__write_once_size
__write_once_size(&(x), __u.__c, sizeof(x)); \
__write_once_size(&(x), __u.__c, sizeof(x)); \
__write_once_size((__unqual_typeof(x) *)&(x), __u.__c, sizeof(x)); \
__write_once_size(&(x), __u.__c, sizeof(x)); \