Skip site navigation (1)Skip section navigation (2)

FreeBSD Manual Pages


home | help
cpp(1)				 User Commands				cpp(1)

       cpp - the C language preprocessor

       /usr/lib/cpp  [-BCHMpPRT]  [-undef]  [-Dname] [ -Dname =	def] [-Idirec-
       tory] [-Uname] [-Ydirectory] [ input-file [output-file]]

       cpp is the C language preprocessor. It is invoked as the	first pass  of
       any  C  compilation  started  with the cc(1B) command. However, cpp can
       also be used as a first-pass preprocessor for other Sun compilers.

       Although	cpp can	be used	as a macro processor,  this  is	 not  normally
       recommended, as its output is geared toward that	which would be accept-
       able as input to	a compiler's second pass. Thus,	the preferred  way  to
       invoke  cpp  is	through	 the cc(1B) command, or	some other compilation
       command.	For general-purpose macro-processing, see m4(1).

       cpp optionally accepts two filenames as arguments. input-file and  out-
       put-file	 are,  respectively,  the  input and output files for the pre-
       processor. They default to the standard input and the standard output.

       The following options are supported:

       -B	       Supports	the C++	comment	indicator `//'.	With this  in-
		       dicator,	everything on the line after the // is treated
		       as a comment.

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

       -H	       Prints the pathnames of included	files, one per line on
		       the standard error.

       -M	       Generates  a  list  of  makefile	dependencies and write
		       them to the standard output. This list  indicates  that
		       the object file which would be generated	from the input
		       file depends on the input file as well as  the  include
		       files referenced.

       -p	       Uses  only  the	first  eight characters	to distinguish
		       preprocessor symbols, and issue a warning if extra  to-
		       kens  appear  at	 the end of a line containing a	direc-

       -P	       Preprocesses the	input without producing	the line  con-
		       trol  information  used	by the next pass of the	C com-

       -R	       Allows recursive	macros.

       -T	       Uses only the first eight characters for	distinguishing
		       different  preprocessor	names. This option is included
		       for backward compatibility with	systems	 which	always
		       use only	the first eight	characters.

       -undef	       Removes initial definitions for all predefined symbols.

       -Dname	       Defines	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 process-

       -Dname=def      Defines 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 process-
		       ing. The	-D option has lower precedence than the	-U op-
		       tion.  That  is,	 if the	same name is used in both a -U
		       option and a -D option, the name	will be	undefined  re-
		       gardless	of the order of	the options.

       -Idirectory     Inserts	directory  into	 the  search path for #include
		       files with names	not beginning with `/'.	 directory  is
		       inserted	 ahead of the standard list of ``include'' di-
		       rectories. Thus,	#include files with names enclosed  in
		       double-quotes  (") are searched for first in the	direc-
		       tory of the file	with the #include line,	then in	direc-
		       tories  named  with -I options, and lastly, in directo-
		       ries 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
		       Details below for exact details of this search order.

       -Uname	       Removes any initial definition of name, where name is a
		       symbol that is predefined by a particular preprocessor.
		       Here  is	 a  partial list of symbols that may be	prede-
		       fined, depending	upon  the architecture of the system:

		       Operating System:       ibm, gcos, os, tss and unix

		       Hardware:	       interdata,  pdp11,  u370,  u3b,
					       u3b2, u3b5, u3b15, u3b20d, vax,
					       ns32000,	iAPX286, i386,	sparc,
					       and sun

		       UNIX system variant:    RES, and	RT

		       The lint	command:       lint

		       The  symbols   sun,  sparc and unix are defined for all
		       Sun systems.

       -Ydirectory     Uses directory in place of the standard list of	direc-
		       tories when searching for #include files.

       All  cpp	directives start with a	hash symbol (#)	as the first character
       on a line. White	space (SPACE or	TAB characters)	can appear  after  the
       initial # for proper indentation.

       #define name token-string

	   Replace subsequent instances	of name	with token-string.

