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From:   Masahiro Yamada <masahiroy@kernel.org>
Date:   Wed, 9 Mar 2022 18:29:14 +0900
Message-ID: <CAK7LNAQnAgOqd1Zr3R0KBuGJps8K+Z7PGH5av9nA-VpJwZ4MeQ@mail.gmail.com>
Subject: Re: [PATCH v2] kbuild: Make $(LLVM) more flexible
To:     Matthew Wilcox <willy@infradead.org>
Cc:     Nick Desaulniers <ndesaulniers@google.com>,
        Nathan Chancellor <nathan@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Shuah Khan <shuah@kernel.org>, llvm@lists.linux.dev,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        "open list:DOCUMENTATION" <linux-doc@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "open list:KERNEL SELFTEST FRAMEWORK" 
        <linux-kselftest@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
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On Wed, Mar 9, 2022 at 1:36 AM Matthew Wilcox <willy@infradead.org> wrote:
>
> On Mon, Mar 07, 2022 at 11:08:29AM -0800, Nick Desaulniers wrote:
> > > +``LLVM=0`` is not the same as omitting ``LLVM`` altogether, it will behave like
> > > +``LLVM=1``.
> >
> > Hmm... I can see someone's build wrappers setting LLVM=1, then them
> > being surprised that appending LLVM=0 doesn't disable LLVM=1 as they
> > might expect.  But Masahiro says let's fix this later which is fine.
>
> What happens if you say LLVM= instead of LLVM=0 ?  Would that "undo"
> a prior LLVM=1 and use GCC instead?

I think so.


-- 
Best Regards
Masahiro Yamada