FENCEPOST_HEAD    849 lj_alloc.c           chunk_plus_offset(p, psize)->head = FENCEPOST_HEAD;
FENCEPOST_HEAD    876 lj_alloc.c           chunk_plus_offset(newp, psize)->head = FENCEPOST_HEAD;
FENCEPOST_HEAD    976 lj_alloc.c         p->head = FENCEPOST_HEAD;