From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: master d0c77a1: Remove some assumptions about timestamp format Date: Tue, 25 Sep 2018 18:09:39 -0700 Organization: UCLA Computer Science Department Message-ID: References: <20180925021527.10418.61555@vcs0.savannah.gnu.org> <20180925021528.9A119204E8@vcs0.savannah.gnu.org> <87bm8lanwu.fsf@gmx.de> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit X-Trace: blaine.gmane.org 1537924874 29752 195.159.176.226 (26 Sep 2018 01:21:14 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Wed, 26 Sep 2018 01:21:14 +0000 (UTC) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.0 To: Michael Albinus , emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Wed Sep 26 03:21:10 2018 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by blaine.gmane.org with esmtp (Exim 4.84_2) (envelope-from ) id 1g4yVo-0007c1-1m for ged-emacs-devel@m.gmane.org; Wed, 26 Sep 2018 03:21:08 +0200 Original-Received: from localhost ([::1]:55912 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g4yXu-0007sf-GE for ged-emacs-devel@m.gmane.org; Tue, 25 Sep 2018 21:23:18 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:36934) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1g4yXE-0007s6-B1 for emacs-devel@gnu.org; Tue, 25 Sep 2018 21:22:40 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1g4yKk-0007gD-8h for emacs-devel@gnu.org; Tue, 25 Sep 2018 21:09:47 -0400 Original-Received: from zimbra.cs.ucla.edu ([131.179.128.68]:48618) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1g4yKj-0007fQ-VL for emacs-devel@gnu.org; Tue, 25 Sep 2018 21:09:42 -0400 Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 408AF161624; Tue, 25 Sep 2018 18:09:40 -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 wdUdC5jmsLV2; Tue, 25 Sep 2018 18:09:39 -0700 (PDT) Original-Received: from localhost (localhost [127.0.0.1]) by zimbra.cs.ucla.edu (Postfix) with ESMTP id 6ACA9161698; Tue, 25 Sep 2018 18:09:39 -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 q6qfLYzs617V; Tue, 25 Sep 2018 18:09:39 -0700 (PDT) Original-Received: from Penguin.CS.UCLA.EDU (Penguin.CS.UCLA.EDU [131.179.64.200]) by zimbra.cs.ucla.edu (Postfix) with ESMTPSA id 4D03A161624; Tue, 25 Sep 2018 18:09:39 -0700 (PDT) Openpgp: preference=signencrypt Autocrypt: addr=eggert@cs.ucla.edu; prefer-encrypt=mutual; keydata= xsFNBEyAcmQBEADAAyH2xoTu7ppG5D3a8FMZEon74dCvc4+q1XA2J2tBy2pwaTqfhpxxdGA9 Jj50UJ3PD4bSUEgN8tLZ0san47l5XTAFLi2456ciSl5m8sKaHlGdt9XmAAtmXqeZVIYX/UFS 96fDzf4xhEmm/y7LbYEPQdUdxu47xA5KhTYp5bltF3WYDz1Ygd7gx07Auwp7iw7eNvnoDTAl KAl8KYDZzbDNCQGEbpY3efZIvPdeI+FWQN4W+kghy+P6au6PrIIhYraeua7XDdb2LS1en3Ss mE3QjqfRqI/A2ue8JMwsvXe/WK38Ezs6x74iTaqI3AFH6ilAhDqpMnd/msSESNFt76DiO1ZK QMr9amVPknjfPmJISqdhgB1DlEdw34sROf6V8mZw0xfqT6PKE46LcFefzs0kbg4GORf8vjG2 Sf1tk5eU8MBiyN/bZ03bKNjNYMpODDQQwuP84kYLkX2wBxxMAhBxwbDVZudzxDZJ1C2VXujC OJVxq2kljBM9ETYuUGqd75AW2LXrLw6+MuIsHFAYAgRr7+KcwDgBAfwhPBYX34nSSiHlmLC+ KaHLeCLF5ZI2vKm3HEeCTtlOg7xZEONgwzL+fdKo+D6SoC8RRxJKs8a3sVfI4t6CnrQzvJbB n6gxdgCu5i29J1QCYrCYvql2UyFPAK+do99/1jOXT4m2836j1wARAQABzSBQYXVsIEVnZ2Vy dCA8ZWdnZXJ0QGNzLnVjbGEuZWR1PsLBfgQTAQIAKAUCTIByZAIbAwUJEswDAAYLCQgHAwIG FQgCCQoLBBYCAwECH In-Reply-To: <87bm8lanwu.fsf@gmx.de> 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:230077 Archived-At: On 9/25/18 3:09 AM, Michael Albinus wrote: > In the different tramp*.el files, '(0 0) is explicitly quoted as "don't > know value". This is there for ages. > > If you want to change this in the tests, it shall be changed in > tramp*.el as well. Maybe it would be even worth an own constant? > Something like > > (defconst time-dont-know (seconds-to-time 0) > "A time value indicating an unknown time.") > > If you like, it could even have the value 0 instead of (seconds-to-time > 0). But this would also introduce "some assumptions of Lisp code on > timestamp format" - what you try to avoid. A constant like that would make things clearer, yes. Either 0 or (0 0 0 0) or (0 0) should do, so I suggest just 0 as it's simplest. While you're at it, you might consider changing the number from 0 to a negative value, say -1 (the value that POSIX uses for invalid time_t), since that's less likely to collide with actual file timestamps (timestamp 0 is far more common than timestamp -1 in real filesystems in my experience). The Tramp code shouldn't care whether the constant is 0 or (0 0) or (0 0 0 0) [or -1 or (-1 65535) or (-1 65535 0 0)], because the code should compare time stamps via time-less-p (or float-time, if the timestamps are known to be small like 0 or -1, or maybe we should add time-equal?), not via 'equal'. The idea is that the Lisp timestamp format has changed in the past and is likely to change in the future and one should not assume any particular format if one wants the code to be portable.