/sys$common/syshlp/helplib.hlb CC, Messages, INCOMPVALUE  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        <Context> "<expression>" has incomplete type, and so
                cannot be used as an rvalue.

 Description    It is not possible to get the value of an expression
                with incomplete type.

 User Action    Complete the type before its value is used.