__u128_halves
union __u128_halves {
union __u128_halves r, o = { .full = (old) }, \
union __u128_halves r, o = { .full = (old) }, \
union __u128_halves __old, __new, __ret; \
union __u128_halves __hn = { .full = (n) }; \
union __u128_halves __ho = { .full = (__o) }; \
union __u128_halves o = { .full = (_old), }, \
union __u128_halves o = { .full = *(_oldp), }, \