From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([209.51.188.92]:53135) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1h1GhU-0000jG-Jm for qemu-devel@nongnu.org; Tue, 05 Mar 2019 15:30:09 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1h1GhT-0000xi-Oc for qemu-devel@nongnu.org; Tue, 05 Mar 2019 15:30:08 -0500 Received: from mail-wr1-f65.google.com ([209.85.221.65]:39418) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1h1GhT-0000pF-Gm for qemu-devel@nongnu.org; Tue, 05 Mar 2019 15:30:07 -0500 Received: by mail-wr1-f65.google.com with SMTP id l5so10925196wrw.6 for ; Tue, 05 Mar 2019 12:30:01 -0800 (PST) References: <1551723614-1823-1-git-send-email-pbonzini@redhat.com> <150efd5f-dea0-93bd-c74c-6d012f4ab7d1@redhat.com> From: =?UTF-8?Q?Philippe_Mathieu-Daud=c3=a9?= Message-ID: <4956a66a-a254-cd18-fe50-992ceb25028e@redhat.com> Date: Tue, 5 Mar 2019 21:29:58 +0100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit Subject: Re: [Qemu-devel] [PULL 00/54] Kconfig conversion, excluding ARM and MIPS List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , Thomas Huth , Peter Maydell , Paolo Bonzini Cc: Yang Zhong , QEMU Developers On 3/5/19 9:08 PM, Eric Blake wrote: > On 3/5/19 1:45 PM, Thomas Huth wrote: > >>> If there are special instructions for what to do with >>> build trees over the transition to kconfig, the pullreq >>> cover letter would be a good place to mention them :-) >> >> I think you've got to do a "make distclean" inbetween... that's the old >> problem when a default-configs/*.mak file gets added or erased - we do >> not properly re-generate the dependencies in that case. > > As in this? > > upgrade path: > build old commit > make distclean > git pull/branch/... make distclean again? > build new commit > > downgrade path (when bisecting, backporting, ...) > build new commit > make distclean > git branch/reset/... make distclean again? > build old commit > > We obviously can't fix old commits to recognize when we are downgrading > from a new commit, but is there anything we can do when upgrading to a > newer commit to more gracefully inform the user if they forgot a 'make > distclean' (or even better, to not make a 'make distclean' on upgrade > mandatory)?  In particular, once this patch series lands, developers > doing a blind 'git pull' will end up in the situation: > > build old commit > git pull > build new commit # oops > > but may not realize that they first have to reset back to the old commit > prior to 'make distclean' to guarantee that it will work. Unless I'm > mistaken and 'make distclean' on an incremental build will work in spite > of the missing dependencies on *.mak files even when you forgot to clean > before upgrading. > > 'make distclean' is a heavy hammer, is there anything smaller in scope > that will fix the problem without nuking everything, such as a strategic > touch or rm of one particular file? >