wasmtime / issue #8003 Index out of bounds when iterating... · git-wasmtime

Stream: git-wasmtime

Topic: wasmtime / issue #8003 Index out of bounds when iterating...

Wasmtime GitHub notifications bot (Feb 27 2024 at 23:00):

jugglerchris added the bug label to Issue #8003.

Wasmtime GitHub notifications bot (Feb 27 2024 at 23:00):

jugglerchris opened issue #8003:

Test Case

A trivial component built with this wit (complete test at https://github.com/jugglerchris/wasmtime-index-error-test ; commit a129bcaf4207eb6b6d49f58c70e518cd91e65304 in case anything changes):

package comp:test;

world w {
    export foo: interface {
        resource myres;
        make: func() -> myres;
    }
}

and this host code:

    let engine = Engine::new(&Config::new()).unwrap();
    let linker = Linker::<()>::new(&engine);
    let component = Component::from_file(&engine, "target/comp.wasm").unwrap();

    let component_ty =
         linker
        .substituted_component_type(&component)
        .unwrap();
    let exports = component_ty.exports();
    for (name, item) in exports {
        dbg!((name, &item));
        match item {
            ComponentItem::ComponentInstance(instance) => {
                for item in instance.exports() {
                    dbg!(item);
                }
            }
            _ => ()
        }
    }

Steps to Reproduce

First build the component (make in the above repo)
cargo run

Expected Results

The test program lists exports from the "foo" interface including the "make" function

Actual Results

A panic when iterating over the nested exports:

[src/main.rs:16:9] (name, &item) = (
    "foo",
    ComponentInstance(
        ComponentInstance(
            Handle {
                index: TypeComponentInstanceIndex(
                    0,
                ),
            },
        ),
    ),
)
thread 'main' panicked at /home/chris/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-18.0.1/src/runtime/component/types.rs:925:66:
index out of bounds: the len is 0 but the index is 0

Versions and Environment

Wasmtime version or commit: 18.0.1

Operating system: Ubuntu 22.04.3

Architecture: amd64

Extra Info

I can't rule out me doing something dumb - I'm early in my WASM and Wasmtime journey - but I think an index OOB seems like an issue.

Wasmtime GitHub notifications bot (Feb 28 2024 at 20:02):

alexcrichton commented on issue #8003:

Definitely a bug in Wasmtime, thanks for the report! I'll try to take a look at this later this week.

Wasmtime GitHub notifications bot (Feb 29 2024 at 19:19):

fitzgen closed issue #8003: