CONS_BLOCK       2668 src/alloc.c      GETMARKBIT (CONS_BLOCK (fptr), CONS_INDEX ((fptr)))
CONS_BLOCK       2671 src/alloc.c      SETMARKBIT (CONS_BLOCK (fptr), CONS_INDEX ((fptr)))
CONS_BLOCK       2674 src/alloc.c      UNSETMARKBIT (CONS_BLOCK (fptr), CONS_INDEX ((fptr)))