BTW I just also noticed the following error in libcxx/include/list line 1603: list<_Tp, _Alloc>::pop_back() { _LIBCPP_ASSERT(!empty(), "list::pop_front() called with empty list"); pop_front should read pop_back -- Shriramana Sharma ஶ்ரீரமணஶர்மா श्रीरमणशर्मा