From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50264) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YDxGo-0004d6-1C for qemu-devel@nongnu.org; Wed, 21 Jan 2015 10:32:49 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YDxGl-0001JU-0Y for qemu-devel@nongnu.org; Wed, 21 Jan 2015 10:32:37 -0500 Received: from mail-wg0-x236.google.com ([2a00:1450:400c:c00::236]:64663) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YDxGk-0001J7-OT for qemu-devel@nongnu.org; Wed, 21 Jan 2015 10:32:34 -0500 Received: by mail-wg0-f54.google.com with SMTP id b13so10335219wgh.13 for ; Wed, 21 Jan 2015 07:32:34 -0800 (PST) Sender: Paolo Bonzini Message-ID: <54BFC68E.20105@redhat.com> Date: Wed, 21 Jan 2015 16:32:30 +0100 From: Paolo Bonzini MIME-Version: 1.0 References: <1420790680-3266-1-git-send-email-blaschka@linux.vnet.ibm.com> <1420790680-3266-3-git-send-email-blaschka@linux.vnet.ibm.com> <87h9vln5tm.fsf@blackfin.pond.sub.org> <20150120110348.66afc423.cornelia.huck@de.ibm.com> <87ppa9iqco.fsf@blackfin.pond.sub.org> <87bnlthaqe.fsf@blackfin.pond.sub.org> <20150120142052.GA44419@tuxmaker.boeblingen.de.ibm.com> <87bnltryii.fsf@blackfin.pond.sub.org> <87twzkmjqx.fsf@blackfin.pond.sub.org> <87mw5cfdyy.fsf@blackfin.pond.sub.org> In-Reply-To: <87mw5cfdyy.fsf@blackfin.pond.sub.org> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH 2/3 V3] s390: implement pci instructions List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Markus Armbruster , Peter Maydell Cc: Cornelia Huck , Christian Borntraeger , Frank Blaschka , Frank Blaschka , QEMU Developers On 21/01/2015 14:41, Markus Armbruster wrote: > I suspect we shift signed values all over the place, without regard for > signed overflow. Machines are fine with that, but some day some > compiler wiseguy may find a way to save a femtosecond or two for some > program that never does that, breaking programs that do it, and then > we'll be in trouble. As I said before, if there was a way to save those femtoseconds, they would have already tried. More likely, the compiler people know they would become the main attractions at pitch and feather spectacles, so they're not going to treat that as undefined behavior. Paolo