From owner-freebsd-current@FreeBSD.ORG Tue Mar 16 15:28:47 2004 Return-Path: Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 9A0DE16A4CE; Tue, 16 Mar 2004 15:28:47 -0800 (PST) Received: from tigra.ip.net.ua (tigra.ip.net.ua [82.193.96.10]) by mx1.FreeBSD.org (Postfix) with ESMTP id C3B9F43D2D; Tue, 16 Mar 2004 15:28:46 -0800 (PST) (envelope-from ru@ip.net.ua) Received: from heffalump.ip.net.ua (heffalump.ip.net.ua [82.193.96.213]) by tigra.ip.net.ua (8.12.10/8.12.9) with ESMTP id i2GNX8ee051102 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); Wed, 17 Mar 2004 01:33:10 +0200 (EET) (envelope-from ru@ip.net.ua) Received: (from ru@localhost) by heffalump.ip.net.ua (8.12.11/8.12.11) id i2GNSmj5062513; Wed, 17 Mar 2004 01:28:48 +0200 (EET) (envelope-from ru) Date: Wed, 17 Mar 2004 01:28:48 +0200 From: Ruslan Ermilov To: Dag-Erling Sm?rgrav Message-ID: <20040316232848.GR3462@ip.net.ua> References: <20040316225230.GO3462@ip.net.ua> Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha1; protocol="application/pgp-signature"; boundary="soWJpSPh+l8Y6Fy7" Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.6i X-Spam-Checker-Version: SpamAssassin 2.55 (1.174.2.19-2003-05-19-exp) cc: current@freebsd.org cc: net@freebsd.org Subject: Re: libalias patch for review / testing X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 16 Mar 2004 23:28:47 -0000 --soWJpSPh+l8Y6Fy7 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Wed, Mar 17, 2004 at 12:07:52AM +0100, Dag-Erling Sm?rgrav wrote: > Ruslan Ermilov writes: > > I know this code quite well. Where do you suspect could be a bug > > affecting -O2 compiles, or you just simply fixed -O2 and hope it > > will auto-fix the (possible) bugs in -O2? >=20 > Since there is no inline asm, the most likely suspect is aliasing, > which is what my patch tries to address. >=20 Hmm, read this again: : `-fstrict-aliasing' : Allows the compiler to assume the strictest aliasing rules : applicable to the language being compiled. For C (and C++), this : activates optimizations based on the type of expressions. In : particular, an object of one type is assumed never to reside at : the same address as an object of a different type, unless the : types are almost the same. For example, an `unsigned int' can : alias an `int', but not a `void*' or a `double'. A character type : may alias any other type. And asking myself a question: should those (void *)'s in your patch be (char *)'s instead, e.g., in twowords() and DifferentialChecksum(), or am I misreading the above? Also, the easiest way to check if strict aliasing is guilty for not working libalias compiled with -O2, is to compile the original code with -O2 -fno-strict-aliasing. You guys who have seen a problem, can you please check and confirm that? Cheers, --=20 Ruslan Ermilov FreeBSD committer ru@FreeBSD.org --soWJpSPh+l8Y6Fy7 Content-Type: application/pgp-signature Content-Disposition: inline -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.2.4 (FreeBSD) iD8DBQFAV42wUkv4P6juNwoRAjfoAKCFmQfpsRXd7YlDm94ly3fatLaGgQCfb0kR H9QhpVVaijqCfWVt877nLd8= =UvNf -----END PGP SIGNATURE----- --soWJpSPh+l8Y6Fy7--