From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Eric Blake Newsgroups: gmane.comp.sysutils.autoconf.bugs,gmane.lisp.guile.bugs Subject: Re: bug in check for stack growth direction in _AC_LIBOBJ_ALLOCA Date: Mon, 20 Jun 2011 11:56:22 -0600 Organization: Red Hat Message-ID: <4DFF89C6.5040906@redhat.com> References: <87d3ic92sc.fsf@pobox.com> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="------------enigF954552397E53B6200F7DDE6" X-Trace: dough.gmane.org 1308596011 3002 80.91.229.12 (20 Jun 2011 18:53:31 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Mon, 20 Jun 2011 18:53:31 +0000 (UTC) Cc: bug-guile , bug-autoconf@gnu.org To: Andy Wingo Original-X-From: bug-autoconf-bounces+gnu-bug-autoconf=m.gmane.org@gnu.org Mon Jun 20 20:53:27 2011 Return-path: Envelope-to: gnu-bug-autoconf@m.gmane.org Original-Received: from lists.gnu.org ([140.186.70.17]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1QYjbB-0002N7-6M for gnu-bug-autoconf@m.gmane.org; Mon, 20 Jun 2011 20:53:25 +0200 Original-Received: from localhost ([::1]:58888 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QYjbA-0004bg-41 for gnu-bug-autoconf@m.gmane.org; Mon, 20 Jun 2011 14:53:24 -0400 Original-Received: from eggs.gnu.org ([140.186.70.92]:34588) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QYii2-0004so-2g for bug-autoconf@gnu.org; Mon, 20 Jun 2011 13:56:27 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QYii0-00039M-FS for bug-autoconf@gnu.org; Mon, 20 Jun 2011 13:56:25 -0400 Original-Received: from mx1.redhat.com ([209.132.183.28]:30048) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QYihz-00036l-Sk; Mon, 20 Jun 2011 13:56:24 -0400 Original-Received: from int-mx12.intmail.prod.int.phx2.redhat.com (int-mx12.intmail.prod.int.phx2.redhat.com [10.5.11.25]) by mx1.redhat.com (8.14.4/8.14.4) with ESMTP id p5KHuM6g031678 (version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); Mon, 20 Jun 2011 13:56:23 -0400 Original-Received: from [10.3.113.98] (ovpn-113-98.phx2.redhat.com [10.3.113.98]) by int-mx12.intmail.prod.int.phx2.redhat.com (8.14.4/8.14.4) with ESMTP id p5KHuM2l020158; Mon, 20 Jun 2011 13:56:22 -0400 User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc14 Lightning/1.0b3pre Mnenhy/0.8.3 Thunderbird/3.1.10 In-Reply-To: <87d3ic92sc.fsf@pobox.com> X-Enigmail-Version: 1.1.2 OpenPGP: url=http://people.redhat.com/eblake/eblake.gpg X-Scanned-By: MIMEDefang 2.68 on 10.5.11.25 X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 209.132.183.28 X-BeenThere: bug-autoconf@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: Bug reports for autoconf List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-autoconf-bounces+gnu-bug-autoconf=m.gmane.org@gnu.org Original-Sender: bug-autoconf-bounces+gnu-bug-autoconf=m.gmane.org@gnu.org Xref: news.gmane.org gmane.comp.sysutils.autoconf.bugs:7959 gmane.lisp.guile.bugs:5684 Archived-At: This is an OpenPGP/MIME signed message (RFC 2440 and 3156) --------------enigF954552397E53B6200F7DDE6 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable On 06/17/2011 04:21 AM, Andy Wingo wrote: > wingo@badger:/tmp$ gcc -O1 -o test foo.c > wingo@badger:/tmp$ ./test; echo $? > 1 > wingo@badger:/tmp$ gcc -O3 -o test foo.c > wingo@badger:/tmp$ ./test; echo $? > 0 If I understand correctly, 0 is a correct result, just not optimal. Improvements for getting the optimal result in spite of gcc optimizations are welcome (the more we can determine at compile time, the less work we have to do at runtime), but any correctly written program should already handle the case of an indeterminate compile-time probe (the probe should return 1 or -1 for known directions, and 0 for undetermined direction). --=20 Eric Blake eblake@redhat.com +1-801-349-2682 Libvirt virtualization library http://libvirt.org --------------enigF954552397E53B6200F7DDE6 Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1.4.11 (GNU/Linux) Comment: Public key at http://people.redhat.com/eblake/eblake.gpg Comment: Using GnuPG with Fedora - http://enigmail.mozdev.org/ iQEcBAEBCAAGBQJN/4nGAAoJEKeha0olJ0NqrsEH/iHwsufm53Au3SpqcEZLkl/H WUZJD57hQ91mXcdikzHMdwx5MYmUDUt0TYx9Af6TzSkRG9Ih3mL58hUCvFcqs6py XINZP+RHe7irZRP7p9SiI1S0ChyWkB7JaaAqR2RQs44vpi7tOsaiofCZ7aVzj9QE qULuGS5b5r+6YJ19eEfFML2nZ9sqWjfM6+SAFH9wpI3ZvXjJZt5slG0U8O9Rrab3 SFJtoqx1b30CHASa3AL7+jIDD+7pqoPMI8+8OpFhM4jGCzOtRMe/r2hTFHaSzM9d p3pOTGuXM7/aeJPLkmetsgP894Ljs4WSnkWjpgB0SEAW/VF3jhMYgvn7SyPMIP0= =C9nP -----END PGP SIGNATURE----- --------------enigF954552397E53B6200F7DDE6--