From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: [Emacs-diffs] master 6cd5678: Clarify compiler-pacifier in frame.c Date: Mon, 26 Aug 2019 21:39:17 +0300 Message-ID: <83a7bvg4a2.fsf@gnu.org> 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> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: 8bit Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="34515"; mail-complaints-to="usenet@blaine.gmane.org" Cc: emacs-devel@gnu.org To: =?iso-8859-1?Q?=D3scar?= Fuentes Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Aug 26 20:39:29 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 1i2Jtp-0008sj-9W for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 20:39:29 +0200 Original-Received: from localhost ([::1]:56516 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2Jtn-0000dI-Ph for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 14:39:27 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:59870) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2Jte-0000bC-Er for emacs-devel@gnu.org; Mon, 26 Aug 2019 14:39:19 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]:44824) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1i2Jtd-0004am-V4; Mon, 26 Aug 2019 14:39:18 -0400 Original-Received: from [176.228.60.248] (port=4520 helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:RSA_AES_256_CBC_SHA1:256) (Exim 4.82) (envelope-from ) id 1i2Jtd-00021E-BA; Mon, 26 Aug 2019 14:39:17 -0400 In-reply-to: <87ftln4wm0.fsf@telefonica.net> (message from =?iso-8859-1?Q?=D3scar?= Fuentes on Mon, 26 Aug 2019 20:20:23 +0200) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] 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:239583 Archived-At: > From: Óscar Fuentes > Date: Mon, 26 Aug 2019 20:20:23 +0200 > > Valgrind knows nothing about UNINIT as it works with machine code, not > with source code. But AFAIK that macro is conditionally defined to "=0" > (for silencing bogus gcc warnings) or to nothing (for leaving the > variable uninitalized at the declaration point). The later allows > Valgrind to do a proper check. > > Simply changing > > int x; > > to > > int x = 0; > > just for silencing the gcc warning can hide a bug that Valgrind would > detect otherwise. 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. The initialization in this case was added because GCC flagged a potential use-before-define. After that, there's no more bug for Valgrind to find, so I see no reason to leave UNINIT around. I could understand using UNINIT (or something similar) when the developer has no idea what not initializing could cause. But this is not that case.