cDAC: Implement ISOSDacInterface::GetRCWData by Copilot · Pull Request #125426 · dotnet/runtime

Copilot · 2026-03-11T04:36:03Z

Replace URTAggregatedMask, URTContainedMask, MarshalingTypeMask, MarshalingTypeFreeThreadedValue raw const uint fields with a [Flags] private enum RCWFlags : uint in BuiltInCOM_1.cs, matching the style of existing CCWFlags/ComMethodTableFlags/ComWrapperFlags enums
Update all three usages (GetRCWData ×2, GetRCWCleanupList ×1) to use enum casts
Contracts project and unit tests build cleanly

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Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

…M GetRCWData tests Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

dotnet-policy-service · 2026-03-11T04:56:58Z

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Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

…iltInCOM_1 Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

Copilot

Pull request overview

Implements ISOSDacInterface::GetRCWData via the BuiltInCOM contract, expanding the RCW data descriptor/model and adding dump + unit tests to validate RCW data and interface cache behavior.

Changes:

Added IBuiltInCOM.GetRCWData and implemented it in BuiltInCOM_1, including RCW flag decoding and disconnected detection.
Extended cDAC data descriptors/models for RCW and CtxEntry, and wired legacy SOS DAC GetRCWData to the new contract.
Added/updated dump-test documentation and introduced new RCW dump tests + unit tests for GetRCWData.

Reviewed changes

Copilot reviewed 15 out of 16 changed files in this pull request and generated 6 comments.

Show a summary per file

File	Description
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/BuiltInCOM_1.cs	Adds RCW flags enum, disconnected detection, and implements `GetRCWData`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Abstractions/Contracts/IBuiltInCOM.cs	Introduces `RCWData` and adds `GetRCWData` to contract interface.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/RCW.cs	Extends RCW processed-data model to read additional fields used by `GetRCWData`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Data/CtxEntry.cs	Adds `CtxCookie` to support RCW disconnected detection.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs	Implements `ISOSDacInterface.GetRCWData` using cDAC `BuiltInCOM`.
src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ISOSDacInterface.cs	Adds `DacpRCWData` struct and updates `GetRCWData` signature.
src/native/managed/cdac/tests/BuiltInCOMTests.cs	Adds mock descriptors + unit tests covering `GetRCWData` and disconnected scenarios.
src/native/managed/cdac/tests/DumpTests/RCWDumpTests.cs	Adds dump-based tests for RCW interfaces and `GetRCWData` behavior.
src/native/managed/cdac/tests/DumpTests/Debuggees/RCWInterfaces/Program.cs	Expands debuggee to create both plain and contained RCWs and pins them for dump discovery.
src/native/managed/cdac/tests/DumpTests/README.md	Documents new dump type and test mapping for RCW.
src/coreclr/vm/runtimecallablewrapper.h	Adds cDAC field offsets for additional RCW fields; documents contract dependency on bit encoding.
src/coreclr/vm/datadescriptor/datadescriptor.inc	Adds new RCW/CtxEntry fields to cDAC data descriptor.
src/coreclr/vm/comcache.h	Adds `CtxEntry::CtxCookie` field offset for cDAC.
docs/design/datacontracts/BuiltInCOM.md	Documents `RCWData`, new fields, flags, and disconnected detection logic.

Copilot · 2026-03-12T00:31:34Z

src/native/managed/cdac/tests/DumpTests/RCWDumpTests.cs

+/// </summary>
+public class RCWDumpTests : DumpTestBase
+{
+    protected override string DebuggeeName => "RCW";


DebuggeeName is set to "RCW", but the updated debuggee lives under Debuggees/RCWInterfaces/Program.cs in this diff. If the debuggee/project name wasn’t also renamed to RCW elsewhere, this test will fail to locate/run the debuggee. Align the dump test’s DebuggeeName with the actual debuggee target name (or rename/move the debuggee project/folder so the name is truly RCW).

Suggested change

protected override string DebuggeeName => "RCW";

protected override string DebuggeeName => "RCWInterfaces";

Copilot · 2026-03-12T00:31:35Z

src/native/managed/cdac/tests/DumpTests/README.md

 | SyncBlockDumpTests | SyncBlock | SyncBlock |
 | BuiltInCOMDumpTests | BuiltInCOM | CCWInterfaces |
 | RCWCleanupListDumpTests | BuiltInCOM | RCWCleanupList |
+| RCWInterfacesDumpTests | BuiltInCOM | RCW |


The README maps the new RCW dump type to RCWInterfacesDumpTests, but RCWInterfacesDumpTests.cs was removed and replaced by RCWDumpTests.cs in this PR. Update this row (and any related naming in the README) to reference the actual test class/file name to avoid confusion and stale documentation.

Suggested change

| RCWInterfacesDumpTests | BuiltInCOM | RCW |

| RCWDumpTests | BuiltInCOM | RCW |

Copilot · 2026-03-12T00:31:35Z

...ve/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/BuiltInCOM_1.cs

+    // Mirrors IUnkEntry::IsDisconnected in src/coreclr/vm/comcache.h.
+    private bool IsRCWDisconnected(Data.RCW rcw)
+    {
+        if (rcw.UnknownPointer == DisconnectedSentinel)


rcw.UnknownPointer is a TargetPointer, while DisconnectedSentinel is a ulong. This comparison is very likely either a compile-time type mismatch or (worse) an unintended comparison via implicit conversion/operator overload. To make the check unambiguous and portable, compare like-for-like (e.g., create a TargetPointer sentinel value once and compare against that).

