space_ref_t
space_ref_t *sr;
const space_ref_t *sr1 = (const space_ref_t *)x1;
const space_ref_t *sr2 = (const space_ref_t *)x2;
sizeof (space_ref_t), offsetof(space_ref_t, sr_node));
space_ref_t *sr;
space_ref_t *sr;