+extern int _PDCLIB_errno;
+int * _PDCLIB_errno_func( void );
+
+/* ERANGE and EDOM are specified by the standard. */
+#define _PDCLIB_ERANGE 1
+#define _PDCLIB_EDOM 2
+/* Used in the example implementation for any kind of I/O error. */
+#define _PDCLIB_EIO 3
+/* Used in the example implementation for "unknown error". */
+#define _PDCLIB_EUNKNOWN 4
+/* Used in the example implementation for "invalid parameter value". */
+#define _PDCLIB_EINVAL 5
+/* Used in the example implementation for "I/O retries exceeded". */
+#define _PDCLIB_ERETRY 6
+/* One larger than the largest used errno */
+#define _PDCLIB_EMAX 7
+
+/* TODO: Doing this via a static array is not the way to do it. */
+char const * _PDCLIB_errno_texts[ _PDCLIB_EMAX ];