✔ WASI with WASM Components · general

Hello again :) I'm trying to load a WASM component module that is compiled to target WASI. I have so far created the Engine, hooked up the WasiHostCtx, and created the store. However, it seems like wasmtime_wasi::preview2::preview1::add_to_linker expects a wasmtime::Linker vs a wastime::component::Linker, whereas MyWorld::add_to_linker expects a wasmtime::component::Linker instead :sweat_smile:

I _think_ I need a single linker with both of those hooked up in order to be able to run code from the WASM component module, is that correct? If so, is what I'm trying to do possible today? and how can I accomplish that? I'm using version 17.0.1 of both wasmtime and wasmtime-wasi for reference

Alex Crichton (Feb 15 2024 at 22:41):

You're correct that you'll need to use a single linker. If you're using wasmtime::component::bindgen! then you'll need to use wasmtime::component::Linker since you're working with components rather than modules. In that case you'll want to call wasmtime_wasi::preview2::bindings::add_to_linker. The preview1 module is specifically intended for compatibility with modules, not components.

(you probably already heard this before but apologies for the state of the docs, we're working on making them better!)

很酷的傢伙 (Feb 15 2024 at 22:55):

很酷的傢伙 (Feb 16 2024 at 21:28):

hey @Alex Crichton , sorry to bother you again. I'm looking for wasmtime_wasi::preview2::bindings::add_to_linker but I'm not seeing that symbol. Should I be looking for something else?

很酷的傢伙 (Feb 16 2024 at 21:41):

hmmmmm ok I found the add_to_linker functions under sync_io::* and those seem to work with a component::Linker. I'm still running into a runtime error when trying to run my component though :) The guest is built from Rust targeting wasm32-wasi and I've then run wasm-tools component new out.wasm -o out.component.wasm --adapt wasi_snapshot_preview1.reactor.wasm to create the component. However I'm seeing the following error:

called `Result::unwrap()` on an `Err` value: import `wasi:cli/environment@0.2.0` has the wrong type

Caused by:
    0: instance export `get-environment` has the wrong type
    1: expected func found nothing

很酷的傢伙 (Feb 16 2024 at 21:47):

Ok interesting, if I compile my guest with target wasm32-unknown-unknown it seems to load and run correctly and everything, which is exciting. However, I believe that means I don't have access to e.g. the filesystem from the guest, is that correct? Is... there currently a way to do I/O in the guest?

Joel Dice (Feb 16 2024 at 21:48):

Notification Bot (Feb 16 2024 at 21:48):

很酷的傢伙 (Feb 16 2024 at 21:49):

很酷的傢伙 (Feb 16 2024 at 21:54):

called `Result::unwrap()` on an `Err` value: Custom { kind: Uncategorized, error: "failed to find a pre-opened file descriptor through which \"/tmp/test\" could be opened" }

which makes me think I need to do something with cap-std to allow that to be read :thinking: will continue investigating, but thanks for the help so far!

Joel Dice (Feb 16 2024 at 21:55):

When you create a WasiCtx using WasiCtxBuilder, you have the opportunity to map host directories into the guest filesystem. You'll need to do that in order for the guest to access any part of the host filesystem.

Joel Dice (Feb 16 2024 at 21:56):

很酷的傢伙 (Feb 16 2024 at 21:57):

Joel Dice (Feb 16 2024 at 21:57):

Joel Dice (Feb 16 2024 at 21:59):

很酷的傢伙 (Feb 16 2024 at 22:04):

ahhhhhh there we go! finally :D was able to read a file from the guest! thank you all so much for the help :grinning_face_with_smiling_eyes: