linux-kernel - Re: [PATCH v2 01/39] kbuild: Fix clang build

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Message-ID: <202203021039.0DF89D3F2C@keescook>
Date:   Wed, 2 Mar 2022 10:40:43 -0800
From:   Kees Cook <keescook@...omium.org>
To:     Nathan Chancellor <nathan@...nel.org>
Cc:     Nick Desaulniers <ndesaulniers@...gle.com>,
        Peter Zijlstra <peterz@...radead.org>, x86@...nel.org,
        joao@...rdrivepizza.com, hjl.tools@...il.com, jpoimboe@...hat.com,
        andrew.cooper3@...rix.com, linux-kernel@...r.kernel.org,
        samitolvanen@...gle.com, mark.rutland@....com,
        alyssa.milburn@...el.com, mbenes@...e.cz, rostedt@...dmis.org,
        mhiramat@...nel.org, alexei.starovoitov@...il.com,
        Masahiro Yamada <masahiroy@...nel.org>,
        Linux Kbuild mailing list <linux-kbuild@...r.kernel.org>,
        llvm@...ts.linux.dev
Subject: Re: [PATCH v2 01/39] kbuild: Fix clang build

On Wed, Mar 02, 2022 at 09:37:04AM -0700, Nathan Chancellor wrote:
> However, I think we could still address Peter's complaint of "there
> should be an easier way for me to use the tools that are already in my
> PATH" with his first iteration of this patch [1], which I feel is
> totally reasonable:
> 
> $ make LLVM=-14
> 
> It is still easy to use (in fact, it is shorter than 'CC=clang-14') and
> it does not change anything else about how we build with LLVM. We would
> just have to add something along the lines of
> 
> "If your LLVM tools have a suffix like Debian's (clang-14, ld.lld-14,
> etc.), use LLVM=<suffix>.
> 
> $ make LLVM=-14"
> 
> to Documentation/kbuild/llvm.rst.
> 
> I might change the patch not to be so clever though:
> 
> ifneq ($(LLVM),)
> ifneq ($(LLVM),1)
> LLVM_SFX := $(LLVM)
> endif
> endif

I like this idea! I think it's much easier to control than PATH (though
I see the rationale there too).

-- 
Kees Cook