From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from list by lists.gnu.org with archive (Exim 4.71) id 1Z5aJK-0005A7-Ld for mharc-qemu-trivial@gnu.org; Thu, 18 Jun 2015 09:56:54 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57909) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5aJI-00057G-4u for qemu-trivial@nongnu.org; Thu, 18 Jun 2015 09:56:53 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z5aJH-0002GF-8w for qemu-trivial@nongnu.org; Thu, 18 Jun 2015 09:56:52 -0400 Received: from mx1.redhat.com ([209.132.183.28]:39667) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5aJ9-0002AP-9I; Thu, 18 Jun 2015 09:56:43 -0400 Received: from int-mx10.intmail.prod.int.phx2.redhat.com (int-mx10.intmail.prod.int.phx2.redhat.com [10.5.11.23]) by mx1.redhat.com (Postfix) with ESMTPS id D13FD2F6687; Thu, 18 Jun 2015 13:56:42 +0000 (UTC) Received: from nilsson.home.kraxel.org (ovpn-116-40.ams2.redhat.com [10.36.116.40]) by int-mx10.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id t5IDuerS003644; Thu, 18 Jun 2015 09:56:41 -0400 Message-ID: <1434635799.4968.33.camel@redhat.com> From: Gerd Hoffmann To: Frediano Ziglio Date: Thu, 18 Jun 2015 15:56:39 +0200 In-Reply-To: <789608027.17460503.1434624352586.JavaMail.zimbra@redhat.com> References: <1434028677-26160-1-git-send-email-fziglio@redhat.com> <1434028677-26160-2-git-send-email-fziglio@redhat.com> <5581CA0E.6080906@msgid.tls.msk.ru> <834587703.17443662.1434621536154.JavaMail.zimbra@redhat.com> <1434622723.4968.16.camel@redhat.com> <789608027.17460503.1434624352586.JavaMail.zimbra@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.68 on 10.5.11.23 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 209.132.183.28 Cc: qemu-trivial@nongnu.org, Michael Tokarev , qemu-devel@nongnu.org Subject: Re: [Qemu-trivial] [Qemu-devel] [PATCH 2/2] Check value for invalid negative values X-BeenThere: qemu-trivial@nongnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 18 Jun 2015 13:56:53 -0000 On Do, 2015-06-18 at 06:45 -0400, Frediano Ziglio wrote: > > On Do, 2015-06-18 at 05:58 -0400, Frediano Ziglio wrote: > > > For the same reason there is the v >= l test. > > > The v >= l test state that the value can be out of range so it not always a > > > constant in the range. > > > Adding the v < 0 check for every invalid value. As these are executed only > > > for logging should not be a performance penalty. > > > I also hope the compiler is able to optimize > > > > > > if (v < 0 || v >= l) > > > > > > with > > > > > > if ((unsigned) v >= l) > > > > Just make v explicitly unsigned? > > > > cheers, > > Gerd > > > > Do you mean in the prototype? Yes. > Well, this could have side effect due to different conversions so is not a so trivial patch. What side effects? I don't expect any for in-range values, and how exactly we catch out-of-range values doesn't really matter ... cheers, Gerd From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:57891) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Z5aJD-00052K-EL for qemu-devel@nongnu.org; Thu, 18 Jun 2015 09:56:51 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Z5aJ9-0002AW-EF for qemu-devel@nongnu.org; Thu, 18 Jun 2015 09:56:47 -0400 Message-ID: <1434635799.4968.33.camel@redhat.com> From: Gerd Hoffmann Date: Thu, 18 Jun 2015 15:56:39 +0200 In-Reply-To: <789608027.17460503.1434624352586.JavaMail.zimbra@redhat.com> References: <1434028677-26160-1-git-send-email-fziglio@redhat.com> <1434028677-26160-2-git-send-email-fziglio@redhat.com> <5581CA0E.6080906@msgid.tls.msk.ru> <834587703.17443662.1434621536154.JavaMail.zimbra@redhat.com> <1434622723.4968.16.camel@redhat.com> <789608027.17460503.1434624352586.JavaMail.zimbra@redhat.com> Content-Type: text/plain; charset="UTF-8" Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [Qemu-trivial] [PATCH 2/2] Check value for invalid negative values List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Frediano Ziglio Cc: qemu-trivial@nongnu.org, Michael Tokarev , qemu-devel@nongnu.org On Do, 2015-06-18 at 06:45 -0400, Frediano Ziglio wrote: > > On Do, 2015-06-18 at 05:58 -0400, Frediano Ziglio wrote: > > > For the same reason there is the v >= l test. > > > The v >= l test state that the value can be out of range so it not always a > > > constant in the range. > > > Adding the v < 0 check for every invalid value. As these are executed only > > > for logging should not be a performance penalty. > > > I also hope the compiler is able to optimize > > > > > > if (v < 0 || v >= l) > > > > > > with > > > > > > if ((unsigned) v >= l) > > > > Just make v explicitly unsigned? > > > > cheers, > > Gerd > > > > Do you mean in the prototype? Yes. > Well, this could have side effect due to different conversions so is not a so trivial patch. What side effects? I don't expect any for in-range values, and how exactly we catch out-of-range values doesn't really matter ... cheers, Gerd