AVL_SETPARENT
AVL_SETPARENT(cright, node);
AVL_SETPARENT(node, child);
AVL_SETPARENT(child, parent);
AVL_SETPARENT(gright, node);
AVL_SETPARENT(gleft, child);
AVL_SETPARENT(child, gchild);
AVL_SETPARENT(node, gchild);
AVL_SETPARENT(gchild, parent);
AVL_SETPARENT(node, parent);
AVL_SETPARENT(node->avl_child[left], node);
AVL_SETPARENT(node->avl_child[right], node);
AVL_SETPARENT(delete->avl_child[which_child], delete);
AVL_SETPARENT(node, parent);
#define RB_CLEAR_NODE(nodep) AVL_SETPARENT(nodep, nodep);