From mboxrd@z Thu Jan  1 00:00:00 1970
Received: with ECARTIS (v1.0.0; list linux-mips); Mon, 14 Sep 2009 17:40:46 +0200 (CEST)
Received: from mail3.caviumnetworks.com ([12.108.191.235]:17030 "EHLO
	mail3.caviumnetworks.com" rhost-flags-OK-OK-OK-OK)
	by ftp.linux-mips.org with ESMTP id S1492834AbZINPkj (ORCPT
	<rfc822;linux-mips@linux-mips.org>); Mon, 14 Sep 2009 17:40:39 +0200
Received: from caexch01.caveonetworks.com (Not Verified[192.168.16.9]) by mail3.caviumnetworks.com with MailMarshal (v6,5,4,7535)
	id <B4aae63e50000>; Mon, 14 Sep 2009 08:40:21 -0700
Received: from caexch01.caveonetworks.com ([192.168.16.9]) by caexch01.caveonetworks.com with Microsoft SMTPSVC(6.0.3790.3959);
	 Mon, 14 Sep 2009 08:40:25 -0700
Received: from dd1.caveonetworks.com ([12.108.191.236]) by caexch01.caveonetworks.com over TLS secured channel with Microsoft SMTPSVC(6.0.3790.3959);
	 Mon, 14 Sep 2009 08:40:24 -0700
Message-ID: <4AAE63E7.90909@caviumnetworks.com>
Date:	Mon, 14 Sep 2009 08:40:23 -0700
From:	David Daney <ddaney@caviumnetworks.com>
User-Agent: Thunderbird 2.0.0.21 (X11/20090320)
MIME-Version: 1.0
To:	Geert Uytterhoeven <geert@linux-m68k.org>
CC:	Michael Buesch <mb@bu3sch.de>, linuxppc-dev@lists.ozlabs.org,
	torvalds@linux-foundation.org, akpm@linux-foundation.org,
	linux-mips@linux-mips.org,
	Heiko Carstens <heiko.carstens@de.ibm.com>,
	linuxppc-dev@ozlabs.org, Paul Mackerras <paulus@samba.org>,
	"H. Peter Anvin" <hpa@zytor.com>, linux-s390@vger.kernel.org,
	linux-am33-list@redhat.com, Helge Deller <deller@gmx.de>,
	x86@kernel.org, Ingo Molnar <mingo@redhat.com>,
	Mike Frysinger <vapier@gentoo.org>,
	Ivan Kokshaysky <ink@jurassic.park.msu.ru>,
	uclinux-dist-devel@blackfin.uclinux.org,
	Thomas Gleixner <tglx@linutronix.de>,
	Richard Henderson <rth@twiddle.net>,
	Haavard Skinnemoen <hskinnemoen@atmel.com>,
	linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org,
	ralf@linux-mips.org, Kyle McMartin <kyle@mcmartin.ca>,
	linux-alpha@vger.kernel.org,
	Martin Schwidefsky <schwidefsky@de.ibm.com>,
	linux390@de.ibm.com,
	Koichi Yasutake <yasutake.koichi@jp.panasonic.com>
Subject: Re: [PATCH 01/10] Add support for GCC-4.5's __builtin_unreachable()
 	to compiler.h
References: <4AA991C1.1050800@caviumnetworks.com>	 <1252627011-2933-1-git-send-email-ddaney@caviumnetworks.com>	 <200909111633.00665.mb@bu3sch.de>	 <4AAA73A4.9010601@caviumnetworks.com> <10f740e80909120022m72ad5ea7t692fba93cd3114e9@mail.gmail.com>
In-Reply-To: <10f740e80909120022m72ad5ea7t692fba93cd3114e9@mail.gmail.com>
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 7bit
X-OriginalArrivalTime: 14 Sep 2009 15:40:24.0988 (UTC) FILETIME=[AD5125C0:01CA3551]
Return-Path: <David.Daney@caviumnetworks.com>
X-Envelope-To: <"|/home/ecartis/ecartis -s linux-mips"> (uid 0)
X-Orcpt: rfc822;linux-mips@linux-mips.org
Original-Recipient: rfc822;linux-mips@linux-mips.org
X-archive-position: 24030
X-ecartis-version: Ecartis v1.0.0
Sender: linux-mips-bounce@linux-mips.org
Errors-to: linux-mips-bounce@linux-mips.org
X-original-sender: ddaney@caviumnetworks.com
Precedence: bulk
X-list: linux-mips

Geert Uytterhoeven wrote:
> On Fri, Sep 11, 2009 at 17:58, David Daney<ddaney@caviumnetworks.com> wrote:
>> Michael Buesch wrote:
>>> On Friday 11 September 2009 01:56:42 David Daney wrote:
>>>> +/* Unreachable code */
>>>> +#ifndef unreachable
>>>> +# define unreachable() do { for (;;) ; } while (0)
>>>> +#endif
>>> # define unreachable() do { } while (1)
>>>
>>> ? :)
>> Clearly I was not thinking clearly when I wrote that part.  RTH noted the
>> same thing.  I will fix it.
> 
> However, people are so used to seeing the `do { } while (0)' idiom,
> that they might miss
> there's a `1' here, not a `0'.
> 
> So perhaps it's better to use plain `for (;;)' for infinite loops?
> 

I don't think so.  The only valid token that can follow 'do { } while 
(1)' is ';', any statement may follow 'for (;;)', so there is a greater 
possibility to silently screw things up with the for(;;) form.

David Daney