The project has some serious restrictions and unsound footguns (e.g. around TLS), but otherwise it's usable enough. There are also a number of C/C++ libraries, but I can not comment on those.
Interestingly, may-minihttp is faring very well in the TechEmpower benchmark [1], for whatever those benchmarks are worth. The code is also surprisingly straightforward [2].
I do think implementations like that are not particularly useful though.
You want a runtime to handle and multiplex blocking calls - otherwise if you perform any blocking calls (mostly I/O) in one fiber, you block everything - so what use are those fibers ?
The answer is the same as in async Rust, right? "Don't do that."
If you wanted to use this for managing a bunch of I/O contexts per OS thread then you would need to bring an event loop and a bunch of functions that hook up your event loop to whatever asynchronous I/O facilities your OS provides. Sort of like in async Rust.
