Don't create a COM weak reference if the object is an aggregated COMWrappers RCW.

src/coreclr/vm/interoplibinterface.h

@@ -34,7 +34,7 @@ class ComWrappersNative
     static void MarkWrapperAsComActivated(_In_ IUnknown* wrapperMaybe);
 
 public: // Unwrapping support
-    static IUnknown* GetIdentityForObject(_In_ OBJECTREF* objectPROTECTED, _In_ REFIID riid, _Out_ INT64* wrapperId);
+    static IUnknown* GetIdentityForObject(_In_ OBJECTREF* objectPROTECTED, _In_ REFIID riid, _Out_ INT64* wrapperId, _Out_ bool* isAggregated);
     static bool HasManagedObjectComWrapper(_In_ OBJECTREF object, _Out_ bool* isActive);
 
 public: // GC interaction

src/coreclr/vm/interoplibinterface_comwrappers.cpp

@@ -53,6 +53,9 @@ namespace
             // The EOC is "detached" and no longer used to map between identity and a managed object.
             // This will only be set if the EOC was inserted into the cache.
             Flags_Detached = 8,
+
+            // This EOC is an aggregated instance
+            Flags_Aggregated = 16
         };
         DWORD Flags;
 
@@ -901,6 +904,12 @@ namespace
                             (uniqueInstance
                                 ? ExternalObjectContext::Flags_None
                                 : ExternalObjectContext::Flags_InCache);
+
+                if (flags & CreateObjectFlags::CreateObjectFlags_Aggregated)
+                {
+                    eocFlags |= ExternalObjectContext::Flags_Aggregated;
+                }
+
                 ExternalObjectContext::Construct(
                     resultHolder.GetContext(),
                     identity,
@@ -1774,7 +1783,7 @@ bool GlobalComWrappersForTrackerSupport::TryGetOrCreateObjectForComInstance(
         objRef);
 }
 
-IUnknown* ComWrappersNative::GetIdentityForObject(_In_ OBJECTREF* objectPROTECTED, _In_ REFIID riid, _Out_ INT64* wrapperId)
+IUnknown* ComWrappersNative::GetIdentityForObject(_In_ OBJECTREF* objectPROTECTED, _In_ REFIID riid, _Out_ INT64* wrapperId, _Out_ bool* isAggregated)
 {
     CONTRACTL
     {
@@ -1807,6 +1816,7 @@ IUnknown* ComWrappersNative::GetIdentityForObject(_In_ OBJECTREF* objectPROTECTE
     {
         ExternalObjectContext* context = reinterpret_cast<ExternalObjectContext*>(contextMaybe);
         *wrapperId = context->WrapperId;
+        *isAggregated = (context->Flags & ExternalObjectContext::Flags_Aggregated) != 0;
 
         IUnknown* identity = reinterpret_cast<IUnknown*>(context->Identity);
         GCX_PREEMP();

src/coreclr/vm/weakreferencenative.cpp

@@ -108,6 +108,7 @@ struct WeakHandleSpinLockHolder
 //
 // In order to qualify to be used with a HNDTYPE_WEAK_NATIVE_COM, the incoming object must:
 //  * be an RCW
+//  * not be an aggregated RCW
 //  * respond to a QI for IWeakReferenceSource
 //  * succeed when asked for an IWeakReference*
 //
@@ -149,7 +150,14 @@ NativeComWeakHandleInfo* GetComWeakReferenceInfo(OBJECTREF* pObject)
 #endif
     {
 #ifdef FEATURE_COMWRAPPERS
-        pWeakReferenceSource = reinterpret_cast<IWeakReferenceSource*>(ComWrappersNative::GetIdentityForObject(pObject, IID_IWeakReferenceSource, &wrapperId));
+        bool isAggregated = false;
+        pWeakReferenceSource = reinterpret_cast<IWeakReferenceSource*>(ComWrappersNative::GetIdentityForObject(pObject, IID_IWeakReferenceSource, &wrapperId, &isAggregated));
+        if (isAggregated)
+        {
+            // If the RCW is an aggregated RCW, then the managed object cannot be recreated from the IUnknown as the outer IUnknown wraps the managed object.
+            // In this case, don't create a weak reference backed by a COM weak reference.
+            pWeakReferenceSource = nullptr;
+        }
 #endif
     }
 
@@ -448,7 +456,7 @@ FCIMPL3(void, WeakReferenceNative::Create, WeakReferenceObject * pThisUNSAFE, Ob
     _ASSERTE(gc.pThis->GetMethodTable()->CanCastToClass(pWeakReferenceMT));
 
     // Create the handle.
-#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS) 
+#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS)
     NativeComWeakHandleInfo *comWeakHandleInfo = nullptr;
     if (gc.pTarget != NULL)
     {
@@ -690,7 +698,7 @@ FCIMPL1(Object *, WeakReferenceNative::GetTarget, WeakReferenceObject * pThisUNS
 
     OBJECTREF pTarget = GetWeakReferenceTarget(pThis);
 