Suggested change

if (rcw.UnknownPointer == DisconnectedSentinel)

ulong unknownPointer = rcw.UnknownPointer;

if (unknownPointer == DisconnectedSentinel)

Copilot · 2026-03-12T00:31:35Z

...ve/managed/cdac/Microsoft.Diagnostics.DataContractReader.Contracts/Contracts/BuiltInCOM_1.cs

+    // Mirrors RCW::RCWFlags bits in src/coreclr/vm/runtimecallablewrapper.h.
+    private enum RCWFlags : uint
+    {
+        URTAggregated          = 0x010u, // bit 4: m_fURTAggregated
+        URTContained           = 0x020u, // bit 5: m_fURTContained
+        MarshalingTypeMask     = 0x180u, // bits 7-8: m_MarshalingType
+        MarshalingTypeFreeThreaded = 0x100u, // MarshalingType_FreeThreaded (2) in bits 7-8
+    }


The PR description says this should be a [Flags] private enum RCWFlags : uint, but the enum in code is missing the [Flags] attribute. Add [Flags] to match the stated intent and existing style (e.g., CCWFlags/ComWrapperFlags) since this enum is used for bitmask operations.

Copilot · 2026-03-12T00:31:35Z

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/ISOSDacInterface.cs

+public struct DacpRCWData
+{
+    public ClrDataAddress identityPointer;
+    public ClrDataAddress unknownPointer;
+    public ClrDataAddress managedObject;
+    public ClrDataAddress jupiterObject;
+    public ClrDataAddress vtablePtr;
+    public ClrDataAddress creatorThread;
+    public ClrDataAddress ctxCookie;
+    public int refCount;
+    public int interfaceCount;
+    public Interop.BOOL isJupiterObject;
+    public Interop.BOOL supportsIInspectable;
+    public Interop.BOOL isAggregated;
+    public Interop.BOOL isContained;
+    public Interop.BOOL isFreeThreaded;
+    public Interop.BOOL isDisconnected;
+}


Since DacpRCWData is part of the COM-facing SOS DAC surface, it’s safer to explicitly enforce blittable layout (e.g., [StructLayout(LayoutKind.Sequential)]). This avoids any ambiguity around field ordering/packing assumptions and makes the interop contract clearer.

Copilot · 2026-03-12T00:31:36Z

src/native/managed/cdac/Microsoft.Diagnostics.DataContractReader.Legacy/SOSDacImpl.cs

+            data->creatorThread = rcwData.CreatorThread.ToClrDataAddress(_target);
+            data->ctxCookie = rcwData.CtxCookie.ToClrDataAddress(_target);
+            data->refCount = (int)rcwData.RefCount;
+            data->interfaceCount = builtInCom.GetRCWInterfaces(rcwPtr).Count();


Count() will enumerate the full IEnumerable returned by GetRCWInterfaces, which may repeatedly read target memory and allocate enumerator state. If this API is expected to be called frequently (e.g., by diagnostics tooling), consider adding a dedicated contract method that returns interface count without enumerating (or adjusting GetRCWInterfaces to return a collection/array where the count is cheap).

Copilot AI and others added 4 commits March 11, 2026 03:55

Initial plan

1089169

cDAC: Implement SosDacImpl GetRCWData

a4cb8e4

Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

cDAC: Implement ISOSDacInterface::GetRCWData

c5f8cda

Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

cDAC: Add DacpRCWData, implement SOSDacImpl.GetRCWData, add BuiltInCO…

6d48b7b

…M GetRCWData tests Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

Copilot AI assigned Copilot and rcj1 Mar 11, 2026

Copilot finished work on behalf of rcj1 March 11, 2026 04:36

Copilot started work on behalf of rcj1 March 11, 2026 04:45 View session

github-actions bot added the area-Diagnostics-coreclr label Mar 11, 2026

cDAC: Add GetRCWData dump test to RCWInterfacesDumpTests

a680e61

Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

Copilot finished work on behalf of rcj1 March 11, 2026 05:01

Copilot started work on behalf of rcj1 March 11, 2026 05:02 View session

cDAC: Replace raw RCW flag constants with RCWFlags [Flags] enum in Bu…

bc6648b

…iltInCOM_1 Co-authored-by: rcj1 <77995559+rcj1@users.noreply.github.com>

Copilot finished work on behalf of rcj1 March 11, 2026 05:15

This was referenced Mar 11, 2026

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rcj1 requested a review from Copilot March 12, 2026 00:26

Copilot AI reviewed Mar 12, 2026

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	protected override string DebuggeeName => "RCW";
	protected override string DebuggeeName => "RCWInterfaces";

	\| RCWInterfacesDumpTests \| BuiltInCOM \| RCW \|
	\| RCWDumpTests \| BuiltInCOM \| RCW \|

	if (rcw.UnknownPointer == DisconnectedSentinel)
	ulong unknownPointer = rcw.UnknownPointer;
	if (unknownPointer == DisconnectedSentinel)

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Copilot AI commented Mar 11, 2026 •

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