void XtAppSetErrorHandler(app_context, handler) 
      XtAppContext app_context;
 
      XtErrorHandler handler;
 
void XtAppSetWarningHandler(app_context, handler) 
      XtAppContext app_context;
 
      XtErrorHandler handler;
 
void XtAppWarning(app_context, message) 
      XtAppContext app_context;
 
      String message;
 
The XtAppSetErrorHandler function registers the specified procedure, which is called when a fatal error condition occurs.
The XtAppSetWarningHandler registers the specified procedure, which is called when a nonfatal error condition occurs.
The XtAppWarning function calls the installed nonfatal error procedure and passes the specified message.