# elif LONG_MAX>=9223372036854775807LL
# define CLZ64_OFFS ((int)sizeof(unsigned long)*CHAR_BIT)
# define CLZ64(_x) (__builtin_clzl(_x))
-# elif LLONG_MAX>=9223372036854775807LL
+# else /* long long must be >= 64 bits according to ISO C */
# define CLZ64_OFFS ((int)sizeof(unsigned long long)*CHAR_BIT)
# define CLZ64(_x) (__builtin_clzll(_x))
# endif