[cute_boi]

zero cost abstraction and no gc

[mseepgood]

All design trade-offs have a cost. In this case the costs are reduced usability and async struggles.

[carlmr]

Zero-cost abstractions is used to mean zero runtime cost (in release builds), so if an abstraction would break that it wouldn't be suitable for this goal.

Like adding a GC for the async feature.

[pjmlp]

Same could be said for C++, and yet while C++20 also doesn't have an official runtime on std (C++23 will fix that assuming executors land), the vocabulary types required for interoperability across runtimes are part of the co-routines design.

[varajelle]

Rust also has the vocabulary types required for interoperability, such as Future and Waker. Or what exactly make C++ more interoperable?

[pjmlp]

Does it? https://book.async.rs/overview/std-and-library-futures.html

C++ ones can interoperate with any type that plugs into the compiler magic expected by the co-routines code rewrite.

If you want to deep dive into how Visual C++ does it, and how WinRT gets plugged into C++ co-routines, here is a very lengthy set of blog posts.

https://devblogs.microsoft.com/oldnewthing/20210504-01/?p=10...

Now back to Rust, how can I interoperate across tokio, async-std, smol and fuchsia-std, as easy as I can between WinRT, and others?

[varajelle]

The std::future::Future from the rust standard library works with every runtime.

Not sure I understand, what kind of interoperability you are talking about. What kinds of code works in C++ across runtimes, for which the equivalent in Rust doesn't?

[pjmlp]

In C++ you don't have the scenario like in Rust, where one is forced to use a specific async runtime for library xyz, because it depends on having tokio as runtime.

Or has that situation been sorted out by now?

[varajelle]

In Rust you only are forced to use a specific runtime if you want to use its API. For example to spawn new tasks, or to block on a future. I believe that would be the same in C++.

In Rust, you don't need to use a specific runtime if you just want to use async function in your library.