linux-kernel - Re: [PATCH v2] kbuild: Check for unknown options with cc-option usage in Kconfig and clang

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Message-ID: <CAK7LNASoNRsMHHBW=d_Lkjo7eLpq5=gkU_g+k8NwEB0BwV37ZQ@mail.gmail.com>
Date:   Tue, 30 Jul 2019 23:28:20 +0900
From:   Masahiro Yamada <yamada.masahiro@...ionext.com>
To:     Stephen Boyd <swboyd@...omium.org>
Cc:     Michal Marek <michal.lkml@...kovi.net>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        clang-built-linux <clang-built-linux@...glegroups.com>,
        Peter Smith <peter.smith@...aro.org>,
        Nathan Chancellor <natechancellor@...il.com>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Douglas Anderson <dianders@...omium.org>
Subject: Re: [PATCH v2] kbuild: Check for unknown options with cc-option usage
 in Kconfig and clang

On Mon, Jul 29, 2019 at 11:23 PM Stephen Boyd <swboyd@...omium.org> wrote:
>
> Quoting Masahiro Yamada (2019-07-29 03:02:40)
> >
> > Thanks for catching this.
> >
> > I wonder if we could fix this issue
> > by one-liner, like this:
> >
> >
> > diff --git a/scripts/Kconfig.include b/scripts/Kconfig.include
> > index 8a5c4d645eb1..4bbf4fc163a2 100644
> > --- a/scripts/Kconfig.include
> > +++ b/scripts/Kconfig.include
> > @@ -25,7 +25,7 @@ failure = $(if-success,$(1),n,y)
> >
> >  # $(cc-option,<flag>)
> >  # Return y if the compiler supports <flag>, n otherwise
> > -cc-option = $(success,$(CC) -Werror $(1) -E -x c /dev/null -o /dev/null)
> > +cc-option = $(success,$(CC) -Werror $(CLANG_FLAGS) $(1) -E -x c
> > /dev/null -o /dev/null)
> >
> >  # $(ld-option,<flag>)
> >  # Return y if the linker supports <flag>, n otherwise
> >
> >
> >
> > This propagates not only -Werror=unknown-warning-option
> > but also other clang flags to Kconfig.
> >
> >
> > Currently, we do not pass the target triplet to Kconfig.
> > This means, cc-option in Kconfig evaluates the given flags
> > against host-arch instead of target-arch.
> > The compiler flags are mostly independent of the architecture,
> > and this is not a big deal, I think.
> > But, maybe, would it make more sense to pass the other
> > basic clang flags as well?
> >
>
> Yes that also works and I had that earlier. I wanted to mirror what was
> done in scripts/Kbuild.include where there's a CC_OPTION_CFLAGS
> variable. I'm happy either way, so it's up to you.
>

Can you post v3 with $(CLANG_FLAGS) ?

Thanks.

-- 
Best Regards
Masahiro Yamada