Simple use of C++11 thread support

#define _GLIBCXX_USE_NANOSLEEP 1
#include <thread>
#include <condition_variable>
#include <iostream>
#include <unistd.h>

void runthread(::std::mutex &m, ::std::condition_variable &v, bool &started)
{
   ::std::this_thread::sleep_for(::std::chrono::milliseconds(500));
   {
      ::std::unique_lock< ::std::mutex> lock(m);
      started = true;
      v.notify_one();
   }
   ::std::cerr << "I am the new thread!\n";
}

int main()
{
   ::std::mutex m;
   ::std::condition_variable v;
   bool started = false;
   ::std::thread newthread(runthread, ::std::ref(m), ::std::ref(v), ::std::ref(started));
   {
      ::std::unique_lock< ::std::mutex> lock(m);
      while (!started) {
         v.wait(lock);
      }
   }
   ::std::cerr << "Both I and the new thread are running.\n";
   newthread.join();
   return 0;
}