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Subject: Re: [PATCH] kbuild: Enable -Wimplicit-fallthrough for clang 14.0.0+
To:     Nathan Chancellor <nathan@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Philip Li <philip.li@intel.com>
Cc:     Masahiro Yamada <masahiroy@kernel.org>,
        Linus Torvalds <torvalds@linux-foundation.org>,
        "Gustavo A. R. Silva" <gustavoars@kernel.org>,
        Nick Desaulniers <ndesaulniers@google.com>,
        Linux Kbuild mailing list <linux-kbuild@vger.kernel.org>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        clang-built-linux <clang-built-linux@googlegroups.com>,
        linux-hardening@vger.kernel.org
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From:   "Gustavo A. R. Silva" <gustavo@embeddedor.com>
Message-ID: <1f05cd38-c576-0ded-81b6-fe0b49a5059e@embeddedor.com>
Date:   Tue, 17 Aug 2021 18:40:25 -0500
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On 8/17/21 18:23, Nathan Chancellor wrote:
>>>> # Warn about unmarked fall-throughs in switch statement.
>>>> # Clang prior to 14.0.0 warned on unreachable fallthroughs with
>>>> # -Wimplicit-fallthrough, which is unacceptable due to IS_ENABLED().
>>>> # https://bugs.llvm.org/show_bug.cgi?id=51094
>>>> ifeq ($(firstword $(sort $(CONFIG_CLANG_VERSION) 140000)),140000)
>>>> KBUILD_CFLAGS += -Wimplicit-fallthrough
>>>> endif
> 
> Very clever and nifty trick! I have verified that it works for clang 13 and 14 along with a theoretical clang 15. Gustavo, feel free to stick a
> 
> Reviewed-by: Nathan Chancellor <nathan@kernel.org>
> Tested-by: Nathan Chancellor <nathan@kernel.org>
> 
> if you so desire.

Yep; I just tested it locally with clang 13 and 14, too.

Thanks
--
Gustavo