Why can't I create a vector of threads on the fly like this

Question

Why is creation of vector of threads on the fly is wrong ? I am getting compilation error C:\Program Files (x86)\Microsoft Visual Studio 12.0\VC\include\xmemory0(593): error C2280: 'std::thread::thread(const std::thread &)' : attempting to reference a deleted function followed by a lot of other stuff. ``` #include #include #include using std::vector; using std::thread; using std::cout; class obj_on_thread { public: void operator()() { std::cout << "obj on thread "; } }; void function_on_thread() { std::cout << "function on thread "; } auto named_lambda = []() { std::cout << "named_lambda_on_thread "; }; int main(){ obj_on_thread obj; vector pool { thread{ obj }, thread{ function_on_thread }, thread{ named_lambda }, thread{ []() { cout << "anonymous lambda on thread "; } } }; cout << "main thread "; for(auto& t : pool) { if (t.joinable()) { cout << "Joinable = true"; t.join(); //if called must be called once. } else { cout << "this shouldn't ge…

Accepted Answer

`std::vector`'s constructor which uses `initializer_list` requires the elements to be copy-constructible, because `initializer_list` itself requires that (its underlying "storage" is implemented as a temporary array which is copy-constructed). `std::thread` is not copy-constructible (this constructor is deleted).

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

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

There's no good way to solve this problem - you cannot initialize all your threads at once, but you can use (multiple calls, one for each thread - unfortunately):

`emplace_back()`:

```
pool.emplace_back(obj);
```

`push_back()` with rvalues:

```
pool.push_back(thread{obj});
```

`push_back()` with explicit `move()`s:

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

Why can't I create a vector of threads on the fly like this

Solution

Problem