[PATCH] arm64: fix clang warning about TRAMP_VALIAS

[Nick Desaulniers]

On Fri, Mar 18, 2022 at 12:52 PM Nick Desaulniers
<ndesaulniers at google.com> wrote:
>
> On Fri, Mar 18, 2022 at 12:11 PM Robin Murphy <robin.murphy at arm.com> wrote:
> >
> > On 2022-03-16 18:38, Arnd Bergmann wrote:
> > > From: Arnd Bergmann <arnd at arndb.de>
> > >
> > > The newly introduced TRAMP_VALIAS definition causes a build warning
> > > with clang-14:
> > >
> > > arch/arm64/include/asm/vectors.h:66:31: error: arithmetic on a null pointer treated as a cast from integer to pointer is a GNU extension [-Werror,-Wnull-pointer-arithmetic]
> >
> > Tangentially, all the other GNU extensions we depend on throughout Linux
> > are also GNU extensions. Do we know what's special about this one?
>
> My first thought is that -Wnull-pointer-arithmetic should be in the
> -Wgnu flag group, such that -Wno-gnu (as set by Kbuild) implies
> -Wno-null-pointer-arithmetic.
>
> One issue seems to be that -Wnull-pointer-arithmetic seems to control
> at least 2 different checks in clang.
>
> https://godbolt.org/z/hdYYejj3d
>
> So it's likely these two checks should have 2 distinct flags, such
> that the warning we're observing can be grouped under -Wgnu.
>
> Filed: https://github.com/llvm/llvm-project/issues/54444

Fix should be landing shortly:
https://reviews.llvm.org/D122224

-- 
Thanks,
~Nick Desaulniers