From owner-freebsd-arch  Tue Aug 20 18:15: 9 2002
Delivered-To: freebsd-arch@freebsd.org
Received: from mx1.FreeBSD.org (mx1.FreeBSD.org [216.136.204.125])
	by hub.freebsd.org (Postfix) with ESMTP
	id 194B137B400; Tue, 20 Aug 2002 18:15:06 -0700 (PDT)
Received: from InterJet.dellroad.org (adsl-63-194-81-26.dsl.snfc21.pacbell.net [63.194.81.26])
	by mx1.FreeBSD.org (Postfix) with ESMTP
	id 8CD7343E42; Tue, 20 Aug 2002 18:15:05 -0700 (PDT)
	(envelope-from archie@dellroad.org)
Received: from arch20m.dellroad.org (arch20m.dellroad.org [10.1.1.20])
	by InterJet.dellroad.org (8.9.1a/8.9.1) with ESMTP id SAA88061;
	Tue, 20 Aug 2002 18:01:43 -0700 (PDT)
Received: (from archie@localhost)
	by arch20m.dellroad.org (8.11.6/8.11.6) id g7L110m03801;
	Tue, 20 Aug 2002 18:01:00 -0700 (PDT)
	(envelope-from archie)
From: Archie Cobbs <archie@dellroad.org>
Message-Id: <200208210101.g7L110m03801@arch20m.dellroad.org>
Subject: Re: NULL
In-Reply-To: <20020821002116.GA33223@dragon.nuxi.com> "from David O'Brien at
 Aug 20, 2002 05:21:16 pm"
To: obrien@freebsd.org
Date: Tue, 20 Aug 2002 18:01:00 -0700 (PDT)
Cc: freebsd-arch@freebsd.org
X-Mailer: ELM [version 2.4ME+ PL88 (25)]
MIME-Version: 1.0
Content-Transfer-Encoding: 7bit
Content-Type: text/plain; charset=US-ASCII
Sender: owner-freebsd-arch@FreeBSD.ORG
Precedence: bulk
List-ID: <freebsd-arch.FreeBSD.ORG>
List-Archive: <http://docs.freebsd.org/mail/> (Web Archive)
List-Help: <mailto:majordomo@FreeBSD.ORG?subject=help> (List Instructions)
List-Subscribe: <mailto:majordomo@FreeBSD.ORG?subject=subscribe%20freebsd-arch>
List-Unsubscribe: <mailto:majordomo@FreeBSD.ORG?subject=unsubscribe%20freebsd-arch>
X-Loop: FreeBSD.ORG

David O'Brien writes:
> > Simple question...
> > Why isn't NULL defined to be "((void *)0)" instead of "0" ?
> 
> In C++ this is not legal:
> 
>     void blah(void) {
>         int *foo;
>         void *bar;
>         bar = foo;
>         foo = bar;
>     }
> 
> it is in C, but we share the definition.
> A benefit of "(void *)0" is that this would be caught:
> 
>     char c = NULL;
> 
> rather than the correct:
>     char c = '\0';
> 

When you say "not legal" do you mean it causes an error or a warning?

If it's just a warning, then are you saying the reason we don't use
(void *)0 is because we would lose the C++ warning to gain the C warning?
Seems like a fair trade to me :-)

FYI, this question came up when porting some code to redhat Linux, where
NULL is defined as (void *)0.

Thanks,
-Archie

__________________________________________________________________________
Archie Cobbs     *     Packet Design     *     http://www.packetdesign.com

To Unsubscribe: send mail to majordomo@FreeBSD.org
with "unsubscribe freebsd-arch" in the body of the message