From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 4531 invoked by alias); 17 Nov 2004 12:46:49 -0000 Mailing-List: contact gcc-help-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-help-owner@gcc.gnu.org Received: (qmail 4184 invoked from network); 17 Nov 2004 12:46:25 -0000 Received: from unknown (HELO mail.codesourcery.com) (65.74.133.9) by sourceware.org with SMTP; 17 Nov 2004 12:46:25 -0000 Received: (qmail 11069 invoked from network); 17 Nov 2004 12:46:21 -0000 Received: from localhost (HELO digraph.polyomino.org.uk) (joseph@127.0.0.1) by mail.codesourcery.com with DES-CBC3-SHA encrypted SMTP; 17 Nov 2004 12:46:21 -0000 Received: from jsm28 (helo=localhost) by digraph.polyomino.org.uk with local-esmtp (Exim 4.42) id 1CUPCV-0005VP-Bk; Wed, 17 Nov 2004 12:46:19 +0000 Date: Wed, 17 Nov 2004 12:46:00 -0000 From: "Joseph S. Myers" X-X-Sender: jsm28@digraph.polyomino.org.uk To: Steven Bosscher cc: Luca Benini , Dave Korn , 'Gerald Pfeifer' , 'Beschorner Daniel' , gcc@gcc.gnu.org, gcc-help@gcc.gnu.org Subject: Re: gcc 3.3 / i386 / -O2 question In-Reply-To: <907175.1100692433831.SLOX.WebMail.wwwrun@extimap.suse.de> Message-ID: References: <419B3277.9060209@csr.unibo.it> <907175.1100692433831.SLOX.WebMail.wwwrun@extimap.suse.de> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-SW-Source: 2004-11/txt/msg00104.txt.bz2 On Wed, 17 Nov 2004, Steven Bosscher wrote: > Remember, "Undefined behavior" is not the same thing as "Unspecified > behavior". In the latter case, perhaps you're right. Unspecified > behavior should be consistent independent of the compiler options > (and this behavior should be documented). But for undefined behavior > you shouldn't expect anything. No, it's implementation-defined behavior that is documented. Unspecified behavior has bounds of variation but need not be documented. For example, in evaluating "x = f() + g()", the order in which f() and g() are evaluated is unspecified and could vary with compiler options, but their evaluation is not interleaved. -- Joseph S. Myers http://www.srcf.ucam.org/~jsm28/gcc/ jsm@polyomino.org.uk (personal mail) joseph@codesourcery.com (CodeSourcery mail) jsm28@gcc.gnu.org (Bugzilla assignments and CCs)