CPlusPlusThings/learn_class/modern_cpp_30/memorymodel_atomic/iazysingleton.cpp

//
// Created by light on 20-2-6.
//

class singleton {
private:
    singleton() {}
    static singleton *p;
public:
    static singleton *instance();
};

singleton *singleton::p = nullptr;

singleton* singleton::instance() {
    if (p == nullptr)
        p = new singleton();
    return p;
}