More complex example of thread local storage in c++

tlscomplexcpp.cpp

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

std::mutex log_mutex;

thread_local int tl=0;

void logit( int num, const char * val )
{
  log_mutex.lock();
  std::cout << num << " " << tl << " " << val << std::endl;
  std::cout << num << " " << tl << " " << val << std::endl;
  log_mutex.unlock();
}

void doit( int num )
{
  logit(num, "apple");
  tl = num;
  logit(num, "banana");
}

int main()
{
  std::thread t1 = std::thread(doit,1);
  std::thread t2 = std::thread(doit,2);

  t1.join();
  t2.join();
}