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 <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;
}
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));
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