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: Wed, 17 Oct 2012 15:08:52 -0700 Message-ID: <507F2C74.4070107@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> 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 1350511782 20550 80.91.229.3 (17 Oct 2012 22:09:42 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Wed, 17 Oct 2012 22:09:42 +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 00:09:49 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 1TOboD-0004nA-8G for ged-emacs-devel@m.gmane.org; Thu, 18 Oct 2012 00:09:49 +0200 Original-Received: from localhost ([::1]:47143 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TObo5-00077K-RK for ged-emacs-devel@m.gmane.org; Wed, 17 Oct 2012 18:09:41 -0400 Original-Received: from eggs.gnu.org ([208.118.235.92]:57646) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TObo3-000772-Ka for emacs-devel@gnu.org; Wed, 17 Oct 2012 18:09:40 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1TObo1-00057c-Ib for emacs-devel@gnu.org; Wed, 17 Oct 2012 18:09:39 -0400 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:34883) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1TObo0-00056m-14; Wed, 17 Oct 2012 18:09:36 -0400 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id 8073CA60004; Wed, 17 Oct 2012 15:09:28 -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 xR9Z6SgQjnhC; Wed, 17 Oct 2012 15:09:28 -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 1D02DA60003; Wed, 17 Oct 2012 15:09:28 -0700 (PDT) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:16.0) Gecko/20121009 Thunderbird/16.0 In-Reply-To: <83bog03jyf.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:154393 Archived-At: On 10/17/2012 01:46 PM, Eli Zaretskii wrote: >> How do you convert the integer into the C struct pointer? > struct foo *pwatch = (struct foo *)XLI (watch_descriptor); > > where watch_descriptor is a Lisp integer. Won't this have problems on platforms where (EMACS_INT) pwatch < MOST_NEGATIVE_FIXNUM, or where MOST_POSITIVE_FIXNUM < (EMACS_INT) pwatch? Also, suppose someone makes up a random integer and then passes it as the watch descriptor -- wouldn't Emacs dump core?