-#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS) 
+#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS)
     // If we found an object, or we're not a native COM weak reference, then we're done.  Othewrise
     // we can try to create a new RCW to the underlying native COM object if it's still alive.
     if (pTarget != NULL || !IsNativeComWeakReferenceHandle(pThis->m_Handle))
@@ -718,7 +726,7 @@ FCIMPL1(Object *, WeakReferenceOfTNative::GetTarget, WeakReferenceObject * pThis
     OBJECTREF pTarget = GetWeakReferenceTarget(pThis);
 
 
-#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS) 
+#if defined(FEATURE_COMINTEROP) || defined(FEATURE_COMWRAPPERS)
     // If we found an object, or we're not a native COM weak reference, then we're done.  Othewrise
     // we can try to create a new RCW to the underlying native COM object if it's still alive.
     if (pTarget != NULL || !IsNativeComWeakReferenceHandle(pThis->m_Handle))

src/tests/Interop/COM/ComWrappers/WeakReference/WeakReferenceNative.cpp

@@ -167,8 +167,122 @@ namespace
             return UnknownImpl::DoRelease();
         }
     };
+
+    struct WeakReferenceSource : public IWeakReferenceSource, public IInspectable
+    {
+    private:
+        IUnknown* _outerUnknown;
+        ComSmartPtr<WeakReference> _weakReference;
+    public:
+        WeakReferenceSource(IUnknown* outerUnknown)
+            :_outerUnknown(outerUnknown),
+            _weakReference(new WeakReference(this, 1))
+        {
+        }
+
+        STDMETHOD(GetWeakReference)(IWeakReference** ppWeakReference)
+        {
+            _weakReference->AddRef();
+            *ppWeakReference = _weakReference;
+            return S_OK;
+        }
+
+        STDMETHOD(QueryInterface)(
+            /* [in] */ REFIID riid,
+            /* [iid_is][out] */ void ** ppvObject)
+        {
+            if (riid == __uuidof(IWeakReferenceSource))
+            {
+                *ppvObject = static_cast<IWeakReferenceSource*>(this);
+                _weakReference->AddStrongRef();
+                return S_OK;
+            }
+            return _outerUnknown->QueryInterface(riid, ppvObject);
+        }
+        STDMETHOD_(ULONG, AddRef)(void)
+        {
+            return _weakReference->AddStrongRef();
+        }
+        STDMETHOD_(ULONG, Release)(void)
+        {
+            return _weakReference->ReleaseStrongRef();
+        }
+
+        STDMETHOD(GetRuntimeClassName)(HSTRING* pRuntimeClassName)
+        {
+            return E_NOTIMPL;
+        }
+
+        STDMETHOD(GetIids)(
+            ULONG *iidCount,
+            IID   **iids)
+        {
+            return E_NOTIMPL;
+        }
+
+        STDMETHOD(GetTrustLevel)(TrustLevel *trustLevel)
+        {
+            *trustLevel = FullTrust;
+            return S_OK;
+        }
+    };
+
+    struct AggregatedWeakReferenceSource : IInspectable
+    {
+    private:
+        IUnknown* _outerUnknown;
+        ComSmartPtr<WeakReferenceSource> _weakReference;
+    public:
+        AggregatedWeakReferenceSource(IUnknown* outerUnknown)
+            :_outerUnknown(outerUnknown),
+            _weakReference(new WeakReferenceSource(outerUnknown))
+        {
+        }
+
+        STDMETHOD(GetRuntimeClassName)(HSTRING* pRuntimeClassName)
+        {
+            return E_NOTIMPL;
+        }
+
+        STDMETHOD(GetIids)(
+            ULONG *iidCount,
+            IID   **iids)
+        {
+            return E_NOTIMPL;
+        }
+
+        STDMETHOD(GetTrustLevel)(TrustLevel *trustLevel)
+        {
+            *trustLevel = FullTrust;
+            return S_OK;
+        }
+
+        STDMETHOD(QueryInterface)(
+            /* [in] */ REFIID riid,
+            /* [iid_is][out] */ void ** ppvObject)
+        {
+            if (riid == __uuidof(IWeakReferenceSource))
+            {
+                return _weakReference->QueryInterface(riid, ppvObject);
+            }
+            return _outerUnknown->QueryInterface(riid, ppvObject);
+        }
+        STDMETHOD_(ULONG, AddRef)(void)
+        {
+            return _outerUnknown->AddRef();
+        }
+        STDMETHOD_(ULONG, Release)(void)
+        {
+            return _outerUnknown->Release();
+        }
+    };
 }
 extern "C" DLL_EXPORT WeakReferencableObject* STDMETHODCALLTYPE CreateWeakReferencableObject()
 {
     return new WeakReferencableObject();
 }
+
+extern "C" DLL_EXPORT AggregatedWeakReferenceSource* STDMETHODCALLTYPE CreateAggregatedWeakReferenceObject(IUnknown* pOuter)
+{
+    return new AggregatedWeakReferenceSource(pOuter);
+}