From owner-freebsd-hackers  Fri Feb 14 20:36:34 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.5/8.8.5) id UAA28434
          for hackers-outgoing; Fri, 14 Feb 1997 20:36:34 -0800 (PST)
Received: from godzilla.zeta.org.au (godzilla.zeta.org.au [203.2.228.19])
          by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id UAA28429
          for <hackers@FreeBSD.ORG>; Fri, 14 Feb 1997 20:36:30 -0800 (PST)
Received: (from bde@localhost) by godzilla.zeta.org.au (8.8.3/8.6.9) id PAA04488; Sat, 15 Feb 1997 15:32:00 +1100
Date: Sat, 15 Feb 1997 15:32:00 +1100
From: Bruce Evans <bde@zeta.org.au>
Message-Id: <199702150432.PAA04488@godzilla.zeta.org.au>
To: hackers@FreeBSD.ORG, j@uriah.heep.sax.de
Subject: Re: NULL as ((void*)0) (was Re: strlen() question)
Sender: owner-hackers@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

>anyway.  Passing (void *)0 into a vararg list is as invalid as passing
>0 there if the target type is e.g. char *.

I think `char *' is required to have the same representation as `void *',
so this particular pointer mismatch must work.

>encouraged) C code.  Inside a function call, you only need to cast it
>into the correct target type if: 1) it's in a vararg list, or 2) it's
>in an arg list of a function declared with obsolete K&R style only.

If it's in an arg list of a function declared with obsolescent K&R style
period.  `void foo __P((bar_t *));' is declared with obsolescent K&R
style if __P(x) expands to ().  There is not much point in using __P()
if you don't write K&R code (or in using prototypes and depending on
K&R misfeatures).

Bruce