#include <iostream>
#include <thread>
#include <mutex>
#include <memory>

struct Consumer {
  void consume(const std::shared_ptr<int> aBar)
  {
    const std::lock_guard<std::mutex> myLock(theMutex);
    thePtr = aBar;
  }

  void main_loop() {
    while(1) {
      std::shared_ptr<int> myLocal;
      {
        const std::lock_guard<std::mutex> myLock(theMutex);
        myLocal = thePtr;
      }
      myLocal.use_count();
    }
  }

  std::shared_ptr<int> thePtr;
  std::mutex           theMutex;
};

struct Producer {
  Producer(Consumer& aConsumer) : theConsumer(aConsumer) {}
  void main_loop() {
    while(1) {
      std::shared_ptr<int> myBar(new int(3));
      theConsumer.consume(myBar);
      myBar.use_count();
    }
  }

  Consumer& theConsumer;
};

int main() {
  Consumer myConsumer;
  Producer myProducer(myConsumer);

  std::thread myConsumerThread(&Consumer::main_loop, std::ref(myConsumer));
  std::thread myProducerThread(&Producer::main_loop, std::ref(myProducer));

  myProducerThread.join();
  myConsumerThread.join();
}