Calcualte all possible values of utf8

I want to print all possible UTF-8 values. Something similar to this:

  uint32_t max = 0xFFFFFFFF;
  for (uint32_t i = 0; i <= max; i++)
  {
    std::cout << std::hex << i << std::endl;    
  }

But I'm printing a lot of impossible cases. Any better idea?