-#ifndef _INTMAX_T
-#define _INTMAX_T
-#ifdef __INTMAX_TYPE__
-typedef __INTMAX_TYPE__ intmax_t;
-#else /* __INTMAX_TYPE__ */
-typedef long long intmax_t;
-#endif /* __INTMAX_TYPE__ */
-#endif /* _INTMAX_T */
-
-#ifndef _UINTMAX_T
-#define _UINTMAX_T
-#ifdef __UINTMAX_TYPE__
-typedef __UINTMAX_TYPE__ uintmax_t;
-#else /* __UINTMAX_TYPE__ */
-typedef unsigned long long uintmax_t;
-#endif /* __UINTMAX_TYPE__ */
-#endif /* _UINTMAX_T */
+#include <_types/_intmax_t.h>
+#include <_types/_uintmax_t.h>
+
+/* 7.18.4 Macros for integer constants */
+#define INT8_C(v) (v)
+#define INT16_C(v) (v)
+#define INT32_C(v) (v)
+#define INT64_C(v) (v ## LL)
+
+#define UINT8_C(v) (v)
+#define UINT16_C(v) (v)
+#define UINT32_C(v) (v ## U)
+#define UINT64_C(v) (v ## ULL)
+
+#ifdef __LP64__
+#define INTMAX_C(v) (v ## L)
+#define UINTMAX_C(v) (v ## UL)
+#else
+#define INTMAX_C(v) (v ## LL)
+#define UINTMAX_C(v) (v ## ULL)
+#endif