VMS Help CC, Messages, TAGDIFFER  *Conan The Librarian (sorry for the slow response - running on an old VAX)

 Message        <Context> the tag "<name>" differs from the tag
                "<name>" used in an earlier declaration of this
                function.

 Description    This function declaration contains a parameter that
                is a pointer to a struct or union type whose tag
                differs from the tag of the struct or union type
                referenced by a pointer type in an earlier
                declaration of this function.  In most modes of the
                compiler, this will cause the function declarations
                to be incompatible.

 User Action    Multiple declarations of a function should use
                exactly the same parameter types.