#include <GL/glx.h>
#include <GL/gl.h>
#include <unistd.h>
#include <stdio.h>

int main (int argc, char ** argv)
{
	pid_t pid = fork();

	// Sleep so that the child can create all GLX resources
	if (pid != 0)
		sleep(2);

	Display *dpy = XOpenDisplay(NULL);
 
	int nelements;
	GLXFBConfig *fbc = glXChooseFBConfig(dpy, DefaultScreen(dpy), 0, &nelements);
 
	static int attributeList[] = { GLX_RGBA, GLX_DOUBLEBUFFER, GLX_RED_SIZE, 1, GLX_GREEN_SIZE, 1, GLX_BLUE_SIZE, 1, None };
	XVisualInfo *vi = glXChooseVisual(dpy, DefaultScreen(dpy), attributeList);
 
	XSetWindowAttributes swa;
	swa.colormap = XCreateColormap(dpy, RootWindow(dpy, vi->screen), vi->visual, AllocNone);
	swa.border_pixel = 0;
	swa.event_mask = StructureNotifyMask;
 
 	// It is crucial that the context is created before the window
	GLXContext ctx = glXCreateContext(dpy, vi, 0, GL_FALSE);

	Window win = XCreateWindow(dpy, RootWindow(dpy, vi->screen), 0, 0, 100, 100, 0, vi->depth, InputOutput, vi->visual, CWBorderPixel|CWColormap|CWEventMask, &swa);
 
	XMapWindow (dpy, win);

	glXMakeCurrent(dpy, win, ctx);
 
	if (pid == 0) {
	 	// The child needs to wait for the parent to take over
	 	// the current context in the X server
		sleep(3);
	} else {
		// Wait for the child to terminate, which will trigger the
		// cleanup routines in the X server.
		int status;
	 	wait(&status);

		// This call will crash the X server as it believes that
		// this parent process is holding the active context, but
		// the cleanup from the child cleared the dispatch table.
		glGetString(GL_VENDOR);
 	}
 
	glXDestroyContext(dpy, ctx); 
}