__unconst(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

CDEFS(3)						   BSD Library Functions Manual 						  CDEFS(3)

NAME

     cdefs -- common definitions and macros

SYNOPSIS

     #include <sys/cdefs.h>

DESCRIPTION

     The <sys/cdefs.h> header includes some common definitions and macros typical to the C language conventions of NetBSD.  Among these are:

	   o   Certain C language properties and definitions that are versioned according to the support in compilers.	Examples include the
	       __func__ keyword and the restrict type qualifier from C99.

	   o   Macros and definitions specific to compilers, preprocessors, and linkers; see __CONCAT(3), __UNCONST(3), __insn_barrier(3), and
	       attribute(3).

	   o   Utility macros provided for convenience; see __arraycount(3) and bits(3).

     The header also contains the __RCSID() and __KERNEL_RCSID() macros used for version control system (VCS) identifiers.  Thus, all NetBSD
     source code files typically include <sys/cdefs.h>, included as the first thing right after any possible copyright texts;

	   /*-
	    * Copyright (c) 1984 John Doe
	    * All rights reserved.
	    *
	    * Redistribution and use in source and binary forms,
	    * with or without modification, are permitted.
	    */

	   #include <sys/cdefs.h>
	   __RCSID("$NetBSD: cdefs.3,v 1.3 2011/04/08 07:55:04 jruoho Exp $");

     It is possible to identify the RCS keyword strings by using ident(1).

SEE ALSO

     ident(1), param(3), stddef(3), types(3), c(7)

HISTORY

     The <sys/cdefs.h> header was originally imported from 386BSD.

BSD
								   April 8, 2011							       BSD