thread_issue.cpp

#include <vector>

std::size_t counter = 0;
std::mutex cout_mutex;
void foo()
{
    {
        std::lock_guard<std::mutex> lock(cout_mutex);
        std::cout << "T" << get_thread_id() << " increasing counter" << std::endl;
    }

    counter++;
}

int main()
{
    std::vector<std::thread> v;
    for(int n = 0; n < 2; ++n) {
        v.emplace_back(foo);
    }

    for(auto& t : v) {
        t.join();
    }
}