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: Mon, 28 Nov 2016 19:37:10 +0200 Message-ID: <83bmwzzet5.fsf@gnu.org> References: <66485157-00cd-4704-a421-cbfe84299cae@cs.ucla.edu> <805F5A19-BFAF-4CA4-AAD6-497C6D554830@raeburn.org> <6e5c928f-8130-08a6-d72d-1b64cc022846@cs.ucla.edu> <1CB11DFF-E6C2-4A1B-BE7E-8877DC38DB0A@raeburn.org> <83inr7zjjf.fsf@gnu.org> Reply-To: Eli Zaretskii NNTP-Posting-Host: blaine.gmane.org X-Trace: blaine.gmane.org 1480354646 24539 195.159.176.226 (28 Nov 2016 17:37:26 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 28 Nov 2016 17:37:26 +0000 (UTC) Cc: raeburn@raeburn.org, emacs-devel@gnu.org, eggert@cs.ucla.edu To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Nov 28 18:37:22 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 1cBPrl-0005VC-II for ged-emacs-devel@m.gmane.org; Mon, 28 Nov 2016 18:37:21 +0100 Original-Received: from localhost ([::1]:60331 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBPrn-0001ZZ-Iy for ged-emacs-devel@m.gmane.org; Mon, 28 Nov 2016 12:37:23 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:47809) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBPrf-0001ZR-KV for emacs-devel@gnu.org; Mon, 28 Nov 2016 12:37:17 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cBPrc-0002mk-Ha for emacs-devel@gnu.org; Mon, 28 Nov 2016 12:37:15 -0500 Original-Received: from fencepost.gnu.org ([2001:4830:134:3::e]:45594) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBPrc-0002mg-Do; Mon, 28 Nov 2016 12:37:12 -0500 Original-Received: from 84.94.185.246.cable.012.net.il ([84.94.185.246]:2983 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA1:128) (Exim 4.82) (envelope-from ) id 1cBPrb-00056V-JZ; Mon, 28 Nov 2016 12:37:12 -0500 In-reply-to: (message from Stefan Monnier on Mon, 28 Nov 2016 11:15:28 -0500) 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:209656 Archived-At: > From: Stefan Monnier > Cc: Ken Raeburn , eggert@cs.ucla.edu, emacs-devel@gnu.org > Date: Mon, 28 Nov 2016 11:15:28 -0500 > > >> res = Fvector (ito - ifrom, aref_addr (string, ifrom)); > > But 'string' still references the contents array of the vector, so GC > > will mark it when it comes to 'string'. > > But after computing "aref_addr (string, ifrom)", it may very well be > that `string` is dead and the compiler may then decide not to write > it into the stack. It will still be there in the caller.