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//0x20 bytes (sizeof)
struct _DIAGNOSTIC_CONTEXT
{
    enum _REQUESTER_TYPE CallerType;                                        //0x0
    union
    {
        struct
        {
            struct _EPROCESS* Process;                                      //0x8
            ULONG ServiceTag;                                               //0x10
        };
        struct _DEVICE_OBJECT* DeviceObject;                                //0x8
    };
    ULONGLONG ReasonSize;                                                   //0x18
};