From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: [Emacs-diffs] master c66aaa6: Recomplexify =?utf-8?Q?=E2=80=98delete-trailing-whitespace=E2=80=99?= by treating \n as whitespace again Date: Wed, 15 Mar 2017 16:26:59 -0400 Message-ID: References: <20170315023157.29463.36647@vcs0.savannah.gnu.org> <20170315023159.30AA520CAB@vcs0.savannah.gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: blaine.gmane.org 1489609713 24167 195.159.176.226 (15 Mar 2017 20:28:33 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 15 Mar 2017 20:28:33 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Mar 15 21:28:27 2017 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 1coFWz-0005YO-P1 for ged-emacs-devel@m.gmane.org; Wed, 15 Mar 2017 21:28:25 +0100 Original-Received: from localhost ([::1]:39374 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1coFX5-00089U-Pw for ged-emacs-devel@m.gmane.org; Wed, 15 Mar 2017 16:28:31 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:59860) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1coFW3-0007xX-3I for emacs-devel@gnu.org; Wed, 15 Mar 2017 16:27:28 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1coFVy-0008HC-1W for emacs-devel@gnu.org; Wed, 15 Mar 2017 16:27:27 -0400 Original-Received: from [195.159.176.226] (port=34624 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1coFVx-0008FW-Pk for emacs-devel@gnu.org; Wed, 15 Mar 2017 16:27:21 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1coFVi-0006Nc-TS for emacs-devel@gnu.org; Wed, 15 Mar 2017 21:27:06 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 25 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:V7XhSIF/3wl2azA4YT9I1mvCbpk= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 195.159.176.226 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:213055 Archived-At: >>>>> Recomplexify ‘delete-trailing-whitespace’ by treating \n as >>>>> whitespace again >>>>> Mostly reverts "Simplify ‘delete-trailing-whitespace’ by not treating >>>>> \n as whitespace" from 2016-07-04. Setting \n to non-whitespace >>>>> causes the regex engine to backtrack a lot when searching for >>>>> "\\s-+$" (Bug#26079). >>>> Why do we use syntax-tables? >>>> IOW why do we use \s- rather than something like [\s\t]? >>> No clue. But (re-search-forward "[\s\t]+$" nil t) is also slow. >> Slower than "\\s-+$"? > No, seems to be twice as fast actually (this is still horribly slow). I meant slower than the best performance of "\\s-+$"? because "[\s\t]+$" shouldn't backtrack. Using "\\s-+$" with a syntax-table that puts \n in the whitespace syntax is indeed asking for trouble, but I'm surprised "[\s\t]+$" is only twice as fast as this pathological case (and hence presumably much slower than "\\s-+$" when \n is not whitespace). Stefan