Wasi also supports _initialize entry points

[tomaka]

The Wasi standard also supports modules whose entry point is _initialize.
https://github.com/WebAssembly/WASI/blob/master/design/application-abi.md

[tomaka]

Here is some background regarding "reactors": WebAssembly/WASI#13

One advantage of using this scheme in redshirt is that we could force applications to register themselves as interface handler during the call to _initialize. We would thereby have a way of telling that an application will no longer handle any new interface that it doesn't already handle.

[tomaka]

Rust compiler support has just landed in nightly: rust-lang/rust#79997 (comment)