From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: [Emacs-diffs] master 6cd5678: Clarify compiler-pacifier in frame.c Date: Mon, 26 Aug 2019 12:09:32 -0700 Organization: UCLA Computer Science Department Message-ID: <81c10429-fb09-1e6a-0ab5-aca38fc3691e@cs.ucla.edu> References: <835zmnjdjm.fsf@gnu.org> <227db16b-17d1-b44b-97b3-e80211415eef@cs.ucla.edu> <831rx9iupo.fsf@gnu.org> <32f9db09-0c04-df03-4bb7-76fe2aa9a88f@cs.ucla.edu> <83tva4fjkz.fsf@gnu.org> <87cb5a0c-bdd8-726c-80ed-92e9f3518a58@cs.ucla.edu> <83o90cfecf.fsf@gnu.org> <87lfvg3qbi.fsf@telefonica.net> <83imqjgb1g.fsf@gnu.org> <87ftln4wm0.fsf@telefonica.net> <83a7bvg4a2.fsf@gnu.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="163838"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Aug 26 21:09:46 2019 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([209.51.188.17]) by blaine.gmane.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.89) (envelope-from ) id 1i2KN7-000gWn-7X for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 21:09:45 +0200 Original-Received: from localhost ([::1]:56718 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2KN6-0003a6-70 for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 15:09:44 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:36620) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2KMz-0003Zr-Ex for emacs-devel@gnu.org; Mon, 26 Aug 2019 15:09:38 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i2KMx-00042r-PA for emacs-devel@gnu.org; Mon, 26 Aug 2019 15:09:36 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:52212) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i2KMx-00040g-Hr for emacs-devel@gnu.org; Mon, 26 Aug 2019 15:09:35 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 6AD951600CE for ; Mon, 26 Aug 2019 12:09:33 -0700 (PDT) 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 cNIeP1F3ay7O for ; Mon, 26 Aug 2019 12:09:32 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id B1FAC1600E6 for ; Mon, 26 Aug 2019 12:09:32 -0700 (PDT) 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 zAUsh0aUGf06 for ; Mon, 26 Aug 2019 12:09:32 -0700 (PDT) Original-Received: from [192.168.1.9] (cpe-23-242-74-103.socal.res.rr.com [23.242.74.103]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 916121600CE for ; Mon, 26 Aug 2019 12:09:32 -0700 (PDT) In-Reply-To: <83a7bvg4a2.fsf@gnu.org> Content-Language: en-US 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: 2.1.23 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" Xref: news.gmane.org gmane.emacs.devel:239586 Archived-At: Eli Zaretskii wrote: > This is backwards: it would mean we should use UNINIT all over the > place just to be sure we will be able to spot some imaginary bugs by > flipping a compiler switch. That's not what UNINIT is for. It should be used only to pacify GCC. If GCC is happy with plain 'int x;' then UNINIT should not be used. Furthermore, these use-before-set bugs are not "imaginary". In the typical case where GCC's -Wmaybe-uninitialized diagnostics are not false alarms, they are quite useful in spotting and fixing use-before-set bugs. I've fixed many that way myself, typically in my working copy as I develop code. Indeed, 'configure' enables -Wmaybe-uninitialized precisely because its utility outweighs its cost of a few false alarms and resulting need to use UNINIT or unnecessary initializations. UNINIT can improve debugging, whereas unnecessary initializations can make the code look nicer. There's a tradeoff here, and different developers have different preferences of course. Developers who don't use tools that can take advantage of UNINIT may not appreciate or value its advantages.