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

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Date:   Sat, 13 Nov 2021 18:08:56 -0600
From:   "Gustavo A. R. Silva" <gustavoars@...nel.org>
To:     Linus Torvalds <torvalds@...ux-foundation.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 03:20:19PM -0800, Linus Torvalds wrote:
> On Sat, Nov 13, 2021 at 1:36 PM Gustavo A. R. Silva
> <gustavoars@...nel.org> wrote:
[..]
> 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

It doesn't work:

error: unknown warning option '-Wimplicit-fallthrough=5'; did you mean '-Wimplicit-fallthrough'? [-Werror,-Wunknown-warning-option]

However, your patch does work. :)

I'll send it as a proper patch, shortly.

Thanks
--
Gustavo