c++11 promise object gets invalid, but its future object neither returns value nor throw exception

I've got this test code to see, if a promise object is out of lifecycle, what happen to its future object:

#include <chrono>
#include <future>
#include <iostream>
#include <thread>
using namespace std;

void getValue(future<int>& future) {
    cout << "sub process 1 \n";
    try {
        cout << "sub process 2 \n";
        int value = future.get();
        cout << "sub process 3\n";
        cout << value << endl;
    } catch (future_error &e) {
        cerr << e.code() << '\n' << e.what() << endl;
    } catch (exception e) {
        cerr << e.what() << endl;
    }
    cout << "sub process 4\n";
}
int main() {
    thread t;
    {
        promise<int> plocal;
        future<int> flocal = plocal.get_future();
        t = thread(getValue, ref(flocal));
    }
    t.join();
    return 0;
}

I expect that in getValue function, it either prints future::get result, or throws out runtime exception and prints exception info, because plocal has been destructed in "main".

Acturally, this program prints:

sub process 1
sub process 2

and ends.