From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Conservative GC isn't safe Date: Mon, 28 Nov 2016 13:05:57 -0500 Message-ID: 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> <83bmwzzet5.fsf@gnu.org> <83a8cjzdvk.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1480356386 31948 195.159.176.226 (28 Nov 2016 18:06:26 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Mon, 28 Nov 2016 18:06:26 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/25.1.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Nov 28 19:06:19 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 1cBQJn-00073S-Ae for ged-emacs-devel@m.gmane.org; Mon, 28 Nov 2016 19:06:19 +0100 Original-Received: from localhost ([::1]:60442 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBQJp-0001o0-JL for ged-emacs-devel@m.gmane.org; Mon, 28 Nov 2016 13:06:21 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:58694) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cBQJj-0001nk-CG for emacs-devel@gnu.org; Mon, 28 Nov 2016 13:06:16 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cBQJd-0004o5-Md for emacs-devel@gnu.org; Mon, 28 Nov 2016 13:06:15 -0500 Original-Received: from [195.159.176.226] (port=46693 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1cBQJd-0004mI-FR for emacs-devel@gnu.org; Mon, 28 Nov 2016 13:06:09 -0500 Original-Received: from list by blaine.gmane.org with local (Exim 4.84_2) (envelope-from ) id 1cBQJW-0005UD-M7 for emacs-devel@gnu.org; Mon, 28 Nov 2016 19:06:02 +0100 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 16 Original-X-Complaints-To: usenet@blaine.gmane.org Cancel-Lock: sha1:P8ly5ZVhJbz7bhvWLeBuqfX3ATc= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 195.159.176.226 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:209663 Archived-At: >> >> >> 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. >> Only if the caller still needs it after the call. >> That's usually the case, but it's not a given. > If it is not needed after the call, it will be clobbered after the > call, but not during the call. Not necessarily. Depends on details such as the argument passing convention. Stefan