reverse_iterator gotcha

#include <list>
#include <cassert>

template<class reverse_iterator>
typename reverse_iterator::iterator_type reverse_to_normal(reverse_iterator i)
{
  ++i; // look at reverse_iterator documentation why this is necessary
  return i.base();
}

int main()
{
  std::list<int> list; /* same behavior with std::set */

  /* Let's fill our container a bit */
  list.push_back(1);
  list.push_back(2);

  std::list<int>::reverse_iterator back1 = list.rbegin();
  std::list<int>::iterator back2 = reverse_to_normal(back1);
  assert(*back1 == 2);
  assert(*back2 == *back1); /* so far, so good */

  /* Let's fill our container a bit more. set and list guarantee that iterators
   * stay valid so there is no harm in continuing to use back1 and back2, right?
   */
  list.push_back(3);
  assert(*back2 == *back1); /* fails. back1 now points to 3, back2 is still ok */

  /* Lesson learned: Iterator validity only applies to forward iterators */
  return 0;
}