Passing a reference of a vector element to a threaded function - c++

Question

I'm trying to do something like this:
#include <thread>
#include <vector>
void foo(bool &check){
}
int main(){
std::vector<bool> vec(1);
std::thread T(foo, std::ref(vec[0]));
}
Unfortunately gcc throws an error:
prog.cpp: In function 'int main()':
prog.cpp:10:34: error: use of deleted function 'void std::ref(const _Tp&&) [with _Tp = std::_Bit_reference]'
std::thread(foo, std::ref(vec[1]))
^
In file included from /usr/include/c++/4.9/thread:39:0,
from prog.cpp:1:
/usr/include/c++/4.9/functional:453:10: note: declared here
void ref(const _Tp&&) = delete;
However it works with a normal variable:
bool var;
std::thread(foo, std::ref(var));
I have no idea why I can't pass a reference to the vec element. Can someone explain why? Is there any workaround?

Answer 1

Problem is, that you use std::vector<bool>. operator [] for vector<bool> returns not bool, but std::vector<bool>::reference, that is proxy class.
You can use something like:
bool value = vec[0];
std::thread T(foo, std::ref(value));
T.join();
vec[0] = value;

Answer 2

Another workaround (not tested)
#include <thread>
#include <vector>
void foo(vector& v){
//here access v[0] and assign whatever value you'd like
//ideally you could pass an index as well
// if you want to access the Nth element
}
int main(){
std::vector<bool> vec(1);
std::thread T(foo, std::ref(vec));
}