#892 Microsoft::WRL::ComPtr::Attach leaks references

[Jose Fonseca]

MinGW implementation of Microsoft::WRL::ComPtr::Attach leaks references.

https://docs.microsoft.com/en-us/cpp/cppcx/wrl/comptr-class?view=msvc-160#attach is not specific, but https://github.com/microsoft/DirectX-Headers/blob/2620a5ca8af6cb524f0ee77ffb9195edbc12be98/include/wsl/wrladapter.h#L293-L305 clearly shows that ComPtr should assume the given COM object pointer without increasing its reference count. But that's not what MinGW implementation does.

I've attached a test case.

I think the fix should be trivial, something like

diff --git a/mingw-w64-headers/include/wrl/client.h b/mingw-w64-headers/include/wrl/client.h
index 12239e108..aeb886ea8 100644
--- a/mingw-w64-headers/include/wrl/client.h
+++ b/mingw-w64-headers/include/wrl/client.h
@@ -206,7 +206,6 @@ namespace Microsoft {
                 if (ptr_ != other) {
                     InternalRelease();
                     ptr_ = other;
-                    InternalAddRef();
                 }
             }

Detach implementation looks alright AFAICS.

[Jose Fonseca]

https://github.com/Microsoft/DirectXTK/wiki/ComPtr#constructing-assigning-and-copying-comptr also makes this explicit. It says:

If you want to give a raw pointer to a ComPtr without changing the reference count, you need to use Attach.