Failed to pass object reference from my DLL to UE4 Project


I am trying to import my own developed DLL into UE4 C++ Plugin Project. So far I could pass reference of basic data structures to Plugin ( like int, size_t ), But failed to pass self-defined class reference to Plugin ( User in this case, which is defined in my include file ).

UE4 just crashed when I click “Play”. I am not falimiar with UE4 troubleshooting ( any comment, please help ), I don’t where to start debugging in this case, look forward to your response.

Successful Case:
DLL Interface :
void abc(size_t& u);
In Plugin:
size_t u=0;

Failure Case:
DLL Interface :
void abc(User& u);
In Plugin:
User u;

Environment: Windows 10
UE: 4.10.4

If possible can you post the text output when you press Play?

I checked log in Folder “Saved” and didn’t find any useful information. Is there any other log I can use?

Because of the schedule issue, I just replace Object User with several IN&, char&.
Hope someone will help to answer, so that I could make it clear.