From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Mattias =?UTF-8?Q?Engdeg=C3=A5rd?= Newsgroups: gmane.emacs.bugs Subject: bug#22149: 24.4; gdb stack overflow in regexp matcher Date: Fri, 13 Mar 2020 21:11:05 +0100 Message-ID: <30E3666D-A55F-45F1-9357-AA27E4C62D65@acm.org> References: <83y2s46o46.fsf@gnu.org> Mime-Version: 1.0 (Mac OS X Mail 12.4 \(3445.104.11\)) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: quoted-printable Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="45128"; mail-complaints-to="usenet@ciao.gmane.io" Cc: schwab@suse.de, rhymer123@gmail.com, npostavs@gmail.com, 22149@debbugs.gnu.org To: Eli Zaretskii Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane-mx.org@gnu.org Fri Mar 13 21:12:14 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 1jCqfE-000BbH-Eu for geb-bug-gnu-emacs@m.gmane-mx.org; 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Fri, 13 Mar 2020 16:11:43 -0400 X-Authenticated-User: mattiase@bredband.net DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=megamailservers.eu; s=maildub; t=1584130295; bh=g4d5qrdSla05TyZAR0K1ma1LwYk4xe86wloXaQom9yU=; h=Subject:From:In-Reply-To:Date:Cc:References:To:From; b=jp2CYHRvn/PtOwHHl4HV0f/yVaF8vvL6UzOZqbiltOz9/+fcJuNv/H/W7KU1D4sZ5 SGLHScb4d5T17DqFThE+0TKigg5sFQgIn/9jmKM41J/BsJymGELNS0Ar2HDT9aEjHy yUP8ni7cG87ypWFpGRStjlDpuFw9hQJNUD1NNNpA= Feedback-ID: mattiase@acm.or Original-Received: from stanniol.lan (c-6f4fe655.032-75-73746f71.bbcust.telenor.se [85.230.79.111]) (authenticated bits=0) by mail266c50.megamailservers.eu (8.14.9/8.13.1) with ESMTP id 02DKBX3Y026324; Fri, 13 Mar 2020 20:11:34 +0000 In-Reply-To: <83y2s46o46.fsf@gnu.org> X-Mailer: Apple Mail (2.3445.104.11) X-CTCH-RefID: str=0001.0A782F18.5E6BE8E2.0063, ss=1, re=0.000, recu=0.000, reip=0.000, cl=1, cld=1, fgs=0 X-CTCH-VOD: Unknown X-CTCH-Spam: Unknown X-CTCH-Score: 0.000 X-CTCH-Flags: 0 X-CTCH-ScoreCust: 0.000 X-CSC: 0 X-CHA: v=2.3 cv=A5MSwJeG c=1 sm=1 tr=0 a=fHaj9vQUQVKQ4sUldAaXuQ==:117 a=fHaj9vQUQVKQ4sUldAaXuQ==:17 a=jpOVt7BSZ2e4Z31A5e1TngXxSK0=:19 a=kj9zAlcOel0A:10 a=M51BFTxLslgA:10 a=mDV3o1hIAAAA:8 a=9XgUyneWwQr9YoI31uAA:9 a=CjuIK1q_8ugA:10 a=_FVE-zBwftR9WsbkzFJk:22 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: 209.51.188.43 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-mx.org@gnu.org Original-Sender: "bug-gnu-emacs" Xref: news.gmane.io gmane.emacs.bugs:177298 Archived-At: 13 mars 2020 kl. 20.39 skrev Eli Zaretskii : > I don't understand what that does to fix the problem, and don't really > see why it would be urgent to fix in Emacs 27. Can you explain? It's not urgent, but it is a bug that gdb-mi crashes with a regexp stack = overflow for certain strings. What the patch does is replacing the regexp fragment (* (or (not (any ?\" ?\\)) (seq ?\\ nonl))) with (* (or (seq ?\\ nonl) (not (any ?\" ?\\)))) Ie, try the least likely branch first (backslash-escaped char) in the = inner loop, so that the successful branch is last and won't grow the = regexp stack. The effect is readily seen in an even simpler example: (string-match "^\\(?:a\\|b\\)*c" (make-string 160000 ?a)) crashes, but (string-match "^\\(?:b\\|a\\)*c" (make-string 160000 ?a)) works (ie, fails to match). It was suggested for Emacs 27 since it's a known bug with a simple = solution. Then again, it's not a regression from a recent release.