Can someone explain the following strange function declarations?

Question

std::thread f()
{
  void some_function(); // <- here
  return std::thread(some_function);
}

std::thread g()
{
  void some_other_function(int); // <- here
  std::thread t(some_other_function,42);
  return t;
}

Answer 1

Lines like:

void some_function();

simply declare a function which will be defined later. Functions don't necessarily have to be declared outside of function scope.