From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17111 invoked by alias); 28 Jun 2005 09:49:14 -0000 Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Received: (qmail 16584 invoked by uid 22791); 28 Jun 2005 09:49:01 -0000 Received: from nile.gnat.com (HELO nile.gnat.com) (205.232.38.5) by sourceware.org (qpsmtpd/0.30-dev) with ESMTP; Tue, 28 Jun 2005 09:49:01 +0000 Received: from localhost (localhost [127.0.0.1]) by filtered-nile.gnat.com (Postfix) with ESMTP id 2CE31963D; Tue, 28 Jun 2005 05:49:00 -0400 (EDT) Received: from nile.gnat.com ([127.0.0.1]) by localhost (nile.gnat.com [127.0.0.1]) (amavisd-new, port 10024) with LMTP id 01683-01-4; Tue, 28 Jun 2005 05:49:00 -0400 (EDT) Received: from [127.0.0.1] (taconic.gnat.com [205.232.38.103]) by nile.gnat.com (Postfix) with ESMTP id F037A9642; Tue, 28 Jun 2005 05:48:59 -0400 (EDT) Message-ID: <42C11D0A.1000604@adacore.com> Date: Tue, 28 Jun 2005 09:49:00 -0000 From: Robert Dewar User-Agent: Mozilla Thunderbird 0.8 (Windows/20040913) MIME-Version: 1.0 To: Michael Veksler CC: Andrew Pinski , gcc mailing list Subject: Re: signed is undefined and has been since 1992 (in GCC) References: In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2005-06/txt/msg01089.txt.bz2 Michael Veksler wrote: > I don't mind MAX_INT+1 being undefined by gcc. I object to drawing from > "undefined" to conclude that is_modulo should be true. This does not > make a practical sense. Drawing conclusions from "undefined" can yield > absurd results. Yes, but trying to define what you mean by disallowing "drawing conclusions" is close to impossible. You can say that informally, and we sort of know what you mean, but if you try to formalize this at the level of standardized semantics you will run into trouble. This reflects the fact that the notion of forbidding it is not clear, it will be like pornography and the supreme court. For a given example, you will know whether you like it or not, but you will find it hard to generalize the rule.