Rule 18-4-1 (ban of dynamic heap memory allocation)

[shanz]

One of the most commonly quoted advantages of object orientation is polymorphism.
C++ often relies on dynamically allocated pointers to achieve (run-time) polymorphism.

How can polymorphism be achieved without resorting to dynamic memory allocation?
I suspect that preallocating pointers on the stack is the answer but can someone please write some example code?

Thanks.