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: (select-window nil) crash with gcc-8.2.0 Date: Sun, 7 Apr 2019 11:33:22 -0700 Organization: UCLA Computer Science Department Message-ID: <37a9098c-d566-1813-1c9f-0c5c32c813cf@cs.ucla.edu> References: <0993F546-D21B-4722-8300-7A9CDDCE7EB8@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="122508"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.6.1 Cc: emacs-devel@gnu.org To: Madhu Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sun Apr 07 20:34:09 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 (TLS1.0:RSA_AES_256_CBC_SHA1:256) (Exim 4.89) (envelope-from ) id 1hDCcJ-000VfG-Bp for ged-emacs-devel@m.gmane.org; Sun, 07 Apr 2019 20:34:08 +0200 Original-Received: from localhost ([127.0.0.1]:42212 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hDCcD-0006e5-43 for ged-emacs-devel@m.gmane.org; Sun, 07 Apr 2019 14:34:01 -0400 Original-Received: from eggs.gnu.org ([209.51.188.92]:45616) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1hDCbf-0006dn-C5 for emacs-devel@gnu.org; Sun, 07 Apr 2019 14:33:28 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1hDCbe-0003dl-H3 for emacs-devel@gnu.org; Sun, 07 Apr 2019 14:33:27 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:45084) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1hDCbe-0003dV-7A for emacs-devel@gnu.org; Sun, 07 Apr 2019 14:33:26 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id EEBF8161683; Sun, 7 Apr 2019 11:33:24 -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 TQODLXdO1TjS; Sun, 7 Apr 2019 11:33:24 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 1F2A4161692; Sun, 7 Apr 2019 11:33:23 -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 27PSn6vqYJzP; Sun, 7 Apr 2019 11:33:23 -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 E1B8816168A; Sun, 7 Apr 2019 11:33:22 -0700 (PDT) In-Reply-To: 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: 2.1.21 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:235080 Archived-At: I reproduced the bug with GCC 8.3.1 20190223 (Red Hat 8.3.1-2) on x86-64. It's clearly a compiler bug with -O2 -Os. The machine code for select_window starts this way: select_window: pushq %r13 movl %edx, %r13d pushq %r12 pushq %rbp movq %rsi, %rbp pushq %rbx movq %rdi, %rbx pushq %rcx call WINDOWP movq 75(%rbx), %r12 xorl %edi, %edi testb %al, %al je .L981 and that last movq dereferences the window pointer in %rbx before the result of WINDOWP is checked to verify that the argument (originally in %rdi, now in %rbx) is indeed a window. Could you file a GCC bug report for this? And in the meantime, I wouldn't use -Os.