On Sat, Oct 05, 2019 at 07:17:36PM +0200, Miguel Ojeda wrote: > Hi Joe, > > On Sat, Oct 5, 2019 at 6:46 PM Joe Perches <[email protected]> wrote: > > > > 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 must end in one of: > > > > break; > > fallthrough; > > goto <label>; > > return [expression]; > > continue; > > > > fallthough is gcc's __attribute__((__fallthrough__)) which was introduced > > in gcc version 7.. > > Nits: double period, missing "r" in fallthough. > > > fallthrough devolves to an empty "do {} while (0)" if the compiler > > version (any version less than gcc 7) does not support the attribute. > > Perhaps add a short note why (empty statement warnings maybe? I don't > remember them but it was months ago so maybe it changed). > > > Signed-off-by: Joe Perches <[email protected]> > > Acked-by: Peter Zijlstra (Intel) <[email protected]> > > Please add Dan's Suggested-by and copy the things I wrote in the > commit message when I proposed this: > > > https://github.com/ojeda/linux/commit/668f011a2706ea555987e263f609a5deba9c7fc4
Perhaps just take this patch directly with Miguel's authorship into the series and tweak the __fallthrough to fallthrough in subject and body. -Kees > > > --- > > include/linux/compiler_attributes.h | 17 +++++++++++++++++ > > 1 file changed, 17 insertions(+) > > > > diff --git a/include/linux/compiler_attributes.h > > b/include/linux/compiler_attributes.h > > index 6b318efd8a74..cdf016596659 100644 > > --- a/include/linux/compiler_attributes.h > > +++ b/include/linux/compiler_attributes.h > > @@ -40,6 +40,7 @@ > > # define __GCC4_has_attribute___noclone__ 1 > > # define __GCC4_has_attribute___nonstring__ 0 > > # define __GCC4_has_attribute___no_sanitize_address__ (__GNUC_MINOR__ >= 8) > > +# define __GCC4_has_attribute___fallthrough__ 0 > > This goes after __externally_visible__. > > > #endif > > > > /* > > @@ -185,6 +186,22 @@ > > # define __noclone > > #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 > > This also goes after __externally_visible__. > > Please add: > > * Optional: only supported since gcc >= 7.1 > * Optional: only supported since clang >= 10 > * Optional: not supported by icc > > As well as: > > clang: https://clang.llvm.org/docs/AttributeReference.html#fallthrough > > See how I did it in the link above: > > > https://github.com/ojeda/linux/commit/668f011a2706ea555987e263f609a5deba9c7fc4 > > > + */ > > +#if __has_attribute(__fallthrough__) > > +# define fallthrough __attribute__((__fallthrough__)) > > +#else > > +# define fallthrough do {} while (0) /* fallthrough */ > > +#endif > > + > > /* > > * Note the missing underscores. > > * > > -- > > 2.15.0 > > > > Cheers, > Miguel -- Kees Cook
