Why is the virtual keyword needed?

Question

In other words, why doesn\'t the compiler just \"know\" that if the definition of a function is changed in a derived class, and a pointer to dynamically allocated memory of

Answer 1

One of the main designing principles of C++ is that C++ does not incur overhead for features that are not used (the "zero-overhead principle"). This is because of a focus on high performance

This is why you need to opt in to features like virtual functions while in languages like Java, functions are virtual by default.