       #define name(argument [,	argument] ... )	token-string

	   There can be	no space between name and the  `('. Replace subsequent
	   instances of	name, followed by a parenthesized list	of  arguments,
	   with	 token-string, where each occurrence of	an argument in the to-
	   ken-string is replaced by the corresponding token in	the comma-sep-
	   arated list.	When a macro with arguments is expanded, the arguments
	   are placed into the expanded	token-string unchanged.	After the  en-
	   tire	 token-string  has  been  expanded, cpp	re-starts its scan for
	   names to expand at the beginning of the newly created token-string.

       #undef name

	   Remove any definition for the symbol	name. No additional tokens are
	   permitted on	the directive line after name.

       #include	"filename"
       #include	<filename>

	   Read	 in  the  contents  of filename	at this	location. This data is
	   processed by	cpp as if it were part of the current file.  When  the
	   <filename>  notation	 is used, filename is only searched for	in the
	   standard ``include''	directories. See the -I	and -Y	options	 above
	   for	more  detail. No additional tokens are permitted on the	direc-
	   tive	line after the final `"' or `>'.

       #line integer-constant "filename"

	   Generate line control information for the next pass of the  C  com-
	   piler.  integer-constant  is	 interpreted as	the line number	of the
	   next	line and filename is interpreted as the	 file  from  where  it
	   comes.  If  "filename"  is  not  given, the current filename	is un-
	   changed. No additional tokens are permitted on the  directive  line
	   after the optional filename.

       #if constant-expression

	   Subsequent  lines up	to the matching	#else, #elif, or #endif	direc-
	   tive, appear	in the output only  if	constant-expression  yields  a
	   nonzero  value.  All	 binary	 non-assignment	C operators, including
	   `&&', `||', and `,',	are legal in constant-expression. The `?:' op-
	   erator,  and	 the unary `-',	`!', and `~' operators,	are also legal
	   in constant-expression.

	   The precedence of these operators is	the same as that for C.	In ad-
	   dition, the unary operator defined, can be used in constant-expres-
	   sion	in these two forms: `defined ( name )' or `defined name'. This
	   allows  the	effect of #ifdef and #ifndef directives	(described be-
	   low)	in the #if directive.	Only  these  operators,	 integer  con-
	   stants,  and	names that are known by	cpp should be used within con-
	   stant-expression. In	particular, the	size of	operator is not	avail-

       #ifdef name

	   Subsequent  lines up	to the matching	#else, #elif, or #endif	appear
	   in the output only if name has been defined,	either with a  #define
	   directive or	a -D option, and in the	absence	of an intervening #un-
	   def directive. Additional tokens after name on the  directive  line
	   will	be silently ignored.

       #ifndef name

	   Subsequent  lines up	to the matching	#else, #elif, or #endif	appear
	   in the output only if name has not been defined, or if its  defini-
	   tion	 has  been removed with	an #undef directive. No	additional to-
	   kens	are permitted on the directive line after name.

       #elif constant-expression

	   Any number of #elif directives may appear between an	 #if,  #ifdef,
	   or  #ifndef directive and a matching	#else or #endif	directive. The
	   lines following the #elif directive appear in the  output  only  if
	   all of the following	conditions hold:

	     o	The  constant-expression in the	preceding #if directive	evalu-
		ated to	zero, the name in the preceding	#ifdef is not defined,
		or the name in the preceding #ifndef directive was defined.

	     o	The  constant-expression  in  all intervening #elif directives
		evaluated to zero.

	     o	The current constant-expression	evaluates to non-zero.

	   If the constant-expression evaluates	to non-zero, subsequent	 #elif
	   and	#else  directives  are	ignored	up to the matching #endif. Any
	   constant-expression allowed in an #if directive is  allowed	in  an
	   #elif directive.


