From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1035206AbdEZEnu (ORCPT ); Fri, 26 May 2017 00:43:50 -0400 Received: from mail-pf0-f194.google.com ([209.85.192.194]:34713 "EHLO mail-pf0-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762756AbdEZEnr (ORCPT ); Fri, 26 May 2017 00:43:47 -0400 Date: Thu, 25 May 2017 21:43:43 -0700 From: Nick Desaulniers To: Michal Hocko Cc: akpm@linux-foundation.org, hannes@cmpxchg.org, mgorman@techsingularity.net, vbabka@suse.cz, minchan@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [Patch v2] mm/vmscan: fix unsequenced modification and access warning Message-ID: <20170526044343.autu63rpfigbzhyi@lostoracle.net> References: <20170510071511.GA31466@dhcp22.suse.cz> <20170510082734.2055-1-nick.desaulniers@gmail.com> <20170510083844.GG31466@dhcp22.suse.cz> <20170516082746.GA2481@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20170516082746.GA2481@dhcp22.suse.cz> User-Agent: NeoMutt/20170113 (1.7.2) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, May 16, 2017 at 10:27:46AM +0200, Michal Hocko wrote: > I guess it is worth reporting this to clang bugzilla. Could you take > care of that Nick? >>From https://bugs.llvm.org//show_bug.cgi?id=33065#c5 it seems that this is indeed a sequence bug in the previous version of this code and not a compiler bug. You can read that response for the properly-cited wording but my TL;DR/understanding is for the given code: struct foo bar = { .a = (c = 0), .b = c, }; That the compiler is allowed to reorder the initializations of bar.a and bar.b, so what the value of c here might not be what you expect.