Hi Nathan, On Sun, Mar 8, 2020 at 4:34 PM Nathan Chancellor <natechancellor@xxxxxxxxx> wrote: > > Clang's -Wpointer-to-int-cast deviates from GCC in that it warns when > casting to enums. The kernel does this in certain places, such as device > tree matches to set the version of the device being used, which allows > the kernel to avoid using a gigantic union. > > https://elixir.bootlin.com/linux/v5.5.8/source/drivers/ata/ahci_brcm.c#L428 > https://elixir.bootlin.com/linux/v5.5.8/source/drivers/ata/ahci_brcm.c#L402 > https://elixir.bootlin.com/linux/v5.5.8/source/include/linux/mod_devicetable.h#L264 > > To avoid a ton of false positive warnings, disable this particular part > of the warning, which has been split off into a separate diagnostic so > that the entire warning does not need to be turned off for clang. > > Cc: stable@xxxxxxxxxxxxxxx > Link: https://github.com/ClangBuiltLinux/linux/issues/887 > Link: https://github.com/llvm/llvm-project/commit/2a41b31fcdfcb67ab7038fc2ffb606fd50b83a84 > Signed-off-by: Nathan Chancellor <natechancellor@xxxxxxxxx> > --- > Makefile | 4 ++++ > 1 file changed, 4 insertions(+) > > diff --git a/Makefile b/Makefile > index 86035d866f2c..90e56d5657c9 100644 > --- a/Makefile > +++ b/Makefile > @@ -748,6 +748,10 @@ KBUILD_CFLAGS += -Wno-tautological-compare > # source of a reference will be _MergedGlobals and not on of the whitelisted names. > # See modpost pattern 2 > KBUILD_CFLAGS += -mno-global-merge > +# clang's -Wpointer-to-int-cast warns when casting to enums, which does not match GCC. > +# Disable that part of the warning because it is very noisy across the kernel and does > +# not point out any real bugs. > +KBUILD_CFLAGS += $(call cc-disable-warning, pointer-to-enum-cast) > else I'd rather want to fix all the call-sites (97 drivers?) instead of having -Wno-pointer-to-enum-cast forever. If it is tedious to fix them all for now, can we add it into scripts/Makefile.extrawarn so that this is disabled by default, but shows up with W=1 builds? (When we fix most of them, we will be able to make it a real warning.) What do you think? Thanks. > # These warnings generated too much noise in a regular build. > -- > 2.25.1 > > -- > You received this message because you are subscribed to the Google Groups "Clang Built Linux" group. > To unsubscribe from this group and stop receiving emails from it, send an email to clang-built-linux+unsubscribe@xxxxxxxxxxxxxxxx. > To view this discussion on the web visit https://groups.google.com/d/msgid/clang-built-linux/20200308073400.23398-1-natechancellor%40gmail.com. -- Best Regards Masahiro Yamada
