Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752259Ab0KBUIr (ORCPT ); Tue, 2 Nov 2010 16:08:47 -0400 Received: from mail-ww0-f44.google.com ([74.125.82.44]:47380 "EHLO mail-ww0-f44.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752073Ab0KBUIn (ORCPT ); Tue, 2 Nov 2010 16:08:43 -0400 MIME-Version: 1.0 X-Originating-IP: [94.246.127.91] In-Reply-To: <4CD06B45.2070704@s5r6.in-berlin.de> References: <20101102182911.GE25614@thunk.org> <4CD06B45.2070704@s5r6.in-berlin.de> Date: Tue, 2 Nov 2010 23:08:40 +0300 Message-ID: Subject: Re: ext4_lazyinit_thread: 'ret' may be used uninitialized in this function From: Brian Gitonga Marete To: Stefan Richter Cc: Lukas Czerner , kevin granade , "Ted Ts'o" , linux-ext4@vger.kernel.org, linux-kernel@vger.kernel.org Content-Type: text/plain; charset=ISO-8859-1 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2144 Lines: 56 Indeed. In clause 4 of Section 6.5.13 of C99, short circuit evaluation is guaranteed in addition to left to right evaluation. On 11/2/10, Stefan Richter wrote: > Lukas Czerner wrote: >> On Tue, 2 Nov 2010, kevin granade wrote: >>> + if (time_after_eq(jiffies, elr->lr_next_sched) && >>> + ext4_run_li_request(elr) != 0) { >>> + /* error, remove the lazy_init job */ >>> + ext4_remove_li_request(elr); >>> + continue; >>> } >>> >>> if (time_before(elr->lr_next_sched, next_wakeup)) >>> -- >>> >>> Though obviously it's a pretty subjective style issue. >>> Kevin Granade >> >> Hmm this relies on the fact that if the first part of the condition >> would not be true, the second part (after and) would never be invoked, >> however I am not really sure that we can rely on that on every >> architecture, or can we ? > > It is not about architecture but a C language feature. It is relied upon > everywhere in the kernel. For example, > > if (p != NULL && p->m == something) { > ... > > is very common. The || operator has the same property: Evaluation stops as > soon as the end result is known. I do not know since when this minimum > evaluation feature is guaranteed in the language, but it has to be ages now. > > (This is not an endorsement of one or the other coding of the patch. :-) > -- > Stefan Richter > -=====-==-=- =-== ---=- > http://arcgraph.de/sr/ > -- > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html > Please read the FAQ at http://www.tux.org/lkml/ > -- Brian Gitonga Marete Toshnix Systems Tel: +254722151590 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/