Calling `IMMDevice.Activate()` results in a NullReferenceException about cswin32 HOT 4 CLOSED

I hit this as well. The nullable pActivationParams isn't being handled correctly here, ends up trying to access pActivationParams.HasValue.

Poking @AArnott for prioritization 😅

from cswin32.

This bug was surprisingly difficult to solve.

from cswin32.

I don't think there's anything wrong with calling pActivationParams.HasValue in the friendly overload, as that is a nullable struct, so it can't throw NRE.

I suspect the issue is that the .NET interop layer cannot handle a null reference passed into an in struct parameter on a COM interface. That seems unfortunate because the COM side should only need the address, and taking the address of a null reference is allowed in C# and produces a null pointer as intended.

But on the flip side, I don't know why CsWin32 is generating the COM interface with an in PROPVARIANT rather than PROPVARIANT* in the first place. Given it's an [Optional] parameter, CsWin32 should be (I think) be preferring pointers. That's the first thing I'll look into.

from cswin32.

Yay, thanks @AArnott. Will try it out tonight.

from cswin32.