From mboxrd@z Thu Jan 1 00:00:00 1970 From: Leo Famulari Subject: Re: [PATCH 1/1] gnu: eudev: Update home-page URL. Date: Sun, 27 Dec 2015 19:43:42 -0500 Message-ID: <20151228004342.GA14699@jasmine> References: <90bc2f88cc102cb5b39104aa8a3bc9414945cc23.1450939186.git.leo@famulari.name> <87poxu62kn.fsf@netris.org> <20151226060159.GA29304@jasmine> <87k2nzq4hn.fsf@netris.org> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: Received: from eggs.gnu.org ([2001:4830:134:3::10]:42245) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aDLuc-0000JT-Iy for guix-devel@gnu.org; Sun, 27 Dec 2015 19:43:47 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1aDLuZ-00008d-CB for guix-devel@gnu.org; Sun, 27 Dec 2015 19:43:46 -0500 Received: from out3-smtp.messagingengine.com ([66.111.4.27]:59184) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1aDLuZ-00008Z-8m for guix-devel@gnu.org; Sun, 27 Dec 2015 19:43:43 -0500 Content-Disposition: inline In-Reply-To: <87k2nzq4hn.fsf@netris.org> 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: Mark H Weaver Cc: guix-devel@gnu.org On Sun, Dec 27, 2015 at 10:46:12AM -0500, Mark H Weaver wrote: > 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. Thank you for taking the time to explain this. For everyone reading along, there is some more information about fixed-output derivations in the manual here: https://www.gnu.org/software/guix/manual/html_node/Derivations.html