.\" Copyright (c) 1991, 1992, 1993 Free Software Foundation       \-*-Text-*-
.\" See section COPYING for conditions for redistribution
.TH cpp 1 "30apr1993" "GNU Tools" "GNU Tools"
.SH NAME
cccp, cpp \- The GNU C-Compatible Compiler Preprocessor.
.SH SYNOPSIS
.hy 0
.na
.TP
.B cccp
.RB "[\|" \-$ "\|]"
.RB "[\|" \-A \c
.I predicate\c
.RB [ (\c
.I value\c
.BR ) ]\|]
.RB "[\|" \-C "\|]" 
.RB "[\|" \-D \c
.I name\c
.RB [ =\c
.I definition\c
\&]\|]
.RB "[\|" \-dD "\|]"
.RB "[\|" \-dM "\|]"
.RB "[\|" "\-I\ "\c
.I directory\c
\&\|]
.RB "[\|" \-H "\|]"
.RB "[\|" \-I\- "\|]" 
.RB "[\|" "\-imacros\ "\c
.I file\c
\&\|]
.RB "[\|" "\-include\ "\c
.I file\c
\&\|]
.RB "[\|" "\-idirafter\ "\c
.I dir\c
\&\|]
.RB "[\|" "\-iprefix\ "\c
.I prefix\c
\&\|]
.RB "[\|" "\-iwithprefix\ "\c
.I dir\c
\&\|]
.RB "[\|" \-lang\-c "\|]"
.RB "[\|" \-lang\-c++ "\|]"
.RB "[\|" \-lang\-objc "\|]"
.RB "[\|" \-lang\-objc++ "\|]"
.RB "[\|" \-lint "\|]"
.RB "[\|" \-M\  [ \-MG "\|]]"
.RB "[\|" \-MM\  [ \-MG "\|]]"
.RB "[\|" \-MD\  \c
.I file\ \c
\&\|]
.RB "[\|" \-MMD\  \c
.I file\ \c
\&\|]
.RB "[\|" \-nostdinc "\|]" 
.RB "[\|" \-nostdinc++ "\|]" 
.RB "[\|" \-P "\|]" 
.RB "[\|" \-pedantic "\|]"
.RB "[\|" \-pedantic\-errors "\|]"
.RB "[\|" \-traditional "\|]" 
.RB "[\|" \-trigraphs "\|]" 
.RB "[\|" \-U \c
.I name\c
\&\|]
.RB "[\|" \-undef "\|]"
.RB "[\|" \-Wtrigraphs "\|]"
.RB "[\|" \-Wcomment "\|]"
.RB "[\|" \-Wall "\|]"
.RB "[\|" \-Wtraditional "\|]"
.br
.RB "[\|" \c
.I infile\c
.RB | \- "\|]" 
.RB "[\|" \c
.I outfile\c
.RB | \- "\|]"  
.ad b
.hy 1
.SH DESCRIPTION
The C preprocessor is a \c
.I macro processor\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
.I macros\c
\&,
which are brief abbreviations for longer constructs.

The C preprocessor provides four separate facilities that you can use as
you see fit:
.TP
\(bu
Inclusion of header files.  These are files of declarations that can be
substituted into your program.
.TP
\(bu
Macro expansion.  You can define \c
.I macros\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.
.TP
\(bu
Conditional compilation.  Using special preprocessing directives, you
can include or exclude parts of the program according to various
conditions.
.TP
\(bu
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.
.PP
C preprocessors vary in some details.  For a full explanation of the
GNU C preprocessor, see the
.B info
file `\|\c
.B cpp.info\c
\&\|', or the manual
.I The C Preprocessor\c
\&.  Both of these are built from the same documentation source file, `\|\c
.B cpp.texinfo\c
\&\|'.  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 `\|\c
.B \-trigraphs\c
\&\|', `\|\c
.B \-undef\c
\&\|' and `\|\c
.B \-pedantic\c
\&\|', 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
(\c
.B cpp\c
\& or \c
.B cccp\c
\&) will do\(em\&they are completely synonymous.

The C preprocessor expects two file names as arguments, \c
.I infile\c
\& and
\c
.I outfile\c
\&.  The preprocessor reads \c
.I infile\c
\& together with any other
files it specifies with `\|\c
.B #include\c
\&\|'.  All the output generated by the
combined input files is written in \c
.I outfile\c
\&.

Either \c
.I infile\c
\& or \c
.I outfile\c
\& may be `\|\c
.B \-\c
\&\|', which as \c
.I infile\c
\&
means to read from standard input and as \c
.I outfile\c
\& means to write to
standard output.  Also, if \c
.I outfile\c
\& or both file names are omitted,
the standard output and standard input are used for the omitted file names.
.SH 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 preprocessor when it is invoked by
the compiler. 
.TP
.B \-P
Inhibit generation of `\|\c
.B #\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
`\|\c
.B #\c
\&\|'-lines.
.TP
.B \-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.
.TP
.B \-traditional
Try to imitate the behavior of old-fashioned C, as opposed to ANSI C.
.TP
.B \-trigraphs
Process ANSI standard trigraph sequences.  These are three-character
sequences, all starting with `\|\c
.B ??\c
\&\|', that are defined by ANSI C to
stand for single characters.  For example, `\|\c
.B ??/\c
\&\|' stands for
`\|\c
.BR "\e" "\|',"
so `\|\c
.B '??/n'\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
.B \-trigraphs\c
\&\|' is used, but if
you ever notice the difference it will be with relief.

