Hi,
> On 8 Jan 2021, at 14:46, Rahul Singh <rahul.si...@arm.com> wrote:
>
> -Wimplicit-fallthrough warns when a switch case falls through. Warning
> can be suppress by either adding a /* fallthrough */ comment, or by
> using a null statement: __attribute__ ((fallthrough))
>
> Define the pseudo keyword 'fallthrough' for the ability to convert the
> various case block /* fallthrough */ style comments to null statement
> "__attribute__((__fallthrough__))"
>
> In C mode, GCC supports the __fallthrough__ attribute since 7.1,
> the same time the warning and the comment parsing were introduced.
>
> fallthrough devolves to an empty "do {} while (0)" if the compiler
> version (any version less than gcc 7) does not support the attribute.
>
> Signed-off-by: Rahul Singh <rahul.si...@arm.com>
Reviewed-by: Bertrand Marquis <bertrand.marq...@arm.com>
Cheers
Bertrand
> ---
> Changes in V4:
> - This patch is introduce in this verison.
> ---
> xen/include/xen/compiler.h | 16 ++++++++++++++++
> 1 file changed, 16 insertions(+)
>
> diff --git a/xen/include/xen/compiler.h b/xen/include/xen/compiler.h
> index e643e69128..0ec0b4698e 100644
> --- a/xen/include/xen/compiler.h
> +++ b/xen/include/xen/compiler.h
> @@ -33,6 +33,22 @@
> #define unreachable() __builtin_unreachable()
> #endif
>
> +/*
> + * Add the pseudo keyword 'fallthrough' so case statement blocks
> + * must end with any of these keywords:
> + * break;
> + * fallthrough;
> + * goto <label>;
> + * return [expression];
> + *
> + * gcc:
> https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
> + */
> +#if (!defined(__clang__) && (__GNUC__ >= 7))
> +# define fallthrough __attribute__((__fallthrough__))
> +#else
> +# define fallthrough do {} while (0) /* fallthrough */
> +#endif
> +
> #ifdef __clang__
> /* Clang can replace some vars with new automatic ones that go in .data;
> * mark all explicit-segment vars 'used' to prevent that. */
> --
> 2.17.1
>
