netbsd man page for __builtin_object_size

__BUILTIN_OBJECT_SIZE(3)				   BSD Library Functions Manual 				  __BUILTIN_OBJECT_SIZE(3)

NAME
     __builtin_object_size -- return the size of the given object

SYNOPSIS
     size_t
     __builtin_object_size(void *ptr, int type);

DESCRIPTION
     The __builtin_object_size() function is a gcc(1) built-in function that returns the size of the ptr object if known at compile time and the
     object does not have any side effects.

RETURN VALUES
     If the size of the object is not known or it has side effects the __builtin_object_size() function returns:

	   (size_t)-1  for type 0 and 1.

	   (size_t)0   for type 2 and 3.

     If the size of the object is known, then the __builtin_object_size() function returns the maximum size of all the objects that the compiler
     knows that they can be pointed to by ptr when type & 2 == 0, and the minimum size when type & 2 != 0.

SEE ALSO
     gcc(1), __builtin_return_address(3), attribute(3), ssp(3)

HISTORY
     The __builtin_object_size() appeared in GCC 4.1.

CAVEATS
     This is a non-standard, compiler-specific extension.

BSD
								 December 19, 2010							       BSD