Modern C++ singleton

singleton.cpp

#include <iostream>

class singleton_interface {
  public:
	virtual ~singleton_interface() = default;
	virtual void do_something() const = 0;
};

class singleton : public singleton_interface {
  public:
	void do_something() const override { std::cout << "singleton::do_something()\n"; }
};

singleton_interface *instance = nullptr;

singleton_interface *get_singleton_interface() {
	static bool init = []() {
		if (!instance) {
			static singleton s;
			instance = &s;
		}
		return true;
	}();
	return instance;
}
void set_singleton_interface(singleton_interface *persistence) { instance = persistence; }

int main() { get_singleton_interface()->do_something(); }