you can probably compile c to webassembly using clang/llvm

That's not what the parent was asking. They were asking if WASM has an FFI interface for runtimes that want to not execute the WASM code entirely sandboxed from the host, but rather want to allow you to dlload(2) code into the OS process hosting the WASM interpreter and call it through WASM ops.

Presumably, https://github.com/CraneStation/wasmtime would benefit from such an FFI API being specified.

That sounds like ActiveX 2.0 at best, and an utter security nightmare at worst.

Precisely. Do you think this is a feature the WebAssembly team should standardize or is it a bad fit for the language?

That should be doable! (Disclaimer: I work at Wasmer https://github.com/wasmerio/wasmer )

Genuine question here: if you’re already going to be shipping native code, why would you need WebAssembly in the mix, especially if you’re not targeting a browser?

For example, if you want to execute "native" code in a restricted environment. WebAssembly is quite fast when (jit)compiled. Therefore, it's very tempting to use it to embed extension logic.

Yes, emscripten/llvm builds C code into webassembly. I'd say a significant portion of webassembly is C/C++ sourced.

You can't use emscripten/llvm with, #include <windows.h> to provide a GUI per se, can you?

Nope. There are iirc specific bindings for that in a browser context. I think there's been a lot of work for other runtimes.