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: Lisp object that refers to a C struct Date: Thu, 18 Oct 2012 09:42:14 -0700 Message-ID: <50803166.6000002@cs.ucla.edu> References: <83ehkz4edw.fsf@gnu.org> <83bog33wdr.fsf@gnu.org> <837gqq49j7.fsf@gnu.org> <83r4ox3frd.fsf@gnu.org> <83ipa92i95.fsf@gnu.org> <83bog03jyf.fsf@gnu.org> <507F2C74.4070107@cs.ucla.edu> <83391c2xjq.fsf@gnu.org> <507FADAB.5060108@cs.ucla.edu> <83y5j411fl.fsf@gnu.org> NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1350578551 7083 80.91.229.3 (18 Oct 2012 16:42:31 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Thu, 18 Oct 2012 16:42:31 +0000 (UTC) Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Oct 18 18:42:39 2012 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 1TOtB6-0003fJ-PT for ged-emacs-devel@m.gmane.org; Thu, 18 Oct 2012 18:42:36 +0200 Original-Received: from localhost ([::1]:43005 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOtAz-0008Qi-M5 for ged-emacs-devel@m.gmane.org; Thu, 18 Oct 2012 12:42:29 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:38716) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOtAt-0008Ck-LH for emacs-devel@gnu.org; Thu, 18 Oct 2012 12:42:28 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TOtAs-00041m-LF for emacs-devel@gnu.org; Thu, 18 Oct 2012 12:42:23 -0400 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:49256) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TOtAr-00040r-4g; Thu, 18 Oct 2012 12:42:21 -0400 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id C5E26A60005; Thu, 18 Oct 2012 09:42:19 -0700 (PDT) X-Virus-Scanned: amavisd-new at smtp.cs.ucla.edu Original-Received: from smtp.cs.ucla.edu ([127.0.0.1]) by localhost (smtp.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id e+6iKe91rKCe; Thu, 18 Oct 2012 09:42:19 -0700 (PDT) Original-Received: from penguin.cs.ucla.edu (Penguin.CS.UCLA.EDU [131.179.64.200]) by smtp.cs.ucla.edu (Postfix) with ESMTPSA id 6F92239E810E; Thu, 18 Oct 2012 09:42:19 -0700 (PDT) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121009 Thunderbird/16.0 In-Reply-To: <83y5j411fl.fsf@gnu.org> X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6 (newer, 3) X-Received-From: 131.179.128.62 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:154412 Archived-At: On 10/18/2012 04:09 AM, Eli Zaretskii wrote: >> but in general it's not safe to convert a pointer to >> > an Emacs fixnum, as this can lose information: the payload >> > of an Emacs fixnum is typically narrower than a pointer. > A pointer that is properly aligned has no problem with this. It can have problems on hosts where USE_LSB_TAG is 0, because the conversion to Emacs fixnum can lose high-order bits in the pointer.