linux-kernel - Re: [GIT PULL] Enable -Wimplicit-fallthrough for Clang for 5.16-rc1

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Message-ID: <CAHk-=wj-yyR1s1LcnTspgpcriyX-nDruzSmEneA2U=bOj9gCuQ@mail.gmail.com>
Date:   Sat, 13 Nov 2021 15:20:19 -0800
From:   Linus Torvalds <torvalds@...ux-foundation.org>
To:     "Gustavo A. R. Silva" <gustavoars@...nel.org>
Cc:     Kees Cook <keescook@...omium.org>,
        Nathan Chancellor <nathan@...nel.org>,
        Nick Desaulniers <ndesaulniers@...gle.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        linux-hardening@...r.kernel.org
Subject: Re: [GIT PULL] Enable -Wimplicit-fallthrough for Clang for 5.16-rc1

On Sat, Nov 13, 2021 at 1:36 PM Gustavo A. R. Silva
<gustavoars@...nel.org> wrote:
>
> This patch has been baking in linux-next for a couple of developement
> cycles, now. So, I think we are pretty much ready to merge it into
> mainline.

Ugh. It's also very ugly.

Wouldn't something like this (TOTALLY UNTESTED!) work and do the right thing?

This seems like a natural for a Kconfig decision.

Also, does -Wimplicit-fallthrough=5 work with clang too? That would
simplify things a bit, and then we could just use a regular boolean
and do

  KBUILD_CFLAGS-$(CC_IMPLICIT_FALLTHROUGH) += -Wimplicit-fallthrough=5

in the Makefile, which is more in like with what we do for other
config-time cflags..

           Linus

View attachment "patch.diff" of type "text/x-patch" (1537 bytes)