-char *
-vasnprintf (char *resultbuf, size_t *lengthp, const char *format, va_list args)
+#if WIDE_CHAR_VERSION
+# define VASNPRINTF vasnwprintf
+# define CHAR_T wchar_t
+# define DIRECTIVE wchar_t_directive
+# define DIRECTIVES wchar_t_directives
+# define PRINTF_PARSE wprintf_parse
+# define USE_SNPRINTF 1
+# if HAVE_DECL__SNWPRINTF
+ /* On Windows, the function swprintf() has a different signature than
+ on Unix; we use the _snwprintf() function instead. */
+# define SNPRINTF _snwprintf
+# else
+ /* Unix. */
+# define SNPRINTF swprintf
+# endif
+#else
+# define VASNPRINTF vasnprintf
+# define CHAR_T char
+# define DIRECTIVE char_directive
+# define DIRECTIVES char_directives
+# define PRINTF_PARSE printf_parse
+# define USE_SNPRINTF (HAVE_DECL__SNPRINTF || HAVE_SNPRINTF)
+# if HAVE_DECL__SNPRINTF
+ /* Windows. */
+# define SNPRINTF _snprintf
+# else
+ /* Unix. */
+# define SNPRINTF snprintf
+# endif
+#endif
+
+CHAR_T *
+VASNPRINTF (CHAR_T *resultbuf, size_t *lengthp, const CHAR_T *format, va_list args)