From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!.POSTED!not-for-mail From: Stefan Monnier Newsgroups: gmane.emacs.devel Subject: Re: Compiled code in Emacs-26 will fail in Emacs-25 if use pcase [was: Add new bytecode op `switch' for implementing branch tables.] Date: Thu, 23 Feb 2017 08:39:49 -0500 Message-ID: References: <1b07c68a-873e-83c8-246d-423bc83a3881@gmail.com> <83y3xg4ldw.fsf@gnu.org> NNTP-Posting-Host: blaine.gmane.org Mime-Version: 1.0 Content-Type: text/plain X-Trace: blaine.gmane.org 1487857363 13483 195.159.176.226 (23 Feb 2017 13:42:43 GMT) X-Complaints-To: usenet@blaine.gmane.org NNTP-Posting-Date: Thu, 23 Feb 2017 13:42:43 +0000 (UTC) User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.0.50 (gnu/linux) Cc: cpitclaudel@gmail.com, Eli Zaretskii , Vibhav Pant , Emacs developers To: Tino Calancha Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Thu Feb 23 14:42:39 2017 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 1cgtfK-0002y8-4N for ged-emacs-devel@m.gmane.org; Thu, 23 Feb 2017 14:42:38 +0100 Original-Received: from localhost ([::1]:58833 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cgtfQ-0006Hq-0A for ged-emacs-devel@m.gmane.org; Thu, 23 Feb 2017 08:42:44 -0500 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:53343) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1cgtch-0003p2-Lg for emacs-devel@gnu.org; Thu, 23 Feb 2017 08:39:56 -0500 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1cgtcg-0002do-VP for emacs-devel@gnu.org; Thu, 23 Feb 2017 08:39:55 -0500 Original-Received: from ironport2-out.teksavvy.com ([206.248.154.181]:25765) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1cgtcd-0002bx-2B; Thu, 23 Feb 2017 08:39:51 -0500 X-IronPort-Anti-Spam-Filtered: true X-IronPort-Anti-Spam-Result: A0C+BADT5a5Y/5iQSC1dGgEBAQECAQEBAQgBAQEBg1BBhDaLSJBpKQGXF4YcBAICgxpEFAECAQEBAQEBAWIohHEBBAFWIwULCzQHCxQYDSSKAAiwZYtBAQEIAiaLO4o5BZBMi0icWoZbkyg2IYEAIRQILIUJHRmBZiKLewEBAQ X-IPAS-Result: A0C+BADT5a5Y/5iQSC1dGgEBAQECAQEBAQgBAQEBg1BBhDaLSJBpKQGXF4YcBAICgxpEFAECAQEBAQEBAWIohHEBBAFWIwULCzQHCxQYDSSKAAiwZYtBAQEIAiaLO4o5BZBMi0icWoZbkyg2IYEAIRQILIUJHRmBZiKLewEBAQ X-IronPort-AV: E=Sophos;i="5.35,197,1484024400"; d="scan'208";a="293601781" Original-Received: from 45-72-144-152.cpe.teksavvy.com (HELO pastel.home) ([45.72.144.152]) by smtp.teksavvy.com with ESMTP; 23 Feb 2017 08:39:49 -0500 Original-Received: by pastel.home (Postfix, from userid 20848) id 45E7C6570F; Thu, 23 Feb 2017 08:39:49 -0500 (EST) In-Reply-To: (Tino Calancha's message of "Thu, 23 Feb 2017 13:35:54 +0900 (JST)") X-detected-operating-system: by eggs.gnu.org: Genre and OS details not recognized. X-Received-From: 206.248.154.181 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:212543 Archived-At: > I) Compile under master branch. > II) Load the resultant .elc with Emacs-25 As explained by Richard, this is usually considered acceptable. We don't really try to provide forward compatibility of byte-code files between major versions. This said, occasionally we try to reduce the pain a little: e.g. in Emacs-25 a similar incompatibility was introduced for the compilation of catch&condition-case, but the bytecodes were introduced a bit earlier. IOW the incompatibility was fundamentally introduced in 24.4 (IIRC), but the use of the this new feature was only enabled in Emacs-25.1, so files compiled with 25.1 will usually work in 24.5 as well. Stefan