All base classes of an exportable class must be exportable. If not, a compiler warning is generated. Moreover, all accessible members that are also classes must be exportable. This rule permits a dllexport class to inherit from a dllimport class, and a dllimport class to inherit from a dllexport class (though the latter is not recommended). As a rule, everything that is accessible to the DLL’s client (according to C++ access rules) should be part of the exportable interface. This includes private data members referenced in inline functions.