CPP

Section: User Commands (1)
Updated: 30 May 1993
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NAME

cpp - a stand-alone C preprocessor

SYNOPSIS

cpp [ -CTV ] [ -P[012] ] [ -Dname ]
      [ -Dname=def ] [ -Idirectory ] [ -Uname ]
      [ -ansi ] [ -f[no-]c++-comments ] [ -W[no-]bad-chars ]
      [ -W[no-]nested-comments ] [ input-file [ output-file ] ]

DESCRIPTION

cpp is a stand-alone C preprocessor, intended for use with C compilers such as HSC which do not provided access to preprocessor output. It implements as closely as possible an ANSI standard C preprocessor, including trigraphs, token pasting and stringizing.

cpp optionally accepts two filenames as arguments. input-file and output-file are, respectively, the input and output files for the preprocessor. If not specified, or if given as `-', they default to the standard input and the standard output, respectively.

OPTIONS

-C

Pass all comments (except those that appear on cpp directive lines) through the preprocessor. By default, cpp strips out C-style comments.

-P[012]

Preprocess the input without producing the line control information used by the next pass of the C compiler. A numeric argument can be passed to -P: 0 specifies that no line control information control is generated, and is equivalent to -P; 1 specifies that normal line control information is generated, which is the default; and 2 specifies that line control information is generated in the form of preprocessor #line directives.

-T

Translate trigraphs in the input file. This behavior is implied by the -ansi option.

-D name

Define name as 1 (one). This is the same as if a -Dname=1 option appeared on the cpp command line, or as if a

: #define name 1

line appeared in the source file that cpp is processing.

-Dname=def

Define name as if by a #define directive. This is the same as if a

: #define name def

line appeared in the source file that cpp is processing. The -D option has lower precedence than the -U option; that is, if the same name is used in both a -U option and a -D option, the name will be undefined regardless of the order of the options.

-Idirectory

Insert directory into the search path for #include files with names not beginning with `/', `\\', or a drive specifier. directory is inserted ahead of the standard list of ``include'' directories. Thus, #include files with names enclosed in double-quotes (") are searched for first in the directory of the file with the #include line, then in directories named with -I options, and lastly, in directories from the standard list. For #include files with names enclosed in angle-brackets (<>), the directory of the file with the #include line is not searched. See USAGE below for exact details of this search order.

-Uname

Remove any initial definition of name, where name is a symbol that is predefined by the preprocessor.

-V

Print version information to stderr.

-ansi

Define the preprocessor token __STDC__ to have value 1, and enable trigraph translation. To get __STDC__ without trigraph translation, you can specify the options -ansi -T.

The following -f and -W options can be negated by adding a no- before the option name. Some are on by default.

-fc++-comments: Support the C++ comment indicator `//'. With this option active, everything on the line after the // is treated as a comment. Off by default.
-Wbad-chars: Issue a warning if a character that cannot legally appear in a C program appears in the input. On by default.
-Wnested-comments: Issue a warning if a comment-start character sequence (`/*', and `//' if -fc++-comments is active) appears in a comment. Off by default.

USAGE

If you are familiar with C, you should already know about the basic workings of cpp. We will not go into a detailed description here, since any good book on C could do better; instead, we will describe details particular to this implementation.

Directory Search Order

A file specified in an #include directive will be searched for in the following directories, in order:

1.: The directory of the file that contains the #include directive, if the directive is of the form `#include ``filename'''.
2.: The directories specified by -I options, in the order they were specified.
3.: The list of directories specified in the INCLUDE environment variable, in order.

Special Names

The following macros are predefined by cpp:

__STDC__: Expands to 1 if the -ansi option is specified.
__LINE__: Expands to an integer constant representing the current line number in the current input file.
__FILE__: Expands to a string constant representing the name of the current input file.
__DATE__: Expands to a string constant of the form "Mmm dd yyyy" representing the date on which preprocessing was initiated.
__TIME__: Expands to a string constant of the form "hh:mm:ss" representing the system time at which preprocessing was initiated.
__INCLUDE_LEVEL__: Expands to an integer constant representing the current depth of nested #include files.

DIAGNOSTICS

The error messages produced by cpp are intended to be self-explanatory. The line number and filename where the error occurred are printed along with the diagnostic.

BUGS

None that I know of, but there's almost always One More Bug(TM). If you should find one, please report it to me, Scott Bigham, at dsb@cs.duke.edu.

SEE ALSO

DIAGNOSTICS

BUGS

This document was created by man2html, using the manual pages.
Time: 02:58:25 GMT, January 17, 2025