From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Tomas Hlavaty Newsgroups: gmane.emacs.devel Subject: Re: using finalizers Date: Fri, 31 Dec 2021 07:28:40 +0100 Message-ID: <875yr5p9t3.fsf@logand.com> References: <878rw1pvcw.fsf@logand.com> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="1741"; mail-complaints-to="usenet@ciao.gmane.io" Cc: emacs-devel@gnu.org To: LdBeth Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Fri Dec 31 07:33:53 2021 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1n3BU8-0000DE-Sz for ged-emacs-devel@m.gmane-mx.org; Fri, 31 Dec 2021 07:33:52 +0100 Original-Received: from localhost ([::1]:50150 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1n3BU7-0007PO-HZ for ged-emacs-devel@m.gmane-mx.org; Fri, 31 Dec 2021 01:33:51 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:37586) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1n3BPC-0004DZ-SQ for emacs-devel@gnu.org; Fri, 31 Dec 2021 01:28:46 -0500 Original-Received: from logand.com ([37.48.87.44]:53918) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1n3BPB-0005u0-4D for emacs-devel@gnu.org; Fri, 31 Dec 2021 01:28:46 -0500 Original-Received: by logand.com (Postfix, from userid 1001) id 4647A19EC86; Fri, 31 Dec 2021 07:28:42 +0100 (CET) X-Mailer: emacs 27.2 (via feedmail 11-beta-1 I) In-Reply-To: Received-SPF: pass client-ip=37.48.87.44; envelope-from=tom@logand.com; helo=logand.com X-Spam_score_int: 0 X-Spam_score: -0.0 X-Spam_bar: / X-Spam_report: (-0.0 / 5.0 requ) SPF_HELO_PASS=-0.001, SPF_PASS=-0.001 autolearn=unavailable autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:283718 Archived-At: On Fri 31 Dec 2021 at 10:46, LdBeth wrote: >>>>>> In <878rw1pvcw.fsf@logand.com> Tomas Hlavaty wrote: > You are probably taking the wrong assumption about the effect of letrec > So, `close' is nil and the lambda is never set as the finalizer. You are right, the order was wrong. >> What is the expected example usage of finalizers in Emacs Lisp? >> How can I verify, that my finalizer works? > > (setq bar nil) > (setq foo (make-finalizer (lambda () (setq bar t)))) > (setq foo nil) > (garbage-collect) > bar ; => t Nice, that works. One more question: Because make-finalizer in Emacs Lisp does not take the object into account, I have to make sure to hold the reference to the finalizer somehow. However, this might not be trivial, because a smart compiler could eliminate the reference. Is this not an issue? Shouldn't make-finalizer take the object as an argument and not rely on me holding the reference explicitly? Thank you!