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: Sun, 27 Mar 2011 15:29:54 +0200 Message-ID: <87bp0wzo6l.fsf@gnu.org> References: <87fwqrqbzg.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 1301232622 32078 80.91.229.12 (27 Mar 2011 13:30:22 GMT) X-Complaints-To: usenet@dough.gmane.org NNTP-Posting-Date: Sun, 27 Mar 2011 13:30:22 +0000 (UTC) To: guile-devel@gnu.org Original-X-From: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Sun Mar 27 15:30:15 2011 Return-path: Envelope-to: guile-devel@m.gmane.org Original-Received: from lists.gnu.org ([199.232.76.165]) by lo.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Q3q2o-0006TI-CI for guile-devel@m.gmane.org; Sun, 27 Mar 2011 15:30:14 +0200 Original-Received: from localhost ([127.0.0.1]:37433 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q3q2n-0005bp-Rx for guile-devel@m.gmane.org; Sun, 27 Mar 2011 09:30:13 -0400 Original-Received: from [140.186.70.92] (port=56009 helo=eggs.gnu.org) by lists.gnu.org with esmtp (Exim 4.43) id 1Q3q2k-0005bh-JJ for guile-devel@gnu.org; Sun, 27 Mar 2011 09:30:11 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1Q3q2j-0004xz-C9 for guile-devel@gnu.org; Sun, 27 Mar 2011 09:30:10 -0400 Original-Received: from lo.gmane.org ([80.91.229.12]:41951) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Q3q2j-0004xm-5B for guile-devel@gnu.org; Sun, 27 Mar 2011 09:30:09 -0400 Original-Received: from list by lo.gmane.org with local (Exim 4.69) (envelope-from ) id 1Q3q2g-0006Pj-2G for guile-devel@gnu.org; Sun, 27 Mar 2011 15:30:06 +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 ; Sun, 27 Mar 2011 15:30:06 +0200 Original-Received: from ludo by reverse-83.fdn.fr with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Sun, 27 Mar 2011 15:30:06 +0200 X-Injected-Via-Gmane: http://gmane.org/ Original-Lines: 24 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: 7 Germinal 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/5.110013 (No Gnus v0.13) Emacs/23.3 (gnu/linux) Cancel-Lock: sha1:bX+VmPSwYOCHZDsxdzz6YbZydHg= 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: 2.1.5 Precedence: list List-Id: "Developers list for Guile, the GNU extensibility library" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Original-Sender: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Errors-To: guile-devel-bounces+guile-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.lisp.guile.devel:12010 Archived-At: Hello! 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? :-) Thanks, Ludo’.