Add cDAC ObjectiveCMarshal contract and IsTrackedReferenceWithFinalizer API

[Copilot]

Summary

Implements cDAC APIs for Objective-C interop diagnostics as a new ObjectiveCMarshal contract, plus adds IsTrackedReferenceWithFinalizer to the RuntimeTypeSystem contract. Based on draft PR #118250, adjusted per review feedback (contract renamed, TargetNUInt instead of nuint, APIs in dedicated contract).

Note

This PR was generated with GitHub Copilot.

Changes

New ObjectiveCMarshal cDAC Contract

• IObjectiveCMarshal (Abstractions/Contracts/IObjectiveCMarshal.cs): Interface with a single API:

  TargetPointer GetTaggedMemory(TargetPointer address, out TargetNUInt size);

  Returns the tagged memory pointer for an Objective-C tracked reference object (or TargetPointer.Null if none). Sets size to 2 * pointerSize bytes only on success.

• ObjectiveCMarshal_1 (Contracts/ObjectiveCMarshal_1.cs): Version 1 implementation — reads the sync block from the object header, then extracts InteropSyncBlockInfo.TaggedMemory.

• ObjectiveCMarshalFactory (Contracts/ObjectiveCMarshalFactory.cs): Contract factory.

• Registered in ContractRegistry and CachingContractRegistry.

• datadescriptor.inc: Added TaggedMemory field to InteropSyncBlockInfo type (under #ifdef FEATURE_OBJCMARSHAL) and CDAC_GLOBAL_CONTRACT(ObjectiveCMarshal, 1) (also guarded).

• syncblk.h: Added TaggedMemory offset to cdac_data<InteropSyncBlockInfo> under #ifdef FEATURE_OBJCMARSHAL.

• InteropSyncBlockInfo.cs (Data class): Added TaggedMemory property using TryGetValue to handle the optional FEATURE_OBJCMARSHAL field.

IsTrackedReferenceWithFinalizer on RuntimeTypeSystem

• Added IsTrackedReferenceWithFinalizer = 0x04000000 to WFLAGS_HIGH enum in MethodTableFlags_1.cs, plus a convenience property bool IsTrackedReferenceWithFinalizer.

• Added IsTrackedReferenceWithFinalizer(TypeHandle) to IRuntimeTypeSystem.cs and implemented it in RuntimeTypeSystem_1.cs.

SOSDacImpl.cs — ISOSDacInterface11

Replaced the stub implementations of IsTrackedType and GetTaggedMemory with full cDAC implementations:

• IsTrackedType: uses IRuntimeTypeSystem.IsTrackedReferenceWithFinalizer and IObjectiveCMarshal.GetTaggedMemory; returns S_OK if tracked, S_FALSE if not, E_INVALIDARG for null inputs.
• GetTaggedMemory: uses IObjectiveCMarshal.GetTaggedMemory; returns S_OK with address and size if tagged memory exists, S_FALSE otherwise.

Both methods include #if DEBUG assertions against the legacy DAC implementation for validation.

Documentation

• docs/design/datacontracts/ObjectiveCMarshal.md: New contract documentation.
• docs/design/datacontracts/RuntimeTypeSystem.md: Added IsTrackedReferenceWithFinalizer to API listing and pseudocode.

Testing

All 1322 existing cDAC unit tests pass. The new contract will be exercised when running on an Apple platform with FEATURE_OBJCMARSHAL enabled.

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[max-charlamb]

We need to add this to the RuntimeTypeSystem.md markdown file.