C++ 11原子和侵入式共享指针引用计数

#include <iostream>
#include <atomic>

std::atomic<int> counter(0);

void increment() {
    counter.fetch_add(1);
}

int main() {
    std::thread t1(increment);
    std::thread t2(increment);
    t1.join();
    t2.join();
    std::cout << counter << std::endl;
    return 0;
}

#include <iostream>
#include <shared_ptr>

class MyClass {
public:
    MyClass() { std::cout << "MyClass 构造函数" << std::endl; }
    ~MyClass() { std::cout << "MyClass 析构函数" << std::endl; }
};

int main() {
    std::shared_ptr<MyClass> obj1(new MyClass());
    std::shared_ptr<MyClass> obj2 = obj1;
    std::cout << "obj1 的引用计数: " << obj1.use_count() << std::endl;
    std::cout << "obj2 的引用计数: " << obj2.use_count() << std::endl;
    return 0;
}

#include <iostream>
#include <memory>

class MyClass {
public:
    MyClass() { std::cout << "MyClass 构造函数" << std::endl; }
    ~MyClass() { std::cout << "MyClass 析构函数" << std::endl; }
};

int main() {
    std::shared_ptr<MyClass> obj1(new MyClass());
    std::shared_ptr<MyClass> obj2 = obj1;
    std::cout << "obj1 的引用计数: " << obj1.use_count() << std::endl;
    std::cout << "obj2 的引用计数: " << obj2.use_count() << std::endl;

    // 创建一个弱指针，用于解决循环引用问题
    std::weak_ptr<MyClass> obj3 = obj1;

    if (obj3.expired()) {
        std::cout << "obj3 已过期, 无效" << std::endl;
    } else {
        std::shared_ptr<MyClass> obj3_shared = obj3.lock();
        std::cout << "obj3 的引用计数: " << obj3_shared.use_count() << std::endl;
    }

    return 0;
}