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

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Message-ID: <20091222141212.GA15356@n2100.arm.linux.org.uk>
Date:	Tue, 22 Dec 2009 14:12:12 +0000
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	Dave Korn <dave.korn.cygwin@...glemail.com>
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()

On Tue, Dec 22, 2009 at 02:09:02PM +0000, Dave Korn wrote:
> 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.

Neither do I - AFAIK the existing code works fine.

I think this is just a noisy thread about people wanting to use the
latest and greated compiler "features" whether they make sense to or
not, and this thread should probably die until some problem has actually
been identified.

If it ain't broke, don't fix.
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