You don't want to know any more about trigraphs.
.TP
.B \-pedantic
Issue warnings required by the ANSI C standard in certain cases such
as when text other than a comment follows `\|\c
.B #else\c
\&\|' or `\|\c
.B #endif\c
\&\|'.
.TP
.B \-pedantic\-errors
Like `\|\c
.B \-pedantic\c
\&\|', except that errors are produced rather than
warnings.
.TP
.B \-Wtrigraphs
Warn if any trigraphs are encountered (assuming they are enabled).
.TP
.B \-Wcomment
.TP
.B \-Wcomments
Warn whenever a comment-start sequence `\|\c
.B /*\c
\&\|' appears in a comment.
(Both forms have the same effect).
.TP
.B \-Wall
Requests both `\|\c
.B \-Wtrigraphs\c
\&\|' and `\|\c
.B \-Wcomment\c
\&\|' (but not
`\|\c
.B \-Wtraditional\c
\&\|'). 
.TP
.B \-Wtraditional
Warn about certain constructs that behave differently in traditional and
ANSI C.
.TP
.BI "\-I " directory\c
\&
Add the directory \c
.I directory\c
\& 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
.B \-I\c
\&\|' option,
the directories are scanned in left-to-right order; the standard
system directories come after.
.TP
.B \-I\-
Any directories specified with `\|\c
.B \-I\c
\&\|' options before the `\|\c
.B \-I\-\c
\&\|'
option are searched only for the case of `\|\c
.B #include "\c
.I file\c
\&"\c
\&\|';
they are not searched for `\|\c
.B #include <\c
.I file\c
\&>\c
\&\|'.

If additional directories are specified with `\|\c
.B \-I\c
\&\|' options after
the `\|\c
.B \-I\-\c
\&\|', these directories are searched for all `\|\c
.B #include\c
\&\|'
directives.

In addition, the `\|\c
.B \-I\-\c
\&\|' option inhibits the use of the current
directory as the first search directory for `\|\c
.B #include "\c
.I file\c
\&"\c
\&\|'.
Therefore, the current directory is searched only if it is requested
explicitly with `\|\c
.B \-I.\c
\&\|'.  Specifying both `\|\c
.B \-I\-\c
\&\|' and `\|\c
.B \-I.\c
\&\|'
allows you to control precisely which directories are searched before
the current one and which are searched after.
.TP
.B \-nostdinc
Do not search the standard system directories for header files.
Only the directories you have specified with `\|\c
.B \-I\c
\&\|' options
(and the current directory, if appropriate) are searched.
.TP
.B \-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++.)
.TP
.BI "\-D " "name"\c
\&
Predefine \c
.I name\c
\& as a macro, with definition `\|\c
.B 1\c
\&\|'.
.TP
.BI "\-D " "name" = definition
\&
Predefine \c
.I name\c
\& as a macro, with definition \c
.I definition\c
\&.
There are no restrictions on the contents of \c
.I definition\c
\&, 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 `\|\c
.B \-D\c
\&\|' for the same
.I name\c
\&, the rightmost definition takes effect.
.TP
.BI "\-U " "name"\c
\&
Do not predefine \c
.I name\c
\&.  If both `\|\c
.B \-U\c
\&\|' and `\|\c
.B \-D\c
\&\|' are
specified for one name, the `\|\c
.B \-U\c
\&\|' beats the `\|\c
.B \-D\c
\&\|' and the name
is not predefined.
.TP
.B \-undef
Do not predefine any nonstandard macros.
.TP
.BI "\-A " "name(" value )
Assert (in the same way as the \c
.B #assert\c
\& directive)
the predicate \c
.I name\c
\& with tokenlist \c
.I value\c
\&.  Remember to escape or quote the parentheses on
shell command lines.

You can use `\|\c
.B \-A-\c
\&\|' to disable all predefined assertions; it also
undefines all predefined macros.
.TP
.B \-dM
Instead of outputting the result of preprocessing, output a list of
`\|\c
.B #define\c
\&\|' 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 `\|\c
.B foo.h\c
\&\|', the command
.sp
.br
touch\ foo.h;\ cpp\ \-dM\ foo.h
.br
.sp
will show the values of any predefined macros.
.TP
.B \-dD
Like `\|\c
.B \-dM\c
\&\|' except in two respects: it does \c
.I not\c
\& include the
predefined macros, and it outputs \c
.I both\c
\& the `\|\c
.B #define\c
\&\|'
directives and the result of preprocessing.  Both kinds of output go to
the standard output file.
.PP
.TP
.BR \-M\  [ \-MG ]
Instead of outputting the result of preprocessing, output a rule
suitable for \c
.B make\c
\& describing the dependencies of the main
source file.  The preprocessor outputs one \c
.B make\c
\& 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 `\|\c
.B \\\\\c
\&\|'-newline.

