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: Compiler warnings in dispnew.c Date: Mon, 29 Nov 2021 18:53:17 +0100 Message-ID: <8735neq25u.fsf@igel.home> References: <87fsrg7gdt.fsf.ref@yahoo.com> <87fsrg7gdt.fsf@yahoo.com> <83tufwwo7z.fsf@gnu.org> <87bl247dbn.fsf@yahoo.com> <87wnksfsiy.fsf@linux-m68k.org> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="34670"; mail-complaints-to="usenet@ciao.gmane.io" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) Cc: Po Lu , Eli Zaretskii , emacs-devel@gnu.org To: Stefan Monnier Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Mon Nov 29 18:54:40 2021 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 1mrkrP-0008mc-Is for ged-emacs-devel@m.gmane-mx.org; Mon, 29 Nov 2021 18:54:39 +0100 Original-Received: from localhost ([::1]:46114 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1mrkrO-000428-E8 for ged-emacs-devel@m.gmane-mx.org; Mon, 29 Nov 2021 12:54:38 -0500 Original-Received: from eggs.gnu.org ([209.51.188.92]:38074) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mrkqJ-00035S-24 for emacs-devel@gnu.org; Mon, 29 Nov 2021 12:53:31 -0500 Original-Received: from mail-out.m-online.net ([212.18.0.10]:44294) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1mrkqB-0006Z1-L9; Mon, 29 Nov 2021 12:53:30 -0500 Original-Received: from frontend01.mail.m-online.net (unknown [192.168.8.182]) by mail-out.m-online.net (Postfix) with ESMTP id 4J2tHf5wbpz1sCwX; Mon, 29 Nov 2021 18:53:18 +0100 (CET) Original-Received: from localhost (dynscan1.mnet-online.de [192.168.6.70]) by mail.m-online.net (Postfix) with ESMTP id 4J2tHf5RXbz1qqkG; Mon, 29 Nov 2021 18:53:18 +0100 (CET) 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 Ado6A96SoV7v; Mon, 29 Nov 2021 18:53:18 +0100 (CET) X-Auth-Info: 5EvOOscSq0IT/LC2254zEzEcRWy67B/54UB6tRc5Iwye5v4ZgLBrUdfMkymuRaBO Original-Received: from igel.home (ppp-46-244-182-103.dynamic.mnet-online.de [46.244.182.103]) (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; Mon, 29 Nov 2021 18:53:18 +0100 (CET) Original-Received: by igel.home (Postfix, from userid 1000) id 760012C3994; Mon, 29 Nov 2021 18:53:17 +0100 (CET) X-Yow: Life is selling REVOLUTIONARY HAIR PRODUCTS! In-Reply-To: (Stefan Monnier's message of "Mon, 29 Nov 2021 12:49:56 -0500") Received-SPF: pass client-ip=212.18.0.10; 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=0.248, RCVD_IN_DNSWL_LOW=-0.7, RCVD_IN_MSPIKE_H3=0.001, RCVD_IN_MSPIKE_WL=0.001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001 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:280500 Archived-At: On Nov 29 2021, Stefan Monnier wrote: > Andreas Schwab [2021-11-28 12:07:01] wrote: >> - memcpy (&to->x, &from->x, sizeof *to - off); >> + memcpy ((char *) to + off, (char *) from + off, sizeof *to - off); > > I wonder: is the (char*) cast sufficient or is it necessary to > "obfuscate" the code by writing `to + off` instead of `&to->x`? I think the point is that the address expression is not based on the subobject. Andreas. -- 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."