__unvolatile(3) [netbsd man page]

__UNCONST(3)						   BSD Library Functions Manual 					      __UNCONST(3)

NAME

     __UNCONST -- compile time cast-away macro

SYNOPSIS

     #include <sys/cdefs.h>

     void
     __UNCONST(x);

     void
     __UNVOLATILE(x);

DESCRIPTION

     The __UNCONST() macro can be used to omit warnings produced by certain compilers when operating with pointers declared with the const type
     qualifier in a context without such qualifier.  Examples include passing a pointer declared with the const qualifier to a function without
     such qualifier, and variable assignment from a const pointer to a non-const pointer.  In the same vein, the __UNVOLATILE() macro can be used
     to exclude warnings related to the volatile type qualifier.

IMPLEMENTATION NOTES

     These macros are implemented by explicitly using unsigned long instead of intptr_t, a signed type guaranteed to hold a pointer.

SEE ALSO

     cc(1), cdefs(3)

CAVEATS

     As both macros may hide valid errors, their usage is not recommended unless there is a well-thought reason for a cast.  A typical use case
     for __UNCONST() involve an API that does not follow the so-called ``const correctness'' even if it would be appropriate.  Valid use cases of
     __UNVOLATILE() include passing a volatile pointer to memset(3).

BSD
								 December 16, 2010							       BSD

__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