Where is ID3D11DeviceChild::GetPrivateDataInterface?

ID3D11DeviceChild similarly to a few other related interfaces offers methods including:

SetPrivateDataInterface option extends SetPrivateData by adding COM reference management to application defined data. However there is no GetPrivateDataInterface… A reasonable assumption is that it is a single collection of keyed application defined data so it is possible to read interface values using GetPrivateData method. The behavior should have been documented to avoid confusion.

I would perhaps not have posted this if there was no additional aspect. If I could read my interface values attached by SetPrivateDataInterface using GetPrivateData method, should I expect the returned values to be IUnknown::AddRef‘ed or not?

ID3D11DeviceChild* p = …
IUnknown* pUnknownA = …
p->SetPrivateDataInterface(__uuidof(MyKey), pUnknownA);
IUnknown* pUnknownB;
UINT nDataSize = sizeof pUnknownB;
p->GetPrivateData(__uuidof(MyKey), &nDataSize, &pUnknownB);
// QUES: pUnknownB is AddRef'ed or not?

It is indeed possible to retrieve the interface data. With no documented behavior I would expect no IUnknown::AddRef to be done. Rationale: after all I am using the method from the pair which is not supposed to deal with interface pointers. An argument against is that even though taking a raw copy of pointer is not a big deal, in multi-thread environment it might so happen that the returned unreferenced pointer is gone and invalidated if a concurrent thread replaces the collection value and internal IUnknown::Release on the pointer results in object disposal.

My guess on the behavior in part of COM referencing was incorrect: the API does do IUnknown::AddRef. Also this behavior is documented in the DXGI section for IDXGIObject::GetPrivateData method:

If the data returned is a pointer to an IUnknown, or one of its derivative classes, previously set by IDXGIObject::SetPrivateDataInterface, you must call ::Release() on the pointer before the pointer is freed to decrement the reference count.

Presumably the same behavior applies to APIs having no explicitly mentioned documented behavior, including ID3D11Device::GetPrivateData method, ID3D12Object::GetPrivateData method and other.

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