From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: ludo@gnu.org (Ludovic =?iso-8859-1?Q?Court=E8s?=) Newsgroups: gmane.lisp.guile.devel Subject: Re: =?utf-8?B?4oCYc2V0LWNkciHigJk=?= and weak-cdr pairs Date: Thu, 05 May 2011 20:20:20 +0200 Message-ID: <87aaf1nh5n.fsf@gnu.org> References: <87fwqrqbzg.fsf@gnu.org> <87bp0wzo6l.fsf@gnu.org> NNTP-Posting-Host: lo.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: dough.gmane.org 1304619655 19052 80.91.229.12 (5 May 2011 18:20:55 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Thu, 5 May 2011 18:20:55 +0000 (UTC) To: guile-devel@gnu.org Original-X-From: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Thu May 05 20:20:51 2011 Return-path: Envelope-to: guile-devel@m.gmane.org Original-Received: from lists.gnu.org ([140.186.70.17]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1QI3AN-0004jQ-Sk for guile-devel@m.gmane.org; Thu, 05 May 2011 20:20:48 +0200 Original-Received: from localhost ([::1]:37701 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QI3AN-0004np-73 for guile-devel@m.gmane.org; Thu, 05 May 2011 14:20:47 -0400 Original-Received: from eggs.gnu.org ([140.186.70.92]:53085) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QI3AJ-0004nW-IT for guile-devel@gnu.org; Thu, 05 May 2011 14:20:44 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1QI3AI-00037K-Gg for guile-devel@gnu.org; Thu, 05 May 2011 14:20:43 -0400 Original-Received: from lo.gmane.org ([80.91.229.12]:37276) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1QI3AI-00037E-5b for guile-devel@gnu.org; Thu, 05 May 2011 14:20:42 -0400 Original-Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1QI3AC-0004ad-5t for guile-devel@gnu.org; Thu, 05 May 2011 20:20:36 +0200 Original-Received: from reverse-83.fdn.fr ([80.67.176.83]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 05 May 2011 20:20:36 +0200 Original-Received: from ludo by reverse-83.fdn.fr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Thu, 05 May 2011 20:20:36 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 37 Original-X-Complaints-To: usenet@dough.gmane.org X-Gmane-NNTP-Posting-Host: reverse-83.fdn.fr X-URL: http://www.fdn.fr/~lcourtes/ X-Revolutionary-Date: 16 =?iso-8859-1?Q?Flor=E9al?= an 219 de la =?iso-8859-1?Q?R=E9volution?= X-PGP-Key-ID: 0xEA52ECF4 X-PGP-Key: http://www.fdn.fr/~lcourtes/ludovic.asc X-PGP-Fingerprint: 83C4 F8E5 10A3 3B4C 5BEA D15D 77DD 95E2 EA52 ECF4 X-OS: x86_64-unknown-linux-gnu User-Agent: Gnus/5.110017 (No Gnus v0.17) Emacs/24.0.50 (gnu/linux) Cancel-Lock: sha1:sz1GhWqptYjPqx921zkR9H/S3W8= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-Received-From: 80.91.229.12 X-BeenThere: guile-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Developers list for Guile, the GNU extensibility library" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Original-Sender: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.devel:12433 Archived-At: Hello! Andy Wingo writes: > On Sun 27 Mar 2011 15:29, ludo@gnu.org (Ludovic Courtès) writes: > >> Andy Wingo writes: >> >>> On Sun 13 Mar 2011 16:25, ludo@gnu.org (Ludovic Courtès) writes: >>> >>>> The problem is that ‘hash-create-handle!’ above created a weak-cdr >>>> pair—i.e., a pair whose cdr is /not/ scanned for pointers—but ‘set-cdr!’ >>>> did not register a disappearing link from O to K+V. Consequently, O >>>> eventually gets collected, but K+V remains; the storage of O then gets >>>> reused, and the cdr of K+V ends up containing either an unrelated or >an >>>> invalid Scheme object. >>> >>> Given that we don't expose weak-pair constructors or accessors to >>> Scheme, we should not expose weak pairs to Scheme. What do you think >>> about making it an error to hash-create-handle! on a weak table? That >>> way you never expose a weak pair to Scheme. It does appear possible to >>> discriminate in C between calls to create-handle! that occur due to ref >>> / set! and those that are called explicitly. >> >> Yes, sounds good. Would you like to work on it? :-) > > I have done this now. There were a few places within Guile that were > using the get-handle / create-handle! API with weak hash tables, which I > fixed. It's quite possible that user code also does this, but between > random failures to `(car x)' and preventative errors, I chose the > latter. We can back it down to a warning if that's the right thing to > do, though. Cool, thanks for working on it! I skimmed over the relevant patches and it looks good to me. Ludo’.