From: Andrew Morton
> Sent: 03 August 2023 18:25
>
> On Thu, 3 Aug 2023 16:19:18 +0300 Andy Shevchenko <andriy.shevchenko@xxxxxxxxxxxxxxx> wrote:
>
> > abs_diff() belongs to math.h. Move it there.
> > This will allow others to use it.
> >
> > ...
> >
> > --- a/include/linux/math.h
> > +++ b/include/linux/math.h
> > @@ -155,6 +155,13 @@ __STRUCT_FRACT(u32)
> > __builtin_types_compatible_p(typeof(x), unsigned type), \
> > ({ signed type __x = (x); __x < 0 ? -__x : __x; }), other)
> >
> > +#define abs_diff(a, b) ({ \
> > + typeof(a) __a = (a); \
> > + typeof(b) __b = (b); \
> > + (void)(&__a == &__b); \
> > + __a > __b ? (__a - __b) : (__b - __a); \
> > +})
>
> Can we document it please?
>
> Also, the open-coded type comparison could be replaced with __typecheck()?
>
> And why the heck isn't __typecheck() in typecheck.h, to be included by
> minmax.h.
And why would you want to use __typecheck() anyway?
It pretty much isn't the test you are looking for.
If you are trying to explicitly avoid converting negative value
to large positive unsigned ones then you want something like:
is_signed_type(typeof(a)) == is_signed_type(typeof(b))
but it isn't even that simple :-)
David
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