[LTP] [PATCH] Add __clear_cache declaration for clang

[Petr Vorel]

Hi Khem, Cyril,

> Hi!
> > __clear_cache was enabled on RISCV recently with 7352ba02390116f1cd6a9b583860ba28aa0a1b7a
> > however it fails to compile with clang19 on RISCV
> > With this error

> >   hugemmap15.c:51:2: error: call to undeclared function '__clear_cache'; ISO C99 and later do not support implicit function declarations [-Wimplicit-function-declaration]
> >       51 |         __clear_cache(p, p + COPY_SIZE);
> >          |         ^

> This sounds like a clnag bug. The __clear_cache() is a pre-defined
> function and as such the signature should be part of the compiler.

> Is the call even supported by clang19 on RISCV?

I think Cyril is correct. IMHO __clear_cache() on riscv64 was added in

https://github.com/llvm/llvm-project/commit/9d469b5988bfb1c2e99533f863b1f9eb5b0c58b7

which was added in llvmorg-20.1.0-rc1.

BTW we have m4 check for __clear_cache(), I'll send a patch.

Kind regards,
Petr

> > Signed-off-by: Khem Raj <raj.khem@gmail.com>
> > Cc: Hui Min Mina Chou <minachou@andestech.com>
> > ---
> >  testcases/kernel/mem/hugetlb/hugemmap/hugemmap15.c | 1 +
> >  1 file changed, 1 insertion(+)

> > diff --git a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap15.c b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap15.c
> > index a84ba6476..856e22ff3 100644
> > --- a/testcases/kernel/mem/hugetlb/hugemmap/hugemmap15.c
> > +++ b/testcases/kernel/mem/hugetlb/hugemmap/hugemmap15.c
> > @@ -21,6 +21,7 @@

> >  #if defined(__clang__)
> >  	#pragma clang optimize off
> > +	void __clear_cache(void *start, void *end);
> >  #endif