From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mark H Weaver Subject: Re: [PATCH 1/1] gnu: eudev: Update home-page URL. Date: Sun, 27 Dec 2015 10:46:12 -0500 Message-ID: <87k2nzq4hn.fsf@netris.org> References: <90bc2f88cc102cb5b39104aa8a3bc9414945cc23.1450939186.git.leo@famulari.name> <87poxu62kn.fsf@netris.org> <20151226060159.GA29304@jasmine> Mime-Version: 1.0 Content-Type: text/plain Return-path: Received: from eggs.gnu.org ([2001:4830:134:3::10]:37656) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aDDWd-00041N-BL for guix-devel@gnu.org; Sun, 27 Dec 2015 10:46:28 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aDDWY-0002g3-BM for guix-devel@gnu.org; Sun, 27 Dec 2015 10:46:27 -0500 Received: from world.peace.net ([50.252.239.5]:49492) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aDDWY-0002fy-7J for guix-devel@gnu.org; Sun, 27 Dec 2015 10:46:22 -0500 In-Reply-To: <20151226060159.GA29304@jasmine> (Leo Famulari's message of "Sat, 26 Dec 2015 01:01:59 -0500") List-Id: "Development of GNU Guix and the GNU System distribution." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org Sender: guix-devel-bounces+gcggd-guix-devel=m.gmane.org@gnu.org To: Leo Famulari Cc: guix-devel@gnu.org Leo Famulari writes: > On Fri, Dec 25, 2015 at 09:11:04AM -0500, Mark H Weaver wrote: >> Leo Famulari writes: >> > * gnu/packages/linux.scm (eudev)[home-page]: Add up-to-date URL. >> >> Looks good, please push! >> >> This won't require any rebuilds, because the 'home-page' field is not >> included in the generated derivations. > > Ah, right, of course! Because it doesn't affect the sha256 hash of the > source. It's true that it doesn't affect the hash of the source, but that would not be sufficient to ensure no rebuilds. Adding a new phase would not change the hash of the source, but it would affect the _derivation_ (as serialized in the *.drv file) and thus would require rebuilds. The 'home-page' field is not included in the derivation. > And the same for the source URI? Changing the source URI affects the derivation that downloads the source, however, that derivation is of a special kind called a "fixed output derivation", which means that the sha256 hash of the output is known in advance. Such derivations do not need to be rebuilt even if the derivation changes, as long as the hash stays the same, because it is presumed that the output would not change. Regards, Mark