wasmtime / issue #11666 component model async: panic in t... · git-wasmtime

Stream: git-wasmtime

Topic: wasmtime / issue #11666 component model async: panic in t...

Wasmtime GitHub notifications bot (Sep 10 2025 at 14:40):

BigOrangeQWQ opened issue #11666:

Test Case

composed.wasm
runner-c.wasm
test-c.wasm

Steps to Reproduce

Use the WIT interface:
package my:test;

interface i {
  ping: async func(x: future<string>, y: string) -> future<string>;
  pong: async func(x: future<string>) -> string;
}

world test {
  export i;
}

world runner {
  import i;
}
Compile two components: runner.wasm (UTF-8) and test.wasm (UTF-16).

Compose these components into a single composed.wasm using wasm-tools component compose.

Run composed.wasm using Wasmtime.

Expected Results

The async function should complete successfully, and the task.return operation should not panic.

Actual Results
Error: failed to run main module `composed.wasm`

Caused by:
    0: failed to invoke `run` function
    1: error while executing at wasm backtrace:
           0:  0x2ca9f - test-c.core.wasm!exports_test_async_ping_return
           1:  0x2bf63 - test-c.core.wasm!exports_test_async_ping_callback
           2:  0x2ca51 - test-c.core.wasm!__wasm_export_exports_test_async_ping_callback
       note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information
    2: invalid `task.return` signature and/or options for current task
Versions and Environment

Wasmtime version or commit: wasmtime 38.0.0 (024db5b4e 2025-09-08)

Operating system: MacOS 15.6.1

Architecture: arm64

Extra Info

The async lift of the function's signature contains UTF-16 encoding information. If this encoding is modified to UTF-8, the program will continue to run.

Wasmtime GitHub notifications bot (Sep 10 2025 at 14:40):

BigOrangeQWQ added the bug label to Issue #11666.

Wasmtime GitHub notifications bot (Sep 10 2025 at 14:44):

BigOrangeQWQ edited issue #11666:

Test Case

composed.wasm
runner-c.wasm
test-c.wasm

Steps to Reproduce

Use the WIT interface:
package my:test;

interface i {
  ping: async func(x: future<string>, y: string) -> future<string>;
  pong: async func(x: future<string>) -> string;
}

world test {
  export i;
}

world runner {
  import i;
}
Compile two components: runner-c.wasm (UTF-8) and test-c.wasm (UTF-16). Both of these components are built from wit-bindgen tests

Compose these components into a single composed.wasm using wasm-tools component compose.

Run composed.wasm using Wasmtime.

Expected Results

The async function should complete successfully, and the task.return operation should not panic.

Actual Results
Error: failed to run main module `composed.wasm`

Caused by:
    0: failed to invoke `run` function
    1: error while executing at wasm backtrace:
           0:  0x2ca9f - test-c.core.wasm!exports_test_async_ping_return
           1:  0x2bf63 - test-c.core.wasm!exports_test_async_ping_callback
           2:  0x2ca51 - test-c.core.wasm!__wasm_export_exports_test_async_ping_callback
       note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information
    2: invalid `task.return` signature and/or options for current task
Versions and Environment

Wasmtime version or commit: wasmtime 38.0.0 (024db5b4e 2025-09-08)

Operating system: MacOS 15.6.1

Architecture: arm64

Extra Info

The async lift of the function's signature contains UTF-16 encoding information. If this encoding is modified to UTF-8, the program will continue to run.

Wasmtime GitHub notifications bot (Sep 10 2025 at 14:45):

BigOrangeQWQ edited issue #11666:

Test Case

composed.wasm
runner-c.wasm
test-c.wasm

Steps to Reproduce

Use the WIT interface:
package my:test;

interface i {
  ping: async func(x: future<string>, y: string) -> future<string>;
  pong: async func(x: future<string>) -> string;
}

world test {
  export i;
}

world runner {
  import i;
}
Compile two components: runner-c.wasm (UTF-8) and test-c.wasm (UTF-16). Both of these components are built from wit-bindgen ping-pong test

Compose these components into a single composed.wasm using wasm-tools component compose.

Run composed.wasm using Wasmtime.

Expected Results

The async function should complete successfully, and the task.return operation should not panic.

Actual Results
Error: failed to run main module `composed.wasm`

Caused by:
    0: failed to invoke `run` function
    1: error while executing at wasm backtrace:
           0:  0x2ca9f - test-c.core.wasm!exports_test_async_ping_return
           1:  0x2bf63 - test-c.core.wasm!exports_test_async_ping_callback
           2:  0x2ca51 - test-c.core.wasm!__wasm_export_exports_test_async_ping_callback
       note: using the `WASMTIME_BACKTRACE_DETAILS=1` environment variable may show more debugging information
    2: invalid `task.return` signature and/or options for current task
Versions and Environment

Wasmtime version or commit: wasmtime 38.0.0 (024db5b4e 2025-09-08)

Operating system: MacOS 15.6.1

Architecture: arm64

Extra Info

The async lift of the function's signature contains UTF-16 encoding information. If this encoding is modified to UTF-8, the program will continue to run.

Last updated: Jan 10 2026 at 02:36 UTC