Stream: wasmtime

Topic: release-13.0.0 branch + cargo-component?

Jeff Parsons (Sep 17 2023 at 02:55):

Hello! Should one expect to be able to produce components using cargo-component and then instantiate them in Wasmtime from the v13 branch? Is there in general some way that people keep track of compatible versions, and are there generally compatible versions of other tools like cargo-component around each Wasmtime release or is that not always the case? Thanks! :heart:

Jeff Parsons (Sep 17 2023 at 07:35):

Extra context for how I ended up asking this question:

Toolchain versions:

> rustc --version
rustc 1.72.0 (5680fa18f 2023-08-23)
> cargo component --version
cargo-component-component 0.1.0 (36c221e 2023-09-07 wasi:134dddc)

Guest world:

package component:guest

world example {
    export hello-world: func() -> string
}

Host setup:

let mut config = Config::new();
config.wasm_component_model(true);
let engine = Engine::new(&config).context("Failed to create engine")?;
let component = Component::from_file(&engine, "../guest/target/wasm32-wasi/debug/guest.wasm")
    .context("Failed to load guest component")?;

let mut linker = Linker::new(&engine);

let mut table = Table::new();
let mut store = Store::new(
    &engine,
    MyState {
        wasi: WasiCtxBuilder::new().inherit_stdio().build(&mut table)?,
        table,
    },
);

wasmtime_wasi::preview2::command::sync::add_to_linker(&mut linker)
    .context("Failed to set up WASI")?;

let (bindings, _) = Example::instantiate(&mut store, &component, &linker)
    .context("Failed to instantiate guest component")?;

Output:

Error: Failed to instantiate guest component

Caused by:
    0: import `wasi:io/streams` has the wrong type
    1: instance export `write` has the wrong type
    2: type mismatch with results
    3: expected 0-tuple, found 2-tuple

I assume (from ignorance) that this is because of recent changes to WASI and Wasmtime's implementation. Does that sound about right? Or maybe I just stuffed something up?

Pat Hickey (Sep 17 2023 at 20:12):

the 13 branch has changes to streams that landed in the spec repo as this PR: https://github.com/WebAssembly/wasi-io/pull/45

Pat Hickey (Sep 17 2023 at 20:13):

cargo-component's wasi preview 1 adapter was built prior to those changes, so cargo-component needs an update to include them

Pat Hickey (Sep 17 2023 at 20:13):

i believe there is a way to override what adapter cargo-component uses, but i don't know it off the top of my head, and its a weekend. so, if you can figure out how to feed it the wasi-preview1-component-adapter built from the 13 branch, that ought to fix your problem

Jeff Parsons (Sep 17 2023 at 21:46):

Wonderful, thanks! :)

I didn't figure out how to override what adapter cargo-component uses; instead I just did the update in the source. So — for anyone else who finds this and wants to do a similar thing — my steps were:

• Clone the cargo-component repo locally.
• Clone the wasmtime repo locally (don't forget to init submodules!)
• Follow instructions for building both variants (reactor, command) of the adapter here: https://github.com/bytecodealliance/wasmtime/tree/main/crates/wasi-preview1-component-adapter. For each variant of the adapter, copy the built .wasm file following the existing naming convention under the adapters/ dir. I.e. new subdir with abbreviated wasmtime commit sha, with files named wasi_snapshot_preview1.reactor.wasm and wasi_snapshot_preview1.command.wasm inside.
• Update WASI_ADAPTER_VERSION in cargo-component's build.rs to point to your new directory.
• Build your new version of cargo-component: cargo install --path .
• Rebuild your guest component. (Might need to explicitly clean first; not sure if changing the version of cargo-component will invalidate the build cache.)

Peter Huene (Sep 18 2023 at 06:08):

Hi Jeff, feel free to put up a PR for updating the adapter; I'll also try to add an option for overriding the adapter tomorrow

Jeff Parsons (Sep 18 2023 at 22:01):

PR for adapters bump is here: https://github.com/bytecodealliance/cargo-component/pull/140

Thanks!

Pat Hickey (Sep 18 2023 at 22:01):

thanks jeff!

Last updated: Nov 22 2024 at 17:03 UTC