From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:55310) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZydeG-0002x4-PC for qemu-devel@nongnu.org; Tue, 17 Nov 2015 05:38:05 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZydeD-0001nc-Hr for qemu-devel@nongnu.org; Tue, 17 Nov 2015 05:38:04 -0500 Received: from mx1.redhat.com ([209.132.183.28]:44198) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZydeD-0001nY-Ct for qemu-devel@nongnu.org; Tue, 17 Nov 2015 05:38:01 -0500 References: <1447754381-29882-1-git-send-email-pbonzini@redhat.com> <564B0150.7030400@redhat.com> From: Paolo Bonzini Message-ID: <564B0386.4030701@redhat.com> Date: Tue, 17 Nov 2015 11:37:58 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 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: QEMU Developers On 17/11/2015 11:36, Peter Maydell wrote: > > If and when this happens we will add "-fno-strict-overflow" for clang, > > just like we are using "-fno-strict-aliasing" already. > > -fno-strict-overflow in clang is AFAICT just an alias for -fwrapv. > These options control handling of signed overflow of addition, > subtraction and multiplication; there is nothing I can find in the > gcc or clang docs that suggests they have any effect on shift operations. In the case of GCC, that's a corollary of the compiler not treating that overflow as undefined. Probably the same is true for clang. Paolo