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

[Josef Bacik]

On Tue, Dec 20, 2016 at 11:34 AM, David Binderman  
wrote:


Hello there,


From: Alexei Starovoitov 
I've tried 4.9 and 5.2 and don't see this warning.


As expected - I used a development version of gcc.
Latest released version is 6.2


Is this 6.x gcc?


7.0 would be more accurate.


I suspect it will have such warnings all over the kernel.


Indeed it has hundreds, but the subject under discussion is file
kernel/bpf/verifier.c.

I am still not sure if I have found a fallthrough bug or not.


You haven't, this is intended so is a useless warning.  Thanks,

Josef

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

[Alexei Starovoitov]

On Tue, Dec 20, 2016 at 3:20 AM, David Binderman  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.