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[wasm][coreclr] GetUnmanagedCallersOnlyThunk: unknown thunk for unmanaged callers only method #124219
Description
Some runtime tests have methods decorated with UnmanagedCallersOnly attribute. These will require native relinking.
They fail like this:
11:48:33.449 Running test: JIT/opt/Regressions/Regression3_Regressions/Regression3_Regressions.dll
ASSERT FAILED
Expression: false && "GetUnmanagedCallersOnlyThunk: unknown thunk for unmanaged callers only method"
Location: /__w/1/s/src/coreclr/vm/wasm/helpers.cpp:746
Function: GetUnmanagedCallersOnlyThunk
Process: 42
Frame (InlinedCallFrame): 0x4fdc54
Skipping 0x4fdc54
Frame (InterpreterFrame): 0x4fede8
0) dynamicClass::IL_STUB_PInvoke, IR_004a
1) System.Reflection.RuntimeAssembly::GetTypeCore, IR_015c
2) System.Reflection.RuntimeAssembly::GetTypeCore, IR_006d
3) System.Reflection.TypeNameResolver::GetType, IR_0278
4) System.Reflection.TypeNameResolver::GetSimpleType, IR_00bb
5) System.Reflection.TypeNameResolver::Resolve, IR_0018
6) System.Reflection.TypeNameResolver::GetType, IR_0099
7) System.Reflection.RuntimeAssembly::GetType, IR_002a
8) System.Reflection.Assembly::GetType, IR_001b
9) Program::TestEntryPoint, IR_002e
10) Program::<<Main>$>g__TestExecutor134|0_135, IR_005b
11) Program::<Main>$, IR_07b9
Reacted by Frulfump
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dotnet-policy-service commentedon Feb 10, 2026
Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
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dotnet-policy-service commentedon Feb 10, 2026
Tagging subscribers to this area: @agocke
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Re-enable Runtime_105619 on Mono full-AOT
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lewing commentedon Jul 15, 2026
Status (still valid): the assert is intact at
src/coreclr/vm/wasm/helpers.cpp:1489(GetUnmanagedCallersOnlyThunk: unknown thunk ...), fired whenLookupThunk(pMD)finds no reverse-thunk for a[UnmanagedCallersOnly]method. Runtime tests (src/tests) still have no per-test native relink, so they run against the bakedlibcoreclr_gen_static.atable (generated at runtime-build time) and hit this for any test-introduced UCO method.Currently gating these wasm runtime tests via
[ActiveIssue(#124219, IsWasm)]:src/tests/Loader/classloader/Casting/Functionpointer.cssrc/tests/JIT/opt/Regressions/Regression3_Regressions.cssrc/tests/JIT/Regression/JitBlue/Runtime_72265/Runtime_72265.cssrc/tests/JIT/Regression/JitBlue/Runtime_105619/Runtime_105619.csPath to resolution: the fix is the per-app native relink noted in the description. That mechanism now exists for library tests — #130129 /
src/mono/wasi/build/WasiApp.CoreCLR.targetsrunsManagedToNativeGeneratorover the bundle, compiles the generated callhelpers, and relinks the host swapping out the bakedcoreclr_gen_static(validated: fullSystem.Runtime.Testssuite runs on a relinkedcorerun). Extending the same relink to thesrc/testsbuild would cover runtime-test UCO methods and let the four[ActiveIssue]s above be re-enabled.Companion fix: #130740 corrects the reverse-thunk key for nested
[UnmanagedCallersOnly]types (reflection namespace vs empty metadata namespace) — nested UCO callbacks in runtime tests would still miss even after relinking without it. Distinct from #130634 (R2Rcall_indirect).Note
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