On Mon, 2019-08-12 at 15:14 -0700, Nathan Huckleberry wrote: > Clang does not support the use of comments to label > intentional fallthrough. This patch replaces some uses > of comments to attributesto cut down a significant number > of warnings on clang (from ~50000 to ~200). Only comments > in commonly used header files have been replaced. > > Since there is still quite a bit of noise, this > patch moves -Wimplicit-fallthrough to > Makefile.extrawarn if you are compiling with > clang. Unmodified clang does not emit this warning without a patch. > diff --git a/Makefile b/Makefile [] > @@ -846,7 +846,11 @@ NOSTDINC_FLAGS += -nostdinc -isystem $(shell $(CC) -print-file-name=include) > KBUILD_CFLAGS += -Wdeclaration-after-statement > > # Warn about unmarked fall-throughs in switch statement. > +# If the compiler is clang, this warning is only enabled if W=1 in > +# Makefile.extrawarn > +ifndef CONFIG_CC_IS_CLANG > KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough,) > +endif It'd be better to remove CONFIG_CC_IS_CLANG everywhere eventually as it adds complexity and makes .config files not portable to multiple systems. > diff --git a/include/linux/compiler_attributes.h b/include/linux/compiler_attributes.h [] > @@ -253,4 +253,8 @@ > */ > #define __weak __attribute__((__weak__)) > > +#if __has_attribute(fallthrough) > +#define __fallthrough __attribute__((fallthrough)) This should be __attribute__((__fallthrough__)) And there is still no agreement about whether this should be #define fallthrough or #define __fallthrough https://lore.kernel.org/patchwork/patch/1108577/ > diff --git a/include/linux/jhash.h b/include/linux/jhash.h [] > @@ -86,19 +86,43 @@ static inline u32 jhash(const void *key, u32 length, u32 initval) [] > + case 12: > + c += (u32)k[11]<<24; > + __fallthrough; You might consider trying out the scripted conversion tool attached to this email: https://lore.kernel.org/lkml/61ddbb86d5e68a15e24ccb06d9b399bbf5ce2da7.camel@xxxxxxxxxxx/
