[vacuity]

That's like saying Rust has GC because GC libraries/runtimes can be implemented in/for Rust. Rust recognizes allocations on a language basis, but does not provide the same level of control over allocations on a language basis as Zig does. For instance, there is no stable interface for custom allocators for alloc/std.

[timschmidt]

std may not yet provide a stable interface for custom allocators (the Allocator API appears to be available in unstable presently), but use of custom allocators is common in no-std rust environments like embedded. Reading through https://github.com/irbull/custom_allocators the Allocator API doesn't seem particularly complicated. I think it's fair to expect that it will stabilize in time.

> That's like saying Rust has GC because GC libraries/runtimes can be implemented in/for Rust.

Quite a few have already been implemented and are available as libraries exactly as you describe, today. I wouldn't phrase that as "Rust has GC" because that might imply that the GC is required. But if your application might benefit from GC, it's certainly available in the language. I might say "GC is optionally available in Rust if desired" to be more accurate.

[vacuity]

https://news.ycombinator.com/item?id=46684673 (reply to sibling)

> I think it's fair to expect that it will stabilize in time.

The allocator work is facing a lot of obstacles, unfortunately. I prefer it to be unstable for as long as it needs, though.

> Quite a few have already been implemented and are available as libraries exactly as you describe, today. I wouldn't phrase that as "Rust has GC" because that might imply that the GC is required.

This is exactly my point. Rust does not prevent GC by any means, but Rust also does not encourage GC by any means. The same goes for custom allocators, aside from the highly-unstable Allocator API.

[timschmidt]

> The allocator work is facing a lot of obstacles, unfortunately.

Got any links? Sounds like interesting reading. Seriously. Kind of thing I come here for. I'd really appreciate it. Or I can ask the AI for some.

> I prefer it to be unstable for as long as it needs, though.

Sure, same. Fully baking things is a process, and it's nice when things are fully baked. So I agree. I think Rust's async could be a bit more ergonomic, though it wasn't too difficult to wrap my head around, and sort of shockingly simple to implement a basic no-std async executor (~10 lines), so maybe I'm coming around. I was pleased to find out that it was simple enough that I could do it, and understand how it worked, as I try to do with all my microcontroller code, and wasn't dependent on a big async runtime like Tokio if I didn't need it's features (or bloat).

[vacuity]

https://old.reddit.com/r/rust/comments/1op6g64/whats_the_sta...

This Github thread is also interesting (transitively reached from the above Reddit thread):

https://github.com/rust-lang/rust/issues/32838#issuecomment-...

[timschmidt]

Thanks, I'll give 'em a read.

[Measter]

No, it isn't. Because that distinction is significant if you are using the language in an environment where those libraries are not available or suitable, such as the Linux project which uses a custom fork of Alloc which provides collections for different allocators.

[vacuity]

So, that is not done at the language level but the library level. Unless the compiler is modified for Linux, but even if it is, that's entirely bespoke and unstable. This is not comparable to Zig's design. I'm aware that anything can be done if the right things are implemented; I'm talking about what Rust-the-language currently does for control over allocation. If the answer comes down to "we're doing something custom", then the language is soewhat or largely sidestepped. C-the-language certainly doesn't have panics or exceptions, even though longjmp or a custom runtime could be used.

[steveklabnik]

Rust the language knows nothing about allocations. It’s purely a library concern.

[vacuity]

For the time being, I consider alloc and std to be part of the language, and the compiler also has provisions for them if they are used. If the alternative is supposed to be only using core, then the language does not provide for control over allocations the way Zig does. Imposing allocations with no control and not providing allocations at all are both failure modes. With enough effort, anyone could do anything, but programming languages exist to control and enhance certain things under their purview. Rust does not have a comparable facility to control allocations like it controls ownership and borrowing. Just as C-with-tooling being safe isn't the same as C being safe, Rust-with-libraries providing control over allocations isn't the same as Rust providing control over allocations.