From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: Dynamic loading progress Date: Fri, 20 Nov 2015 12:47:59 -0800 Organization: UCLA Computer Science Department Message-ID: <564F86FF.6030202@cs.ucla.edu> References: <87io5bv1it.fsf@lifelogs.com> <87egfzuwca.fsf@lifelogs.com> <876118u6f2.fsf@lifelogs.com> <8737w3qero.fsf@lifelogs.com> <831tbn9g9j.fsf@gnu.org> <878u5upw7o.fsf@lifelogs.com> <83ziya8xph.fsf@gnu.org> <83y4du80xo.fsf@gnu.org> <564E6081.9010805@cs.ucla.edu> <564E6352.20701@cs.ucla.edu> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1448052526 24030 80.91.229.3 (20 Nov 2015 20:48:46 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Fri, 20 Nov 2015 20:48:46 +0000 (UTC) Cc: emacs-devel@gnu.org To: Philipp Stephani , Eli Zaretskii , Ted Zlatanov , =?UTF-8?Q?Aur=c3=a9lien_Aptel?= Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Fri Nov 20 21:48:37 2015 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1Zzsbb-0006cR-3h for ged-emacs-devel@m.gmane.org; Fri, 20 Nov 2015 21:48:27 +0100 Original-Received: from localhost ([::1]:49802 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1Zzsba-0000r1-CE for ged-emacs-devel@m.gmane.org; Fri, 20 Nov 2015 15:48:26 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:39796) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZzsbH-0000pm-9s for emacs-devel@gnu.org; Fri, 20 Nov 2015 15:48:08 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZzsbG-0002EA-Gm for emacs-devel@gnu.org; Fri, 20 Nov 2015 15:48:07 -0500 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:56012) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZzsbA-0002Dh-Sh; Fri, 20 Nov 2015 15:48:01 -0500 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 3DCD7160D74; Fri, 20 Nov 2015 12:48:00 -0800 (PST) Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10032) with ESMTP id wbxUT9-Uxc0r; Fri, 20 Nov 2015 12:47:59 -0800 (PST) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 8B0FC160DFD; Fri, 20 Nov 2015 12:47:59 -0800 (PST) X-Virus-Scanned: amavisd-new at zimbra.cs.ucla.edu Original-Received: from zimbra.cs.ucla.edu ([127.0.0.1]) by localhost (zimbra.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10026) with ESMTP id 0tztqMpHoR15; Fri, 20 Nov 2015 12:47:59 -0800 (PST) Original-Received: from [192.168.1.9] (pool-100-32-155-148.lsanca.fios.verizon.net [100.32.155.148]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 63670160D74; Fri, 20 Nov 2015 12:47:59 -0800 (PST) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.3.0 In-Reply-To: X-detected-operating-system: by eggs.gnu.org: GNU/Linux 3.x X-Received-From: 131.179.128.68 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 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.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:194897 Archived-At: Philipp Stephani wrote: > This member will typically be used as follows: > > if (env->size >= sizeof *env) { > // good, object is at least as big as expected > } else { > // Emacs is too old > } I'm leery of recommending this sort of checking. In practice incompatible structure layout changes so often involve something more than merely extending a structure, that a size check is not worth the trouble; you really want a version check. I might be persuaded that it's a good idea if I saw some code doing it effectively, but currently there is no such code in the Emacs sources (the module test function doesn't check sizes -- why not?).