From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754714AbZDGMpU (ORCPT ); Tue, 7 Apr 2009 08:45:20 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1751528AbZDGMpG (ORCPT ); Tue, 7 Apr 2009 08:45:06 -0400 Received: from bombadil.infradead.org ([18.85.46.34]:47363 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751159AbZDGMpE (ORCPT ); Tue, 7 Apr 2009 08:45:04 -0400 Subject: Re: [PATCH] intel-iommu: fix build with CONFIG_BRANCH_TRACER=y From: David Woodhouse To: Ingo Molnar Cc: torvalds@linux-foundation.org, iommu@lists.linux-foundation.org, linux-kernel@vger.kernel.org In-Reply-To: <20090407121457.GC11641@elte.hu> References: <1238839639.3560.37.camel@macbook.infradead.org> <20090407053739.GA10500@elte.hu> <1239083045.22733.383.camel@macbook.infradead.org> <20090407054818.GA5557@elte.hu> <20090407055245.GA10406@elte.hu> <1239084280.22733.404.camel@macbook.infradead.org> <20090407061558.GA31261@elte.hu> <20090407084950.GA1467@elte.hu> <20090407090229.GA2467@elte.hu> <1239104035.22733.443.camel@macbook.infradead.org> <20090407121457.GC11641@elte.hu> Content-Type: text/plain Date: Tue, 07 Apr 2009 05:44:23 -0700 Message-Id: <1239108263.22733.492.camel@macbook.infradead.org> Mime-Version: 1.0 X-Mailer: Evolution 2.26.0 (2.26.0-2.fc11) Content-Transfer-Encoding: 7bit X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org See http://www.infradead.org/rpr.html Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org 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@intel.com Intel Corporation