msdn：
     

HRESULT

An opaque result handle defined to be zero for a successful return from a function and nonzero if error or status information is returned. To convert an HRESULT into the more detailed SCODE, applications call GetScode(). See also SCODE.

感觉就有点类似于指针中的void类型，而HRESULT是句柄中的void，只不过他用于返回值，回调函数中就有的用，不知对否，高手说声哈