Stream: wasmtime

Topic: Error "assertion `left == right` failed" on Wasm module init

view this post on Zulip Alex (Dec 02 2024 at 11:25):

I'm trying to run a Kotlin-produced Wasm module in Rust-embedded Wasmtime. Kotlin requires Wasm GC proposal support from the runtime which Wasmtime officially has now since version 27.0.0.

Unfortunately it fails at module init. I'm new to Rust and maybe I'm making some obvious mistake so I would appreciate any pointers on how to debug/fix this issue.

Actually I am able to run the Kotlin-produced guest when Wasmtime is embedded in Go with wasmtime-go bindings (manually updated to use Wasmtime 27.0.0). There are some issues with that too (#wasmtime > How to deal with "GC heap out of memory" errors? ) but at least it doesn't fail on module init so I assume it should work when Wasmtime is embedded in Rust too.

I've removed almost everything from the Kotlin guest, it only contains this now:

fun main() {}

And this is the host code, taken from the docs with very few modifications:

use wasmtime::*;
use wasi_common::sync::WasiCtxBuilder;

fn main() -> Result<()> {
    let mut config = Config::new();
    config
        .wasm_gc(true)
        .wasm_function_references(true);

    let engine = Engine::new(&mut config)?;
    let mut linker = Linker::new(&engine);
    wasi_common::sync::add_to_linker(&mut linker, |s| s)?;

    let wasi = WasiCtxBuilder::new()
        .inherit_stderr()
        .inherit_stdout()
        .build();
    let mut store = Store::new(&engine, wasi);

    let module = Module::from_file(&engine, "kotlin.wasm")?;
    linker.instantiate(&mut store, &module)?;

    Ok(())
}

This fails at linker.instantiate call with an error:

thread 'main' panicked at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/type_registry.rs:271:17:
assertion `left == right` failed
  left: WasmSubType { is_final: true, supertype: None, composite_type: WasmCompositeType { inner: Struct(WasmStructType { fields: [] }), shared: false } }
 right: WasmSubType { is_final: true, supertype: Some(Engine(VMSharedTypeIndex(19))), composite_type: WasmCompositeType { inner: Struct(WasmStructType { fields: [] }), shared: false } }

stack backtrace:
   0: rust_begin_unwind
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/std/src/panicking.rs:662:5
   1: core::panicking::panic_fmt
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/panicking.rs:74:14
   2: core::panicking::assert_failed_inner
   3: core::panicking::assert_failed
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/panicking.rs:367:5
   4: <wasmtime::runtime::type_registry::RegisteredType as core::cmp::PartialEq>::eq
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/type_registry.rs:271:17
   5: core::cmp::impls::<impl core::cmp::PartialEq<&B> for &A>::eq
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/cmp.rs:1661:13
   6: <Q as hashbrown::Equivalent<K>>::equivalent
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hashbrown-0.14.5/src/lib.rs:172:9
   7: hashbrown::map::equivalent_key::{{closure}}
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hashbrown-0.14.5/src/map.rs:229:14
   8: hashbrown::raw::inner::RawTable<T,A>::find_or_find_insert_slot::{{closure}}
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hashbrown-0.14.5/src/raw/mod.rs:1425:68
   9: hashbrown::raw::inner::RawTableInner::find_or_find_insert_slot_inner
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hashbrown-0.14.5/src/raw/mod.rs:1983:27
  10: hashbrown::raw::inner::RawTable<T,A>::find_or_find_insert_slot
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hashbrown-0.14.5/src/raw/mod.rs:1423:19
  11: hashbrown::map::HashMap<K,V,S,A>::insert
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hashbrown-0.14.5/src/map.rs:1754:15
  12: hashbrown::set::HashSet<T,S,A>::insert
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/hashbrown-0.14.5/src/set.rs:1115:9
  13: wasmtime::runtime::store::StoreOpaque::insert_gc_host_alloc_type
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/store.rs:1797:9
  14: wasmtime::runtime::gc::enabled::structref::StructRefPre::_new
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/gc/enabled/structref.rs:74:9
  15: wasmtime::runtime::vm::const_expr::ConstEvalContext::struct_new
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/vm/const_expr.rs:93:25
  16: wasmtime::runtime::vm::const_expr::ConstEvalContext::struct_new_default
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/vm/const_expr.rs:153:18
  17: wasmtime::runtime::vm::const_expr::ConstExprEvaluator::eval
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/vm/const_expr.rs:278:31
  18: wasmtime::runtime::vm::instance::allocator::initialize_globals
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/vm/instance/allocator.rs:779:13
  19: wasmtime::runtime::vm::instance::allocator::initialize_instance
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/vm/instance/allocator.rs:826:5
  20: wasmtime::runtime::vm::instance::InstanceHandle::initialize
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/vm/instance.rs:1541:9
  21: wasmtime::runtime::instance::Instance::new_raw
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/instance.rs:343:9
  22: wasmtime::runtime::instance::Instance::new_started_impl
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/instance.rs:206:33
  23: wasmtime::runtime::instance::Instance::new_started
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/instance.rs:194:9
  24: wasmtime::runtime::instance::InstancePre<T>::instantiate
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/instance.rs:876:18
  25: wasmtime::runtime::linker::Linker<T>::instantiate
             at ~/.cargo/registry/src/index.crates.io-6f17d22bba15001f/wasmtime-27.0.0/src/runtime/linker.rs:1112:9
  26: jobexecutor::main
             at ./src/main.rs:25:5
  27: core::ops::function::FnOnce::call_once
             at /rustc/f6e511eec7342f59a25f7c0534f1dbea00d01b14/library/core/src/ops/function.rs:250:5

It seems to be Wasm GC-related, it could have been some incompatibility between Wasmtime and Kotlin-produced Wasm but then it is not clear how is it possible that Go-embedded Wasmtime is able to init the module without issues.

view this post on Zulip Alex (Dec 02 2024 at 12:18):

The same Wasm file can be executed successfully in the standalone mode with wasmtime -W function-references,gc.

view this post on Zulip Alex Crichton (Dec 02 2024 at 18:02):

Thanks for the report! Could you file an issue in the Wasmtime repository for this?

view this post on Zulip Alex (Dec 03 2024 at 06:29):

Sure, created a Github issue: https://github.com/bytecodealliance/wasmtime/issues/9714

Error `assertion left == right failed` on Wasm module init in Rust-embedded Wasmtime · Issue #9714 · bytecodealliance/wasmtime
Test Case I'm trying to run a Kotlin-produced Wasm module in Rust-embedded Wasmtime. Kotlin requires support for the Wasm GC proposal, which Wasmtime officially has since version 27.0.0. Unfortunat...

Last updated: Dec 23 2024 at 14:03 UTC