, the current di-
              rectory is searched only if it is requested explic-
              itly  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 speci-
              fied 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 defini-
              tion.  There are no restrictions on the contents of
              definition, but if you are invoking the  preproces-
              sor from a shell or shell-like program you may need
              to use the shell's quoting syntax to protect  char-
              acters  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 ef-
              fect.

       -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 asser-
              tions; 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  prepro-
              cessor,  including  predefined  macros.  This gives
              you a way of finding out what is predefined in your



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              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  in-
              clude  the  predefined  macros, and it outputs both
              the `#define' directives and the result of  prepro-
              cessing.   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 de-
              pendencies of the main source file.  The preproces-
              sor  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 gener-
              ated files and assume they live in the same  direc-
              tory  as  the source file.  It must be specified in
              addition to `-M'.

              This feature is used in automatic updating of make-
              files.

       -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'  argu-
              ment.  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 multi-
              ple 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.



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       -H     Print the name of each header file used,  in  addi-
              tion 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 discard-
              ed, 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 pro-
              cessing `-imacros file' .

       -include file
              Process file as input, and include all the  result-
              ing  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 in-
              cludes 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 em-
              bedded in  comments,  and  emit  them  preceded  by



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              `#pragma  lint'.   For  example,  the  comment  `/*
              NOTREACHED */' becomes `#pragma lint NOTREACHED'.

              This option is available only when you call cpp di-
              rectly; 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 direct-
              ly; gcc will not pass it from its command line.

SEE ALSO
       `Cpp' entry in info; The C Preprocessor, Richard M. Stall-
       man.
       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 ver-
       sions 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 con-
       ditions for modified versions, except that this permission
       notice may be included in  translations  approved  by  the
       Free  Software  Foundation  instead of in the original En-
       glish.



















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