std::lock_guard shared_ptr

 

 

#include <iostream>
#include <memory>
#include <thread>
#include <chrono>
#include <mutex>

struct Test
{
    Test() { std::cout << "  Test::Test()\n"; }
    ~Test() { std::cout << "  Test::~Test()\n"; }
};

//线程函数
void thr(std::shared_ptr<Test> p)
{
    //线程暂停1s
    std::this_thread::sleep_for(std::chrono::seconds(1));

    //赋值操作, shared_ptr引用计数use_cont加1(c++11中是原子操作)
    std::shared_ptr<Test> lp = p;
    {
        //static变量(单例模式),多线程同步用
        static std::mutex io_mutex;

        //std::lock_guard加锁
        std::lock_guard<std::mutex> lk(io_mutex);
        std::cout << "local pointer in a thread:\n"
                  << "  lp.get() = " << lp.get()
                  << ", lp.use_count() = " << lp.use_count() << '\n';
    }
}

int main()
{
    //使用make_shared一次分配好需要内存
    std::shared_ptr<Test> p = std::make_shared<Test>();
    //std::shared_ptr<Test> p(new Test);

    std::cout << "Created a shared Test\n"
              << "  p.get() = " << p.get()
              << ", p.use_count() = " << p.use_count() << '\n';

    //创建三个线程,t1,t2,t3
    //形参作为拷贝, 引用计数也会加1
    std::thread t1(thr, p), t2(thr, p), t3(thr, p);
    std::cout << "Shared ownership between 3 threads and released\n"
              << "ownership from main:\n"
              << "  p.get() = " << p.get()
              << ", p.use_count() = " << p.use_count() << '\n';
    //等待结束
    t1.join(); t2.join(); t3.join();
    std::cout << "All threads completed, the last one deleted\n";

    return 0;
}

 

 

root@ubuntu:~/c++# ./share4
  Test::Test()
Created a shared Test
  p.get() = 0xaaaaccc75e80, p.use_count() = 1
Shared ownership between 3 threads and released
ownership from main:
  p.get() = 0xaaaaccc75e80, p.use_count() = 4
local pointer in a thread:
  lp.get() = 0xaaaaccc75e80, lp.use_count() = 5
local pointer in a thread:
  lp.get() = 0xaaaaccc75e80, lp.use_count() = 4
local pointer in a thread:
  lp.get() = 0xaaaaccc75e80, lp.use_count() = 3
All threads completed, the last one deleted
  Test::~Test()

 

#include <iostream>
#include <memory>
#include <thread>
#include <chrono>
#include <mutex>

struct Test
{
    Test() { std::cout << "  Test::Test()\n"; }
    ~Test() { std::cout << "  Test::~Test()\n"; }
};

//线程函数
void thr(std::shared_ptr<Test> p)
{
    //线程暂停1s
    std::this_thread::sleep_for(std::chrono::seconds(1));

    //赋值操作, shared_ptr引用计数use_cont加1(c++11中是原子操作)
    std::shared_ptr<Test> lp = p;
    {
        //static变量(单例模式),多线程同步用
        static std::mutex io_mutex;

        //std::lock_guard加锁
        std::lock_guard<std::mutex> lk(io_mutex);
        std::cout << "local pointer in a thread:\n"
                  << "  lp.get() = " << lp.get()
                  << ", lp.use_count() = " << lp.use_count() << '\n';
    }
}

int main()
{
    //使用make_shared一次分配好需要内存
    std::shared_ptr<Test> p = std::make_shared<Test>();
    //std::shared_ptr<Test> p(new Test);

    std::cout << "Created a shared Test\n"
              << "  p.get() = " << p.get()
              << ", p.use_count() = " << p.use_count() << '\n';

    //形参作为拷贝, 引用计数也会加1
    std::thread t1(thr, p);
    std::cout << "Shared ownership between 3 threads and released\n"
              << "ownership from main:\n"
              << "  p.get() = " << p.get()
              << ", p.use_count() = " << p.use_count() << '\n';
    std::cout << "All threads completed, the last one deleted\n";
     t1.join();
    return 0;
}

 

 

 Test::Test()
Created a shared Test
  p.get() = 0xaaaadf9e3e80, p.use_count() = 1
Shared ownership between 3 threads and released
ownership from main:
  p.get() = 0xaaaadf9e3e80, p.use_count() = 2
All threads completed, the last one deleted
local pointer in a thread:
  lp.get() = 0xaaaadf9e3e80, lp.use_count() = 3
  Test::~Test()