kmem_buftag_lite_t
btaddr + offsetof(kmem_buftag_lite_t, bt_history)) == -1)
kmem_buftag_lite_t bt;
pc_t *_s = ((kmem_buftag_lite_t *)(bt))->bt_history; \
(offsetof(kmem_buftag_lite_t, bt_history[f]))