Re: [PATCH next v3 0/5] minmax: Relax type checks in min() and max().

Linus Torvalds
2023-08-23T15:32:31Z

On Wed, 23 Aug 2023 at 01:52, David Laight <David.Laight@aculab.com> wrote:
>
> Linus doesn't like me silently converting unsigned constants
> to signed.

Note that my dislike is more about changing the sign of the
*comparison*, and not warning about it.

It's not the constant conversion itself that ends up being the
problem, but the downstream issues it causes.

Having grepped for those annoying "min_t(size_t..)" uses, lots of them
seem to have perfectly fine signedness, and the 'size_t' is literally
just due to different sizes of unsigned values. In fact, several of
them seem to be due to the unfortunate fact that 'size_t' can be
'unsigned int' on 32-bit architectures, so mixing 'size_t' and
'unsigned long' will sadly warn without it.

So we literally have the issue that 'min(a,b)' will warn even if 'a'
and 'b' have the same signedness *and* the same size, because 'size_t'
and 'unsigned long' are different types.

Your patch 2/5 will fix that. And then I'd certainly be ok with a
"comparing an unsigned value to a signed positive constant" thing
(just not the other way around: "comparing a signed value to an
unsigned positive constant" is wrong)

That might get rid of a number of the more annoying cases.

Linus