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From: gwyn@brl-smoke.ARPA (Doug Gwyn )
Newsgroups: comp.lang.c
Subject: Re: char (*a)[]  (was: Style [++i vs i++ - (nf)
Message-ID: <6443@brl-smoke.ARPA>
Date: Sun, 20-Sep-87 21:08:25 EDT
Article-I.D.: brl-smok.6443
Posted: Sun Sep 20 21:08:25 1987
Date-Received: Mon, 21-Sep-87 03:40:54 EDT
References: <1459@cullvax.UUCP> <48400001@tub.UUCP>
Reply-To: gwyn@brl.arpa (Doug Gwyn (VLD/VMB) <gwyn>)
Organization: Ballistic Research Lab (BRL), APG, MD.
Lines: 11

In article <48400001@tub.UUCP> cabo@tub.UUCP writes:
>	(char *)&((struct foo *)0)->bar - (char *)&((struct foo *)0)->baz
>for computing the relative offset of two structure members in character
>sized units.  I'm not saying that the above is a constant expression
>according to the wording of the draft (I don't have it, unfortunately),
>but I would like it to be one.

Unfortunately, X3J11 cannot guarantee that such use of null pointers
would be portable.  However, they have specified an offsetof() macro
to accomplish what you're trying to do; it's still being debated and
may change or (unlikely) vanish before the second public review.