`\|\c
.B \-MG\c
\&\|' says to treat missing header files as generated files and assume \c
they live in the same directory as the source file.  It must be specified \c
in addition to `\|\c
.B \-M\c
\&\|'.

This feature is used in automatic updating of makefiles.
.TP
.BR \-MM\  [ \-MG ]
Like `\|\c
.B \-M\c
\&\|' but mention only the files included with `\|\c
.B #include
"\c
.I file\c
\&"\c
\&\|'.  System header files included with `\|\c
.B #include
<\c
.I file\c
\&>\c
\&\|' are omitted.
.TP
.BI \-MD\  file
Like `\|\c
.B \-M\c
\&\|' but the dependency information is written to `\|\c
.I file\c
\&\|'.  This is in addition to compiling the file as
specified\(em\&`\|\c
.B \-MD\c
\&\|' does not inhibit ordinary compilation the way
`\|\c
.B \-M\c
\&\|' does.

When invoking gcc, do not specify the `\|\c
.I file\c
\&\|' argument.  Gcc will create file names made by replacing `\|\c
.B .c\c
\&\|' with `\|\c
.B .d\c
\&\|' at the end of the input file names.

In Mach, you can use the utility \c
.B md\c
\& to merge multiple files
into a single dependency file suitable for using with the `\|\c
.B make\c
\&\|'
command.
.TP
.BI \-MMD\  file
Like `\|\c
.B \-MD\c
\&\|' except mention only user header files, not system
header files.
.TP
.B \-H
Print the name of each header file used, in addition to other normal
activities.
.TP
.BI "\-imacros " "file"\c
\&
Process \c
.I file\c
\& as input, discarding the resulting output, before
processing the regular input file.  Because the output generated from
\c
.I file\c
\& is discarded, the only effect of `\|\c
.B \-imacros \c
.I file\c
\&\c
\&\|' is to
make the macros defined in \c
.I file\c
\& available for use in the main
input.  The preprocessor evaluates any `\|\c
.B \-D\c
\&\|' and `\|\c
.B \-U\c
\&\|' options
on the command line before processing `\|\c
.B \-imacros \c
.I file\c
\&\|' \c
\&.
.TP
.BI "\-include " "file"
Process 
.I file
as input, and include all the resulting output,
before processing the regular input file.  
.TP
.BI "-idirafter " "dir"\c
\&
Add the directory \c
.I 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
`\|\c
.B \-I\c
\&\|' adds to).
.TP
.BI "-iprefix " "prefix"\c
\&
Specify \c
.I prefix\c
\& as the prefix for subsequent `\|\c
.B \-iwithprefix\c
\&\|'
options.
.TP
.BI "-iwithprefix " "dir"\c
\&
Add a directory to the second include path.  The directory's name is
made by concatenating \c
.I prefix\c
\& and \c
.I dir\c
\&, where \c
.I prefix\c
\&
was specified previously with `\|\c
.B \-iprefix\c
\&\|'.
.TP
.B \-lang-c
.TP
.B \-lang-c++
.TP
.B \-lang-objc
.TP
.B \-lang-objc++
Specify the source language.  `\|\c
.B \-lang-c++\c
\&\|' makes the preprocessor
handle C++ comment syntax, and includes extra default include
directories for C++, and `\|\c
.B \-lang-objc\c
\&\|' enables the Objective C
`\|\c
.B #import\c
\&\|' directive.  `\|\c
.B \-lang-c\c
\&\|' explicitly turns off both of
these extensions, and `\|\c
.B \-lang-objc++\c
\&\|' enables both.

These options are generated by the compiler driver \c
.B gcc\c
\&, but not
passed from the `\|\c
.B gcc\c
\&\|' command line.
.TP
.B \-lint
Look for commands to the program checker \c
.B lint\c
\& embedded in
comments, and emit them preceded by `\|\c
.B #pragma lint\c
\&\|'.  For example,
the comment `\|\c
.B /* NOTREACHED */\c
\&\|' becomes `\|\c
.B #pragma lint
NOTREACHED\c
\&\|'.

This option is available only when you call \c
.B cpp\c
\& directly;
\c
.B gcc\c
\& will not pass it from its command line.
.TP
.B \-$
Forbid the use of `\|\c
.B $\c
\&\|' in identifiers.  This was formerly required for strict conformance
to the C Standard before the standard was corrected.  \c

This option is available only when you call \c
.B cpp\c
\& directly;
.B gcc\c
\& will not pass it from its command line.
.SH "SEE ALSO"
.RB "`\|" Cpp "\|'"
entry in
.B info\c
\&;
.I The C Preprocessor\c
, Richard M. Stallman.
.br
.BR gcc "(" 1 ");"
.RB "`\|" Gcc "\|'"
entry in 
.B info\c
\&;
.I 
Using and Porting GNU CC (for version 2.0)\c
, Richard M. Stallman.
.SH COPYING
Copyright (c) 1991, 1992, 1993 Free Software Foundation, Inc.
.PP
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.
.PP
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.
.PP
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.