From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.bugs Subject: bug#41321: 27.0.91; Emacs aborts due to invalid pseudovector objects Date: Sat, 30 May 2020 14:31:02 +0300 Message-ID: <831rn1mzgp.fsf@gnu.org> References: <83zha8cgpi.fsf@gnu.org> <83imgublku.fsf@gnu.org> <831rncjuwf.fsf@gnu.org> <83h7w5xvfa.fsf@gnu.org> <83y2phwb9x.fsf@gnu.org> <83r1v9w9vi.fsf@gnu.org> <83mu5xw50d.fsf@gnu.org> <83k110wxte.fsf@gnu.org> <4bab5f55-95fe-cf34-e490-1d4319728395@cs.ucla.edu> <837dwyvi74.fsf@gnu.org> <1484f569-c260-9fb0-bfe1-67897de289d3@cs.ucla.edu> <83blm9tn4j.fsf@gnu.org> <4aeb8963-4fd1-fcd4-e6e1-be409ab54775@cs.ucla.edu> <83tuzzrk30.fsf@gnu.org> <749bc7d0-6376-ec2e-7f84-dcd3a3cea465@cs.ucla.edu> <83sgfjqn49.fsf@gnu.org> <83eer2m0b6.fsf@gnu.org> <83367hn624.fsf@gnu.org> Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="62659"; mail-complaints-to="usenet@ciao.gmane.io" Cc: eggert@cs.ucla.edu, 41321@debbugs.gnu.org, monnier@iro.umontreal.ca To: Pip Cet Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Sat May 30 13:32:18 2020 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jezir-000GDa-S1 for geb-bug-gnu-emacs@m.gmane-mx.org; Sat, 30 May 2020 13:32:17 +0200 Original-Received: from localhost ([::1]:54722 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jeziq-0008OO-Us for geb-bug-gnu-emacs@m.gmane-mx.org; Sat, 30 May 2020 07:32:16 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:38036) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1jezic-0008Iu-RR for bug-gnu-emacs@gnu.org; Sat, 30 May 2020 07:32:02 -0400 Original-Received: from debbugs.gnu.org ([209.51.188.43]:45457) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_128_GCM_SHA256:128) (Exim 4.90_1) (envelope-from ) id 1jezic-0002ze-HU for bug-gnu-emacs@gnu.org; Sat, 30 May 2020 07:32:02 -0400 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1jezic-0006YL-Ci for bug-gnu-emacs@gnu.org; Sat, 30 May 2020 07:32:02 -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, 30 May 2020 11:32:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 41321 X-GNU-PR-Package: emacs Original-Received: via spool by 41321-submit@debbugs.gnu.org id=B41321.159083828123101 (code B ref 41321); Sat, 30 May 2020 11:32:02 +0000 Original-Received: (at 41321) by debbugs.gnu.org; 30 May 2020 11:31:21 +0000 Original-Received: from localhost ([127.0.0.1]:57003 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jezhw-00060C-Mm for submit@debbugs.gnu.org; Sat, 30 May 2020 07:31:21 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:58626) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1jezhu-0005sm-5w for 41321@debbugs.gnu.org; Sat, 30 May 2020 07:31:18 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:33073) by eggs.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jezhj-0002I3-Id; Sat, 30 May 2020 07:31:10 -0400 Original-Received: from [176.228.60.248] (port=4697 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1jezhi-0000q0-Qz; Sat, 30 May 2020 07:31:07 -0400 In-Reply-To: (message from Pip Cet on Sat, 30 May 2020 11:06:52 +0000) X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list 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-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:181222 Archived-At: > From: Pip Cet > Date: Sat, 30 May 2020 11:06:52 +0000 > Cc: eggert@cs.ucla.edu, 41321@debbugs.gnu.org, > Stefan Monnier > > > I understand that part, but my question was why, even before the > > change in max_align_t, did we start requiring 8-byte alignment on > > systems where that is not automatically guaranteed? > > I don't know. As I said, I think that was always buggy on pdumper > systems, though the bug was very subtle. My guess is it predates > pdumper, at which time it was a valid optimization. How is pdumper involved here? > > So this alignment requirement is only due to pthreads being used? > > I'm not sure what you're asking. Obviously there are systems on which > unaligned accesses will fault or be very slow indeed, so we need to > make sure, say, pure space allocations are aligned somehow. That > requires a LISP_ALIGNMENT of 8. Everything beyond that is only for > performance, pthreads, and SIMD types. If the system guarantees 4-byte alignment from malloc (and/or a similar alignment of the runtime C stack), then using that doesn't trigger problems related to unaligned accesses, right? So let me rephrase: why isn't 4-byte alignment "good enough" for us on systems where malloc and the runtime stack are guaranteed to be thus aligned? > > If > > the two 32-bit parts of the object are non-contiguous, will we be able > > to recognize such an object, and will we be able to mark it correctly, > > and if so, how? IOW, don't we need the upper 32-bit (which encodes > > the object type) for the purposes of marking it? > > For everything but symbols, we don't, mark_maybe_pointer called on the > low 32 bits suffices. For symbols, mark_maybe_pointer needs to be > changed to also check the pointer at + &lispsym. Right, that's what I thought. So this issue also has to be fixed on emacs-27 in order for us to provide a stable Emacs 27.