From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2579 invoked by alias); 22 May 2012 09:57:45 -0000 Received: (qmail 2569 invoked by uid 22791); 22 May 2012 09:57:44 -0000 X-SWARE-Spam-Status: No, hits=-4.3 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,KHOP_THREADED X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 22 May 2012 09:57:32 +0000 From: "o.mangold at googlemail dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/53436] Volatile behaves strange with OpenMP Date: Tue, 22 May 2012 09:59:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: o.mangold at googlemail dot com X-Bugzilla-Status: RESOLVED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2012-05/txt/msg02140.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53436 --- Comment #6 from o.mangold at googlemail dot com 2012-05-22 08:32:03 UTC --- Yes, I get, that it's not a good way to do things, as (among other reasons) a volatile access is no memory fence. So accesses to other locations may not be ordered. But just for the sake of correctness, accesses should be ordered, if they all go to volatile variables, no? From the C99-standard, section 5.1.2.3: > At sequence points, volatile objects are stable in the sense that previous accesses are complete and subsequent accesses have not yet occurred. This means buffering the reads to the volatile variable over multiple iterations of the while loop is not allowed, or do I get this wrong?