From: Arnd Bergmann <arnd@arndb.de>
To: David Daney <ddaney@caviumnetworks.com>
Cc: Alexander Beregalov <a.beregalov@gmail.com>,
linux-kernel@vger.kernel.org, David Miller <davem@davemloft.net>,
sam@ravnborg.org, dhowells@redhat.com
Subject: Re: [PATCH] BUG(): CONFIG_BUG=n version of BUG() should be unreachable()
Date: Tue, 5 Jan 2010 12:35:44 +0100 [thread overview]
Message-ID: <201001051235.45568.arnd@arndb.de> (raw)
In-Reply-To: <4B422E0C.1070108@caviumnetworks.com>
On Monday 04 January 2010, David Daney wrote:
> Arnd Bergmann wrote:
> > The alternative "do { } while (1)" is not ideal, because an
> > endless loop still requires more code (typically one instruction)
> > than doing nothing at all.
> >
>
> Well "do { } while (1)" is exactly the expansion of unreachable() for
> GCC < 4.5. Since GCC-4.5 has not been released yet, most people will
> get these extra looping instructions if you change BUG in this way.
Yes, that is why I wrote the final paragraph, saying
> > If there are only than a handful of places that actually cause a warning,
> > using "do { } while (0)" (or __builtin_unreachable where available) and
> > fixing up the code using it might be better.
Arnd
next prev parent reply other threads:[~2010-01-05 11:36 UTC|newest]
Thread overview: 9+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-12-23 1:17 [PATCH] BUG(): CONFIG_BUG=n version of BUG() should be unreachable() Alexander Beregalov
2009-12-23 1:26 ` David Daney
2009-12-23 1:37 ` David Daney
2009-12-30 19:12 ` Arnd Bergmann
2010-01-04 18:06 ` David Daney
2010-01-05 11:35 ` Arnd Bergmann [this message]
2009-12-26 18:47 ` Sam Ravnborg
2010-01-05 17:58 ` David Howells
2010-01-05 18:30 ` Arnd Bergmann
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