[pas]

"async/await" is just syntactic sugar for a function that returns a Future plus a state machine at yield points. You need a library (executor) to run that Future (execute that function).

The Rust standard library's block_on uses a global ThreadPool, and the docs recommend using a LocalPool if you need finer grained control.

So, to answer your question it depends on the executor (the thing that implements block_on).

[steveklabnik]

(To be clear, block_on is not in the Rust standard library.)

[pas]

ah, darn, thanks!

So for anyone reading for the correct details: the block_on I was thinking of is part of the futures crate, which is not in std, it's not an "official library".

[steveklabnik]

It's all good! It was proposed, but decided to have an RFC first. Your point is still correct, just wanted to make sure to clarify this detail :)