__CONCAT(3)						   BSD Library Functions Manual 					       __CONCAT(3)

NAME

     __CONCAT, __STRING -- argument substitution

SYNOPSIS

     #include <sys/cdefs.h>

     xy
     __CONCAT(x, y);

     const char *
     __STRING(x);

DESCRIPTION

     The __CONCAT macro makes use of the cpp(1) preprocessor to concatenate two tokens.  When the macro is expanded, x and y are combined into a
     single token, provided that the result forms a valid token; two tokens that together do not form a valid token can not be concatenated.  This
     is known as ``token concatenation'' or ``token pasting''.

     The __STRING() macro uses the conventional '#' preprocessing operator to replace the argument x with a string literal.  This is also known as
     ``stringification''.

EXAMPLES

     The following two printf(3) calls produce the same output:

	   #define Net	   0x01
	   #define BSD	   0x02

	   #define NetBSD  "NetBSD"

	   (void)printf("%s
", __CONCAT(Net, BSD));
	   (void)printf("%s%s
", __STRING(Net), __STRING(BSD));

SEE ALSO

     cpp(1), cdefs(3)

HISTORY

     The __CONCAT() and __STRING() macros first appeared in NetBSD 1.3.

CAVEATS

     Many small details direct the proper use of the macros.  For example, while all leading and trailing whitespace is ignored when __STRING() is
     used, it is undefined whether cpp(1) puts white space between the tokens when __CONCAT() is used.	It can be also noted that the C preproces-
     sor converts all comments to whitespace before any macros are even considered.  The use of either macro is discouraged in complex constructs.

BSD
								 December 16, 2010							       BSD