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Assert failure: !"OBJECTREF being accessed while thread is in preemptive GC mode." #131925

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Assert failure: !"OBJECTREF being accessed while thread is in preemptive GC mode."#131925
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Known Build ErrorUse this to report build issues in the .NET Helix tabarch-wasmWebAssembly architecturearea-VM-coreclrblocking-outerloopBlocking the 'runtime-coreclr outerloop' and 'runtime-libraries-coreclr outerloop' runsdisabled-testThe test is disabled in source code against the issue
Milestone
Future

Description

@VincentBu
VincentBu
opened on Aug 6, 2026

Failed in: runtime-coreclr outerloop 20260805.6

Failed tests:

coreclr browser wasm Checked @ (Ubuntu.2604.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-26.04-helix-webassembly-amd64@sha256:0be8725e08b6d0f58ec0290f3f3b70c449123e78b2b33853e9049df84b912fa8
- Loader/ContextualReflection/ContextualReflection/ContextualReflection.cmd
coreclr browser wasm Checked no_tiered_compilation @ (Ubuntu.2604.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-26.04-helix-webassembly-amd64@sha256:0be8725e08b6d0f58ec0290f3f3b70c449123e78b2b33853e9049df84b912fa8
- Loader/ContextualReflection/ContextualReflection/ContextualReflection.cmd

Error message:

Out-of-process wrapper failed with exit code 1.
BEGIN EXECUTION
Running with node
CORE_ROOT: /root/helix/work/correlation
ExePath: /root/helix/work/workitem/e/Loader/ContextualReflection/ContextualReflection/ContextualReflection.dll
CLRTestExecutionArguments:
node version: v23.11.1
Timeout in ms: 900000
Running: node --experimental-wasm-exnref --stack-size=8192 /root/helix/work/correlation/corerun.js -c /root/helix/work/correlation -p System.Reflection.Metadata.MetadataUpdater.IsSupported=false -p System.Runtime.Serialization.EnableUnsafeBinaryFormatterSerialization=true /root/helix/work/workitem/e/Loader/ContextualReflection/ContextualReflection/ContextualReflection.dll
ASSERT FAILED
	Expression: !"OBJECTREF being accessed while thread is in preemptive GC mode."
	Location:   /__w/1/s/src/coreclr/vm/object.cpp:514
	Function:   Validate
	Process:    42
Frame (InterpreterFrame): 0x4ff358
   0) Xunit.Assert::GetEqualityComparer, IR_0007
   1) Xunit.Assert::Equal, IR_0010
   2) ContextualReflectionTest.TestResolve::Assert, IR_002e
   3) ContextualReflectionTest.TestResolve::Assert, IR_001c
   4) ContextualReflectionTest.Program::TestResolveMissingAssembly, IR_002f
   5) ContextualReflectionTest.Program::TestAssemblyLoad, IR_0031
   6) ContextualReflectionTest.Program::TestAssemblyLoad, IR_00b8
   7) ContextualReflectionTest.Program::RunTests, IR_0011
   8) ContextualReflectionTest.Program::RunTests, IR_004e
   9) ContextualReflectionTest.Program::TestEntryPoint, IR_0013
  10) __GeneratedMainWrapper::Main, IR_0020
node:internal/process/promises:392
      new UnhandledPromiseRejection(reason);
      ^

UnhandledPromiseRejection: This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason "Debugger not attached".
    at throwUnhandledRejectionsMode (node:internal/process/promises:392:7)
    at processPromiseRejections (node:internal/process/promises:475:17)
    at process.processTicksAndRejections (node:internal/process/task_queues:106:32) {
  code: 'ERR_UNHANDLED_REJECTION'
}

Node.js v23.11.1
Kill watchdog with PID 674
Expected: 100
Actual: 1
END EXECUTION - FAILED

Stack trace:

   at Xunit.Assert.True(Nullable`1 condition, String userMessage) in /_/src/arcade/src/Microsoft.DotNet.XUnitAssert/src/BooleanAsserts.cs:line 135
   at Xunit.Assert.True(Boolean condition, String userMessage) in /_/src/arcade/src/Microsoft.DotNet.XUnitAssert/src/BooleanAsserts.cs:line 117
   at TestLibrary.OutOfProcessTest.ImportPrecomputedResult(String assemblyPath, String testPathPrefix) in /__w/1/s/src/tests/Common/CoreCLRTestLibrary/OutOfProcessTest.cs:line 285
   at TestLibrary.OutOfProcessTest.RunOutOfProcessTest(String assemblyPath, String testPathPrefix) in /__w/1/s/src/tests/Common/CoreCLRTestLibrary/OutOfProcessTest.cs:line 84
   at Program.<<Main>$>g__TestExecutor389|0_390(StreamWriter tempLogSw, StreamWriter statsCsvSw, StreamWriter outOfProcessPlanWriter, <>c__DisplayClass0_0&)

Known Issue Error Message

DO NOT USE JSON BELOW IF THIS IS A BUILD BREAK otherwise build analysis will allow pull requests to merge that break the build worse. For a build break, do not use this issue form. Make a regular new issue.

