c++11特性之std::thread–初识
最后更新于：2022-04-01 06:32:03
C++11中已经拥有了一个更好用的用于线程操作的类`std::thread`。
默认构造函数：
thread() noexcept;
构造一个任何线程不执行的线程对象。
初始化函数：
~~~
template <class Fn, class... Args>
explicit thread (Fn&& fn, Args&&... args);
~~~
构造一个线程对象，可以开启线程执行
新执行的线程调用函数fn，并传递args作为参数
fn
可以指向函数，指向成员，或是移动构造函数
args…
传递给fn的参数，这些参数可以移动赋值构造。如果fn是一个成员指针，那么第一个args参数就必须是一个对象，或是引用，或是指向该对象的指针。
拷贝构造函数：
thread (const thread&) = delete;
删除构造的线程
现在介绍几个成员函数：
**std::thread::join**
该函数返回时，线程执行完成。
当 a thread 调用Join方法的时候，MainThread 就被停止执行，直到 a thread 线程执行完毕。
~~~
#include <iostream> // std::cout
#include <thread> // std::thread, std::this_thread::sleep_for
#include <chrono> // std::chrono::seconds
void pause_thread(int n)
{
std::this_thread::sleep_for (std::chrono::seconds(n));
std::cout << "pause of " << n << " seconds ended\n";
}
int main()
{
std::cout << "Spawning 3 threads...\n";
std::thread t1 (pause_thread,1);
std::thread t2 (pause_thread,2);
std::thread t3 (pause_thread,3);
std::cout << "Done spawning threads. Now waiting for them to join:\n";
t1.join();
t2.join();
t3.join();
std::cout << "All threads joined!\n";
return 0;
}
//输出
Output (after 3 seconds):
Spawning 3 threads...
Done spawning threads. Now waiting for them to join:
pause of 1 seconds ended
pause of 2 seconds ended
pause of 3 seconds ended
All threads joined!
~~~
**std::thread::detach**
分离线程的对象，使它们从彼此独立地执行所表示的线程。这两个线程继续没有阻止，也没有以任何方式同步。注意，当任一结束执行，其资源被释放。
~~~
#include <iostream> // std::cout
#include <thread> // std::thread, std::this_thread::sleep_for
#include <chrono> // std::chrono::seconds
void pause_thread(int n)
{
std::this_thread::sleep_for (std::chrono::seconds(n));
std::cout << "pause of " << n << " seconds ended\n";
}
int main()
{
std::cout << "Spawning and detaching 3 threads...\n";
std::thread (pause_thread,1).detach();
std::thread (pause_thread,2).detach();
std::thread (pause_thread,3).detach();
std::cout << "Done spawning threads.\n";
std::cout << "(the main thread will now pause for 5 seconds)\n";
// give the detached threads time to finish (but not guaranteed!):
pause_thread(5);
return 0;
}
//输出
Output (after 5 seconds):
Spawning and detaching 3 threads...
Done spawning threads.
(the main thread will now pause for 5 seconds)
pause of 1 seconds ended
pause of 2 seconds ended
pause of 3 seconds ended
pause of 5 seconds ended
~~~
上一段代码 深入理解：
~~~
#include <iostream>
#include <thread>
using namespace std;
class Foo
{
void bar_i() { cout << "hello" << endl; }
public:
void bar()
{
auto func = std::bind(&Foo::bar_i, this);
std::thread t(&Foo::bar_i, std::ref(*this));
t.join();
}
};
int main()
{
Foo f;
f.bar();
}
~~~
如果你使用的是VS2015，那么恭喜你，上面的代码你不会运行成功。