[ci-scan] Test failure: WASM GetCookieForManagedMethod unknown thunk signature assert in browser wasm JIT/Regression #133561

Build Information

Build: https://dev.azure.com/dnceng-public/public/_build/results?buildId=1588672

Failure

Browser-wasm CoreCLR outer-loop failed in JIT/Regression/JitBlue/GitHub_19361, Repro.Program.TestEntryPoint(), in the Regressions / Regression_NoOptimize_r_1 coverage:

Starting stress loop
WASM calli missing for key: MS56Tp
ASSERT FAILED
Expression: !"GetCookieForManagedMethod: unknown thunk signature"
Location: src/coreclr/vm/wasm/helpers.cpp:1488
Function: GetCookieForManagedMethod

Observed in builds 1588256, 1588672, and 1589561.

Correct routing and signature

The test uses ordinary managed LINQ and Parallel.For; it does not use P/Invoke, UnmanagedCallersOnly, explicit function pointers, or reverse P/Invoke.

MS56Tp is a managed interpreter-to-R2R thunk key:

• M: managed interpreter-to-R2R transition
• S56: 56-byte value-type return through a return buffer
• T: instance method
• p: portable-entrypoint argument

The shape comes from the large ValueTuple<DateTime, CompositeSource, decimal> returned by a generic enumerator Current path. This is managed-call thunk lookup for a generic/value-type instantiation.

Resolution

This case was fixed by #133516. Structural sharing can find a Wasm R2R unboxing stub for a generic instantiation Crossgen2 never compiled, but that does not guarantee that the exact managed transition adapter (such as MS56Tp) exists. #133516 now retains exact per-target M and I transition dependencies for compiled targets and refuses to publish the structural native unboxing path when the exact incoming cookie is unavailable, falling back to the existing interpreted IL stub.

On current main, the exact Regression_NoOptimize_r_1 test reaches Starting stress loop, completes normally, and exits 100. A Checked debug diagnostic may still print WASM calli missing for key: MS56Tp while probing the structural unboxing optimization; that miss is now expected and causes the safe interpreted fallback rather than reaching GetCookieForManagedMethod with an unusable native target.

Build Analysis match

{
  "ErrorMessage": [
    "Expression: !\"GetCookieForManagedMethod: unknown thunk signature\"",
    "src/coreclr/vm/wasm/helpers.cpp:1488"
  ],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1588672
Error message validated: [Expression: !"GetCookieForManagedMethod: unknown thunk signature" src/coreclr/vm/wasm/helpers.cpp:1488]
Result validation: ❌ Known issue did not match with the provided build.
Validation performed at: 9/10/2026 3:23:44 AM UTC