core: Add core::ffi::c_intptr_t and core::ffi::c_uintptr_t

[lygstate]

This is a complement to c_ptrdiff_t

Tracking issue: #88345

[rustbot]

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[tgross35]

There are some unresolved questions there that unfortunately haven't made much progress. I'm not sure it's worth adding more types without having a better story there.

[lygstate]

There are some unresolved questions there that unfortunately haven't made much progress. I'm not sure it's worth adding more types without having a better story there.

libc is looking for release 1.0 I think it's time to resolve those questions. What's the questions comes from, can you give me the link.

[tgross35]

libc is looking for release 1.0 I think it's time to resolve those questions. What's the questions comes from, can you give me the link.

As far as libc 1.0 is concerned, the only thing I'd like is for the lang team to say that size_t is always usize, if that's something we can rely on, because then we can delete the size_t alias. Anything else is not blocking, we can update aliases if/when things stabilize.

Info is scattered, see discussion around #88345 (comment) https://internals.rust-lang.org/t/pre-rfc-usize-semantics/19444/22, https://rust-lang.zulipchat.com/#narrow/channel/213817-t-lang/topic/Compat.20with.20size_t.2C.20ptrdiff_t.2C.20intptr_t.2C.20fnptr-sized.20int/with/547982505, and a few other places on Zulip.

[arichardson]

Thanks for adding this type it is IMO essential. On platforms such as CHERI for RISCV (RVY), we can change this typedef to be apointer type instead.

View changes since the review

[arichardson]

CC: @xdoardo

[tgross35]

For anybody who has opinions here about CHERI or otherwise, it would be good to hop in to the ongoing discussion at #t-lang > Compat with size_t, ptrdiff_t, intptr_t, fnptr-sized int.