Use join() to wait for background threads before terminating an application.

#include <iostream>
#include <thread>
 
void ShowMessage()
{
  std::cout << "Hello World" << std::endl;
}
 
int main()
{
  std::thread t1(ShowMessage);
  //t1.join();  // Not joining to the main thread will cause a crash!
  return 0;
}

Here are some ways to fix this:

int main()
{
  std::thread t1(ShowMessage);
  t1.join();   // Join t1 to the main thread.
  return 0;
}

int main()
{
  std::thread t1(ShowMessage);
  t1.detach();  // Detach t1 from main thread.
  return 0;
}