I want to be able to develop Xlib applications on DSL, so I installed the XFree86-devel package. When I try to compile sample source generated with Anjuta with the following command:

gcc xstim.c -L/usr/X11R6/lib -lX11

it compiles successfully, but the binary doesn't work. Here's the source of xstim.c:

/* Created by Anjuta version 1.2.4a */
/* This file will not be overwritten */

/*Program closes with a mouse click or keypress */

#include <stdlib.h>
#include <stdio.h>
#include <X11/Xlib.h>

int main (int argc, char *argv[])
{
Display *dpy;
Visual *visual;
int depth;
XSetWindowAttributes attributes;
Window win;
XFontStruct *fontinfo;
XColor color, dummy;
XGCValues gr_values;
GC gc;
XKeyEvent event;

dpy = XOpenDisplay(NULL);
visual = DefaultVisual(dpy, 0);
depth = DefaultDepth(dpy, 0);
attributes.background_pixel = XWhitePixel(dpy, 0);
/* create the application window */
win = XCreateWindow(dpy, XRootWindow(dpy, 0),
50, 50, 400, 400, 5, depth,
InputOutput, visual, CWBackPixel,
&attributes);
XSelectInput(dpy, win, ExposureMask | KeyPressMask |
ButtonPressMask | StructureNotifyMask);

fontinfo = XLoadQueryFont(dpy, "6x10");
XAllocNamedColor(dpy, DefaultColormap(dpy, 0),
"green", &color, &dummy);
gr_values.font = fontinfo->fid;
gr_values.foreground = color.pixel;
gc = XCreateGC(dpy, win, GCFont+GCForeground, &gr_values);
XMapWindow(dpy, win);

/* run till key press */
while(1){
XNextEvent(dpy, &event);
switch(event.type) {
case Expose:
XDrawLine(dpy, win, gc, 0, 0, 100, 100);
XDrawRectangle(dpy, win, gc, 140, 140, 50, 50);
XDrawString(dpy, win, gc, 100, 100, "hello X world", 13);
break;
case ButtonPress:
case KeyPress:
XUnloadFont(dpy, fontinfo->fid);
XFreeGC(dpy, gc);
XCloseDisplay(dpy);
exit(0);
break;
case ConfigureNotify:
/* reconfigure size of window here */
break;
default:
break;
}
}
return(0);
}


It runs fine until it gets to case Expose:, where it has a segmentation fault. case KeyPress: also does it.

Oh, by the way, I can make a program with Xlib that runs fine on DSL if I compile it on Fedora Core 5 using Xorg.

I figured it out. The example was bugged. An XKeyEvent is not as large as an XEvent, and there are many types of events larger than XKeyEvent that the window can receive. When one of these events is received, whatever's after the XKeyEvent is hosed.

I guess the implementation of Xlib on Fedora Core 5 makes all event structures the same size.