I'm curious how small a conforming WASM implementation can be (Luna looks extremely small, but not conforming).

In particular I'm curious how feasible it is to create WASM polyfills for various languages. Imagine you have a nice C kernel that you want to wrap in various languages. In many cases you can use native extensions to wrap your C kernel through an FFI, and on the web you can use WASM in supported browsers. But what about cases where people can't use your native extension? Suppose they are using a browser that doesn't support WASM. It's nice to be able to offer a polyfill that at least works, even if it is slower.

The feasibility of this idea hinges on how easily you can write a conforming implementation of WASM in a bunch of different languages. But I don't know the WASM spec well enough to know how big of an undertaking this is.