cccp, cpp - The GNU C-Compatible Compiler Preprocessor.
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]
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
C preprocessors vary in some details. For a full explanation
of the GNU C preprocessor, see the info file `cpp.in-
fo', or the manual The C Preprocessor. Both of these are
built from the same documentation source file, `cpp.texin-
fo'. 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 `-pedan-
tic', 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
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 together
with any other files it specifies with `#include'. All
the output generated by the combined input files is written
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.
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.
Try to imitate the behavior of old-fashioned C, as
opposed to ANSI C.
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.
Issue warnings required by the ANSI C standard in
certain cases such as when text other than a comment
follows `#else' or `#endif'.
Like `-pedantic', except that errors are produced
rather than warnings.
Warn if any trigraphs are encountered (assuming
they are enabled).
Warn whenever a comment-start sequence `/*' appears
in a comment. (Both forms have the same effect).
-Wall Requests both `-Wtrigraphs' and `-Wcomment' (but
Warn about certain constructs that behave differently
in traditional and ANSI C.
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 `#in-
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
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.
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
Predefine name as a macro, with definition `1'.
Predefine name as a macro, with definition defini-
tion. 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.
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.
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
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
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.
Like `-M' but mention only the files included with
`#include "file"'. System header files included
with `#include <file>' are omitted.
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.
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.
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' .
Process file as input, and include all the resulting
output, before processing the regular input
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).
Specify prefix as the prefix for subsequent
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
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.
`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.
Copyright (c) 1991, 1992, 1993 Free Software Foundation,
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.
GNU Tools 30apr1993 cpp(1)
[ Back ]