C++: What is CRTP (Curiously Recurring Template Pattern)?

CRTP — derived class passes itself as template argument.

1template <typename Derived>
2class Base {
3public:
4    void interface() {
5        static_cast<Derived*>(this)->implementation();
6    }
7};
8
9class MyClass : public Base<MyClass> {
10public:
11    void implementation() { /* ... */ }
12};

Benefits:

• Static polymorphism (no vtable overhead)
• Compile-time polymorphism
• Can be inlined

Use cases:

• Static polymorphism
• Mixins
• Expression templates
• Avoiding virtual function overhead

vs virtual:

• CRTP: compile-time, no overhead
• Virtual: runtime, flexible