From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Philipp Stephani Newsgroups: gmane.emacs.bugs Subject: bug#30373: Support finalizers for functions created in dynamic modules Date: Mon, 23 Dec 2019 21:41:16 +0100 Message-ID: References: Mime-Version: 1.0 Content-Type: text/plain; charset="UTF-8" Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="243427"; mail-complaints-to="usenet@blaine.gmane.org" Cc: 30373@debbugs.gnu.org To: Samir Jindel Original-X-From: bug-gnu-emacs-bounces+geb-bug-gnu-emacs=m.gmane.org@gnu.org Mon Dec 23 21:42:12 2019 Return-path: Envelope-to: geb-bug-gnu-emacs@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1ijUWo-0011D0-18 for geb-bug-gnu-emacs@m.gmane.org; Mon, 23 Dec 2019 21:42:10 +0100 Original-Received: from localhost ([::1]:32872 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1ijUWm-0002YB-PU for geb-bug-gnu-emacs@m.gmane.org; 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Feb. 2018 um 22:43 Uhr schrieb Samir Jindel : > > Hi, > > I'm very excited by the possibilities opened through the new dynamic module interface, "emacs-module.h". > > However, I have a concern about the API for creating Lisp functions bound to native functions: > > ```c > > emacs_value (*make_function) (emacs_env *env, > ptrdiff_t min_arity, > ptrdiff_t max_arity, > emacs_value (*function) (emacs_env *env, > ptrdiff_t nargs, > emacs_value args[], > void *) > EMACS_NOEXCEPT, > const char *documentation, > void *data); > > ``` > > I presume the "data" pointer here is provided to enable native functions to work like closures, > carrying additional, possibly dynamically allocated data. However, this functionality is limited by > the absence of a finalization function pointer, like the "user_ptr" values have: > > ```c > > emacs_value (*make_user_ptr) (emacs_env *env, > void (*fin) (void *) EMACS_NOEXCEPT, > void *ptr); > > ``` > > Without the ability to provide a finalizer, a module can only safely make the "data" pointer to > "make_function" point to static memory. > Sorry for not responding for so long. I think this makes a lot of sense, and we should definitely introduce function finalizers. I can think of three possible interface choices for this: 1. Add a make_finalizable_function environment function that is like make_function but accepts a finalizer. 2. Add a set_function_finalizer(env, emacs_value, void(*)(void)) environment function. 3. Allow set_user_finalizer to also set function finalizers. I'd lean away from (1) since it makes an already complex interface even more complex. (2) seems cleanest, but requires adding a new environment function. (3) would require the least amount of changes, but it would also be slightly less clean than (2), and would break backwards compatibility in a subtle way (users relying on set_user_finalizer raising an error if a non-user-pointer object is passed would break). Overall, I'd slightly lean towards (2). Other opinions?