From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.bugs Subject: bug#17893: 24.4.50; (error "Marker does not point anywhere") Date: Mon, 20 Nov 2017 11:51:45 -0500 Message-ID: References: <8facd635-be88-4990-8e7d-538db19c3e1a@default> <04af8576-c419-4d35-9c6e-7170828ac949@default> <83h8tpdkd4.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1511197044 23872 195.159.176.226 (20 Nov 2017 16:57:24 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 20 Nov 2017 16:57:24 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) Cc: 17893@debbugs.gnu.org, "Charles A. Roelli" To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Mon Nov 20 17:57:20 2017 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 1eGpNl-0005Va-71 for geb-bug-gnu-emacs@m.gmane.org; Mon, 20 Nov 2017 17:57:17 +0100 Original-Received: from localhost ([::1]:58273 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eGpNn-0000ei-7g for geb-bug-gnu-emacs@m.gmane.org; Mon, 20 Nov 2017 11:57:19 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:52182) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eGpJn-0004zB-0u for bug-gnu-emacs@gnu.org; Mon, 20 Nov 2017 11:53:12 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eGpJi-0004QG-6e for bug-gnu-emacs@gnu.org; Mon, 20 Nov 2017 11:53:11 -0500 Original-Received: from debbugs.gnu.org ([208.118.235.43]:40578) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1eGpJi-0004Or-2z for bug-gnu-emacs@gnu.org; Mon, 20 Nov 2017 11:53:06 -0500 Original-Received: from Debian-debbugs by debbugs.gnu.org with local (Exim 4.84_2) (envelope-from ) id 1eGpJe-0001WB-A0 for bug-gnu-emacs@gnu.org; Mon, 20 Nov 2017 11:53:02 -0500 X-Loop: help-debbugs@gnu.org Resent-From: Stefan Monnier Original-Sender: "Debbugs-submit" Resent-CC: bug-gnu-emacs@gnu.org Resent-Date: Mon, 20 Nov 2017 16:53:02 +0000 Resent-Message-ID: Resent-Sender: help-debbugs@gnu.org X-GNU-PR-Message: followup 17893 X-GNU-PR-Package: emacs X-GNU-PR-Keywords: Original-Received: via spool by 17893-submit@debbugs.gnu.org id=B17893.15111967245771 (code B ref 17893); Mon, 20 Nov 2017 16:53:02 +0000 Original-Received: (at 17893) by debbugs.gnu.org; 20 Nov 2017 16:52:04 +0000 Original-Received: from localhost ([127.0.0.1]:49259 helo=debbugs.gnu.org) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eGpIi-0001V0-Gw for submit@debbugs.gnu.org; Mon, 20 Nov 2017 11:52:04 -0500 Original-Received: from pmta11.teksavvy.com ([76.10.157.34]:60665) by debbugs.gnu.org with esmtp (Exim 4.84_2) (envelope-from ) id 1eGpIf-0001UV-UW for 17893@debbugs.gnu.org; Mon, 20 Nov 2017 11:52:02 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A2GKJQB+BxNa/3HQSC1bHAEBAQQBAQoBAYM8gVSDW4VYhHmPQYF9lnKCAYVFAoR/QxQBAQEBAQEBAQEDaCiFIAEEAXkFCwsNJxIUGDEuigIIqwEhAopSAQEBAQYCASWDNIIHgz6DK4UEhg8FkwiGGokcoH8ohzGXbDYjgXQ0IQgySYJlhHwjjAIBAQE X-IPAS-Result: A2GKJQB+BxNa/3HQSC1bHAEBAQQBAQoBAYM8gVSDW4VYhHmPQYF9lnKCAYVFAoR/QxQBAQEBAQEBAQEDaCiFIAEEAXkFCwsNJxIUGDEuigIIqwEhAopSAQEBAQYCASWDNIIHgz6DK4UEhg8FkwiGGokcoH8ohzGXbDYjgXQ0IQgySYJlhHwjjAIBAQE X-IronPort-AV: E=Sophos;i="5.44,428,1505793600"; d="scan'208";a="9836692" Original-Received: from unknown (HELO pastel.home) ([45.72.208.113]) by smtp.teksavvy.com with ESMTP; 20 Nov 2017 11:51:46 -0500 Original-Received: by pastel.home (Postfix, from userid 20848) id DCCC5614F0; Mon, 20 Nov 2017 11:51:45 -0500 (EST) In-Reply-To: <83h8tpdkd4.fsf@gnu.org> (Eli Zaretskii's message of "Mon, 20 Nov 2017 17:45:43 +0200") 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:140143 Archived-At: > Bother: this is actually the tip of an iceberg. Buffer local > variables that get cloned by clone-buffer could hold any number of > markers pointing into the original buffer. Indeed. > E.g., info.el itself maintains a per-buffer marker in > Info-tag-table-marker; evaluate it after M-n and see what it > tells you. And for that reason, clone-buffer runs `clone-buffer-hook`, which Info-mode uses to do: (defun Info-clone-buffer () (when (bufferp Info-tag-table-buffer) (setq Info-tag-table-buffer (with-current-buffer Info-tag-table-buffer (clone-buffer)))) (let ((m Info-tag-table-marker)) (when (markerp m) (setq Info-tag-table-marker (if (and (marker-position m) (bufferp Info-tag-table-buffer)) (with-current-buffer Info-tag-table-buffer (copy-marker (marker-position m))) (make-marker)))))) which I believe DTRT. > For mark-ring, I think it's easier to just reset it to nil in the new > clone (it's arguably even more correct, since this is a fresh buffer), I didn't think about it when I saw Charles's patch, but yes resetting it to nil would make sense. > but in general this is a ticking bomb, unless I'm missing something. > If I'm right, the only solution is to walk all the markers that point > to the parent buffer and clone them to point to the cloned buffer > (this has to be done in C). This can't be done in C because after creating those new markers, where would we store them? E.g. cloning all the markers that are in `mark-ring` would just create new markers but it would fail to create a new list holding those markers, stored in the new buffer-local value of `mark-ring` (walking the markers doesn't tell us that they're referred to from `mark-ring`). Hence clone-buffer-hook, which doesn't solve the problem in itself, but makes it possible to fix it manually where needed. Stefan