linux-kernel - Re: [PATCH] kbuild: initialize CLANG_FLAGS correctly in the top Makefile

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Message-ID: <CAKwvOdnU8tLQ=wYAKs9Fy+3c2e_NmKL6H4kRKsRxH=sv16+8cQ@mail.gmail.com>
Date:   Mon, 29 Jul 2019 09:21:33 -0700
From:   Nick Desaulniers <ndesaulniers@...gle.com>
To:     Nathan Chancellor <natechancellor@...il.com>
Cc:     Masahiro Yamada <yamada.masahiro@...ionext.com>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        Stephen Boyd <swboyd@...omium.org>,
        "# 3.4.x" <stable@...r.kernel.org>,
        Michal Marek <michal.lkml@...kovi.net>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] kbuild: initialize CLANG_FLAGS correctly in the top Makefile

On Mon, Jul 29, 2019 at 9:04 AM Nathan Chancellor
<natechancellor@...il.com> wrote:
>
> On Mon, Jul 29, 2019 at 06:15:17PM +0900, Masahiro Yamada wrote:
> > CLANG_FLAGS is initialized by the following line:
> >
> >   CLANG_FLAGS     := --target=$(notdir $(CROSS_COMPILE:%-=%))
> >
> > ..., which is run only when CROSS_COMPILE is set.
> >
> > Some build targets (bindeb-pkg etc.) recurse to the top Makefile.
> >
> > When you build the kernel with Clang but without CROSS_COMPILE,
> > the same compiler flags such as -no-integrated-as are accumulated
> > into CLANG_FLAGS.
> >
> > If you run 'make CC=clang' and then 'make CC=clang bindeb-pkg',
> > Kbuild will recompile everything needlessly due to the build command
> > change.
> >
> > Fix this by correctly initializing CLANG_FLAGS.
> >
> > Fixes: 238bcbc4e07f ("kbuild: consolidate Clang compiler flags")
> > Cc: <stable@...r.kernel.org> # v4.20+
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@...ionext.com>
>
> Reviewed-by: Nathan Chancellor <natechancellor@...il.com>

Acked-by: Nick Desaulniers <ndesaulniers@...gle.com>

-- 
Thanks,
~Nick Desaulniers