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Message-ID: <4B30D2FE.9020209@gmail.com>
Date: Tue, 22 Dec 2009 14:09:02 +0000
From: Dave Korn <dave.korn.cygwin@googlemail.com>
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To: Russell King - ARM Linux <linux@arm.linux.org.uk>
CC: Richard Henderson <rth@redhat.com>,
       Richard Guenther <richard.guenther@gmail.com>,
       David Daney <ddaney@caviumnetworks.com>,
       "gcc@gcc.gnu.org" <gcc@gcc.gnu.org>, Jamie Lokier <jamie@shareable.org>,
       linux-kernel@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
       =?ISO-8859-1?Q?Uwe_Kleine-K=F6ni?= =?ISO-8859-1?Q?g?= 
	<u.kleine-koenig@pengutronix.de>
Subject: Re: [PATCH] ARM: Convert BUG() to use unreachable()
References: <1260266138-17684-1-git-send-email-u.kleine-koenig@pengutronix.de> <20091217150120.GD24967@shareable.org> <4B2A65C6.7080009@caviumnetworks.com> <84fc9c000912170917y4b2772d0n47bb4dabc74b91ef@mail.gmail.com> <20091217181718.GA4440@n2100.arm.linux.org.uk> <4B2FCCE3.1090209@redhat.com> <20091221201059.GD11669@n2100.arm.linux.org.uk>
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Russell King - ARM Linux wrote:
> On Mon, Dec 21, 2009 at 11:30:43AM -0800, Richard Henderson wrote:
>> On 12/17/2009 10:17 AM, Russell King - ARM Linux wrote:
>>> How is "size-optimal trap" defined?
>> E.g. Sparc and MIPS have "tcc" instructions that trap based on the
>> condition codes, and so we eliminate the branch.  That's the only
>> optimization we apply with __builtin_trap.
>>
>>> Let me put it another way: I want this function to terminate with an
>>> explicit NULL pointer dereference in every case.
>> Then just use that.
> 
> That's precisely what we have been using for many years.

  I don't understand.  It should still work just fine; the original version
posted appears to simply lack 'volatile' on the (int *) cast.

    cheers,
      DaveK
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