Wanted: struct's address from member's address please.

[Ronald S H Khoo]

Can someone give me a pointer to relevant bits of the Standard please ?

I'd like to know if

	1) I can have a strictly conforming portable function that returns
	   the address of a structure, given the address of a member of
	   said structure,

	2) Is this function the one I want ? (and is it strictly conforming?)

	#include <stddef.h>

	/* typedefs to define type1 and type2 */

	struct foo {
		type1 first_bit;
		type2 second_bit;
	};

	struct foo *
	func(type2 *arg)
	{
		return  (struct foo *) ((char *)arg -
			offsetof(struct foo, second_bit));
	}
-- 
ronald at robobar.co.uk +44 81 991 1142 (O) +44 71 229 7741 (H)