Yes I intend to write precisely that, if we ban unsigned types.
However I'm not really convinced that throwing out unsigned types is
the right move.
For instance, one of the optimizations mentioned in the linked video
seems to not mention that using (unsigned!) size_t instead of uint32_t
(like you're sort of supposed to) should also improve code generation
in the same way as using int32_t.
It is, however, super poignant to me that uint32_t-indexing-on-x64 is
pessimal, as that's precisely what our ns* containers (nsTArray) use
for size, /unlike/ their std::vector counterparts, which will be using
the more-optimal size_t.
I'm not saying there's nothing wrong with unsigned types, but rather
than I feel their faults are being overblown, and the arguments
against them feel cherry-picked, which in a language like C++, is easy
to do.
On Thu, Jul 4, 2019 at 4:45 PM Gerald Squelart <gsquel...@mozilla.com> wrote:
>
> (Glad I started this discussion; thank you Nathan for the enlightening links,
> I need to review all my code now!)
>
> Jeff, maybe what we need is a new value type that advertizes that it's
> unsigned, but doesn't have the unwanted 2^N wrapping (and its effects on
> bug-finding tools and compiler optimizations).
> `class Unsigned { int mValue; /* magic API here */ }` -- feels like unsigned,
> but underneath it's all `int` arithmetics, with optional >=0 assertions.
> Would that help?
>
> Gerald
>
>
> On Friday, July 5, 2019 at 5:35:30 AM UTC+10, Jeff Gilbert wrote:
> > That's what CheckedInt is for, and that's what we use.
> >
> > The problems webgl deals with aren't arithmatic. Arithmatic is easy.
> > (CheckedInt!) Reasoning about constraints is hard.
> >
> > We have some entrypoints where negative values are valid, and many
> > where they are not. It's really nice to have a natural way to document
> > which we expect /at compile time/. Saying "no unsigned types" really
> > throws out the baby with the bathwater for me.
> >
> > On Thu, Jul 4, 2019 at 11:46 AM Botond Ballo <bba...@mozilla.com> wrote:
> > >
> > > On Thu, Jul 4, 2019 at 2:03 PM Jeff Gilbert <jgi...@mozilla.com> wrote:
> > > > It's a huge
> > > > help to have a compile-time constraint that values can't be negative.
> > >
> > > The question is, how useful is that guarantee. Suppose you have some
> > > code that decrements an integer too far, past zero. Instead of having
> > > a -1 you'll have a 4294967295. Is that an improvement? Will it give
> > > the code saner behaviour than the -1?
> > >
> > > Cheers,
> > > Botond
>
> _______________________________________________
> dev-platform mailing list
> dev-platform@lists.mozilla.org
> https://lists.mozilla.org/listinfo/dev-platform
_______________________________________________
dev-platform mailing list
dev-platform@lists.mozilla.org
https://lists.mozilla.org/listinfo/dev-platform
