From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Benchmarking temporary Lisp objects [Was: Re: [RFC] temporary Lisp_Strings] Date: Fri, 05 Sep 2014 11:35:31 -0400 Message-ID: References: <5405BE5D.1090003@yandex.ru> <5405DE8B.4050201@yandex.ru> <5406EC21.4060200@yandex.ru> <5407281C.3090302@cs.ucla.edu> <54073621.2040403@yandex.ru> <540744F5.2010804@cs.ucla.edu> <5407F1B7.6090704@yandex.ru> <5407F4E6.2040809@cs.ucla.edu> <5407FDF4.7020504@yandex.ru> <54086B1A.8070506@yandex.ru> <54087B5E.10402@yandex.ru> <54088D63.8010406@cs.ucla.edu> <54093561.2010507@yandex.ru> <5409630B.6030201@cs.ucla.edu> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: ger.gmane.org 1409931387 25788 80.91.229.3 (5 Sep 2014 15:36:27 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 5 Sep 2014 15:36:27 +0000 (UTC) Cc: Dmitry Antipov , Emacs development discussions To: Paul Eggert Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Sep 05 17:36:19 2014 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 1XPvYe-0003nw-QQ for ged-emacs-devel@m.gmane.org; Fri, 05 Sep 2014 17:36:16 +0200 Original-Received: from localhost ([::1]:58555 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPvYe-0005FS-B4 for ged-emacs-devel@m.gmane.org; Fri, 05 Sep 2014 11:36:16 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:37714) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPvYT-00054u-DT for emacs-devel@gnu.org; Fri, 05 Sep 2014 11:36:13 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XPvYL-0001Zf-70 for emacs-devel@gnu.org; Fri, 05 Sep 2014 11:36:05 -0400 Original-Received: from mercure.iro.umontreal.ca ([132.204.24.67]:43324) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XPvYK-0001Zb-Up for emacs-devel@gnu.org; Fri, 05 Sep 2014 11:35:57 -0400 Original-Received: from hidalgo.iro.umontreal.ca (hidalgo.iro.umontreal.ca [132.204.27.50]) by mercure.iro.umontreal.ca (Postfix) with ESMTP id 33CE28504A; Fri, 5 Sep 2014 11:35:56 -0400 (EDT) Original-Received: from lechon.iro.umontreal.ca (lechon.iro.umontreal.ca [132.204.27.242]) by hidalgo.iro.umontreal.ca (Postfix) with ESMTP id 18EA71E5B8A; Fri, 5 Sep 2014 11:35:32 -0400 (EDT) Original-Received: by lechon.iro.umontreal.ca (Postfix, from userid 20848) id F2235B4171; Fri, 5 Sep 2014 11:35:31 -0400 (EDT) In-Reply-To: <5409630B.6030201@cs.ucla.edu> (Paul Eggert's message of "Fri, 05 Sep 2014 00:15:23 -0700") User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/24.4.50 (gnu/linux) X-DIRO-MailScanner-Information: Please contact the ISP for more information X-DIRO-MailScanner: Found to be clean X-DIRO-MailScanner-SpamCheck: n'est pas un polluriel, SpamAssassin (score=-2.82, requis 5, autolearn=not spam, ALL_TRUSTED -2.82, MC_TSTLAST 0.00) X-DIRO-MailScanner-From: monnier@iro.umontreal.ca X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 132.204.24.67 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:174040 Archived-At: > To address Stefan's concern about alloca-allocated thingies escaping to > Elisp, is there some way you can include a runtime test for that, when > checking is enabled? It wouldn't have to catch every escapee, just a high > percentage of them. I'd expect that such escaping would only occur in "unusual setups", as a result of later unrelated changes. E.g. an alloca_string object is passed to DECODE_FILE or to Fexpand_file_name, which will usually stay within C code or even if it escapes to Elisp its lifetime will not escape the stack discipline. And some times later we get random crashes in odd situations because someone figure a clever way to do god-knows-what (e.g. speed things up via a memoization) by storing those refs into some global table. Basically, this risks making Elisp's semantics more murky, so it has to come with a good performance story. Stefan