linux-kernel - Re: [PATCH] ARM: Convert BUG() to use unreachable()

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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@...glemail.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Richard Henderson <rth@...hat.com>,
	Richard Guenther <richard.guenther@...il.com>,
	David Daney <ddaney@...iumnetworks.com>,
	"gcc@....gnu.org" <gcc@....gnu.org>,
	Jamie Lokier <jamie@...reable.org>,
	linux-kernel@...r.kernel.org, linux-arm-kernel@...ts.infradead.org,
	Uwe Kleine-König 
	<u.kleine-koenig@...gutronix.de>
Subject: Re: [PATCH] ARM: Convert BUG() to use unreachable()

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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