From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: David Kastrup Newsgroups: gmane.emacs.devel Subject: Re: [Emacs-diffs] master 8ba156f: Attempt to avoid crashes in plist-member Date: Tue, 13 Oct 2015 17:08:52 +0200 Message-ID: <87zizm7qm3.fsf@fencepost.gnu.org> References: <20151012170324.17966.77@vcs.savannah.gnu.org> <83k2qro5eg.fsf@gnu.org> <561C7C26.3060408@cs.ucla.edu> <83io6azufx.fsf@gnu.org> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1444749033 31265 80.91.229.3 (13 Oct 2015 15:10:33 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Tue, 13 Oct 2015 15:10:33 +0000 (UTC) Cc: Paul Eggert , monnier@iro.umontreal.ca, emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Tue Oct 13 17:10:31 2015 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Zm1De-0002Mr-KV for ged-emacs-devel@m.gmane.org; Tue, 13 Oct 2015 17:10:26 +0200 Original-Received: from localhost ([::1]:36741 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zm1De-0008V1-9b for ged-emacs-devel@m.gmane.org; Tue, 13 Oct 2015 11:10:26 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:39258) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zm1CC-0006XL-9M for emacs-devel@gnu.org; Tue, 13 Oct 2015 11:08:57 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Zm1CB-0007IJ-Dc for emacs-devel@gnu.org; Tue, 13 Oct 2015 11:08:56 -0400 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:35828) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zm1C9-0007I3-Pl; Tue, 13 Oct 2015 11:08:53 -0400 Original-Received: from localhost ([127.0.0.1]:49647 helo=lola) by fencepost.gnu.org with esmtp (Exim 4.82) (envelope-from ) id 1Zm1C8-0001ur-Qo; Tue, 13 Oct 2015 11:08:53 -0400 Original-Received: by lola (Postfix, from userid 1000) id 3A4C4DF4F8; Tue, 13 Oct 2015 17:08:52 +0200 (CEST) In-Reply-To: <83io6azufx.fsf@gnu.org> (Eli Zaretskii's message of "Tue, 13 Oct 2015 17:58:42 +0300") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.0.50 (gnu/linux) X-detected-operating-system: by eggs.gnu.org: Error: Malformed IPv6 address (bad octet value). X-Received-From: 2001:4830:134:3::e X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 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-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:191470 Archived-At: Eli Zaretskii writes: >> Cc: emacs-devel@gnu.org >> From: Paul Eggert >> Date: Mon, 12 Oct 2015 20:36:06 -0700 >> >> QUIT could call some Lisp. >> >> Sure, but Lisp cannot affect the value of CONSP (plist). > > Not the value of CONSP, the list itself. We follow the CONSP test > with XCAR, which crashed. The only way I could imagine that happening > is that the list got modified between the test and the XCAR call. Is > there any other way to explain that? Huh? CONSP only checks some bits on a pointer. It does not verify that the pointer can be dereferenced into an existing cons cell. So there is absolutely no need to modify anything between having a true CONSP test and a crashing XCAR. -- David Kastrup