numbers: Define 128-bit integers if compiler supports
# define UINT64_MAX __MAXUINT__(uint64_t)
# endif
+# ifndef INT128_MAX
+# if defined(__SIZEOF_INT128__) && __SIZEOF_INT128__ == 16
+typedef __int128_t int128_t;
+typedef __uint128_t uint128_t;
+# define INT128_MIN __MININT__(int128_t)
+# define INT128_MAX __MAXINT__(int128_t)
+# define UINT128_MAX __MAXUINT__(uint128_t)
+# endif
+# endif
+
# ifndef SIZE_MAX
# define SIZE_MAX __MAXUINT__(size_t)
# endif
