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Message-Id: <1239108263.22733.492.camel@macbook.infradead.org>
Date: Tue, 07 Apr 2009 05:44:23 -0700
From: David Woodhouse <dwmw2@...radead.org>
To: Ingo Molnar <mingo@...e.hu>
Cc: torvalds@...ux-foundation.org, iommu@...ts.linux-foundation.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] intel-iommu: fix build with CONFIG_BRANCH_TRACER=y
On Tue, 2009-04-07 at 14:14 +0200, Ingo Molnar wrote:
> Well, i consider it a feature that it flags weird if (x, y)
> constructs: and yes, these iterators you introduced, while they are
> legit C, definitely count as 'weird'. If regular code was doing it,
> not a loop abstraction, i'd call it non-obvious and borderline
> broken straight away.
>
> We should _never ever_ put comma statements into if () constructs
> without a _really_ good reason - and if yes, we can flag that we
> know what we are doing, via extra parentheses.
I disagree. I don't think we should be declaring valid C syntax as 'off
limits', however rare it is.
_Especially_ if it only actually fails with a fairly esoteric config
option set. That's just asking for build breakage.
> and if yes, we can flag that we know what we are doing, via extra
> parentheses.
That's hardly much of a barrier. The requirement to sprinkle
gratuitous-looking extra parentheses around the place really isn't going
to give us much of a _benefit_ in return for the build breakage.
--
David Woodhouse Open Source Technology Centre
David.Woodhouse@...el.com Intel Corporation
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