From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Strange problems with data-tests.el Date: Mon, 13 Aug 2018 18:05:06 +0300 Message-ID: <83o9e6joil.fsf@gnu.org> References: <831sb3l9cx.fsf@gnu.org> <486fc1b9-88a7-93e0-dd45-4f8f1d8a77d1@cs.ucla.edu> NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1534172624 26145 195.159.176.226 (13 Aug 2018 15:03:44 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 13 Aug 2018 15:03:44 +0000 (UTC) Cc: emacs-devel@gnu.org To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Aug 13 17:03:40 2018 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1fpENe-0006gJ-Kb for ged-emacs-devel@m.gmane.org; Mon, 13 Aug 2018 17:03:38 +0200 Original-Received: from localhost ([::1]:39955 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fpEPk-0001C2-SX for ged-emacs-devel@m.gmane.org; Mon, 13 Aug 2018 11:05:48 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:49262) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fpEP1-0001Bx-7g for emacs-devel@gnu.org; Mon, 13 Aug 2018 11:05:08 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1fpEOx-0002RY-8h for emacs-devel@gnu.org; Mon, 13 Aug 2018 11:05:03 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:53340) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1fpEOx-0002RM-4S; Mon, 13 Aug 2018 11:04:59 -0400 Original-Received: from [176.228.60.248] (port=3334 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1fpEOw-0006qP-KI; Mon, 13 Aug 2018 11:04:59 -0400 In-reply-to: <486fc1b9-88a7-93e0-dd45-4f8f1d8a77d1@cs.ucla.edu> (message from Paul Eggert on Sun, 12 Aug 2018 15:43:14 -0700) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2001:4830:134:3::e X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:228483 Archived-At: > From: Paul Eggert > Cc: emacs-devel@gnu.org > Date: Sun, 12 Aug 2018 15:43:14 -0700 > > I suspect that it's only bad luck that exposed the problem, that is, that the > recent bignum or misc changes triggered the bug only because they caused GCC to > optimize in a different way. No, it didn't happen because of the bignum merge. I found a 26.0.90 pretest that was built with -Og, and sure enough, the problem is there as well. And when I installed your patch in that version and recompiled, the problem went away. So I think this is a relatively old bug, and we should backport it to the emacs-26 branch. WDYT? > In theory if we're unlucky the bug could recur, since GCC doesn't > make promises in this area. However, I changed arithcompare in such > a way that GCC would have to be pretty perverse to cause the problem > to resurface, and similarly for other C compilers. Thanks.