The specified base class is accessible (as defined in “Pointers to Classes”).A reference to a class can be converted to a reference to a base class in the following cases:
The specified base class is accessible (as defined in “Pointers to Classes”).
The conversion is unambiguous. (See “Multiple Base Classes” in Chapter 9, on topic for more information about ambiguous base-class references.)
The result of the conversion is a pointer to the subobject that represents the base class.
For more information about references, see “References to Objects” in Chapter 2, on topic .