From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: Edebug corrupting point in buffers. Date: Tue, 1 Nov 2022 13:42:03 +0000 Message-ID: References: <83wn8fcgvd.fsf@gnu.org> <83iljydh7e.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="11658"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Tue Nov 01 18:13:29 2022 Return-path: Envelope-to: ged-emacs-devel@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 1opupM-0002tL-PE for ged-emacs-devel@m.gmane-mx.org; Tue, 01 Nov 2022 18:13:28 +0100 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oprWw-00039X-Kx; Tue, 01 Nov 2022 09:42:14 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oprWu-00039O-Ff for emacs-devel@gnu.org; Tue, 01 Nov 2022 09:42:12 -0400 Original-Received: from mx3.muc.de ([193.149.48.5]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oprWq-000656-HF for emacs-devel@gnu.org; Tue, 01 Nov 2022 09:42:12 -0400 Original-Received: (qmail 95659 invoked by uid 3782); 1 Nov 2022 14:42:04 +0100 Original-Received: from acm.muc.de (p4fe15c46.dip0.t-ipconnect.de [79.225.92.70]) (using STARTTLS) by colin.muc.de (tmda-ofmipd) with ESMTP; Tue, 01 Nov 2022 14:42:03 +0100 Original-Received: (qmail 4337 invoked by uid 1000); 1 Nov 2022 13:42:03 -0000 Content-Disposition: inline In-Reply-To: <83iljydh7e.fsf@gnu.org> X-Submission-Agent: TMDA/1.3.x (Ph3nix) X-Primary-Address: acm@muc.de Received-SPF: pass client-ip=193.149.48.5; envelope-from=acm@muc.de; helo=mx3.muc.de X-Spam_score_int: -18 X-Spam_score: -1.9 X-Spam_bar: - X-Spam_report: (-1.9 / 5.0 requ) BAYES_00=-1.9, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: "Emacs-devel" Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:298944 Archived-At: Hello, Eli. On Tue, Nov 01, 2022 at 13:53:09 +0200, Eli Zaretskii wrote: > > Date: Tue, 1 Nov 2022 11:41:02 +0000 > > Cc: emacs-devel@gnu.org > > From: Alan Mackenzie > > > > +If the value is a list of buffer names (recommended), only those > > > > +buffers will have their buffer points restored. Otherwise, t means > > > > +restore all buffers\\=' points, and nil means none. > > > If we indeed need such an option, why shouldn't it be Edebug's > > > business to automatically keep point in all buffers that are displayed > > > in some window? It doesn't strike me as the best UI to burden the > > > user with that task. > > It would be intolerable for users. Say during an edebug session, the > > user makes some notes in buffer my-notes.txt. Execute an instruction, > > then go back to my-notes.txt. Point has been "restored" to before the > > new notes. That would happen in every buffer. > ??? Why would point be restored to the value before the last move of > point? The program you are debugging doesn't affect that buffer with > notes, does it? Probably not, but it might. The point is, edebug can't know [*] which buffers have been modified by edebug itself, and which have been modified by the user. Some might have been modified by both. [*] Without significant enhancement to edebug. > Maybe I don't understand what your patch does, then. I thought it was > supposed to _prevent_ such moves from happening. In the blank line in test-edebug.el, the patch prevents emacs.README's buffer-point being set to the window-point of the window in which the buffer is displayed. > > With test-edebug.el being > > ######################################################################### > > 1 (defun test-edebug () > > 2 (let ((A "*scratch*") (B "emacs.README")) > > 3 (set-buffer A) > > 4 (set-buffer B) > > 5 (goto-char (point-max)) > > 6 (insert "(2022-11-01)\n") > > 7 ;; B's buffer-point is at point-max. > > 8 > > 9 (set-buffer A) > > 10 (set-buffer B) > > 11 ;; B's buffer-point is no longer at point-max. > > 12 (insert "(2022-11-01)a\n"))) > > ######################################################################### > > , > > (i) Emacs -Q. > > (ii) On a single frame, arrange buffers *scratch*, test-edebug.el, and > > some other substantial buffer, that I call emacs.README. > > (iii) Put point in emacs.README somewhere other than point-max. > > (iv) Instrument test-edebug for edebug with C-u C-M-x. > > (v) M-: (test-edebug). > > (vi) Step through test-edebug using the space key. > > (vii) Note that the second text insertion happens where point was in the > > window, not at point-max. This is the bug. > I cannot reproduce this: for me, the insertion is at point-max. Maybe > your recipe description is incomplete? Apologies. I neglected to mention that window-saving (toggled by "W" in an edebug session) must be enabled to trigger the bug. Indeed, I wasn't fully aware of this. > But in any case, I didn't ask _what_ happens, I asked _why_? IOW, I > presumed that you understood why Edebug moves point, and asked for a > detailed description of the code involved and the reason it gets > executed in this scenario. OK, here goes! It's all in the function edebug--display-1, which in the master copy of edebug.el starts at L2573. At L2628, e--display-1 calls edebug-current-windows, which calls current-window-configuration, saving the configuration in edebug-outside-windows. The recursive edit takes place at L2730, in which the user types a space to execute one instruction. Suppose that was L9 from test-edebug.el (see above). The current buffer is now A (*scratch*). At L2754, the function calls edebug-set-windows which calls (set-window-configuration edebug-outside-windows). The program advances one instruction and calls edebug--display-1 again. It calls .... which calls current-window-configuration, which stores the window-point of buffer B (emacs.README) which is no longer the current buffer. In the recursive edit, the user again types space which advances over L10. At L2754 again, ... which calls set-window-configuration. This time B was not the current buffer stored by current-window-configuration, so B's BUFFER-POINT GETS RESTORED TO ITS STORED WINDOW-POINT. This happens at src/window.c function Fset_window_configuration at L7270. This restored point in buffer B is where the second `insert' wrongly takes effect. > Thanks. -- Alan Mackenzie (Nuremberg, Germany).