From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Alan Mackenzie Newsgroups: gmane.emacs.devel Subject: Re: Unbalanced change hooks (part 2) [Documentation fix still remaining] Date: Wed, 10 Aug 2016 15:16:22 +0000 Message-ID: <20160810151622.GA3413@acm.fritz.box> References: <20160808184223.GC7208@acm.fritz.box> <838tw7hyk2.fsf@gnu.org> <20160808195459.GD7208@acm.fritz.box> <83tweugeu9.fsf@gnu.org> <20160809163814.GD4893@acm.fritz.box> <83inv9hkjd.fsf@gnu.org> <83h9ashfgx.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii X-Trace: blaine.gmane.org 1470842240 18632 195.159.176.226 (10 Aug 2016 15:17:20 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 10 Aug 2016 15:17:20 +0000 (UTC) User-Agent: Mutt/1.5.24 (2015-08-30) Cc: emacs-devel@gnu.org To: Stefan Monnier , Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Aug 10 17:17:15 2016 Return-path: Envelope-to: ged-emacs-devel@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 1bXVFr-0004g3-7y for ged-emacs-devel@m.gmane.org; Wed, 10 Aug 2016 17:17:15 +0200 Original-Received: from localhost ([::1]:42226 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bXVFo-00008f-0i for ged-emacs-devel@m.gmane.org; Wed, 10 Aug 2016 11:17:12 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:42548) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bXVFg-00008W-7Y for emacs-devel@gnu.org; Wed, 10 Aug 2016 11:17:06 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1bXVFZ-0004e4-Hb for emacs-devel@gnu.org; Wed, 10 Aug 2016 11:17:03 -0400 Original-Received: from mail.muc.de ([193.149.48.3]:34473) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1bXVFZ-0004dR-7s for emacs-devel@gnu.org; Wed, 10 Aug 2016 11:16:57 -0400 Original-Received: (qmail 90030 invoked by uid 3782); 10 Aug 2016 15:16:55 -0000 Original-Received: from acm.muc.de (p548C65E5.dip0.t-ipconnect.de [84.140.101.229]) by colin.muc.de (tmda-ofmipd) with ESMTP; Wed, 10 Aug 2016 17:16:53 +0200 Original-Received: (qmail 3456 invoked by uid 1000); 10 Aug 2016 15:16:22 -0000 Content-Disposition: inline In-Reply-To: X-Delivery-Agent: TMDA/1.1.12 (Macallan) X-Primary-Address: acm@muc.de X-detected-operating-system: by eggs.gnu.org: FreeBSD 9.x X-Received-From: 193.149.48.3 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.org gmane.emacs.devel:206543 Archived-At: Hello, Stefan and Eli. On Wed, Aug 10, 2016 at 10:56:59AM -0400, Stefan Monnier wrote: > > AFAICT, this is what happens, indeed, > Then the old text was right: it's called before ANY modification. > > except that the call to before-change-functions in some cases does not > > precede the first modification of the series. IOW, by the time the > > hook is called, some modifications were already done. > Sounds like a bug. I concur. > In any case, my point is that the doc should still say "before any > modification" because that's really what the code *should* do. We could > add a blurb in the doc saying that the before and after hooks may not be > properly paired (neither in number of calls nor in the specific value of > BEG/END), You mean we should add commentary saying that BEG and END _usually_ bound the region about to be deleted, but sometimes they don't. And another comment saying that BEG, END, and OLD-LEN are only _usually_ set to what they're currently documented as, the rest of the time they're random numbers vaguely related to a change region. That doesn't sound much better to me. If we're going to treat the code (as opposed to the documentation) as a bug, let's fix it completely, with rigorously paired b-c-f and a-c-f, rather than half-heartedly. Otherwise, let's document fully the circumstances in which before-change-functions doesn't get called (which I don't as yet understand), so that Lisp hackers can use that information in their programs. > but we should still claim that they're both called for any and > all modifications (modulo inhibit-modification-hooks, obviously). Given that the situation has been in place for several decades, I don't see any urgency to fix it in 25.1. But let's fix it properly, whatever we decide the bug is. > Stefan -- Alan Mackenzie (Nuremberg, Germany).