MARK_BITS_SZ      661 gc/include/private/gc_priv.h #   define MARK_BITS_SZ (MARK_BITS_PER_HBLK/2)
MARK_BITS_SZ      667 gc/include/private/gc_priv.h #   define MARK_BITS_SZ (MARK_BITS_PER_HBLK/CPP_WORDSZ)