From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 26328 invoked by alias); 25 Jun 2014 09:48:48 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 26317 invoked by uid 89); 25 Jun 2014 09:48:47 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-3.2 required=5.0 tests=AWL,BAYES_00,T_RP_MATCHES_RCVD autolearn=ham version=3.3.2 X-HELO: mail3-relais-sop.national.inria.fr Received: from mail3-relais-sop.national.inria.fr (HELO mail3-relais-sop.national.inria.fr) (192.134.164.104) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (CAMELLIA256-SHA encrypted) ESMTPS; Wed, 25 Jun 2014 09:48:46 +0000 Received: from stedding.saclay.inria.fr ([193.55.250.194]) by mail3-relais-sop.national.inria.fr with ESMTP/TLS/AES128-SHA; 25 Jun 2014 11:48:41 +0200 Received: from glisse (helo=localhost) by stedding.saclay.inria.fr with local-esmtp (Exim 4.82_1-5b7a7c0-XX) (envelope-from ) id 1Wzjon-0000sj-4J; Wed, 25 Jun 2014 11:48:41 +0200 Date: Wed, 25 Jun 2014 09:48:00 -0000 From: Marc Glisse To: Richard Biener cc: Jakub Jelinek , Bernd Edlinger , "gcc-patches@gcc.gnu.org" Subject: Re: [PATCH] Change default for --param allow-...-data-races to off In-Reply-To: Message-ID: References: <20140620114418.GB24436@virgil.suse> <20140624201933.GB32150@virgil.suse> <20140625085444.GA31640@tucnak.redhat.com> User-Agent: Alpine 2.10 (DEB 1266 2009-07-14) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-SW-Source: 2014-06/txt/msg01994.txt.bz2 On Wed, 25 Jun 2014, Richard Biener wrote: > On Wed, Jun 25, 2014 at 10:54 AM, Jakub Jelinek wrote: >> On Wed, Jun 25, 2014 at 10:14:17AM +0200, Richard Biener wrote: >>>> Perhaps not unsurprisingly, the patch is very similar. Bootstrapped >>>> and tested on x86_64-linux. OK for trunk? >>> >>> Ok - please give the C++/atomics folks a chance to comment. >>> >>> This change of default behavior should also be documented in >>> gcc-4.10/changes.html. >> >> Do we want to allow the store data races by default with -Ofast even in strict >> conformance modes (-std=c++11, -std=c++14, -std=c11)? > > I think so. -Ofast means -Ofast (same issue with fp contraction and other > stuff -ffast-math enables that is not valid in strict conformance mode). One thing I am missing is a -single-thread option that would allow races, remove atomics and thread locals, etc, without breaking conformance as long as no second thread is created. I hope that not too many libraries use threads internally in a way that would break this. -- Marc Glisse