C++11threadjoinable(5)

2016-02-24

字数统计: 671字 | 阅读时长≈ 3分

原文地址：http://www.cplusplus.com/reference/thread/thread/joinable/

public member function

std::thread::joinable

bool joinable() const noexcept;

Check if joinable

Returns whether the thread object is joinable.

返回线程对象是否是joinable的。

A thread object is joinable if it represents a thread of execution.

如果是一个正在执行的线程，那么它是joinable的。

A thread object is not joinable in any of these cases:

下列任一情况都是非joinable

if it was default-constructed.
默认构造器构造的。
if it has been moved from (either constructing another thread object, or assigning to it).
通过移动构造获得的。
if either of its members join or detach has been called.
调用了join或者detach方法的。

例子：

#include
#include
#include
using namespace std;
void delay(double sec)
{
time_t start_time, cur_time; // 变量声明
time(&start_time);
do {
time(&cur_time);
}while((cur_time - start_time) < sec );
};

void show(int n){
cout<<”n=”<<n<<endl;
}
thread returnThread(){
thread tt(show,10);
return tt;
}

int main()
{

thread t(show,18);
cout<<”t is joinable? “<<t.joinable()<<endl;

thread t1(returnThread());
cout<<”t1 is joinable? “<<t1.joinable()<<endl;

thread t2(show,3);
cout<<”t2 is joinable? “<<t2.joinable()<<endl;
t2.join();
cout<<”after t2.join(),t2 is joinable? “<<t2.joinable()<<endl;

thread t3(show,5);
cout<<”t3 is joinable? “<<t3.joinable()<<endl;
t3.detach();
cout<<”after t3.detach(),t3 is joinable? “<<t3.joinable()<<endl;

}

运行结果：

用GDB调试发现一个好神奇的东西。

运行完了

cout<<”after t3.detach(),t3 is joinable? “<<t3.joinable()<<endl;

之后，居然像栈析解一样，好神奇阿，现在还不知道为什么呢。。

先保留着，下次解决。

Parameters

none

Return value

true if the thread is joinable.
false otherwise.

Example

// example for thread::joinable
#include <iostream>       // std::cout
#include <thread>         // std::thread
 
void mythread() 
{
  // do stuff...
}
 
int main() 
{
  std::thread foo;
  std::thread bar(mythread);

  std::cout << "Joinable after construction:\n" << std::boolalpha;
  std::cout << "foo: " << foo.joinable() << '\n';
  std::cout << "bar: " << bar.joinable() << '\n';

  if (foo.joinable()) foo.join();
  if (bar.joinable()) bar.join();

  std::cout << "Joinable after joining:\n" << std::boolalpha;
  std::cout << "foo: " << foo.joinable() << '\n';
  std::cout << "bar: " << bar.joinable() << '\n';

  return 0;
}