[cDAC] Add GetApproxTypeHandle DacDbi API#128921
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Add DacDbi approximate type handle dump tests
Add GetApproxTypeHandle dump tests
Jun 3, 2026
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Pull request overview
This PR adds dump-based coverage for DacDbiImpl.GetApproxTypeHandle by mirroring the existing exact-type-handle dump tests: it enumerates heap objects reachable from GC handles in the ExactTypeHandle debuggee, constructs the flattened DebuggerIPCE_TypeArgData[] tree (a managed port of CordbType::GatherTypeData), round-trips that through GetApproxTypeHandle, and asserts the returned vmTypeHandle matches an independently canonicalized expected MethodTable. To support this, it also adds a managed TypeDataWalk implementation and refactors some type lookup logic into a helper.
Changes:
- Add a new dump test suite
DacDbiApproxTypeHandleDumpTestsimplementing the right-side “gather type data” flattening and expected-handle canonicalization. - Implement managed
GetApproxTypeHandlesupport via a newTypeDataWalkport and supporting helper types. - Replace
IsObjRef(TypeHandle)usage with a newIsCorElementTypeObjRef(CorElementType)helper across tests, the contract, and documentation.
Show a summary per file
| File | Description |
|---|---|
| src/native/managed/cdac/tests/MethodTableTests.cs | Updates objref classification assertions to use IsCorElementTypeObjRef(GetInternalCorElementType(...)). |
| src/native/managed/cdac/tests/DumpTests/RuntimeTypeSystemDumpTests.cs | Updates dump-based RTS “objref consistency” test to use the new helper. |
| src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiObjectDumpTests.cs | Updates reference-type offset logic to use the new helper. |
| src/native/managed/cdac/tests/DumpTests/DacDbi/DacDbiApproxTypeHandleDumpTests.cs | New dump test covering round-trip behavior for GetApproxTypeHandle across reachable handle objects. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/TypeDataWalk.cs | New managed port of the native flattened-type-data walker used by GetApproxTypeHandle. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/IDacDbiInterface.cs | Adds DebuggerIPCE_TypeArgData / TypeInfoList and tightens GetApproxTypeHandle signature to a typed pointer. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DbiHelpers.cs | New helper for resolving typeDef/typeRef MethodTables from an assembly+token via loader lookup tables. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/Dbi/DacDbiImpl.cs | Implements managed GetApproxTypeHandle and switches some ref-type checks to IsCorElementTypeObjRef. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/RuntimeTypeSystem_1.cs | Replaces IsObjRef with IsCorElementTypeObjRef implementation used by the contract. |
| src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IRuntimeTypeSystem.cs | Changes the contract surface by removing IsObjRef(TypeHandle) and adding IsCorElementTypeObjRef(CorElementType). |
| docs/design/datacontracts/RuntimeTypeSystem.md | Updates contract documentation to match the new helper. |
Copilot's findings
- Files reviewed: 11/11 changed files
- Comments generated: 5
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noahfalk
approved these changes
Jun 24, 2026
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/ba-g known DAC failure |
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Add this API using a port of the native type-walk logic and a slight tweak to the RuntimeTypeSystem API that determines if something is a reference type.