From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.ciao.gmane.io!not-for-mail From: Sebastian Miele Newsgroups: gmane.lisp.guile.bugs Subject: bug#41983: Reference Manual: Open Question About Magic Metaness of Vtables Date: Sun, 21 Jun 2020 16:27:43 +0200 Message-ID: <87eeq8o5nk.fsf@gmail.com> Reply-To: sebastian.miele@gmail.com Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="ciao.gmane.io:159.69.161.202"; logging-data="92161"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: mu4e 1.4.10; emacs 26.3 To: 41983@debbugs.gnu.org Original-X-From: bug-guile-bounces+guile-bugs=m.gmane-mx.org@gnu.org Sun Jun 21 16:28:07 2020 Return-path: Envelope-to: guile-bugs@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 1jn0x5-000Nrm-Qd for guile-bugs@m.gmane-mx.org; Sun, 21 Jun 2020 16:28:07 +0200 Original-Received: from localhost ([::1]:54380 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1jn0x4-00062B-Mu for guile-bugs@m.gmane-mx.org; 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That's all we know. X-Spam_score_int: -20 X-Spam_score: -2.1 X-Spam_bar: -- X-Spam_report: (-2.1 / 5.0 requ) BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, FREEMAIL_FROM=0.001, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 autolearn=_AUTOLEARN X-Spam_action: no action X-BeenThere: debbugs-submit@debbugs.gnu.org X-Mailman-Version: 2.1.18 Precedence: list X-BeenThere: bug-guile@gnu.org List-Id: "Bug reports for GUILE, GNU's Ubiquitous Extension Language" List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: bug-guile-bounces+guile-bugs=m.gmane-mx.org@gnu.org Original-Sender: "bug-guile" Xref: news.gmane.io gmane.lisp.guile.bugs:9819 Archived-At: I am on the current master branch. After reading section 6.6.18.4 (Meta-Vtables) of the reference manual there remains an open question. A structure X made from a meta-vtable becomes a meta-vtable if standard-vtable-fields is a prefix of the layout in X's field 0. And if X is a meta-vtable, every structure with X as a vtable must have a valid layout in field 0. Suppose the following: standard-vtable-fields accidentally is a prefix of some valid layout string l. Then (define v (make-vtable l)) (make-struct/no-tail v 'a) raises an exception, because 'a is not a valid layout. But v may not be intended to be a meta-vtable, just a vtable. The reference manual does mention why that can not happen, or why is it accepted that it may happen.