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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 au-
tomatically by the C compiler to transform your program be-
fore actual compilation. It is called a macro processor be-
cause it allows you to define macros, which are brief abbre-
viations 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 declara-
tions that can be substituted into your program.
o Macro expansion. You can define macros, which are ab-
breviations 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 rear-
range 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 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 con-
structs commonly used by today's C programs. Such incompa-
tibility would be inconvenient for users, so the GNU C
preprocessor is configured to accept these constructs by de-
fault. 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 automati-
cally. However, the preprocessor is sometimes useful indi-
vidually.
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, in-
file 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 prepro-
cessor. These options can also be given when compiling a C
program; they are passed along automatically to the prepro-
cessor when it is invoked by the compiler.
-P Inhibit generation of `#'-lines with line-number infor-
mation 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 out-
put 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 op-
posed 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 cer-
tain cases such as when text other than a comment fol-
lows `#else' or `#endif'.
-pedantic-errors
Like `-pedantic', except that errors are produced rath-
er 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 `#in-
clude file"'; they are not searched for `#include
<file>'.
If additional directories are specified with `-I' op-
tions 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 ap-
propriate) 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 build-
ing 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 defini-
tion, 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 es-
cape 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, out-
put a list of `#define' directives for all the macros
defined during the execution of the preprocessor, in-
cluding 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 `#de-
fine' 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, out-
put a rule suitable for make describing the dependen-
cies 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 out-
put, 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 direc-
tories in the main include path (the one that `-I' adds
to).
-iprefix prefix
Specify prefix as the prefix for subsequent `-iwith-
prefix' 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 `-ipre-
fix'.
-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 exten-
sions, 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 direct-
ly; gcc will not pass it from its command line.
-$ Forbid the use of `$' in identifiers. This was former-
ly 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. 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 per-
mission notice are preserved on all copies.
Permission is granted to copy and distribute modified ver-
sions of this manual under the conditions for verbatim copy-
ing, provided that the entire resulting derived work is dis-
tributed 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 condi-
tions for modified versions, except that this permission no-
tice may be included in translations approved by the Free
Software Foundation instead of in the original English.
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