Fill the error message using step by step known issues guidance.

{
  "ErrorMessage": [
    "Loader/ContextualReflection/ContextualReflection/ContextualReflection.cmd",
    "OBJECTREF being accessed while thread is in preemptive GC mode."
  ],
  "ErrorPattern": "",
  "BuildRetry": false,
  "ExcludeConsoleLog": false
}

Known issue validation

Build: 🔎 https://dev.azure.com/dnceng-public/public/_build/results?buildId=1541935
Error message validated: [Loader/ContextualReflection/ContextualReflection/ContextualReflection.cmd OBJECTREF being accessed while thread is in preemptive GC mode.]
Result validation: ✅ Known issue matched with the provided build.
Validation performed at: 8/7/2026 1:59:14 PM UTC

Report

Summary

24-Hour Hit Count 7-Day Hit Count 1-Month Count
0 0 0

Activity

  1. VincentBu
    added
    blocking-outerloopBlocking the 'runtime-coreclr outerloop' and 'runtime-libraries-coreclr outerloop' runs
    on Aug 6, 2026
  2. dotnet-policy-service
    added
    untriagedNew issue has not been triaged by the area owner
    on Aug 6, 2026
  3. github-actions
    added
    area-Interop-coreclr
    on Aug 6, 2026
  4. github-project-automation
    added this to AppModelon Aug 6, 2026

  5. dotnet-policy-service commented on Aug 6, 2026

    @dotnet-policy-service
    dotnet-policy-serviceBot
    on Aug 6, 2026 – with Dotnet Policy Service
    Contributor

    Tagging subscribers to this area: @dotnet/interop-contrib
    See info in area-owners.md if you want to be subscribed.

  6. jkoritzinsky
    added
    arch-wasmWebAssembly architecture
    on Aug 6, 2026

  7. dotnet-policy-service commented on Aug 6, 2026

    @dotnet-policy-service
    dotnet-policy-serviceBot
    on Aug 6, 2026 – with Dotnet Policy Service
    Contributor

    Tagging subscribers to 'arch-wasm': @lewing, @pavelsavara
    See info in area-owners.md if you want to be subscribed.

  8. pavelsavara
    removed this from AppModelon Aug 6, 2026
  9. radekdoulik
    self-assigned this
    on Aug 6, 2026
  10. radekdoulik
    added this to the Future milestone on Aug 6, 2026
  11. radekdoulik
    removed
    untriagedNew issue has not been triaged by the area owner
    on Aug 6, 2026
  12. github-project-automation
    added this to AppModelon Aug 6, 2026
  13. AaronRobinsonMSFT
    added
    area-VM-coreclr
    and removed
    area-Interop-coreclr
    on Aug 6, 2026

  14. dotnet-policy-service commented on Aug 6, 2026

    @dotnet-policy-service
    dotnet-policy-serviceBot
    on Aug 6, 2026 – with Dotnet Policy Service
    Contributor

    Tagging subscribers to this area: @agocke
    See info in area-owners.md if you want to be subscribed.

  15. jkotas
    marked [ci-scan] Test failure: Loader/ContextualReflection asserts OBJECTREF in preemptive GC mode on browser-wasm interpreter #131980 as a duplicate of this issue on Aug 7, 2026
  16. jkotas
    added
    Known Build ErrorUse this to report build issues in the .NET Helix tab
    on Aug 7, 2026

  17. AndyAyersMS commented on Aug 7, 2026

    @AndyAyersMS
    AndyAyersMS
    on Aug 7, 2026
    Member

    More analysis over in #132022.

    We enabled Wasm SPC R2R but the change also more broadly enabled R2R in outerloop.

  18. AndyAyersMS commented on Aug 7, 2026

    @AndyAyersMS
    AndyAyersMS
    on Aug 7, 2026
    Member

    This test broadening surfaced #131924 as well.

  19. VincentBu commented on Aug 10, 2026

    @VincentBu
    VincentBu
    on Aug 10, 2026
    ContributorAuthor

    Failed in: runtime-coreclr outerloop 20260809.3

    Failed tests:

    coreclr browser wasm Checked @ (Ubuntu.2604.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-26.04-helix-webassembly-amd64@sha256:0be8725e08b6d0f58ec0290f3f3b70c449123e78b2b33853e9049df84b912fa8
- Loader/ContextualReflection/ContextualReflection/ContextualReflection.cmd
coreclr browser wasm Checked no_tiered_compilation @ (Ubuntu.2604.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-26.04-helix-webassembly-amd64@sha256:0be8725e08b6d0f58ec0290f3f3b70c449123e78b2b33853e9049df84b912fa8
- Loader/ContextualReflection/ContextualReflection/ContextualReflection.cmd

    Error message:

