read_data function and use it at run time with png_set_read_fn(), rather
than changing the library. */
#ifndef USE_FAR_KEYWORD
+#ifdef __VISAGECPP__
+static void _Optlink
+png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
+#else
static void
png_default_read_data(png_structp png_ptr, png_bytep data, png_size_t length)
+#endif
{
png_size_t check;