On Thu, Aug 15, 2019 at 1:45 PM Nathan Chancellor <natechancellor@xxxxxxxxx> wrote: > > 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? +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 Yeah, I think this might be cleaner. -Wimplicit-fallthrough -Wno-implicit-fallthrough will be passed to Clang, but "last one wins." A smaller patch makes it more likely to be revertable without potentially having to resolve any conflicts. Would you mind sending a V2 with that change? You can include Nathan's Suggested-by tag. -- Thanks, ~Nick Desaulniers
