c++11标准库新增的thread类开始执行的时间？

Question

请问一下C++11中<thread>的，thread具体是什么时候执行赋予它的函数？
相关代码如下：

#include <iostream>
#include <thread>

void hello()
{
    std::cout << "Hello Current World!" << std::endl;
}

int main()
{
    std::thread t(hello);
    std::cout << "before: " << std::endl;
    t.join();
    std::cout << "after: "  << std::endl;
    return 0 ;
}

在windows平台上，IDE DEV-C++，编译器TDM-GCC 5.10,执行程序的结果有可能为

在linux(ubuntu)上，编译器g++ (Ubuntu 5.3.1-14ubuntu2.1) 5.3.1 20160413
执行程序执行了20~30遍一直是

也曾经尝试过直接把t.join()直接注释掉，两个平台都会崩溃，但是windows还是会先输出Hello Current World!之后崩溃，而linux只输出了before和after

看过cppreference里面相关的内容,好像是说在构造函数如果有赋予入口函数的话就会直接开始执行？不过linux里面好像是直到调用join函数或者detach函数才会开始执行？

Answer 1

If you pass in the routine to be executed in the constructor, the thread will start executing after the thread object is created. If you just create a thread object:

thread t;

Then this thread will not start until you assign a routine to this object. The reason why
crashes is that if the thread object does not join or detach before is destructed , then std::terminate will be called to terminate the program (you can look at the destructor implementation of thread), GCC Implementation of:

 ~thread()
    {
      if (joinable())
          std::terminate();
    }

Answer 2

Add a line get char()

The child threads are not running, and the main thread has exited.