From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1762199AbaGRUGQ (ORCPT ); Fri, 18 Jul 2014 16:06:16 -0400 Received: from terminus.zytor.com ([198.137.202.10]:43341 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755035AbaGRUGO (ORCPT ); Fri, 18 Jul 2014 16:06:14 -0400 Message-ID: <53C97E0F.6090601@zytor.com> Date: Fri, 18 Jul 2014 13:05:35 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:24.0) Gecko/20100101 Thunderbird/24.6.0 MIME-Version: 1.0 To: Andy Lutomirski CC: Stephen Rothwell , Thomas Gleixner , Ingo Molnar , Peter Zijlstra , "linux-next@vger.kernel.org" , "linux-kernel@vger.kernel.org" , Linus Torvalds Subject: Re: linux-next: build warning after merge of the tip tree References: <20140718150005.73db8eb9@canb.auug.org.au> <53C97287.5020509@zytor.com> In-Reply-To: X-Enigmail-Version: 1.6 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/18/2014 12:57 PM, Andy Lutomirski wrote: > > This particular warning is IMO in a particularly dumb category: GCC > optimizes some code and then warns about a construct that wasn't there > in the original code. In this case, I think it unrolled a loop and > discovered that one iteration contained a test that was always true. > Big deal. > > (OTOH, the code in question was buggy, but not all for the reason that > GCC thought it was.) > if (syms[sym_vvar_start] > syms[i] + 4096) fail("%s underruns begin_vvar\n", required_syms[i].name); if i == sym_vvar_start then this is at least a valid warning. It could easily be quieted by chaning syms[] to an unsigned array. -hpa