From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Andreas Schwab Newsgroups: gmane.emacs.devel Subject: Re: warnings compiling emacs28 with gcc 12.1 Date: Thu, 28 Jul 2022 20:31:59 +0200 Message-ID: <87sfmlqeao.fsf@igel.home> References: <87h731vrmw.fsf@mail.jao.io> <83o7x9892n.fsf@gnu.org> <87bkt9rwkf.fsf@telefonica.net> <83lesd87e8.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="26939"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/28.1.90 (gnu/linux) Cc: =?utf-8?Q?=C3=93scar?= Fuentes , emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Thu Jul 28 20:33:47 2022 Return-path: Envelope-to: ged-emacs-devel@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 1oH8KR-0006sF-UT for ged-emacs-devel@m.gmane-mx.org; Thu, 28 Jul 2022 20:33:47 +0200 Original-Received: from localhost ([::1]:47282 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1oH8KQ-0003pn-A5 for ged-emacs-devel@m.gmane-mx.org; Thu, 28 Jul 2022 14:33:46 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:37656) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oH8Is-00034N-5z for emacs-devel@gnu.org; Thu, 28 Jul 2022 14:32:10 -0400 Original-Received: from mail-out.m-online.net ([2001:a60:0:28:0:1:25:1]:40142) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1oH8Ip-0000FD-Ug; Thu, 28 Jul 2022 14:32:09 -0400 Original-Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 4Ltzl46QLbz1s7sr; Thu, 28 Jul 2022 20:32:00 +0200 (CEST) Original-Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 4Ltzl468q1z1qqkk; Thu, 28 Jul 2022 20:32:00 +0200 (CEST) X-Virus-Scanned: amavisd-new at mnet-online.de Original-Received: from mail.mnet-online.de ([192.168.8.182]) by localhost (dynscan1.mail.m-online.net [192.168.6.70]) (amavisd-new, port 10024) with ESMTP id q5dAHFR-nOhF; Thu, 28 Jul 2022 20:32:00 +0200 (CEST) X-Auth-Info: CgOUuyXlO4xHnRmegU6wNrxuW7eSBDpDP+8iw9R9p9YASVWaebR98KOI1oXmSkHF Original-Received: from igel.home (ppp-46-244-189-11.dynamic.mnet-online.de [46.244.189.11]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.mnet-online.de (Postfix) with ESMTPSA; Thu, 28 Jul 2022 20:32:00 +0200 (CEST) Original-Received: by igel.home (Postfix, from userid 1000) id 5A2532C39FC; Thu, 28 Jul 2022 20:31:59 +0200 (CEST) X-Yow: INSIDE, I have the same personality disorder as LUCY RICARDO!! In-Reply-To: <83lesd87e8.fsf@gnu.org> (Eli Zaretskii's message of "Thu, 28 Jul 2022 20:38:23 +0300") Received-SPF: pass client-ip=2001:a60:0:28:0:1:25:1; envelope-from=whitebox@nefkom.net; helo=mail-out.m-online.net X-Spam_score_int: -23 X-Spam_score: -2.4 X-Spam_bar: -- X-Spam_report: (-2.4 / 5.0 requ) BAYES_00=-1.9, HEADER_FROM_DIFFERENT_DOMAINS=0.249, RCVD_IN_DNSWL_LOW=-0.7, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, T_SCC_BODY_TEXT_LINE=-0.01 autolearn=ham autolearn_force=no X-Spam_action: no action X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-mx.org@gnu.org Original-Sender: "Emacs-devel" Xref: news.gmane.io gmane.emacs.devel:292802 Archived-At: On Jul 28 2022, Eli Zaretskii wrote: >> From: Óscar Fuentes >> Date: Thu, 28 Jul 2022 19:12:00 +0200 >> >> Eli Zaretskii writes: >> >> >> and there's another one about free that looks a bit scary: >> >> >> >> alloc.c: In function ‘lisp_free’: >> >> alloc.c:1052:3: warning: pointer ‘block’ used after ‘free’ [-Wuse-after-free] >> >> 1052 | mem_delete (mem_find (block)); >> >> | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~ >> >> alloc.c:1050:3: note: call to ‘free’ here >> >> 1050 | free (block); >> >> | ^~~~~~~~~~~~ >> > >> > Another nonsense. Look in mem_find, and you will see that it uses its >> > argument as just a number, it never dereferences it. >> >> The warning is not about dereferencing the pointer. > > What other problems could be caused by using it after freeing it? Evan just reading the value of a pointer after free is undefined. If you want to preserve its bit pattern, you need to convert it to an integer type before the call to free. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1 "And now for something completely different."