From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: Help please! To track down GC trying to free an already freed object. Date: Tue, 2 Apr 2019 20:46:53 +0000 Message-ID: <20190402204653.GC25792@ACM> References: <20190402112537.GA6212@ACM> <835zrwfc21.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="1998"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mutt/1.10.1 (2018-07-13) Cc: Daniel Colascione , emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Apr 02 22:47:17 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1hBQJN-0000GV-9E for ged-emacs-devel@m.gmane.org; Tue, 02 Apr 2019 22:47:13 +0200 Original-Received: from localhost ([127.0.0.1]:41296 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hBQJM-0001NL-80 for ged-emacs-devel@m.gmane.org; Tue, 02 Apr 2019 16:47:12 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:38700) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hBQJ8-0001MJ-1v for emacs-devel@gnu.org; Tue, 02 Apr 2019 16:46:58 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hBQJ6-0002q0-Rl for emacs-devel@gnu.org; Tue, 02 Apr 2019 16:46:58 -0400 Original-Received: from colin.muc.de ([193.149.48.1]:52517 helo=mail.muc.de) by eggs.gnu.org with smtp (Exim 4.71) (envelope-from ) id 1hBQJ6-0002mO-EE for emacs-devel@gnu.org; Tue, 02 Apr 2019 16:46:56 -0400 Original-Received: (qmail 9807 invoked by uid 3782); 2 Apr 2019 20:46:54 -0000 Original-Received: from acm.muc.de (p4FE15EFB.dip0.t-ipconnect.de [79.225.94.251]) by colin.muc.de (tmda-ofmipd) with ESMTP; Tue, 02 Apr 2019 22:46:53 +0200 Original-Received: (qmail 25971 invoked by uid 1000); 2 Apr 2019 20:46:53 -0000 Content-Disposition: inline In-Reply-To: <835zrwfc21.fsf@gnu.org> X-Delivery-Agent: TMDA/1.1.12 (Macallan) X-Primary-Address: acm@muc.de X-detected-operating-system: by eggs.gnu.org: FreeBSD 9.x [fuzzy] X-Received-From: 193.149.48.1 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:234902 Archived-At: Hello, Eli. On Tue, Apr 02, 2019 at 22:21:26 +0300, Eli Zaretskii wrote: > > Date: Tue, 2 Apr 2019 12:09:59 -0700 > > From: "Daniel Colascione" > > Cc: emacs-devel@gnu.org > > > > rr is incredibly helpful for debugging this sort of problem. See > > https://rr-project.org/. You can record an rr session containing the > > crash, replay it, get to the crash, and then reverse-next, reverse-finish, > > and reverse-continue your way through the GC, running it in reverse until > > you find whatever it is that made mark_object on the dead object happen. > GDB supports reverse execution as well, on some platforms. On my GNU/Linux system, I tried to run 'reverse-next', and got the error message: Target multi-thread does not support this command. . :-( I suppose I could reconfigure without multi threading, but then the bug (which is reproducible) probably wouldn't happen in the same place. -- Alan Mackenzie (Nuremberg, Germany).