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: Sun, 25 Aug 2019 23:34:25 -0700 Organization: UCLA Computer Science Department Message-ID: <32f9db09-0c04-df03-4bb7-76fe2aa9a88f@cs.ucla.edu> References: <835zmnjdjm.fsf@gnu.org> <227db16b-17d1-b44b-97b3-e80211415eef@cs.ucla.edu> <831rx9iupo.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="174864"; 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 Cc: emacs-devel@gnu.org To: Eli Zaretskii Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Mon Aug 26 08:34:46 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 1i28aT-000jPQ-Gk for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 08:34:45 +0200 Original-Received: from localhost ([::1]:50266 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i28aR-0001Qa-RO for ged-emacs-devel@m.gmane.org; Mon, 26 Aug 2019 02:34:43 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]:60499) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i28aG-0001QU-59 for emacs-devel@gnu.org; Mon, 26 Aug 2019 02:34:32 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i28aE-0001AR-NI for emacs-devel@gnu.org; Mon, 26 Aug 2019 02:34:31 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:49722) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i28aD-00018w-0j; Mon, 26 Aug 2019 02:34:29 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id D3C41160079; Sun, 25 Aug 2019 23:34:26 -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 tYrRYCaya1gV; Sun, 25 Aug 2019 23:34:26 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 071CD16008F; Sun, 25 Aug 2019 23:34:26 -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 4UvDk4eah7bZ; Sun, 25 Aug 2019 23:34:25 -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 D2B1E160079; Sun, 25 Aug 2019 23:34:25 -0700 (PDT) In-Reply-To: <831rx9iupo.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:239568 Archived-At: >> Newer GCC is smart enough to figure this out, at least with the default >> optimizations. > I believe the warning came from a compilation with GCC 9.2. With default optimizations? In that case an UNINIT is called for indeed. Although it is a bit odd that I'm not seeing a problem with GCC 9.2 (x86-64, built for RHEL 7.6), the oddity could be due to other platform differences. > UNINIT ... only works in a Git repository. > So it's a semi-kludgey semi-solution, not really better > than an explicit initialization with a comment. UNINIT works outside of Git repositories, since it depends on GCC_LINT which can be set independently of whether one is in a Git repository. I regularly use this feature. And UNINIT allows one to use tools other than GCC to diagnose improper use of uninitialized variables, whereas an explicit initialization would prevent using these tools. I use this feature occasionally as well. Admittedly UNINIT is a bit of a kludge, but it's the best kludge we have in the area.