[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH v5 07/10] xen/compiler: import 'fallthrough' keyword from linux
-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.singh@xxxxxxx> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx> --- Changes since v3: - This patch is introduce in this version. Changes since v4: No changes --- --- 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
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