From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:33310) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zyksy-0004ix-3N for qemu-devel@nongnu.org; Tue, 17 Nov 2015 13:21:44 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zykst-0000Sc-4j for qemu-devel@nongnu.org; Tue, 17 Nov 2015 13:21:44 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44344) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zykss-0000SW-Vm for qemu-devel@nongnu.org; Tue, 17 Nov 2015 13:21:39 -0500 References: <1447769349-1767-1-git-send-email-pbonzini@redhat.com> <874mgkh6f5.fsf@blackfin.pond.sub.org> <564B67BE.5040001@redhat.com> From: Paolo Bonzini Message-ID: <564B702E.4070806@redhat.com> Date: Tue, 17 Nov 2015 19:21:34 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v2 for 2.5] QEMU does not care about left shifts of signed negative values List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Peter Maydell Cc: Laszlo Ersek , Markus Armbruster , QEMU Developers On 17/11/2015 19:19, Peter Maydell wrote: > That doesn't seem like more than half-good news to me. In particular, > if ubsan is still diagnosing these cases and they're still a > problem in some constant expressions Constant expressions are standardese for e.g. static int x = 1 << 31; It doesn't mean _all_ constants, and the warning only triggers with -pedantic. Regarding ubsan, give them some time to answer. :) Paolo > If the GCC folks don't want to go any further than that then > I think we should prefer to avoid this UB. (And there's still > the question of clang's position on this.)