How do you exit X11 program without Error

Question

I have a fairly simple \"Hello World\" in X11 at end of question. But when it exits I get the run time error messages below:

$ ./xtest
XIO:  fatal IO error 11 (R         


        

Answer 1

// this code from : https://en.wikibooks.org/wiki/X_Window_Programming/Xlib don't show error...

  /*
   Simple Xlib application drawing a box in a window.
   To Compile: gcc -o test test.c -lX11  */


 #include
 #include
 #include // prevents error for exit on line 18 when compiling with gcc
 int main() {
   Display *d;
   int s;
   Window w;
   XEvent e;


                        /* open connection with the server */
   d=XOpenDisplay(NULL);
   if(d==NULL) {
     printf("Cannot open display\n");
     exit(1);
   }
   s=DefaultScreen(d);


                        /* create window */
   w=XCreateSimpleWindow(d, RootWindow(d, s), 10, 10, 100, 100, 1,
                         BlackPixel(d, s), WhitePixel(d, s));


   // Process Window Close Event through event handler so XNextEvent does Not fail
   Atom delWindow = XInternAtom( d, "WM_DELETE_WINDOW", 0 );
   XSetWMProtocols(d , w, &delWindow, 1);


                        /* select kind of events we are interested in */
   XSelectInput(d, w, ExposureMask | KeyPressMask);


                        /* map (show) the window */
   XMapWindow(d, w);


                        /* event loop */
   while(1) {
     XNextEvent(d, &e);
                        /* draw or redraw the window */
     if(e.type==Expose) {
       XFillRectangle(d, w, DefaultGC(d, s), 20, 20, 10, 10);
     }
                        /* exit on key press */
     if(e.type==KeyPress)
       break;
     // Handle Windows Close Event
     if(e.type==ClientMessage)
        break;
   }
                        /* destroy our window */
   XDestroyWindow(d, w);
                        /* close connection to server */
   XCloseDisplay(d);
   return 0;

}