blocks = update_bkwd_compact(stp);
IF_DEBUG(gc, debugBelch("update_bkwd: %d.%d (compact, old: %d blocks, now %d blocks)\n",
stp->gen->no, stp->no,
blocks = update_bkwd_compact(stp);
IF_DEBUG(gc, debugBelch("update_bkwd: %d.%d (compact, old: %d blocks, now %d blocks)\n",
stp->gen->no, stp->no,