Stream: git-wasmtime

Topic: wasmtime / issue #12391 [CM async] panic performing block...

Wasmtime GitHub notifications bot (Jan 22 2026 at 01:36):

lukewagner added the bug label to Issue #12391.

Wasmtime GitHub notifications bot (Jan 22 2026 at 01:36):

lukewagner opened issue #12391:

Currently, this WAST:

(assert_trap
  (component
    (core module $Memory (memory (export "mem") 1))
    (core instance $memory (instantiate $Memory))
    (core module $M
      (import "" "waitable-set.new" (func $waitable-set.new (result i32)))
      (import "" "waitable-set.wait" (func $waitable-set.wait (param i32 i32) (result i32)))
      (func $start
        (drop (call $waitable-set.wait (call $waitable-set.new) (i32.const 0)))
      )
      (start $start)
    )
    (canon waitable-set.new (core func $waitable-set.new))
    (canon waitable-set.wait (memory $memory "mem") (core func $waitable-set.wait))
    (core instance $m (instantiate $M (with "" (instance
      (export "waitable-set.new" (func $waitable-set.new))
      (export "waitable-set.wait" (func $waitable-set.wait))
    ))))
  )
  "cannot block a synchronous task before returning"
)

panics with:

thread 'main' (2367885) panicked at crates/wasmtime/src/runtime/component/concurrent.rs:1517:39:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: core::option::unwrap_failed
   4: wasmtime::runtime::component::concurrent::<impl wasmtime::runtime::store::StoreOpaque>::check_blocking
   5: wasmtime::runtime::component::concurrent::<impl wasmtime::runtime::component::instance::Instance>::waitable_set_wait

Wasmtime GitHub notifications bot (Jan 22 2026 at 01:46):

lukewagner commented on issue #12391:

This test case and another like it now available to pull in from test/async/dont-block-start.wast on main.

Wasmtime GitHub notifications bot (Jan 22 2026 at 15:56):

alexcrichton commented on issue #12391:

@dicej this should be fixed by https://github.com/bytecodealliance/wasmtime/pull/12379 I think, right?

Wasmtime GitHub notifications bot (Jan 22 2026 at 16:13):

dicej commented on issue #12391:

@dicej this should be fixed by #12379 I think, right?

Yes, it should be. I'll test it on that branch when I get a chance.

Wasmtime GitHub notifications bot (Jan 22 2026 at 16:17):

dicej commented on issue #12391:

Yup, test passes (no panic) on that branch.

Wasmtime GitHub notifications bot (Jan 23 2026 at 18:17):

dicej closed issue #12391:

Currently, this WAST:

(assert_trap
  (component
    (core module $Memory (memory (export "mem") 1))
    (core instance $memory (instantiate $Memory))
    (core module $M
      (import "" "waitable-set.new" (func $waitable-set.new (result i32)))
      (import "" "waitable-set.wait" (func $waitable-set.wait (param i32 i32) (result i32)))
      (func $start
        (drop (call $waitable-set.wait (call $waitable-set.new) (i32.const 0)))
      )
      (start $start)
    )
    (canon waitable-set.new (core func $waitable-set.new))
    (canon waitable-set.wait (memory $memory "mem") (core func $waitable-set.wait))
    (core instance $m (instantiate $M (with "" (instance
      (export "waitable-set.new" (func $waitable-set.new))
      (export "waitable-set.wait" (func $waitable-set.wait))
    ))))
  )
  "cannot block a synchronous task before returning"
)

panics with:

thread 'main' (2367885) panicked at crates/wasmtime/src/runtime/component/concurrent.rs:1517:39:
called `Option::unwrap()` on a `None` value
stack backtrace:
   0: __rustc::rust_begin_unwind
   1: core::panicking::panic_fmt
   2: core::panicking::panic
   3: core::option::unwrap_failed
   4: wasmtime::runtime::component::concurrent::<impl wasmtime::runtime::store::StoreOpaque>::check_blocking
   5: wasmtime::runtime::component::concurrent::<impl wasmtime::runtime::component::instance::Instance>::waitable_set_wait

Last updated: Jan 29 2026 at 13:25 UTC