	   This	 inverts  the  sense of	the conditional	directive otherwise in
	   effect.  If the preceding conditional would indicate	that lines are
	   to be included, then	lines between the  #else and the matching #en-
	   dif are ignored.  If	the preceding conditional indicates that lines
	   would be ignored, subsequent	lines are included in the output. Con-
	   ditional directives	and  corresponding  #else  directives  can  be


	   End	a  section of lines begun by one of the	conditional directives
	   #if,	#ifdef,	or #ifndef. Each such directive	must have  a  matching

       Formal  parameters for macros are recognized in	#define	directive bod-
       ies, even  when	they  occur  inside  character	constants  and	quoted
       strings.	For instance, the output from:

       #define abc(a)|`|a|


       # 1 ""

       The   second  line  is  a   NEWLINE.  The  last	seven  characters  are
       ``|`|xyz|'' (vertical-bar, backquote, vertical-bar, x, y, z,  vertical-
       bar).  Macro  names  are	 not  recognized within	character constants or
       quoted strings during the regular scan. Thus:

       #define abc xyz

       does not	expand abc in the second line, since it	 is  inside  a	quoted
       string that is not part of a  #define macro definition.

       Macros are not expanded while processing	a  #define or #undef. Thus:

       #define abc zingo
       #define xyz abc
       #undef abc

       produces	 abc. The token	appearing immediately after an #ifdef or #ifn-
       def is not expanded.

       Macros are not expanded during the scan which determines	the actual pa-
       rameters	to another macro call. Thus:

       #define reverse(first,second)second first
       #define greeting	hello
       #define greeting	goodbye

       produces	 `` #define hello goodbye  hello''.

       Output  consists	 of a copy of the input	file, with modifications, plus
       lines of	the form:

       #lineno " filename" "level"

       indicating the original source line number and filename of the  follow-
       ing  output  line  and whether this is the first	such line after	an in-
       clude file has been entered (level=1), the first	such line after	an in-
       clude  file has been exited (level=2), or any other such	line (level is

       This section contains usage details.

   Directory Search Order
       #include	files are searched for in the following	order:

       1.  The directory of the	file that contains the	#include request (that
	   is,	 #include  is  relative	to the file being scanned when the re-
	   quest is made).

       2.  The directories specified by	-I options, in left-to-right order.

       3.  The standard	directory(s) (/usr/include on UNIX systems).

   Special Names
       Two special names are understood	by cpp.	The name _ _LINE_ _ is defined
       as  the	current	line number (a decimal integer)	as known by cpp, and _
       _FILE_ _	is defined as the current filename (a C	string)	 as  known  by
       cpp.  They can be used anywhere (including in macros) just as any other
       defined name.

   Newline Characters
       A  NEWLINE character terminates a character constant or quoted  string.
       An  escaped  NEWLINE  (that  is,	 a backslash immediately followed by a
       NEWLINE)	may be used in the body	of a  #define  statement  to  continue
       the  definition onto the	next line. The escaped NEWLINE is not included
       in the macro value.

       Comments	are removed (unless the	-C  option  is	used  on  the  command
       line).  Comments	 are  also ignored, except that	a comment terminates a

       The following exit values are returned:

       0	       Successful completion.

       non-zero	       An error	occurred.

       See attributes(5) for descriptions of the following attributes:

       |      ATTRIBUTE	TYPE	     |	    ATTRIBUTE VALUE	   |
       |Availability		     |SUNWsprot			   |

       cc(1B), m4(1), attributes(5)

       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.

       When NEWLINE characters were found in argument lists for	macros	to  be
       expanded,  some previous	versions of cpp	put out	the NEWLINE characters
       as they were found and expanded.	The current version  of	 cpp  replaces
       them with  <SPACE> characters.

       Because	the  standard directory	for included files may be different in
       different environments, this form of #include directive:

       #include	<file.h>

       should be used, rather than one with an absolute	path, like:

       #include	"/usr/include/file.h"

       cpp warns about the use of the absolute pathname.

       While the compiler allows 8-bit strings and comments,  8-bits  are  not
       allowed anywhere	else.

SunOS 5.10			  1 Nov	1999				cpp(1)


Want to link to this manual page? Use this URL:

home | help