From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 30311 invoked by alias); 24 Sep 2009 16:00:11 -0000 Received: (qmail 30269 invoked by uid 22791); 24 Sep 2009 16:00:08 -0000 X-SWARE-Spam-Status: No, hits=-1.9 required=5.0 tests=AWL,BAYES_00,SPF_FAIL X-Spam-Check-By: sourceware.org Received: from mx20.gnu.org (HELO mx20.gnu.org) (199.232.41.8) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Thu, 24 Sep 2009 16:00:05 +0000 Received: from [65.74.133.4] (helo=mail.codesourcery.com) by mx20.gnu.org with esmtp (Exim 4.60) (envelope-from ) id 1Mqqji-0003Os-Uq for gcc@gcc.gnu.org; Thu, 24 Sep 2009 12:00:03 -0400 Received: (qmail 19096 invoked from network); 24 Sep 2009 16:00:00 -0000 Received: from unknown (HELO digraph.polyomino.org.uk) (joseph@127.0.0.2) by mail.codesourcery.com with ESMTPA; 24 Sep 2009 16:00:00 -0000 Received: from jsm28 (helo=localhost) by digraph.polyomino.org.uk with local-esmtp (Exim 4.69) (envelope-from ) id 1Mqqjf-0005fh-8s; Thu, 24 Sep 2009 15:59:59 +0000 Date: Thu, 24 Sep 2009 16:00:00 -0000 From: "Joseph S. Myers" To: Richard Guenther cc: gcc@gcc.gnu.org Subject: Re: Prague GCC folks meeting summary report In-Reply-To: Message-ID: References: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII X-detected-operating-system: by mx20.gnu.org: GNU/Linux 2.6, seldom 2.4 (older, 4) Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org X-SW-Source: 2009-09/txt/msg00517.txt.bz2 On Thu, 24 Sep 2009, Richard Guenther wrote: > The regular problem of emitting warnings for unreachable code may > be addressed by using a new variant of debug statements. Those > would queue up warnings and if still around emit them during > expansion. Currently queueing a warning can be done with inserting > a __builtin_warning function call. If queueing a warning you need to be careful about i18n - probably queue the exact text that would be emitted (as affected by options such as -fdiagnostics-show-*) and then make sure it does not get passed through translation again. Other cases for queueing warnings are where the issue is not unreachable code but some other property that may be proved during optimization, such as whether an expression implicitly converted from signed to unsigned can ever actually be negative. There are several places where the C front end lowers expressions (calls c_fully_fold) prematurely to avoid bogus warnings in such cases, and if all folding (and probably then the other lowering c_fully_fold does) is to be moved to gimplification time or later then a solution to these warnings is needed. -- Joseph S. Myers joseph@codesourcery.com