From mboxrd@z Thu Jan  1 00:00:00 1970
Received: from mailman by lists.gnu.org with tmda-scanned (Exim 4.43)
	id 1NFTc4-0003pH-E1
	for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:21:56 -0500
Received: from exim by lists.gnu.org with spam-scanned (Exim 4.43)
	id 1NFTbz-0003oB-SZ
	for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:21:55 -0500
Received: from [199.232.76.173] (port=36740 helo=monty-python.gnu.org)
	by lists.gnu.org with esmtp (Exim 4.43) id 1NFTbz-0003o7-LG
	for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:21:51 -0500
Received: from mx20.gnu.org ([199.232.41.8]:50938)
	by monty-python.gnu.org with esmtps (TLS-1.0:RSA_AES_256_CBC_SHA1:32)
	(Exim 4.60) (envelope-from <paul@codesourcery.com>)
	id 1NFTbz-0005mV-Hr
	for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:21:51 -0500
Received: from mail.codesourcery.com ([38.113.113.100])
	by mx20.gnu.org with esmtp (Exim 4.60)
	(envelope-from <paul@codesourcery.com>) id 1NFTby-0008Nz-CT
	for qemu-devel@nongnu.org; Tue, 01 Dec 2009 09:21:50 -0500
From: Paul Brook <paul@codesourcery.com>
Subject: Re: [Qemu-devel] [PATCH] Permit zero-sized qemu_malloc() & friends
Date: Tue, 1 Dec 2009 14:21:45 +0000
References: <m3skbwxgkp.fsf@crossbow.pond.sub.org>
	<200912011257.28121.paul@codesourcery.com>
	<20091201134749.GA23375@mothafucka.localdomain>
In-Reply-To: <20091201134749.GA23375@mothafucka.localdomain>
MIME-Version: 1.0
Content-Type: Text/Plain;
  charset="iso-8859-1"
Content-Transfer-Encoding: 7bit
Message-Id: <200912011421.45396.paul@codesourcery.com>
List-Id: qemu-devel.nongnu.org
List-Unsubscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=unsubscribe>
List-Archive: <http://lists.gnu.org/pipermail/qemu-devel>
List-Post: <mailto:qemu-devel@nongnu.org>
List-Help: <mailto:qemu-devel-request@nongnu.org?subject=help>
List-Subscribe: <http://lists.nongnu.org/mailman/listinfo/qemu-devel>,
	<mailto:qemu-devel-request@nongnu.org?subject=subscribe>
To: qemu-devel@nongnu.org
Cc: Glauber Costa <glommer@redhat.com>, Markus Armbruster <armbru@redhat.com>, Gerd Hoffmann <kraxel@redhat.com>

On Tuesday 01 December 2009, Glauber Costa wrote:
> On Tue, Dec 01, 2009 at 12:57:27PM +0000, Paul Brook wrote:
> > > You might want to have a 'static uint8_t zero_length_malloc[0]' and
> > > return that instead of the magic cookie '1'.  Makes the code more
> > > readable IMHO and you'll also have symbol in gdb when debugging qemu.
> >
> > Having multiple malloc return the same pointer sounds like a really bad
> > idea.
> 
> And why's that?
> 
> Keep in mind that *any* dereference over that address is a bug.

Dereferencing the address is a bug. However testing the addresses themselves 
for equality is valid. This is much the same reason I think returning NULL 
would be a bad idea.

Paul