    Out-of-process wrapper failed with exit code 1.
BEGIN EXECUTION
Running with node
CORE_ROOT: /root/helix/work/correlation
ExePath: /root/helix/work/workitem/e/Loader/ContextualReflection/ContextualReflection/ContextualReflection.dll
CLRTestExecutionArguments:
node version: v23.11.1
Timeout in ms: 900000
Running: node --experimental-wasm-exnref --stack-size=8192 /root/helix/work/correlation/corerun.js -c /root/helix/work/correlation -p System.Reflection.Metadata.MetadataUpdater.IsSupported=false -p System.Runtime.Serialization.EnableUnsafeBinaryFormatterSerialization=true /root/helix/work/workitem/e/Loader/ContextualReflection/ContextualReflection/ContextualReflection.dll
ASSERT FAILED
	Expression: !"OBJECTREF being accessed while thread is in preemptive GC mode."
	Location:   /__w/1/s/src/coreclr/vm/object.cpp:514
	Function:   Validate
	Process:    42
Frame (InterpreterFrame): 0x4ff358
   0) Xunit.Assert::GetEqualityComparer, IR_0007
   1) Xunit.Assert::Equal, IR_0010
   2) ContextualReflectionTest.TestResolve::Assert, IR_002e
   3) ContextualReflectionTest.TestResolve::Assert, IR_001c
   4) ContextualReflectionTest.Program::TestResolveMissingAssembly, IR_002f
   5) ContextualReflectionTest.Program::TestAssemblyLoad, IR_0031
   6) ContextualReflectionTest.Program::TestAssemblyLoad, IR_00b8
   7) ContextualReflectionTest.Program::RunTests, IR_0011
   8) ContextualReflectionTest.Program::RunTests, IR_004e
   9) ContextualReflectionTest.Program::TestEntryPoint, IR_0013
  10) __GeneratedMainWrapper::Main, IR_0020
node:internal/process/promises:392
      new UnhandledPromiseRejection(reason);
      ^

UnhandledPromiseRejection: This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). The promise rejected with the reason "Debugger not attached".
    at throwUnhandledRejectionsMode (node:internal/process/promises:392:7)
    at processPromiseRejections (node:internal/process/promises:475:17)
    at process.processTicksAndRejections (node:internal/process/task_queues:106:32) {
  code: 'ERR_UNHANDLED_REJECTION'
}

Node.js v23.11.1
Kill watchdog with PID 675
Expected: 100
Actual: 1
END EXECUTION - FAILED

    Stack trace:

       at Xunit.Assert.True(Nullable`1 condition, String userMessage) in /_/src/arcade/src/Microsoft.DotNet.XUnitAssert/src/BooleanAsserts.cs:line 135
   at Xunit.Assert.True(Boolean condition, String userMessage) in /_/src/arcade/src/Microsoft.DotNet.XUnitAssert/src/BooleanAsserts.cs:line 117
   at TestLibrary.OutOfProcessTest.ImportPrecomputedResult(String assemblyPath, String testPathPrefix) in /__w/1/s/src/tests/Common/CoreCLRTestLibrary/OutOfProcessTest.cs:line 285
   at TestLibrary.OutOfProcessTest.RunOutOfProcessTest(String assemblyPath, String testPathPrefix) in /__w/1/s/src/tests/Common/CoreCLRTestLibrary/OutOfProcessTest.cs:line 84
   at Program.<<Main>$>g__TestExecutor390|0_391(StreamWriter tempLogSw, StreamWriter statsCsvSw, StreamWriter outOfProcessPlanWriter, <>c__DisplayClass0_0&)

  20. pavelsavara commented on Aug 13, 2026

    @pavelsavara
    pavelsavara
    on Aug 13, 2026
    Member

    This is probably JS exception thrown from emscripten/posix layer or a trap by invalid WASM access.
    The preemptive GC mode is just consequence of unwinding thru the GC mode boundary and then trying to continue running.

    It would be great if we can catch it and report the underlying reason/stack.
    At least in Debug/Checked builds.
    I know that this is unexpected exception/trap and such things are also UB on the PInvoke/ICall layer.
    But the diagnostic we get here is not useful. These things will continue happening with long tail of edge case reasons.

  21. pavelsavara commented on Aug 14, 2026

    @pavelsavara
    pavelsavara
    on Aug 14, 2026
    Member

    Related #123482

  22. pavelsavara
    self-assigned this
    on Aug 14, 2026
  23. radekdoulik
    added a commit that references this issue on Aug 19, 2026

    [browser][CoreCLR] Gate remaining priority-1 outerloop failures (#131957

    a7a9b87
  24. lewing
    added
    disabled-testThe test is disabled in source code against the issue
    on Oct 17, 2026
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Known Build ErrorUse this to report build issues in the .NET Helix tabarch-wasmWebAssembly architecturearea-VM-coreclrblocking-outerloopBlocking the 'runtime-coreclr outerloop' and 'runtime-libraries-coreclr outerloop' runsdisabled-testThe test is disabled in source code against the issue

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