Assert failure: (iOffsetMapping == 0) == (pOffsetMapping == 0)

[JulieLeeMSFT]

Failed in:

• runtime-interpreter 20260501.1

Console Log: Console Log
Source: runtime-interpreter / coreclr windows x64 Checked interpmode3_no_tiered_compilation @ Windows.10.Amd64.Open / Regression_o_2

Failed tests:

- coreclr windows x64 Checked @ Windows.10.Amd64.Open
- coreclr windows x64 Checked interpmode1 @ Windows.10.Amd64.Open
- coreclr windows x64 Checked interpmode1_no_tiered_compilation @ Windows.10.Amd64.Open
- coreclr windows x64 Checked interpmode2 @ Windows.10.Amd64.Open
- coreclr windows x64 Checked interpmode2_no_tiered_compilation @ Windows.10.Amd64.Open
- coreclr windows x64 Checked interpmode3 @ Windows.10.Amd64.Open
- coreclr windows x64 Checked interpmode3_no_tiered_compilation @ Windows.10.Amd64.Open
- coreclr windows x64 Checked no_tiered_compilation @ Windows.10.Amd64.Open
  - CoreMangLib
  - Directed_1
  - Directed_2
  - Directed_3
  - Exceptions
  - ... and 86 more

Error Message:

Assert failure(PID 8876 [0x000022ac], Thread: 8720 [0x2210]): Precondition failure: 
FAILED: (iOffsetMapping == 0) == (pOffsetMapping == 0)

Stack Trace:

coreclr!CHECK::Trigger+0x251
coreclr!CompressDebugInfo::Compress+0x24f
coreclr!CEECodeGenInfo::CompressDebugInfo+0x4c1
coreclr!invokeCompileMethod+0x203
coreclr!UnsafeJitFunctionWorker+0x305
coreclr!UnsafeJitFunction+0x310
coreclr!MethodDesc::JitCompileCodeLocked+0x27f
coreclr!MethodDesc::JitCompileCodeLockedEventWrapper+0x5a7
coreclr!MethodDesc::JitCompileCode+0x547
coreclr!MethodDesc::PrepareCode+0x39d
coreclr!CodeVersionManager::PublishVersionableCodeIfNecessary+0x499
coreclr!MethodDesc::DoPrestub+0xb39
coreclr!PrepareInterpreterCode+0xc9
coreclr!InterpExecMethod+0x64d8
coreclr!ExecuteInterpretedMethod+0x24d
coreclr!InterpreterStub+0x149

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[JulieLeeMSFT]

CC @vitek-karas @BrzVlad @janvorli.

[mangod9]

Some analysis, FYI @tommcdon

Interpreter Assert — CompressDebugInfo::Compress precondition violation

Affected legs: All interpreter CI legs (windows x64/x86/arm64, linux x64/arm64)

Regression from: PR #127469

Symptoms

Assert failure in CompressDebugInfo::Compress — called with m_ILToNativeMapSize = 0 but m_pILToNativeMap != nullptr. Crashes across all interpreter legs.

Root Cause

PR #127469 changed InterpCompiler::EmitCodeIns() in src/coreclr/interpreter/compiler.cpp to only emit IL-to-native mappings for instructions that have the INTERP_INST_FLAG_EMPTY_IL_STACK flag set (~line 1058). However, the m_pILToNativeMap array is unconditionally allocated (~line 1181) based on total instruction count.

When a method has no instructions with INTERP_INST_FLAG_EMPTY_IL_STACK:

1. m_pILToNativeMap is allocated → non-null pointer
2. m_ILToNativeMapSize stays at 0 (no mappings emitted)
3. setBoundaries is called (~line 1262) with (count=0, buffer=non-null)
4. CompressDebugInfo::Compress asserts on the contradictory state

Potential Fix

Option A (minimal): Guard before setBoundaries call:

if (m_ILToNativeMapSize == 0)
{
    m_pILToNativeMap = nullptr;
}

Option B (cleaner): Defer the array allocation until after the emission loop, sizing it to the actual count of instructions with INTERP_INST_FLAG_EMPTY_IL_STACK rather than total instruction count.