From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.io!.POSTED.blaine.gmane.org!not-for-mail From: Eli Zaretskii Newsgroups: gmane.emacs.devel Subject: Re: HAVE_FAST_UNALIGNED_ACCESS Date: Sat, 01 Apr 2023 14:25:10 +0300 Message-ID: <83bkk7zvxl.fsf@gnu.org> References: <87sfdmlgzx.fsf@gmail.com> <94d3de92c50a96d9172f88462bf3bc9c2792600c.camel@gmail.com> <83mt3s244o.fsf@gnu.org> <875yagtopn.fsf@yahoo.com> <838rfc17ja.fsf@gnu.org> <871ql4t8ph.fsf@yahoo.com> <83wn2wyuli.fsf@gnu.org> <63A29442-4C0C-4C3C-B40E-4A3DB91E3009@gmail.com> <83lejcypyw.fsf@gnu.org> <87wn2wrmgc.fsf@yahoo.com> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit Injection-Info: ciao.gmane.io; posting-host="blaine.gmane.org:116.202.254.214"; logging-data="31741"; mail-complaints-to="usenet@ciao.gmane.io" Cc: mattias.engdegard@gmail.com, vibhavp@gmail.com, rpluim@gmail.com, emacs-devel@gnu.org To: Po Lu Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Sat Apr 01 13:25:27 2023 Return-path: Envelope-to: ged-emacs-devel@m.gmane-mx.org Original-Received: from lists.gnu.org ([209.51.188.17]) by ciao.gmane.io with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1piZMN-00083p-QT for ged-emacs-devel@m.gmane-mx.org; Sat, 01 Apr 2023 13:25:27 +0200 Original-Received: from localhost ([::1] helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1piZLu-00083u-Jb; Sat, 01 Apr 2023 07:24:58 -0400 Original-Received: from eggs.gnu.org ([2001:470:142:3::10]) by lists.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1piZLs-00083e-RV for emacs-devel@gnu.org; Sat, 01 Apr 2023 07:24:56 -0400 Original-Received: from fencepost.gnu.org ([2001:470:142:3::e]) by eggs.gnu.org with esmtps (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1piZLs-0004P8-5j; Sat, 01 Apr 2023 07:24:56 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=gnu.org; s=fencepost-gnu-org; h=MIME-version:References:Subject:In-Reply-To:To:From: Date; bh=qtUx/Cd0UiWjehoV4m8tHTjvu485ze7BQXy+HCXgIG0=; b=MgeNNoAdaDHCRHhYCwtc ap5JuedrQZrAB9eA+TlPMvrLZPbxTxNAc9atmKgu6VPydVXyyGM4xyu+4dnu2R4Ppvmxv7lW/Luh0 8FAe7RZij/0G3QYABKUwwxKhAStOhIa5dKfDsVaYcBbDTyJlWrjLHuhHK7vEu295C8P2k58vhk7Ut /6qXayRNQvVSF/mmf1f7sK4xGN9Nmv0qwj0RXt1FVmPmraEkXQkyy5hKCW1kGg8MnJSXK+VsaoVey G7/o5VXc3/D6uH+VfNty/RjmFzgoBryjyXXfCy3NGh4l051zfDdtEstAhqAMjOujRS6UAwRW4/t+0 yJ6Ghcy8+fRxuA==; Original-Received: from [87.69.77.57] (helo=home-c4e4a596f7) by fencepost.gnu.org with esmtpsa (TLS1.2:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.90_1) (envelope-from ) id 1piZLr-0002ar-Lo; Sat, 01 Apr 2023 07:24:55 -0400 In-Reply-To: <87wn2wrmgc.fsf@yahoo.com> (message from Po Lu on Sat, 01 Apr 2023 17:17:07 +0800) X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.29 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-mx.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane-mx.org@gnu.org Xref: news.gmane.io gmane.emacs.devel:304988 Archived-At: > From: Po Lu > Cc: Mattias Engdegård , > vibhavp@gmail.com, > rpluim@gmail.com, emacs-devel@gnu.org > Date: Sat, 01 Apr 2023 17:17:07 +0800 > > Eli Zaretskii writes: > > > IOW, "best engineering practices" are for master; on the release > > branch, using existing code proven by time takes precedence, because > > our ability to predict consequences is limited. > > This problem is not about engineering practices, but basic program > correctness. Look at the GCC bug tracker: every release, a program > that relies on this undefined behavior becomes subtly broken, a bug > is filed against GCC, and is closed by the GCC developers, stating > that this behavior is unsupported. > > Emacs 29 has been in development for less than three years... not nearly > long enough to be sure no subtle miscompilations have taken (or will > take) place. > > If that's ``proven by time'', then so is this: > > null_terminate (buffer, size) > char *buffer; > { > buffer[size] = '\0'; > } > > It might work for a few months, or a year, then suddenly break with a > new compiler release, or perhaps a change to malloc, or something else. I'm still unconvinced, and I said already what will have a chance of convincing me: a specific report about a problem this particular code causes on a specific existing platform we support in Emacs 29 and with a specific compiler.