+#include <float.h>
+
+#define PRIfmt_digits(digits) #digits
+#define PRIfmt(digits, fmt) "." PRIfmt_digits(digits) fmt
+#define PRIfval PRIfmt(FLT_DECIMAL_DIG, "g")
+#define PRIdval PRIfmt(DBL_DECIMAL_DIG, "g")
+#if HAVE_LONG_DOUBLE
+# define PRIldval PRIfmt(LDBL_DECIMAL_DIG, "Lg")
+#endif