compiler_attributes.h: Add 'fallthrough' pseudo keyword for switch/case use
Reserve the pseudo keyword 'fallthrough' for the ability to convert the various case block /* fallthrough */ style comments to appear to be an actual reserved word with the same gcc case block missing fallthrough warning capability. All switch/case blocks now should end in one of: break; fallthrough; goto <label>; return [expression]; continue; 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: Joe Perches <joe@perches.com> Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org> Suggested-by: Dan Carpenter <dan.carpenter@oracle.com> Cc: Miguel Ojeda <miguel.ojeda.sandonis@gmail.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
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@ -40,6 +40,7 @@
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# define __GCC4_has_attribute___noclone__ 1
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# define __GCC4_has_attribute___nonstring__ 0
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# define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8)
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# define __GCC4_has_attribute___fallthrough__ 0
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#endif
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/*
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@ -185,6 +186,22 @@
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# define __noclone
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#endif
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/*
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* Add the pseudo keyword 'fallthrough' so case statement blocks
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* must end with any of these keywords:
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* break;
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* fallthrough;
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* goto <label>;
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* return [expression];
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*
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* gcc: https://gcc.gnu.org/onlinedocs/gcc/Statement-Attributes.html#Statement-Attributes
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*/
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#if __has_attribute(__fallthrough__)
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# define fallthrough __attribute__((__fallthrough__))
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#else
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# define fallthrough do {} while (0) /* fallthrough */
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#endif
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/*
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* Note the missing underscores.
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*
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