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=-1.3 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 D7475C43331 for ; Tue, 31 Mar 2020 16:04:06 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id A951520784 for ; Tue, 31 Mar 2020 16:04:06 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1585670646; bh=hzJ8gUenYPoLNJOWnvATdRk/qvBJfkP5vzoiJRWwqbE=; h=References:In-Reply-To:From:Date:Subject:To:Cc:List-ID:From; b=G71wWPFRWEMgv2Hu4W4ZAzlQ2lGPvT+pc2DRK178UE+DZcNKyv9TKRVun1wpxj2n/ uZQgTqi9vricYNLK2S/ElRpnfkLIKfqSbB0CWCo8hYMHlf1Ej01RXuZbsLEwEpAUS3 vdA9dhkAy+zI9V+a3CgJgjN+cJ1OnHQShwDykm40= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1731355AbgCaQEF (ORCPT ); Tue, 31 Mar 2020 12:04:05 -0400 Received: from conssluserg-01.nifty.com ([210.131.2.80]:47429 "EHLO conssluserg-01.nifty.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1731335AbgCaQEB (ORCPT ); Tue, 31 Mar 2020 12:04:01 -0400 Received: from mail-vs1-f52.google.com (mail-vs1-f52.google.com [209.85.217.52]) (authenticated) by conssluserg-01.nifty.com with ESMTP id 02VG3o86010377; Wed, 1 Apr 2020 01:03:50 +0900 DKIM-Filter: OpenDKIM Filter v2.10.3 conssluserg-01.nifty.com 02VG3o86010377 DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=nifty.com; s=dec2015msa; t=1585670631; bh=g8NpbIU/UC4q+xrWFvooNF2DdilLvEWkxEVzIf5x6dQ=; h=References:In-Reply-To:From:Date:Subject:To:Cc:From; b=pVA71gWrU82P2NSLczJmJtUieM8LJx6belN5whZu4rBJW8UjDvz/3/aa+fU76v3kF E3QZVAdxKh/OvcWvdoGSlAhPAxyMPpkVqg2eYnyFxoKeLHcPTbq00SyIwFat70D4RV MM7xpKEjqsIWm02zkxE8SJgG2BJPXaC1EpqpXfRVOJ1J/mf4bBsm7UQmI7NeiFuA4n MQLo8gaktJ9ClO7NB4OLBGjaIb1VDzV40GzOl+lg4zVMeuGKy4HN+z+oOg0X/moaPR B4uJsrwBG2FaZafQUQwWTQqFtj/qnV34bxak2osj9GzZLXkhH+OiDyPhbSSdxVrGWT pbSfItGW7e79A== X-Nifty-SrcIP: [209.85.217.52] Received: by mail-vs1-f52.google.com with SMTP id s10so13775651vsi.9; Tue, 31 Mar 2020 09:03:50 -0700 (PDT) X-Gm-Message-State: AGi0PuYqicOk1npx14Ni2uhWdNMv+lCedsDMNEXoJ3r91MbPL5pFsJcp IAMoi/871kQ6cciPP15s6SihKjaIiXivLNDplEs= X-Google-Smtp-Source: APiQypID6adS4u5eA7kE/v0+dVrrluNOnmRV1pxnz1uMJaWnu1FGs7pyn+sbb+gOJmtZWscxKLx62+Jdjw1TJXd2HIk= X-Received: by 2002:a67:b01:: with SMTP id 1mr847069vsl.181.1585670629321; Tue, 31 Mar 2020 09:03:49 -0700 (PDT) MIME-Version: 1.0 References: <8c491e3b-a622-14c1-15c3-8cff061017ba@oracle.com> In-Reply-To: <8c491e3b-a622-14c1-15c3-8cff061017ba@oracle.com> From: Masahiro Yamada Date: Wed, 1 Apr 2020 01:03:12 +0900 X-Gmail-Original-Message-ID: Message-ID: Subject: Re: single target builds are broken To: Vegard Nossum Cc: Jens Axboe , LKML , Linux Kbuild mailing list Content-Type: text/plain; charset="UTF-8" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, Mar 31, 2020 at 8:02 PM Vegard Nossum wrote: > > > On 3/31/20 11:49 AM, Masahiro Yamada wrote: > > On Tue, Mar 31, 2020 at 6:16 PM Vegard Nossum wrote: > >> > >> > >> Hi, > >> > >> I often run 'make foo/bar.o' as part of my workflow, even when bar.o is > >> not specified in any kernel makefile, and this has worked just fine for > >> years. > >> > >> This is broken after commit 394053f4a4b3e3eeeaa67b67fc886a9a75bd9e4d > >> (kbuild: make single targets work more correctly) and just gives an error: > >> > >> $ make kernel/test.o > >> CALL scripts/checksyscalls.sh > >> CALL scripts/atomic/check-atomics.sh > >> DESCEND objtool > >> make[2]: *** No rule to make target 'kernel/test.o'. Stop. > >> scripts/Makefile.build:502: recipe for target '__build' failed > >> make[1]: *** [__build] Error 2 > >> Makefile:1670: recipe for target 'kernel' failed > >> make: *** [kernel] Error 2 > > > > > > This is intentional to make the single target builds > > work in the same manner as the normal builds. > > > > > > The necessary CONFIG dependency must be met. > > > > obj-$(CONFIG_FOO) += foo.o > > > > foo.o can be built only when CONFIG_FOO is y/m. > > > > > > > >> For top-level objects (e.g. 'make bar.o') the situation is even worse, > >> since make exits with status 0 without building anything :-/ > > > > > > There is no .c or .S file at the top-level of the kernel source tree. > > > > 'make bar.o' never happens. > > It doesn't happen in mainline, but I often use that to small test things > in an isolated source file. As just one example you can do > > #include > unsigned int task_struct_size = sizeof(struct task_struct); > > and then you can look in the object file to find the size. Or any other > of a million useful things that you might want to do without rebuilding > an actual source file or modifying makefiles. > > >> Is there any chance we can get this back? It was super useful for me. > > > > > > What you want is "Let's build whatever", right? > > It's really useful to be able to build object files separately, but as > if it was part of the kernel (so e.g. with all the gcc flags, include > paths, etc.). > > > No, please add 'obj-y += test.o' if you want to > > test your local file. > > This is a clear workflow regression for me. Why is it so absolutely > necessary to break the way it used to work? Because this is the only way to do this correctly. Previously, 'make foo/bar/baz.o' descended into foo/bar (it always assumed there was Makefile in the directory part) So, there were lots of cases where single builds did not work: https://www.spinics.net/lists/linux-kbuild/msg21921.html The way to do this correctly is to descend directories one by one, parsing Makefiles. With no entry in obj-y/m, Kbuild cannot determine where to build that object. > At the very least, can we find a way to reduce the typing overhead for > testing one-offs like that? 'make STANDALONE=1 test.o' or something? Probably, I do not want to do this. Supporting everybody's demand is not a good idea. So, I draw a line somewhere. Saving some typing is less important. > > > Vegard -- Best Regards Masahiro Yamada