On Thu, Aug 15, 2019 at 11:20:29AM -0700, 'Nathan Huckleberry' via Clang Built Linux wrote: > Clang is updating to support -Wimplicit-fallthrough on C > https://reviews.llvm.org/D64838. Since clang does not > support the comment version of fallthrough annotations > this update causes an additional 50k warnings. Most > of these warnings (>49k) are duplicates from header files. > > This patch is intended to be reverted after the warnings > have been cleaned up. > > Signed-off-by: Nathan Huckleberry <nhuck@xxxxxxxxxx> > --- > Makefile | 4 ++++ > scripts/Makefile.extrawarn | 3 +++ > 2 files changed, 7 insertions(+) > > diff --git a/Makefile b/Makefile > index 1b23f95db176..93b9744e66a2 100644 > --- 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 > > # Variable Length Arrays (VLAs) should not be used anywhere in the kernel > KBUILD_CFLAGS += -Wvla > diff --git a/scripts/Makefile.extrawarn b/scripts/Makefile.extrawarn > index a74ce2e3c33e..e12359d69bb7 100644 > --- a/scripts/Makefile.extrawarn > +++ b/scripts/Makefile.extrawarn > @@ -30,6 +30,9 @@ warning-1 += $(call cc-option, -Wunused-but-set-variable) > warning-1 += $(call cc-option, -Wunused-const-variable) > warning-1 += $(call cc-option, -Wpacked-not-aligned) > warning-1 += $(call cc-option, -Wstringop-truncation) > +ifdef CONFIG_CC_IS_CLANG > +KBUILD_CFLAGS += $(call cc-option,-Wimplicit-fallthrough,) Shouldn't this be warning-1? > +endif > # The following turn off the warnings enabled by -Wextra > warning-1 += -Wno-missing-field-initializers > warning-1 += -Wno-sign-compare > -- > 2.23.0.rc1.153.gdeed80330f-goog > I am still not a huge fan of the CONFIG_CC_IS_CLANG ifdefs but I don't really see a much cleaner way to get around this. Some that come to mind: * Leave Makefile alone and add KBUILD_CFLAGS += -Wno-implicit-fallthrough in the CONFIG_CC_IS_CLANG section of scripts/Makefile.extrawarn * Revert commit bfd77145f35c ("Makefile: Convert -Wimplicit-fallthrough=3 to just -Wimplicit-fallthrough for clang") for the time being and just rely on adding -Wimplicit-fallthrough to KCFLAGS for testing. Regardless: Reviewed-by: Nathan Chancellor <natechancellor@xxxxxxxxx>
