From owner-freebsd-hackers  Fri Feb 14 21:58:25 1997
Return-Path: <owner-hackers>
Received: (from root@localhost)
          by freefall.freebsd.org (8.8.5/8.8.5) id VAA02376
          for hackers-outgoing; Fri, 14 Feb 1997 21:58:25 -0800 (PST)
Received: from labs.usn.blaze.net.au (labs.usn.blaze.net.au [203.17.53.30])
          by freefall.freebsd.org (8.8.5/8.8.5) with ESMTP id VAA02343
          for <hackers@FreeBSD.ORG>; Fri, 14 Feb 1997 21:58:04 -0800 (PST)
Received: (from davidn@localhost)
	by labs.usn.blaze.net.au (8.8.5/8.8.5) id QAA22441;
	Sat, 15 Feb 1997 16:57:00 +1100 (EST)
Message-ID: <19970215165658.18171@usn.blaze.net.au>
Date: Sat, 15 Feb 1997 16:56:58 +1100
From: David Nugent <davidn@labs.usn.blaze.net.au>
To: Bruce Evans <bde@zeta.org.au>
Cc: hackers@FreeBSD.ORG, j@uriah.heep.sax.de
Subject: Re: NULL as ((void*)0) (was Re: strlen() question)
References: <199702150432.PAA04488@godzilla.zeta.org.au>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
X-Mailer: Mutt 0.61
In-Reply-To: <199702150432.PAA04488@godzilla.zeta.org.au>; from Bruce Evans on Feb 02, 1997 at 03:32:00PM
Sender: owner-hackers@FreeBSD.ORG
X-Loop: FreeBSD.org
Precedence: bulk

On Feb 02, 1997 at 03:32:00PM, Bruce Evans wrote:
> >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.

Hmm, I always thought it was "void * must be at least as large as the
largest pointer type" for a given implementation. I must dig out my
copy of the almost-final draft ANSI spec again, but I wasn't aware
that char * should follow this rule too, which is what your statement
implies.


> 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).

__P() is only useful in include files.

FWIW, I think compatibility with K&R is a crock anyway these
days. I follow this rule to keep people (hi Bruce ;-)) happy,
and for the sake of consistency.


Regards,

David Nugent - Unique Computing Pty Ltd - Melbourne, Australia
Voice +61-3-9791-9547  Data/BBS +61-3-9792-3507  3:632/348@fidonet
davidn@freebsd.org davidn@blaze.net.au http://www.blaze.net.au/~davidn/