From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#24764: 25.1.50; Another crash in automatic gc Date: Sat, 22 Oct 2016 15:01:25 +0300 Message-ID: <83a8dwr3sa.fsf@gnu.org> References: <87vawkk9l1.fsf@web.de> <83d1isr94u.fsf@gnu.org> <87vawkboh0.fsf@linux-m68k.org> Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1477137754 2838 195.159.176.226 (22 Oct 2016 12:02:34 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 22 Oct 2016 12:02:34 +0000 (UTC) Cc: michael_heerdegen@web.de, 24764@debbugs.gnu.org To: Andreas Schwab Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Sat Oct 22 14:02:30 2016 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1bxv0B-0006p2-Fb for geb-bug-gnu-emacs@m.gmane.org; Sat, 22 Oct 2016 14:02:15 +0200 Original-Received: from localhost ([::1]:37082 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bxv0D-0004hb-Fr for geb-bug-gnu-emacs@m.gmane.org; Sat, 22 Oct 2016 08:02:17 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:58419) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bxv07-0004hS-Gd for bug-gnu-emacs@gnu.org; Sat, 22 Oct 2016 08:02:12 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bxv03-0001C5-Ke for bug-gnu-emacs@gnu.org; Sat, 22 Oct 2016 08:02:11 -0400 Original-Received: from debbugs.gnu.org ([208.118.235.43]:58728) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1bxv03-0001Bu-HM for bug-gnu-emacs@gnu.org; Sat, 22 Oct 2016 08:02:07 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1bxuzy-0002IL-5m for bug-gnu-emacs@gnu.org; Sat, 22 Oct 2016 08:02:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sat, 22 Oct 2016 12:02:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 24764 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 24764-submit@debbugs.gnu.org id=B24764.14771377048798 (code B ref 24764); Sat, 22 Oct 2016 12:02:02 +0000 Original-Received: (at 24764) by debbugs.gnu.org; 22 Oct 2016 12:01:44 +0000 Original-Received: from localhost ([127.0.0.1]:45894 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bxuzg-0002Hq-Bw for submit@debbugs.gnu.org; Sat, 22 Oct 2016 08:01:44 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:38933) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1bxuze-0002Hd-Vj for 24764@debbugs.gnu.org; Sat, 22 Oct 2016 08:01:43 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bxuzV-0000ti-T5 for 24764@debbugs.gnu.org; Sat, 22 Oct 2016 08:01:37 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:48862) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bxuzV-0000tU-Q3; Sat, 22 Oct 2016 08:01:33 -0400 Original-Received: from 84.94.185.246.cable.012.net.il ([84.94.185.246]:1566 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1bxuzV-0007ml-5m; Sat, 22 Oct 2016 08:01:33 -0400 In-reply-to: <87vawkboh0.fsf@linux-m68k.org> (message from Andreas Schwab on Sat, 22 Oct 2016 13:41:15 +0200) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 208.118.235.43 X-BeenThere: bug-gnu-emacs@gnu.org List-Id: "Bug reports for GNU Emacs, the Swiss army knife of text editors" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.org gmane.emacs.bugs:124821 Archived-At: > From: Andreas Schwab > Cc: Michael Heerdegen , 24764@debbugs.gnu.org > Date: Sat, 22 Oct 2016 13:41:15 +0200 > > >> (gdb) bt full > >> #0 0x000000000058aae0 in unchain_marker (marker=0x88e9968) at marker.c:605 > >> tail = 0x2020200020202020 <<<<<<<<<<<<<<<<<<<<<<<< > >> prev = 0x2020200020202030 <<<<<<<<<<<<<<<<<<<<<<<< > > > > Your marker pointers are actually full of blank (and other ASCII) > > characters. So some code somewhere either writes past the end of some > > stack-based array or otherwise overwrites the stack. > > More likely, BUF_MARKERS is already overwritten. Could be, perhaps because of this: > Or maybe your system, too, uses ralloc.c, and this is one more > manifestation of some buffer or string relocated while some code hangs > to the C pointers of the original contents. > Finding the place where a member of a struct buffer is overwritten > can be done with a watchpoint. Yes. But IME just a watchpoint with no conditions gets triggered too frequently to be useful, which is why a more-or-less specific recipe for reproducing the problem would be beneficial, because then you could activate the watchpoint only when it matters, or specify a condition for it to trigger only when that matters. For starters, I'd try to see whether 'tail' and 'prev' always have these values when GC crashes.