linux-kernel - Re: kernel/bpf/verifier.c: 4 * possible unintended fallthrough ?

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Date:   Tue, 20 Dec 2016 08:17:33 -0800
From:   Alexei Starovoitov <alexei.starovoitov@...il.com>
To:     David Binderman <dcb314@...mail.com>, Josef Bacik <jbacik@...com>
Cc:     "ast@...nel.org" <ast@...nel.org>,
        "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>
Subject: Re: kernel/bpf/verifier.c: 4 * possible unintended fallthrough ?

On Tue, Dec 20, 2016 at 3:20 AM, David Binderman <dcb314@...mail.com> wrote:
> Hello there,
>
> I just tried to compile kernel-4.9 with a recent development
> version of gcc. It said
>
> kernel/bpf/verifier.c:1907:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
> kernel/bpf/verifier.c:1918:23: warning: this statement may fall through [-Wimplicit-fallthrough=]
> kernel/bpf/verifier.c:1859:24: warning: this statement may fall through [-Wimplicit-fallthrough=]
> kernel/bpf/verifier.c:1869:24: warning: this statement may fall through [-Wimplicit-fallthrough=]
>
> Source code for the first one is
>
>     case BPF_JGT:
>         /* Unsigned comparison, the minimum value is 0. */
>         true_reg->min_value = 0;
>     case BPF_JSGT:
>
> Suggest either add the missing break or document the fallthrough
> with a comment something like /* FALLTHROUGH */

I've tried 4.9 and 5.2 and don't see this warning.
Is this 6.x gcc?
I suspect it will have such warnings all over the kernel.