Operator dynamic_cast<> fails when it cannot convert its argument to the desired type. Usually, such a failure results from an attempt to cast an object to a non-related class. But there can be another reason for it–an attempt to cast a derived object to its base class will fail in case of private inheritance:
class Container {/*..*/ };class Allocator{/*..*/};class Stack: public Container, private Allocator {/*..*/ }; void main(){ Stack s; Allocator* p = dynamic_cast (&s); // runtime failure; Allocator is an inaccessible base} In this example, dynamic_cast fails because Stack is not publicly derived from Allocator.
