From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: Conservative GC isn't safe Date: Sat, 26 Nov 2016 11:01:11 +0200 Message-ID: <8360na399k.fsf@gnu.org> References: <66485157-00cd-4704-a421-cbfe84299cae@cs.ucla.edu> <69a1fdf3-7120-125b-8556-d74f5afc6b37@dancol.org> Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1480150922 18844 195.159.176.226 (26 Nov 2016 09:02:02 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Sat, 26 Nov 2016 09:02:02 +0000 (UTC) Cc: eggert@cs.ucla.edu, emacs-devel@gnu.org To: Daniel Colascione Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sat Nov 26 10:01:53 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 1cAYro-0003Vo-NV for ged-emacs-devel@m.gmane.org; Sat, 26 Nov 2016 10:01:52 +0100 Original-Received: from localhost ([::1]:49707 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cAYrs-0002oe-2v for ged-emacs-devel@m.gmane.org; Sat, 26 Nov 2016 04:01:56 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:40644) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cAYrJ-0002nz-RC for emacs-devel@gnu.org; Sat, 26 Nov 2016 04:01:22 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cAYrG-0004ea-SH for emacs-devel@gnu.org; Sat, 26 Nov 2016 04:01:21 -0500 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:38387) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cAYrG-0004eV-Oy; Sat, 26 Nov 2016 04:01:18 -0500 Original-Received: from 84.94.185.246.cable.012.net.il ([84.94.185.246]:3611 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1cAYrG-0004dR-6w; Sat, 26 Nov 2016 04:01:18 -0500 In-reply-to: <69a1fdf3-7120-125b-8556-d74f5afc6b37@dancol.org> (message from Daniel Colascione on Sat, 26 Nov 2016 00:33:13 -0800) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 2001:4830:134:3::e 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:209608 Archived-At: > From: Daniel Colascione > Date: Sat, 26 Nov 2016 00:33:13 -0800 > > >> 2) INTERVAL is GCed, but it's not represented in the memory tree: > >> struct interval isn't a real lisp object and it's allocated as > >> MEM_TYPE_NON_LISP. Even a direct pointer to the start of an interval > >> won't protect it from GC. Shouldn't we treat intervals like conses? > > > > Does the code ever create an interval that is accessible only via locals > > when a GC occurs? If not, Emacs should be OK. (This should also be > > documented better.) > > Anywhere in the code? Forever? I wouldn't be confident saying so. A simple practical solution to such assumptions is to add an assertion in some strategic place(s). I don't think it's TRT to sprinkle our sources with code that is there "just in case", i.e. it will never actually run.