Chapter 8, The Curiously Recurring Template Pattern

1. While not very expensive in absolute numbers (a few nanoseconds at most), a virtual function call is several times more expensive than a non-virtual one, and could easily be an order of magnitude or more slower than an inlined function call. The overhead comes from the indirection: a virtual function is always invoked by a function pointer, and the actual function is unknown at compile time and cannot be inlined.
2. If the compiler knows the exact function that is going to be called, it can optimize away the indirection and may be able to inline the function.
3. Just like the runtime polymorphic calls are made through the pointer to the base class, the static polymorphic calls must be also made through a pointer or reference to the base class. In the case of CRTP and static polymorphism, the base type is actually a whole collection of types generated by the base class template, one for each derived class. To make a polymorphic...