From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: =?utf-8?Q?=C3=93scar_Fuentes?= Newsgroups: gmane.emacs.devel Subject: Re: [Emacs-diffs] master 6cd5678: Clarify compiler-pacifier in frame.c Date: Mon, 26 Aug 2019 20:20:23 +0200 Message-ID: <87ftln4wm0.fsf@telefonica.net> 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> Mime-Version: 1.0 Content-Type: text/plain Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="229120"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.0.50 (gnu/linux) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Aug 26 20:21:51 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 1i2Jck-000xLu-Sv for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 20:21:51 +0200 Original-Received: from localhost ([::1]:56402 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2Jcj-00038a-Lf for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 14:21:49 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:56844) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i2JbU-00037Q-GL for emacs-devel@gnu.org; Mon, 26 Aug 2019 14:20:33 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i2JbT-0002Lo-5o for emacs-devel@gnu.org; Mon, 26 Aug 2019 14:20:32 -0400 Original-Received: from 195-159-176-226.customer.powertech.no ([195.159.176.226]:52114 helo=blaine.gmane.org) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i2JbS-0002Kz-Us for emacs-devel@gnu.org; Mon, 26 Aug 2019 14:20:31 -0400 Original-Received: from list by blaine.gmane.org with local (Exim 4.89) (envelope-from ) id 1i2JbR-000vq9-3Q for emacs-devel@gnu.org; Mon, 26 Aug 2019 20:20:29 +0200 X-Injected-Via-Gmane: http://gmane.org/ Cancel-Lock: sha1:9RWnjzNo2C9q4EDmiDEhZkTSs30= X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 195.159.176.226 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:239582 Archived-At: Eli Zaretskii writes: >> > What debugging tools can make a significant difference here, and how >> > easy/practical is it to use them? I very much doubt they will catch >> > every use-before-set bug anyway. >> >> Valgrind tracks each byte at the machine instruction level. >> >> Given the complexity of the Emacs C code, IMAO it is very useful to test >> for this type of nasty errors. I dislike hacks that pollute the source >> code, but on this case it is warranted. > > Does valgrind know about UNINIT? I'd be surprised, since UNINIT is a > source-level feature. 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.