std::thread::joinable

 

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std::swap(std::thread)

 

bool joinable() const noexcept;		(C++11 起)

检查 std::thread 对象是否标识活跃的执行线程。具体而言，若 get_id() != std::thread::id() 则返回 true 。故默认构造的 thread 不可结合。

结束执行代码，但仍未结合的线程仍被当作活跃的执行线程，从而可结合。

参数

（无）

返回值

若 thread 对象标识活跃的执行线程则为 true ，否则为 false 。

示例

运行此代码

#include <iostream>
#include <thread>
#include <chrono>
 
void foo()
{
    std::this_thread::sleep_for(std::chrono::seconds(1));
}
 
int main()
{
    std::thread t;
    std::cout << "before starting, joinable: " << std::boolalpha << t.joinable()
              << '\n';
 
    t = std::thread(foo);
    std::cout << "after starting, joinable: " << t.joinable() 
              << '\n';
 
    t.join();
    std::cout << "after joining, joinable: " << t.joinable() 
              << '\n';
}

输出：

before starting, joinable: false
after starting, joinable: true
after joining, joinable: false

引用

• C++20 标准（ISO/IEC 14882:2020）：

• 32.4.2.5 Members [thread.thread.member]

• C++17 标准（ISO/IEC 14882:2017）：

• 33.3.2.5 thread members [thread.thread.member]

• C++14 标准（ISO/IEC 14882:2014）：

• 30.3.1.5 thread members [thread.thread.member]

• C++11 标准（ISO/IEC 14882:2011）：

• 30.3.1.5 thread members [thread.thread.member]

参阅

get_id	返回线程的 id (公开成员函数)
join	等待线程完成其执行 (公开成员函数)
detach	容许线程从线程句柄独立开来执行 (公开成员函数)