#0  0x00000030004db048 in poll () from /lib64/libc.so.6
#1  0x0000003003408b6a in _xcb_conn_wait (c=0xcf2900, cond=<value optimized out>, vector=0x0, count=0x0) at xcb_conn.c:313
#2  0x000000300340a1cf in xcb_wait_for_reply (c=0xcf2900, request=3238098, e=0x7fff43b2b9c8) at xcb_in.c:378
#3  0x000000300384db3d in _XReply (dpy=0xd40190, rep=0x7fff43b2ba20, extra=0, discard=0) at xcb_io.c:532
#4  0x0000003015a4f887 in DRI2WaitMSC (dpy=0xd40190, drawable=112, target_msc=0, divisor=2, remainder=1, ust=0x7fff43b2baa8, msc=0x7fff43b2baa0, sbc=
    0x7fff43b2ba98) at dri2.c:616
#5  0x0000003015a4dd93 in dri2WaitForMSC (pdraw=<value optimized out>, target_msc=<value optimized out>, divisor=<value optimized out>, 
    remainder=<value optimized out>, ust=0x7fff43b2bb08, msc=0x7fff43b2bb00, sbc=0x7fff43b2baf8) at dri2_glx.c:346
#6  0x0000003015a27371 in __glXWaitVideoSyncSGI (divisor=2, remainder=1, count=0x7fff43b2bbac) at glxcmds.c:1771
#7  0x000000000040efe8 in waitForVideoSync () at display.c:1286
#8  eventLoop () at display.c:1568
#9  0x000000000040c310 in main (argc=<value optimized out>, argv=<value optimized out>) at main.c:467
Single stepping until exit from function poll,
which has no line number information.
_xcb_conn_wait (c=0xcf2900, cond=<value optimized out>, vector=0x0, count=0x0) at xcb_conn.c:317
317	    } while (ret == -1 && errno == EINTR);
313	        ret = poll(&fd, 1, -1);
317	    } while (ret == -1 && errno == EINTR);
318	    if(ret < 0)
323	    pthread_mutex_lock(&c->iolock);
325	    if(ret)
328	        if((fd.revents & POLLIN) == POLLIN)
332	            ret = ret && _xcb_in_read(c);
335	        if((fd.revents & POLLOUT) == POLLOUT)
342	    if(count)
344	    --c->in.reading;
346	    return ret;
347	}
xcb_wait_for_reply (c=0xcf2900, request=3238098, e=0x7fff43b2b9c8) at xcb_in.c:377
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
378	            if(!_xcb_conn_wait(c, &cond, 0, 0))
377	        while(!poll_for_reply(c, request, &ret, e))
$1 = 3238098
Cannot access memory at address 0x3168d2