bug#58158: 29.0.50; [overlay] Interval tree iteration considered harmful

[Stefan Monnier]

>   static _Rb_tree_node_base*
>   local_Rb_tree_increment(_Rb_tree_node_base* __x) throw ()
>   {
>     if (__x->_M_right != 0)
>       {
>         __x = __x->_M_right;
>         while (__x->_M_left != 0)
>           __x = __x->_M_left;
>       }
>     else
>       {
>         _Rb_tree_node_base* __y = __x->_M_parent;
>         while (__x == __y->_M_right)
>           {
>             __x = __y;
>             __y = __y->_M_parent;
>           }
>         if (__x->_M_right != __y)
>           __x = __y;
>       }
>     return __x;
>   }
>
> I hope one can read that.

I changed the code to store the `visited` bit in the work stack, but if
you could rewrite the `interval_generator_next` along the lines of the
code above that would be great.
[ An alternative would be to try and get rid of the `parent` field :-)  ]


        Stefan