#include <thread>

class thread_guard {
  std::thread& t;

public:
  explicit thread_guard(std::thread& t_) : t(t_) {}
  ~thread_guard()
  {
    if (t.joinable()) {
      t.join();
    }
  }
  thread_guard(thread_guard const&) = delete;
  thread_guard& operator=(thread_guard const&) = delete;
};

void
do_something(int& i)
{
  ++i;
}

struct func {
  int& i;

  func(int& i_) : i(i_) {}

  void operator()()
  {
    for (unsigned j = 0; j < 1000000; ++j) {
      do_something(i);
    }
  }
};

void
do_something_in_current_thread()
{
}

void
f()
{
  int some_local_state;
  func my_func(some_local_state);
  std::thread t(my_func);
  thread_guard g(t);

  do_something_in_current_thread();
}

int
main()
{
  f();
}