C++11创建线程的三种方式

1. 通过函数

thread：标准库的类
join：阻塞主线程并等待

// MultiThread.cpp : Defines the entry point for the console application.
#include "stdafx.h"
#include<iostream>
#include<vector>
#include<map>
#include<string> 
#include<thread>

using namespace std;
void myPrint()
{
    cout << "线程开始运行" << endl;
    cout << "线程运行结束了" << endl;

}

int main()
{
    std::thread my2Obj(myPrint);  // 可调用对象
    my2Obj.join();// 主线程阻塞在这，并等待myPrint()执行完
    cout << "wangtao" << endl;
    return 0;
}

detach(): 将主线程和子线程完全分离，子线程会驻留在后台运行,被C++运行时库接管，失去控制

void myPrint()
{
    cout << "线程开始运行1" << endl;
    cout << "线程开始运行2" << endl;
    cout << "线程开始运行3" << endl;
    cout << "线程开始运行4" << endl;
    cout << "线程开始运行5" << endl;
    cout << "线程开始运行6" << endl;
    cout << "线程开始运行7" << endl;
    cout << "线程开始运行8" << endl;
    cout << "线程开始运行9" << endl;

}

int main()
{
    std::thread my2Obj(myPrint); // 主线程阻塞在这，并等待myPrint()执行完
    my2Obj.detach();
    cout << "wangtao1" << endl;
    cout << "wangtao2" << endl;
    cout << "wangtao3" << endl;
    cout << "wangtao4" << endl;
    cout << "wangtao5" << endl;
    cout << "wangtao6" << endl;
    cout << "wangtao7" << endl;
    cout << "wangtao8" << endl;
    return 0;
}

joinable()：判断是否可以成功使用join()或者detach()

程序说明：detach后不能在实施join

int main()
{
    std::thread my2Obj(myPrint); // 主线程阻塞在这，并等待myPrint()执行完
    if (my2Obj.joinable()){
        cout << "1:joinable() == true" << endl;
    }
    else {
        cout << "1:joinable() == false" << endl;
    }
    my2Obj.detach();

    if (my2Obj.joinable()) {
        cout << "2:joinable() == true" << endl;
    }
    else {
        cout << "2:joinable() == false" << endl;
    }
    cout << "wangtao1" << endl;
    cout << "wangtao2" << endl;
    cout << "wangtao3" << endl;
    cout << "wangtao4" << endl;
    cout << "wangtao5" << endl;
    cout << "wangtao6" << endl;
    cout << "wangtao7" << endl;
    cout << "wangtao8" << endl;
    return 0;
}

int main()
{
    std::thread my2Obj(myPrint); // 主线程阻塞在这，并等待myPrint()执行完
    if (my2Obj.joinable()){
        my2Obj.join();
    }
    cout << "wangtao1" << endl;
    cout << "wangtao2" << endl;
    cout << "wangtao3" << endl;
    cout << "wangtao4" << endl;
    cout << "wangtao5" << endl;
    cout << "wangtao6" << endl;
    cout << "wangtao7" << endl;
    cout << "wangtao8" << endl;
    return 0;
}

2.通过类对象创建线程

class CObject
{
public:
    void operator ()() {
        cout << "线程开始运行" << endl;
        cout << "线程结束运行" << endl;
    }
};


int main()
{
    CObject obj;
    std::thread my2Obj(obj); // 主线程阻塞在这，并等待myPrint()执行完
    if (my2Obj.joinable()){
        my2Obj.join();
    }
    cout << "see you " << endl;
    
    return 0;
}

class CObject
{
    int& m_obj;
public:
    CObject(int& i) :m_obj(i) {}
    void operator ()() { // 不带参数
        cout << "线程开始运行1" << endl;
        cout << "线程开始运行2" << endl;
        cout << "线程开始运行3" << endl;
        cout << "线程开始运行4" << endl;
        cout << "线程开始运行5" << endl;
    }
};
int main()
{
    int i = 6;
    CObject obj(i);
    std::thread my2Obj(obj); // 主线程阻塞在这，并等待myPrint()执行完
    if (my2Obj.joinable()){
        my2Obj.detach();
    }
    cout << "see you " << endl;
    
    return 0;
}

用detach() 主线程结束对象即被销毁，那么子线程的成员函数还能调用吗？

这里的的对象会被复制到子线程中，当主线程结束，复制的子线程对象并不会被销毁

只要是没有引用、指针就不会出现问题

通过复制构造函数和析构函数来验证对象是否复制到了子线程中

// MultiThread.cpp : Defines the entry point for the console application.
//

#include "stdafx.h"
#include<iostream>
#include<vector>
#include<map>
#include<string> 
#include<thread>
using namespace std;
class CObject
{
    int& m_obj;
public:
    CObject(int& i) :m_obj(i) {
        cout << "ctor" << endl;
    }
    CObject(const CObject& m) :m_obj(m.m_obj) {
        cout << "copy ctor" << endl;
    }
    ~CObject(){
        cout << "dtor" << endl;
    }
    void operator ()() { // 不带参数
        cout << "线程开始运行1" << endl;
        cout << "线程开始运行2" << endl;
        cout << "线程开始运行3" << endl;
        cout << "线程开始运行4" << endl;
        cout << "线程开始运行5" << endl;
    }
};
int main()
{
    int i = 6;
    CObject obj(i);
    std::thread my2Obj(obj); // 主线程阻塞在这，并等待myPrint()执行完
    if (my2Obj.joinable()){
        my2Obj.detach();
    }
    cout << "see you " << endl;
    
    return 0;
}

子线程的析构函数在后台执行，所以输出的dtor是主线程的。用join() 结果为：

3.通过lambda表达式创建线程

int main()
{
    auto myLamThread = [] {
        cout << "线程开始运行" << endl;
        cout << "线程结束运行" << endl;
    };
    thread cthread(myLamThread);
    cthread.join();
    std::cout << "see you " << endl;
    
    return 0;
}