dtolnay
Calling Rust async function from C++
In the Async Functions chapter, the book shows how to call a C++ async function from Rust. Is there such a workaround in the opposite direction? I'd like my C++ function to call a Rust async function. Something like this:
async fn doThing(arg: Arg) -> Ret {
Ret {}
}
#[cxx::bridge]
mod ffi {
unsafe extern Rust {
fn doThing(Arg arg) -> rust::Future<Ret>;
}
}
auto ret = co_await doThing();
Following the example in the book, it seems possible if we pass back a function pointer to C++ from Rust that executes rx.await?. However, I see that function pointers with a Result return type are not implemented yet.
Is there any other way we can achieve this? Note that, I'd like creating a channel between Rust and C++ on the Rust side. That is, I'd want to write minimal code on the C++ side to achieve this.
@nasifimtiazohi Did you find any workarounds for the time being? I'm also trying to do something similar
@nasifimtiazohi Did you find any workarounds for the time being? I'm also trying to do something similar
I solved it by using C++ Promise/Future. I sent an opaque C++ Promise type to the Rust side, where I set the promise value through another bridged helper function. On the C++ side, I then waited for the Future to complete.
You might do it using Rust sender/receiver as well. The trick is to not think around passing function pointers. Rather, pass Opaque Rust types/shared types to C++ and execute on those types through some bridged helper functions. It should be doable with more indirections.
