From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-5.8 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 894A5C433FE for ; Wed, 9 Dec 2020 17:40:40 +0000 (UTC) Received: from lists.xenproject.org (lists.xenproject.org [192.237.175.120]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 3DEC520684 for ; Wed, 9 Dec 2020 17:40:40 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 3DEC520684 Authentication-Results: mail.kernel.org; dmarc=fail (p=reject dis=none) header.from=citrix.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=xen-devel-bounces@lists.xenproject.org Received: from list by lists.xenproject.org with outflank-mailman.48602.85952 (Exim 4.92) (envelope-from ) id 1kn3Rn-0006Gf-1w; Wed, 09 Dec 2020 17:40:15 +0000 X-Outflank-Mailman: Message body and most headers restored to incoming version Received: by outflank-mailman (output) from mailman id 48602.85952; Wed, 09 Dec 2020 17:40:15 +0000 Received: from localhost ([127.0.0.1] helo=lists.xenproject.org) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kn3Rm-0006GY-Ue; Wed, 09 Dec 2020 17:40:14 +0000 Received: by outflank-mailman (input) for mailman id 48602; Wed, 09 Dec 2020 17:40:14 +0000 Received: from us1-rack-iad1.inumbo.com ([172.99.69.81]) by lists.xenproject.org with esmtp (Exim 4.92) (envelope-from ) id 1kn3Rl-0006GT-Te for xen-devel@lists.xenproject.org; Wed, 09 Dec 2020 17:40:13 +0000 Received: from esa5.hc3370-68.iphmx.com (unknown [216.71.155.168]) by us1-rack-iad1.inumbo.com (Halon) with ESMTPS id 5c569f61-6e31-4f57-9192-45b3fe65b19d; Wed, 09 Dec 2020 17:40:12 +0000 (UTC) X-BeenThere: xen-devel@lists.xenproject.org List-Id: Xen developer discussion List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Errors-To: xen-devel-bounces@lists.xenproject.org Precedence: list Sender: "Xen-devel" X-Inumbo-ID: 5c569f61-6e31-4f57-9192-45b3fe65b19d DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=citrix.com; s=securemail; t=1607535612; h=date:from:to:cc:subject:message-id:references: mime-version:in-reply-to; bh=oqB04BnwV8YKEAA5lwVIHzO7kV7aixxFQohMpXRA2wM=; b=Bn/Ev2gpq5BssnRDoRi1q/ZloewFlx5Ye4dnH0rihX80YPLclLPPjRRq b9i2olpmjATeeVEjHZQ8NIb/gizCJziMjMS5M6QTCnMC1l/O05HFnsXII OrxtxeSj5mkmRnXxH+9n/znBBIJRho6IYsl2GkVPn62jfrbmno7CEABJ0 c=; Authentication-Results: esa5.hc3370-68.iphmx.com; dkim=none (message not signed) header.i=none IronPort-SDR: GdC42mKzGq431WnKJvGb0mIJlS1Ea7JCAdUR8TFSGJ6TnlKlbkhAb2h5kDZXboXXYKZ3Be8gND Ey2va32GN39YapDsbctRl4zEvLkD6iGpNylkDhV6m6tbjvhgkJpmGUFewcmqaYHo3IMfrSqM3f pLL49Wel5OqCU/PFmjXLWmsRHfPnGX/uYbb9VvFLzl9Io05QJWFfok8wRpq+0zG4KXvfcuB8OW bJf5OrkMCBZXFUK96hGysaEYB8O5QMhwpjsSSeKRhYke89WiANTgqR1rN5OC/Wmg7aM2pKQMAE 1qs= X-SBRS: 5.2 X-MesageID: 32880971 X-Ironport-Server: esa5.hc3370-68.iphmx.com X-Remote-IP: 162.221.158.21 X-Policy: $RELAYED X-IronPort-AV: E=Sophos;i="5.78,405,1599537600"; d="scan'208";a="32880971" Date: Wed, 9 Dec 2020 17:40:07 +0000 From: Anthony PERARD To: Jan Beulich CC: "xen-devel@lists.xenproject.org" , "Andrew Cooper" , George Dunlap , Ian Jackson , Julien Grall , Wei Liu , Stefano Stabellini Subject: Re: [PATCH v3 1/8] xen: fix build when $(obj-y) consists of just blanks Message-ID: References: <1a6bac6a-7d83-f5b6-c5b9-8b3b39824d40@suse.com> <511be84d-9a13-17ae-f3d9-d6daf9c02711@suse.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Disposition: inline In-Reply-To: <511be84d-9a13-17ae-f3d9-d6daf9c02711@suse.com> On Mon, Nov 23, 2020 at 04:20:52PM +0100, Jan Beulich wrote: > This case can occur when combining empty lists > > obj-y := > ... > obj-y += $(empty) > > or > > obj-y := $(empty) $(empty) > > where (only) blanks would accumulate. This was only a latent issue until > now, but would become an active issue for Arm once lib/ gets populated > with all respective objects going into the to be introduced lib.a. > > Also address a related issue at this occasion: When an empty built_in.o > gets created, .built_in.o.d will have its dependencies recorded. If, on > a subsequent incremental build, an actual constituent of built_in.o > appeared, the $(filter-out ) would leave these recorded dependencies in > place. But of course the linker won't know what to do with C header > files. (The apparent alternative of avoiding to pass $(c_flags) or > $(a_flags) would not be reliable afaict, as among these flags there may > be some affecting information conveyed via the object file to the > linker. The linker, finding inconsistent flags across object files, may How about using $(XEN_CFLAGS) instead of $(c_flags)? That should prevent CC from generating the .*.o.d files while keeping the relevant flags. I was planing to do that to avoid the issue, see: https://lore.kernel.org/xen-devel/20200421161208.2429539-10-anthony.perard@citrix.com > then error out.) Using just $(obj-y) won't work either: It breaks when > the same object file is listed more than once. Do we need to worry about having a object file been listed twice? Wouldn't that be a mistake? -- Anthony PERARD