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Date: Sat, 9 Aug 2003 17:23:32 +0100
From: Jamie Lokier <jamie@shareable.org>
To: Alan Cox <alan@lxorguk.ukuu.org.uk>
Cc: "David S. Miller" <davem@redhat.com>, Willy Tarreau <willy@w.ods.org>,
       albert@users.sourceforge.net,
       Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
       chip@pobox.com
Subject: Re: [PATCH] 2.4.22pre10: {,un}likely_p() macros for pointers
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Alan Cox wrote:
> > I believe the C language allows for systems where the NULL pointer is
> > not zero.

The representation is not zero, however in the C language (since ANSI,
not sure about K&R), 0 is a valid name for the NULL pointer whatever
its representation.

> > I can't think of any reason why the NULL macro exists otherwise.
> 
> <OldFart>
> NULL is really important in K&R C because you don't have prototypes and
> sizeof(foo *) may not be the same as sizeof(int). This leads to very
> nasty problems that people nowdays forget about.
> </OldFart>

Not just K&R.  These are different because of varargs:

	printf ("%p", NULL);
	printf ("%p", 0);

-- Jamie