Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S933793AbbEMKXG (ORCPT ); Wed, 13 May 2015 06:23:06 -0400 Received: from mail-wg0-f50.google.com ([74.125.82.50]:35527 "EHLO mail-wg0-f50.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S933423AbbEMKXC (ORCPT ); Wed, 13 May 2015 06:23:02 -0400 Date: Wed, 13 May 2015 12:22:57 +0200 From: Ingo Molnar To: Valdis.Kletnieks@vt.edu Cc: Linus Torvalds , Peter Anvin , Brian Gerst , Thomas Gleixner , Borislav Petkov , Peter Zijlstra , Andy Lutomirski , Louis Langholtz , Denys Vlasenko , linux-kernel@vger.kernel.org Subject: Re: [tip:x86/build] x86/build: Remove -Wno-sign-compare Message-ID: <20150513102257.GB4318@gmail.com> References: <20150512084415.GA6535@gmail.com> <156879.1431503013@turing-police.cc.vt.edu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <156879.1431503013@turing-police.cc.vt.edu> User-Agent: Mutt/1.5.23 (2014-03-12) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2617 Lines: 60 * Valdis.Kletnieks@vt.edu wrote: > On Tue, 12 May 2015 10:44:15 +0200, Ingo Molnar said: > > > Btw., just some feedback, 'random' kernel configs still generate a ton > > of warnings: > > > > randconf: # 9, ed602bbb, Tue_May_12_09_07_25_CEST_2015: 39 kernels/hour, > [ bzImage... 81 secs, modules... 21 secs, done ] (warns: 6) > > randconf: # 10, ed602bbb, Tue_May_12_09_10_10_CEST_2015: 36 kernels/hour, > [ bzImage... 43 secs, modules... 20 secs, done ] (warns: 12) > > randconf: # 11, ed602bbb, Tue_May_12_09_11_52_CEST_2015: 36 kernels/hour, > [ bzImage... 71 secs, modules... 0 secs, done ] (warns: 5) > > randconf: # 12, ed602bbb, Tue_May_12_09_12_56_CEST_2015: 37 kernels/hour, > [ bzImage... 64 secs, modules... 28 secs, done ] (warns: 16) > > randconf: # 13, ed602bbb, Tue_May_12_09_14_07_CEST_2015: 38 kernels/hour, > [ bzImage... 106 secs, modules... 0 secs, done ] (warns: 157) > > randconf: # 14, ed602bbb, Tue_May_12_09_15_40_CEST_2015: 38 kernels/hour, > [ bzImage... 100 secs, modules... 0 secs, done ] (warns: 11) > > randconf: # 15, ed602bbb, Tue_May_12_09_17_27_CEST_2015: 37 kernels/hour, > [ bzImage... 65 secs, modules... 28 secs, done ] (warns: 26) > > randconf: # 16, ed602bbb, Tue_May_12_09_19_08_CEST_2015: 37 kernels/hour, > [ bzImage... 70 secs, modules... 0 secs, done ] (warns: 228) > > > Before I pushed out this -Wno-sign-compare change I made sure there > > are no extra warnings generated on the 8 key configs I monitor > > explicitly: [def|allno|allyes|allmod]config[64|32]. > > It makes my config totally explode on next-20150512 > > % gcc --version > gcc (GCC) 5.1.1 20150422 (Red Hat 5.1.1-1) > > % grep "warning: comparison between signed and unsigned integer expressions" build.default | wc -l > 64148 > > A *lot*of them appear to be exploding inside likely(). Here's all the > exploding for *one file*... That's a prerelease of GCC, right? So I think GCC gets constant propagation from various builtins wrong or so. But ... the output looks horrible, and for years we didn't have the warnings, still after reintroducing it we didn't get any new warnings about truly bogus code. So it does not seem to have much utility, and seems to be horribly broken on fresh GCC. I'll remove the commit. Thanks, Ingo -- 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/