strfilter_node__alloc
cur = strfilter_node__alloc(OP_or, root.r, NULL);
cur->r = strfilter_node__alloc(OP_not, NULL, NULL);
cur->r = strfilter_node__alloc(NULL, NULL, NULL);
root = strfilter_node__alloc(_or ? OP_or : OP_and, filter->root, right);
cur = strfilter_node__alloc(OP_and, last_op->r, NULL);