.\" Copyright (c) 1991, 1992, 1993 Free Software Foundation \-*-Text-*-
.\" See section COPYING for conditions for redistribution
.TH cpp 1 "30apr1993" "GNU Tools" "GNU Tools"
cccp, cpp \- The GNU C-Compatible Compiler Preprocessor.
.RB "[\|" "\-imacros\ "\c
.RB "[\|" "\-include\ "\c
.RB "[\|" "\-idirafter\ "\c
.RB "[\|" "\-iprefix\ "\c
.RB "[\|" "\-iwithprefix\ "\c
.RB "[\|" \-lang\-c "\|]"
.RB "[\|" \-lang\-c++ "\|]"
.RB "[\|" \-lang\-objc "\|]"
.RB "[\|" \-lang\-objc++ "\|]"
.RB "[\|" \-nostdinc "\|]"
.RB "[\|" \-nostdinc++ "\|]"
.RB "[\|" \-pedantic "\|]"
.RB "[\|" \-pedantic\-errors "\|]"
.RB "[\|" \-traditional "\|]"
.RB "[\|" \-trigraphs "\|]"
.RB "[\|" \-Wtrigraphs "\|]"
.RB "[\|" \-Wcomment "\|]"
.RB "[\|" \-Wtraditional "\|]"
The C preprocessor is a \c
\& 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 \c
which are brief abbreviations for longer constructs.
The C preprocessor provides four separate facilities that you can use as
Inclusion of header files. These are files of declarations that can be
substituted into your program.
Macro expansion. You can define \c
\&, 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 preprocessor commands, you
can include or exclude parts of the program according to various
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
\&. Both of these are built from the same documentation source file, `\|\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
practice the consequences of having strict ANSI Standard C make it
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
\&) will do\(em\&they are completely synonymous.
The C preprocessor expects two file names as arguments, \c
\&. The preprocessor reads \c
\& together with any other
files it specifies with `\|\c
\&\|'. All the output generated by the
combined input files is written in \c
means to read from standard input and as \c
standard output. Also, if \c
\& 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
Inhibit generation of `\|\c
\&\|'-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
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 `\|\c
\&\|', that are defined by ANSI C to
stand for single characters. For example, `\|\c
\&\|' is a character constant for a newline.
Strictly speaking, the GNU C preprocessor does not support all
programs in ANSI Standard C unless `\|\c
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 `\|\c
\&\|', except that errors are produced rather than
Warn if any trigraphs are encountered (assuming they are enabled).
Warn whenever a comment-start sequence `\|\c
\&\|' appears in a comment.
(Both forms have the same effect).
Warn about certain constructs that behave differently in traditional and
\& 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 `\|\c
the directories are scanned in left-to-right order; the standard
system directories come after.
Any directories specified with `\|\c
\&\|' options before the `\|\c
option are searched only for the case of `\|\c
they are not searched for `\|\c
If additional directories are specified with `\|\c
\&\|', these directories are searched for all `\|\c
\&\|' option inhibits the use of the current
directory as the first search directory for `\|\c
Therefore, the current directory is searched only if it is requested
\&\|'. Specifying both `\|\c
allows you to control precisely which directories are searched before
the current one and which are searched after.
Do not search the standard system directories for header files.
Only the directories you have specified with `\|\c
(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 building libg++.)
\& as a macro, with definition `\|\c
.BI "\-D " "name" = definition
\& as a macro, with definition \c
There are no restrictions on the contents of \c
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
\&, the rightmost definition takes effect.
specified for one name, the `\|\c
Do not predefine any nonstandard macros.
.BI "\-A " "name(" value )
Assert (in the same way as the \c
\&. Remember to escape or quote the parentheses on
\&\|' to disable all predefined assertions; it also
undefines all predefined macros.
Instead of outputting the result of preprocessing, output a list of
\&\|' commands 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 `\|\c
touch\ foo.h;\ cpp\ \-dM\ foo.h
will show the values of any predefined macros.
\&\|' except in two respects: it does \c
predefined macros, and it outputs \c
commands and the result of preprocessing. Both kinds of output go to
the standard output file.
Instead of outputting the result of preprocessing, output a rule
\& describing the dependencies of the main
source file. The preprocessor outputs one \c
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 `\|\c
This feature is used in automatic updating of makefiles.
\&\|' but mention only the files included with `\|\c
\&\|'. System header files included with `\|\c
\&\|' but the dependency information is written to files with
names made by replacing `\|\c
input file names. This is in addition to compiling the file as
\&\|' does not inhibit ordinary compilation the way
In Mach, you can use the utility \c
into a single dependency file suitable for using with the `\|\c
\&\|' except mention only user header files, not system
Print the name of each header file used, in addition to other normal
.BI "\-imacros " "file"\c
\& as input, discarding the resulting output, before
processing the regular input file. Because the output generated from
\& is discarded, the only effect of `\|\c
make the macros defined in \c
\& available for use in the main
input. The preprocessor evaluates any `\|\c
on the command line before processing `\|\c
as input, and include all the resulting output,
before processing the regular input file.
.BI "-idirafter " "dir"\c
\& 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
.BI "-iprefix " "prefix"\c
\& as the prefix for subsequent `\|\c
.BI "-iwithprefix " "dir"\c
Add a directory to the second include path. The directory's name is
was specified previously with `\|\c
Specify the source language. `\|\c
\&\|' makes the preprocessor
handle C++ comment syntax, and includes extra default include
directories for C++, and `\|\c
\&\|' enables the Objective C
\&\|' explicitly turns off both of
these extensions, and `\|\c
These options are generated by the compiler driver \c
Look for commands to the program checker \c
comments, and emit them preceded by `\|\c
This option is available only when you call \c
\& will not pass it from its command line.
\&\|' in identifiers. This is required for ANSI
\& automatically supplies this option to the
preprocessor if you specify `\|\c
\&\|' option itself\(em\&to use it without the other
\&\|', you must call the preprocessor directly.
Using and Porting GNU CC (for version 2.0)\c
Copyright (c) 1991, 1992, 1993 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of
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are preserved on all copies.
Permission is granted to copy and distribute modified versions of this
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Permission is granted to copy and distribute translations of this
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