Re: [PATCH] selftests: harness: Rework is_signed_type() to avoid collision with overflow.h

[Sean Christopherson]

On Fri, Jun 27, 2025, Kees Cook wrote:
> On Tue, Jun 24, 2025 at 04:19:30PM -0700, Sean Christopherson wrote:
> > Rename is_signed_type() to is_signed_var() to avoid colliding with a macro
> > of the same name defined by linux/overflow.h.  Note, overflow.h's version
> > takes a type as the input, whereas the harness's version takes a variable!
> 
> Can we just update compiler.h to use typeof() and drop duplicates?

I have no objection to doing so, but I'd prefer any such change go on top.  I'd
like to get this fixed in 6.16, and as your diff alludes to, I think tools' version
of compiler.h should follow the kernel's version (and presumably the below isn't
an rc6+ candidate :-) ).

> (typeof() a type is a pass-thru). Totally untested:
> 
> diff --git a/include/linux/compiler.h b/include/linux/compiler.h
> index 6f04a1d8c720..cb925b883806 100644
> --- a/include/linux/compiler.h
> +++ b/include/linux/compiler.h
> @@ -347,7 +347,7 @@ static inline void *offset_to_ptr(const int *off)
>   * Whether 'type' is a signed type or an unsigned type. Supports scalar types,
>   * bool and also pointer types.
>   */
> -#define is_signed_type(type) (((type)(-1)) < (__force type)1)
> +#define is_signed_type(type) (((typeof(type))(-1)) < (__force typeof(type))1)
>  #define is_unsigned_type(type) (!is_signed_type(type))
>  
>  /*
> 
> 
> -- 
> Kees Cook