_Rb_tree_base
struct _Rb_tree_base
_Rb_tree_base(const allocator_type& __a)
~_Rb_tree_base() { _M_put_node(_M_header); }
_Rb_tree_base(const allocator_type&)
~_Rb_tree_base() { _M_put_node(_M_header); }
class _Rb_tree : protected _Rb_tree_base<_Value, _Alloc> {
typedef _Rb_tree_base<_Value, _Alloc> _Base;