cpp(1) General Commands Manual cpp(1)
NAME
cpp - the C language preprocessor
SYNOPSIS
[option]... [ifile [ofile]]
DESCRIPTION
is the C language preprocessor which is invoked as the first pass of any C compilation using the command (see cc(1)). Its purpose is to
process and conditional compilation instructions and macros. Thus the output of is designed to be in a form acceptable as input to the
next pass of the C compiler. As the C language evolves, and the rest of the C compilation package will be modified to follow these
changes. Therefore, the use of in other than this framework is not suggested. The preferred way to invoke is through the command, since
the functionality of may someday be moved elsewhere. See m4(1) for a general macro processor.
optionally accepts two file names as arguments. ifile and ofile are respectively the input and output for the preprocessor. They default
to standard input and standard output if not specified.
Options
The following options are recognized by
Remove all predefined symbols that begin with a letter and
The user is expected to define or when using this option.
By default, strips C-style comments. If the option is specified, all comments (except those found on directive lines) are passed along.
Define name as if by a directive. If no is given, name is defined as The option has lower precedence than the option. Thus, if
the same name is used in both a option and a option, the name is undefined regardless of the order of the options.
Change the internal macro definition table to be
nnn bytes in size. The default buffer size is at least 8188 bytes. This option serves to eliminate "Macro param too
large", "Macro invocation too large", "Macro param too large after substitution", "Quoted macro param too large", "Macro
buffer too small", "Input line too long", and "Catenated input line too long" errors.
Generates included files and sents the results to the file
inclfile. If the argument inclfile is omitted, the result is sent to the standard error.
Change the algorithm for searching for
files whose names do not begin with to look in dir before looking in the directories on the standard list. Thus, files
whose names are enclosed in double quotes ("") are searched for first in the directory of the file containing the line, then
in directories named in options in left-to-right order, and last in directories on a standard list. For files whose names
are enclosed in angle brackets the directory of the file containing the line is not searched. However, directory dir is
still searched.
Generates makefile dependencies and sends the results to the file
makefile. If the argument makefile is omitted, the result is sent to the standard error.
Preprocess the input
without producing the line-control information used by the next pass of the C compiler.
HP-UX no longer restricts preprocessor symbols to eight characters. The option forces to use only the first eight characters for
distinguishing different preprocessor names. This behavior is the same as preprocessors on some other systems with respect
to the length of names, and is included for backward compatibility.
Remove any initial definition of
name, where name is a reserved symbol that is predefined by the particular preprocessor. The current list of these symbols
includes:
Operating system: Hardware: UNIX systems variant: lint(1):
In addition, all symbols that begin with an underscore and either an upper-case letter or another underscore are reserved.
Other symbols may be defined by the variable or other command-line options to the C compiler at compile time (see cc(1)).
All HP-UX systems have the symbols and defined. Each system defines at least one hardware variant, as appropriate. The
lint symbols are defined when lint(1) is running. See
Two special names are understood by is defined as the current line number (as a decimal integer) as counted by is defined as the current
file name (as a C string) as known by They can be used anywhere (including in macros) just as any other defined names.
Directives
All directives start with lines begun by Any number of blanks and tabs are allowed between the and the directive. The directives are:
#define name token-string
Replace subsequent instances of name with token-string. token-string can be null.
#define name(arg, ... , arg) token-string
Replace subsequent instances of name followed by a a list of comma-separated set of arguments, and a by token-string, where
each occurrence of an arg in the token-string is replaced by the corresponding set of tokens in the comma-separated list.
When a macro with arguments is expanded, the arguments are placed into the expanded token-string unchanged. After the
entire token-string has been expanded, restarts its scan for names to expand at the beginning of the newly created token-
string.
Notice that there can be no space between name and the
#endif [text] Ends a section of lines begun by a test directive or Each test directive must have a matching Any text occurring on the same
line as the is ignored and thus may be used to mark matching pairs. This makes it easier, when reading the source, to match
and directives with their associated directive.
#elif constant-expression
Equivalent to:
#else Reverses the notion of the test directive that matches this directive. Thus, if lines previous to this directive are
ignored, the following lines appear in the output, and vice versa.
#if constant-expression
The lines following appear in the output if and only if the constant-expression evaluates to nonzero. All binary nonassign-
ment C operators, the operator, the unary and operators are all legal in constant-expression. The precedence of the opera-
tors is the same as defined by the C language.
There is also a unary operator, which can be used in constant-expression in these two forms: or This allows the use of and
in an directive.
Only these operators, integer constants, and names that are known by should be used in constant-expression. In particular,
the operator is not available.
#ifdef name The lines following appear in the output if and only if name has been the subject of a previous without being the subject of
an intervening
#ifndef name The lines following do not appear in the output if and only if name has been the subject of a previous without being the
subject of an intervening
#include "filename"
#include <filename>
Include at this point the contents of filename (which are then run through See the option above for more detail.
#line integer-constant "filename"
Causes to generate line-control information for the next pass of the C compiler. integer-constant is the line number of the
next line and filename is the file where it comes from. If filename and the quotation marks are omitted, the current file
name is unchanged.
#undef name Cause the definition of name (if any) to be forgotten from now on.
The test directives and the possible directives can be nested. supports names up to 255 characters in length.
Notes
The macro substitution scheme has been changed. Previous versions of saved macros in a macro definition table whose table size is 128000
bytes by default. The current version of replaces this macro definition table with several small buffers. The default size of the small
buffers is 8188 bytes.
EXTERNAL INFLUENCES
Environment Variables
determines the interpretation of comments and string literals as single- or multibyte characters.
determines the language in which messages are displayed.
If is not specified in the environment or is set to the empty string, the value of is used as a default for each unspecified or empty vari-
able. If is not specified or is set to the empty string, it defaults to "C" (see lang(5)). If any internationalization variable contains
an invalid setting, behaves as if all internationalization variables are set to "C". See environ(5).
International Code Set Support
Single- and multibyte character code sets are supported.
DIAGNOSTICS
Error messages produced by are intended to be self-explanatory. The line number and filename where the error occurred are printed along
with the diagnostic.
WARNINGS
When newline characters were found in argument lists for macros to be expanded, previous versions of put out the newlines as they were
found and expanded. The current version of replaces these newlines with blanks to alleviate problems that the previous versions had when
this occurred.
DEPENDENCIES
Workstation
The symbols and are not reserved symbols recognized by the option. They are supplied to either automatically by the compiler, or by the
use of a compiler option. For example, on a Series 700 system, the command:
produces:
(Also see the option of the command.)
FILES
Standard directory for
files
SEE ALSO
m4(1).
STANDARDS CONFORMANCE
cpp(1)