State of the art of the interface types

[rambip]

I installed wasmtime to experiment with wasi recently, and I heard about the "interface types proposal" from bytecodealliance.

So I used the wasm-bindgen crate that already implement this interface from rust to wasi.

And following this tutorial, I installed the wasmtime python library, but I discovered that support for interface types have been removed ! (bytecodealliance/wasmtime#1292)

My question is: what is the current situation for wasmer around this issue ?
Is the wasi interface type proposal stable enough ?
And what are the other ways to make languages communicate via wasm ? I know about files, I/O and sockets, but can you share the ram for example ? I didn't see any example of that with wasmer and wasmtime.

[Hywan]

Hello,

There is a lot of confusion in your message, and I'm glad to address them :-).

There is indeed a WebAssembly Interface Types Proposal, which is —at the time of writing— at Phase 1, i.e. very unstable, not ready to be implemented, experimental.

We have done our own implementation of this proposal in the past (see the wasmer-interface-types crate) but things have moved quite a lot since then.

Nor wasmtime, nor any Wasm runtimes, support Interface Types for the moment because it's changing constantly.

wasm-bindgen on the other side is automatic bindings between Wasm and JavaScript. It's not meant to be used in another host environment (here, JavaScript). It's a hack while waiting on something more universal like Interface Types.

[rambip]

Thank's !
I looked in the wasi documentation, and I saw "iovec", A region of memory for scatter/gather reads.
So is there a way for wasmer to share memory between the host and a wasm module to do ineroperability, or maybe the best idea is to use a temporary file or a socket to share data efficiently ?

[rambip]

If I understand correctly, that means that the languages runtimes for wasi (for example the python module) can only communicate builtins values like i32 and f32 to the exported functions ?
So is there a way, for example, to communicate a string from python to a wasm module, with stdin/stdout ?
I can't see how these packages in these diffetent languages can be usefull if I can't send data to the wasm functions :(

[proohit]

You can access memories of WASM VMs from the host environment but not vice versa (at least not implictly). WASM Modules have exactly one memory, which can also be shared across modules. You can pass around pointers in this memory at which you define your custom data types (e.g. string) and share those i32 integer pointers with other modules | (exported) functions etc. You can also pass a custom function as an import to do stuff in the host env, called from the module.

I've had a discussion about this topic with @Hywan in this issue and written some examples in my repository . There you can find examples for python using wasmer and wasmtime, go using wasmer and javascript/node using V8.

For the time being, we're stuck with this hackish solution of manipulating memory. I don't know of any tools to bridge the time, but it will become obsolete anyway when interface-types are integrated.