Description
string 
fdf_error ( [int error_code] )
   fdf_error() returns a textual description for 
   the fdf error code given in error_code.
   The function uses the internal error code set by the last operation 
   if no error_code is given, so 
   fdf_error() is a convenient shortcut for 
   fdf_error(fdf_errno()).
  
   See also fdf_errno().