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SubjectRe: [PATCH] kbuild: add most of Clang-specific flags unconditionally
Hi.

On Thu, May 9, 2019 at 8:15 PM Nathan Chancellor
<natechancellor@gmail.com> wrote:
>
> On Thu, May 09, 2019 at 03:44:55PM +0900, Masahiro Yamada wrote:
> > We do not support old Clang versions. Upgrade your clang version
> > if any of these flags is unsupported.
> >
> > Let's add flags within ifdef CONFIG_CC_IS_CLANG unconditionally,
> > except -fcatch-undefined-behavior.
> >
> > Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
> > ---
> >
> > Makefile | 10 +++++-----
> > scripts/Makefile.extrawarn | 12 ++++++------
> > 2 files changed, 11 insertions(+), 11 deletions(-)
> >
> > diff --git a/Makefile b/Makefile
> > index bd7ae11947cb..c71ffb6f55b5 100644
> > --- a/Makefile
> > +++ b/Makefile
> > @@ -731,15 +731,15 @@ stackp-flags-$(CONFIG_STACKPROTECTOR_STRONG) := -fstack-protector-strong
> > KBUILD_CFLAGS += $(stackp-flags-y)
> >
> > ifdef CONFIG_CC_IS_CLANG
> > -KBUILD_CPPFLAGS += $(call cc-option,-Qunused-arguments,)
> > -KBUILD_CFLAGS += $(call cc-disable-warning, format-invalid-specifier)
> > -KBUILD_CFLAGS += $(call cc-disable-warning, gnu)
> > +KBUILD_CPPFLAGS += -Qunused-arguments
> > +KBUILD_CFLAGS += -Wno-format-invalid-specifier
> > +KBUILD_CFLAGS += -Wno-gnu
> > # Quiet clang warning: comparison of unsigned expression < 0 is always false
> > -KBUILD_CFLAGS += $(call cc-disable-warning, tautological-compare)
> > +KBUILD_CFLAGS += -Wno-tautological-compare
> > # CLANG uses a _MergedGlobals as optimization, but this breaks modpost, as the
> > # source of a reference will be _MergedGlobals and not on of the whitelisted names.
> > # See modpost pattern 2
> > -KBUILD_CFLAGS += $(call cc-option, -mno-global-merge,)
> > +KBUILD_CFLAGS += -mno-global-merge
> > KBUILD_CFLAGS += $(call cc-option, -fcatch-undefined-behavior)
>
> I think we should just remove this, I'm fairly confident the kernel
> can't be reliably compiled with anything earlier than Clang 4 (Pixel 2
> was shipped with it but had some hacks, this commit is from Clang 3.5):
>
> https://github.com/llvm/llvm-project/commit/cb3f812b6b9fab8f3b41414f24e90222170417b4


Oh, I did not know this was deprecated.

Could you send a patch to remove it
with filling the commit log ?


Thanks.



--
Best Regards
Masahiro Yamada

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