From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: Conservative GC isn't safe Date: Sun, 27 Nov 2016 08:15:36 -0800 Organization: UCLA Computer Science Department Message-ID: <6e5c928f-8130-08a6-d72d-1b64cc022846@cs.ucla.edu> References: <66485157-00cd-4704-a421-cbfe84299cae@cs.ucla.edu> <805F5A19-BFAF-4CA4-AAD6-497C6D554830@raeburn.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: quoted-printable X-Trace: blaine.gmane.org 1480263381 15301 195.159.176.226 (27 Nov 2016 16:16:21 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sun, 27 Nov 2016 16:16:21 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 Cc: emacs-devel@gnu.org To: Ken Raeburn , Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Nov 27 17:16:17 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 1cB27k-0003IC-Ie for ged-emacs-devel@m.gmane.org; Sun, 27 Nov 2016 17:16:16 +0100 Original-Received: from localhost ([::1]:54684 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cB27o-0006Dk-37 for ged-emacs-devel@m.gmane.org; Sun, 27 Nov 2016 11:16:20 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:53278) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cB27F-0006Db-Vi for emacs-devel@gnu.org; Sun, 27 Nov 2016 11:15:46 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cB279-0004U4-Jz for emacs-devel@gnu.org; Sun, 27 Nov 2016 11:15:45 -0500 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:44586) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cB279-0004Tw-E9 for emacs-devel@gnu.org; Sun, 27 Nov 2016 11:15:39 -0500 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 8A931160092; Sun, 27 Nov 2016 08:15:37 -0800 (PST) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id FAK8ffTD9QXc; Sun, 27 Nov 2016 08:15:36 -0800 (PST) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id D8C7B1600B8; Sun, 27 Nov 2016 08:15:36 -0800 (PST) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 7j3lsEckHy2T; Sun, 27 Nov 2016 08:15:36 -0800 (PST) Original-Received: from [192.168.1.9] (unknown [47.153.178.162]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id B9726160092; Sun, 27 Nov 2016 08:15:36 -0800 (PST) In-Reply-To: <805F5A19-BFAF-4CA4-AAD6-497C6D554830@raeburn.org> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x [fuzzy] X-Received-From: 131.179.128.68 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:209632 Archived-At: Ken Raeburn wrote: >> > Indeed. Hans Boehm's done a fair bit of research in this issue, >> > including discussing the underlying assumptions and arguing that >> > compilers should (and usually do) guarantee those assumptions. > I=E2=80=99d be surprised if that held reliably when the last use of a L= isp_Object in some function extracts an object pointer and then never ref= erences the Lisp_Object as such ever again. That's not a problem for Emacs, since the Emacs GC marks the object eithe= r way.