multithreading - 为什么我不能像这样动态创建线程向量

Question

为什么动态创建线程向量是错误的？我收到编译错误

C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\include\xmemory0(593):错误 C2280:'std::thread::thread(const std::thread &)':试图引用已删除的函数

其次是很多其他的东西。

#include <iostream>
#include <thread>
#include <vector>

using std::vector;
using std::thread;
using std::cout;

class obj_on_thread {
public:
    void operator()()
    {
        std::cout << "obj on thread\n";
    }
};

void function_on_thread() {
    std::cout << "function on thread\n";
}

auto named_lambda = []() { std::cout << "named_lambda_on_thread\n"; };

int main(){
    obj_on_thread obj;

    vector<thread> pool {
        thread{ obj },
        thread{ function_on_thread },
        thread{ named_lambda },
        thread{ []() { cout << "anonymous lambda on thread\n"; } }
    };
    cout << "main thread\n";

    for(auto& t : pool)
    {
        if (t.joinable())
        {
            cout << "Joinable = true";
            t.join(); //if called must be called once.
        }
        else
        {
            cout << "this shouldn't get printed, joinable = false\n";
        }
    }
    for (auto& t : pool)
    {
        if (t.joinable())
        {
            cout << " This won't be printed Joinable = true";
        }
        else
        {
            cout << "joinable = false thread are already joint\n";
        }
    }

    return 0;
}

Answer 1

std::vector的构造函数使用 initializer_list要求元素是可复制构造的，因为 initializer_list本身要求(它的底层“存储”被实现为一个复制构造的临时数组)。 std::thread不可复制构造(此构造函数被删除)。

http://en.cppreference.com/w/cpp/utility/initializer_list

The underlying array is a temporary array, in which each element is copy-initialized...

没有解决这个问题的好方法 - 您不能一次初始化所有线程，但您可以使用(多次调用，每个线程一个 - 不幸的是):

emplace_back() :

pool.emplace_back(obj);

push_back()带有右值:

pool.push_back(thread{obj});

push_back()与明确 move() s:

auto t = thread{obj};
pool.push_back(std::move(t));