NAME
cccp, cpp - The GNU C­Compatible 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 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:
·
Inclusion of header files. These are files of declarations that can be sub­
stituted into your program.
·
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 preprocessing directives, you
can include or exclude parts of the program according to various condi­
tions.
·
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 super­
set of the features of ANSI Standard C.
ANSI Standard C requires the rejection of many harmless constructs commonly used by to­
day's C programs. Such incompatibility would be inconvenient for users, so the GNU C pre­
processor 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 prac­
tice 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 individual­
ly.
When you call the preprocessor individually, either name (
cpp or cccp) will do­­they are com­
pletely synonymous.
The C preprocessor expects two file names as arguments,
infile and outfile. The prepro­
cessor 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 preproces­
sor when it is invoked by the compiler.


-P Inhibit generation of ` # '­lines with line­number information in the output
from the preprocessor. This might be useful when running the prepro­
cessor 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. Com­
ments appearing in arguments of a macro call will be copied to the out­
put before the expansion of the macro call.
-traditional
Try to imitate the behavior of old­fashioned C, as opposed to ANSI C.
-trigraphs
Process ANSI standard trigraph sequences. These are three­character
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 prepro­
cessor 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 warn­
ings.
-Wtrigraphs
Warn if any trigraphs are encountered (assuming they are enabled).
-Wcomment
-Wcomments
Warn whenever a comment­start 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 left­to­right 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 di­
rectory is searched only if it is requested explicitly with `
-I. '. Specify­
ing both `
-I- ' and ` -I. ' allows you to control precisely which directo­
ries 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 direc­
tory, 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 re­
strictions on the contents of
definition, but if you are invoking the pre­
processor from a shell or shell­like 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; as­
suming 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 pre­
processor 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 `
\ '­new­
line.
`
-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 ordi­
nary 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 ac­
tivities.


-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 processing
`
-imacros file ' .
-include
file Process file as input, and include all the resulting output, before pro­
cessing 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 pre­
viously with `
-iprefix '.
-lang­c
-lang­c++
-lang­objc
-lang­objc++
Specify the source language. ` -lang­c++ ' makes the preprocessor
handle C++ comment syntax, and includes extra default include directo­
ries for C++, and `
-lang­objc ' enables the Objective C ` #import ' di­
rective. `
-lang­c ' explicitly turns off both of these extensions, and
`
-lang­objc++ ' 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 com­
ments, 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. Stall­
man.
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 condi­
tions 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.