From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#34655: 26.1.92; Segfault in module with --module-assertions Date: Sun, 17 Mar 2019 19:08:01 +0200 Message-ID: <83lg1dwhse.fsf@gnu.org> References: <874l8r1t3a.fsf@tcd.ie> <8336oamu3y.fsf@gnu.org> <87h8c1cv6l.fsf@tcd.ie> Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="145800"; mail-complaints-to="usenet@blaine.gmane.org" Cc: 34655@debbugs.gnu.org, p.stephani2@gmail.com To: "Basil L. Contovounesios" Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Sun Mar 17 18:09:14 2019 Return-path: Envelope-to: geb-bug-gnu-emacs@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 1h5ZHd-000bri-Io for geb-bug-gnu-emacs@m.gmane.org; Sun, 17 Mar 2019 18:09:13 +0100 Original-Received: from localhost ([127.0.0.1]:57978 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h5ZHc-0000ZV-BS for geb-bug-gnu-emacs@m.gmane.org; Sun, 17 Mar 2019 13:09:12 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:48673) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h5ZHT-0000ZD-88 for bug-gnu-emacs@gnu.org; Sun, 17 Mar 2019 13:09:03 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h5ZHS-000286-Gp for bug-gnu-emacs@gnu.org; Sun, 17 Mar 2019 13:09:03 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:34159) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1h5ZHS-00027t-Ag for bug-gnu-emacs@gnu.org; Sun, 17 Mar 2019 13:09:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1h5ZHS-0005sA-0p for bug-gnu-emacs@gnu.org; Sun, 17 Mar 2019 13:09:02 -0400 X-Loop: help-debbugs@gnu.org Resent-From: Eli Zaretskii Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Sun, 17 Mar 2019 17:09:01 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 34655 X-GNU-PR-Package: emacs Original-Received: via spool by 34655-submit@debbugs.gnu.org id=B34655.155284250122520 (code B ref 34655); Sun, 17 Mar 2019 17:09:01 +0000 Original-Received: (at 34655) by debbugs.gnu.org; 17 Mar 2019 17:08:21 +0000 Original-Received: from localhost ([127.0.0.1]:47703 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1h5ZGn-0005rA-4U for submit@debbugs.gnu.org; Sun, 17 Mar 2019 13:08:21 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:34241) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1h5ZGl-0005qw-Nl for 34655@debbugs.gnu.org; Sun, 17 Mar 2019 13:08:20 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:49701) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h5ZGg-0001t2-BF; Sun, 17 Mar 2019 13:08:14 -0400 Original-Received: from [176.228.60.248] (port=3340 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1h5ZGf-0003Vo-OB; Sun, 17 Mar 2019 13:08:14 -0400 In-reply-to: <87h8c1cv6l.fsf@tcd.ie> (contovob@tcd.ie) 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: 209.51.188.43 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:156440 Archived-At: > From: "Basil L. Contovounesios" > Cc: <34655@debbugs.gnu.org>, Philipp Stephani > Date: Sun, 17 Mar 2019 16:38:58 +0000 > > These reveal that value_to_lisp eventually returns a corrupted string, > but I don't know why. Did you try to identify the code which causes the corruption, i.e. the data is valid before that code runs, and invalid after that? If not, can you try? The way to do that is by painstakingly stepping through the code while examining the relevant data, possibly with help of watchpoints and displays set up by the GDB "display" command. > I've seen comments in src/fileio.c referring to string-relocation > during GC; could this be at play here? It could be, if your module code holds onto C pointers to Lisp string data while Emacs runs parts of the interpreter which could GC. Does that happen anywhere in your code or in the code involved in module-assertions? > Either way, do you have any suggestions on how to proceed? See above. I tried at the time to reproduce your problem, and failed. But I did that on Windows, where I needed to replace the non-existent realpath by an equivalent function, so it's not a faithful reproduction. I will see if I can find time to look at this on a GNU machine, unless someone beats me to it. > 8. bt full > 9. f 2 > 10. p p > 11. pr [#] > 12. xpr Why did you expect 'p' to be a valid Lisp object? It's actually a pointer to a Lisp object, i.e. try (gdb) p *p (gdb) xpr