#0  malloc_consolidate (av=av@entry=0x7fd9e2007b20 <main_arena>) at malloc.c:4168
  [Error: malloc.c was not found in source tree]
#1  0x00007fd9e1cc555e in _int_malloc (av=av@entry=0x7fd9e2007b20 <main_arena>, bytes=bytes@entry=1440) at malloc.c:3451
  [Error: malloc.c was not found in source tree]
#2  0x00007fd9e1cc75a4 in __GI___libc_malloc (bytes=bytes@entry=1440) at malloc.c:2914
  [Error: malloc.c was not found in source tree]
#3  0x00007fd9e275f3b4 in XQueryTree (dpy=0x55e34fd2d000, w=<optimized out>, root=root@entry=0x7ffd6129cff8, parent=parent@entry=0x7ffd6129d000, children=children@entry=0x7ffd6129d008, nchildren=nchildren@entry=0x7ffd6129cff4) at ../../src/QuTree.c:55
  [Error: QuTree.c was not found in source tree]
#4  0x000055e34e917524 in raise_window_relative_to_managed_windows (screen=0x55e34fe28610, screen=0x55e34fe28610, xwindow=<optimized out>) at core/stack.c:969
  964:    * or restack any windows before using the XQueryTree results.
  965:    */
  966: 
  967:   meta_error_trap_push_with_return (screen->display);
  968: 
  969:   XQueryTree (screen->display->xdisplay,
  970:               screen->xroot,
  971:               &ignored1, &ignored2, &children, &n_children);
  972: 
  973:   if (meta_error_trap_pop_with_return (screen->display, TRUE) != Success)
  974:     {
#5  stack_sync_to_server (stack=0x55e34fe8ae10) at core/stack.c:1165
  1160:               /* Move *newp below last_window */
  1161:               if (last_window == None)
  1162:                 {
  1163:                   meta_topic (META_DEBUG_STACK, "Using window 0x%lx as topmost (but leaving it in-place)\n", *newp);
  1164: 
  1165:                   raise_window_relative_to_managed_windows (stack->screen,
  1166:                                                             *newp);
  1167:                 }
  1168:               else
  1169:                 {
  1170:                   /* This means that if last_window is dead, but not
#6  0x000055e34e9179b9 in stack_sync_to_server (stack=<optimized out>) at core/stack.c:188
  183: {
  184:   meta_window_set_stack_position_no_sync (window,
  185:                                           stack->n_positions - 1);
  186: 
  187:   stack_sync_to_server (stack);
  188: }
  189: 
  190: void
  191: meta_stack_lower (MetaStack  *stack,
  192:                   MetaWindow *window)
  193: {
#7  meta_stack_raise (stack=<optimized out>, window=window@entry=0x55e34fea63d0) at core/stack.c:187
  182:                   MetaWindow *window)
  183: {
  184:   meta_window_set_stack_position_no_sync (window,
  185:                                           stack->n_positions - 1);
  186: 
  187:   stack_sync_to_server (stack);
  188: }
  189: 
  190: void
  191: meta_stack_lower (MetaStack  *stack,
  192:                   MetaWindow *window)
#8  0x000055e34e920ed8 in meta_window_raise (window=0x0, window@entry=0x55e34fea63d0) at core/window.c:4572
  4567:    * and parent window of the currently active app.  The stacking
  4568:    * constraints in stack.c then magically take care of raising all
  4569:    * the child windows appropriately.
  4570:    */
  4571:   if (window->screen->stack == ancestor->screen->stack)
  4572:     meta_stack_raise (window->screen->stack, ancestor);
  4573:   else
  4574:     {
  4575:       meta_warning (
  4576:                     "Either stacks aren't per screen or some window has a weird "
  4577:                     "transient_for hint; window->screen->stack != "
#9  0x000055e34e900285 in event_callback (event=0x7ffd6129d2f0, data=0x55e34ffa9c00) at core/display.c:2079
  2074:             case META_FOCUS_MODE_CLICK:
  2075:               break;
  2076:             }
  2077: 
  2078:           if (window->type == META_WINDOW_DOCK)
  2079:             meta_window_raise (window);
  2080:         }
  2081:       break;
  2082:     case LeaveNotify:
  2083:       if (display->grab_window == window &&
  2084:           grab_op_is_mouse (display->grab_op))
#10 0x000055e34e943475 in filter_func (xevent=0x7ffd6129d2f0, event=<optimized out>, data=<optimized out>) at ui/ui.c:281
  276:              GdkEvent *event,
  277:              gpointer data)
  278: {
  279:   g_return_val_if_fail (ef != NULL, GDK_FILTER_CONTINUE);
  280: 
  281:   if ((* ef->func) (xevent, ef->data) ||
  282:       maybe_redirect_mouse_event (xevent))
  283:     return GDK_FILTER_REMOVE;
  284:   else
  285:     return GDK_FILTER_CONTINUE;
  286: }
#11 0x00007fd9e53ccc81 in gdk_event_apply_filters (xevent=xevent@entry=0x7ffd6129d2f0, event=event@entry=0x55e350065130, window=window@entry=0x0) at /build/gtk+3.0-hEt8eK/gtk+3.0-3.18.9/./gdk/x11/gdkeventsource.c:81
  [Error: gdkeventsource.c was not found in source tree]
#12 0x00007fd9e53cd27e in gdk_event_source_translate_event (xevent=0x7ffd6129d2f0, event_source=0x55e34fd28740) at /build/gtk+3.0-hEt8eK/gtk+3.0-3.18.9/./gdk/x11/gdkeventsource.c:200
  [Error: gdkeventsource.c was not found in source tree]
#13 _gdk_x11_display_queue_events (display=0x55e34fd39020) at /build/gtk+3.0-hEt8eK/gtk+3.0-3.18.9/./gdk/x11/gdkeventsource.c:343
  [Error: gdkeventsource.c was not found in source tree]
#14 0x00007fd9e539f069 in gdk_display_get_event (display=display@entry=0x55e34fd39020) at /build/gtk+3.0-hEt8eK/gtk+3.0-3.18.9/./gdk/gdkdisplay.c:340
  [Error: gdkdisplay.c was not found in source tree]
#15 0x00007fd9e53ccd02 in gdk_event_source_dispatch (source=<optimized out>, callback=<optimized out>, user_data=<optimized out>) at /build/gtk+3.0-hEt8eK/gtk+3.0-3.18.9/./gdk/x11/gdkeventsource.c:365
  [Error: gdkeventsource.c was not found in source tree]
#16 0x00007fd9e30db227 in g_main_context_dispatch () from /tmp/apport_sandbox_QG6BeY/lib/x86_64-linux-gnu/libglib-2.0.so.0
#17 0x00007fd9e30db480 in g_main_context_iterate.isra () from /tmp/apport_sandbox_QG6BeY/lib/x86_64-linux-gnu/libglib-2.0.so.0
#18 0x00007fd9e30db7a2 in g_main_loop_run () from /tmp/apport_sandbox_QG6BeY/lib/x86_64-linux-gnu/libglib-2.0.so.0
#19 0x000055e34e8ef5d7 in main (argc=1, argv=0x7ffd6129dbb8) at core/main.c:579
  574:     meta_prefs_set_force_fullscreen (FALSE);
  575: 
  576:   if (!meta_display_open ())
  577:     meta_exit (META_EXIT_ERROR);
  578: 
  579:   g_main_loop_run (meta_main_loop);
  580: 
  581:   meta_finalize ();
  582: 
  583:   if (meta_restart_after_quit)
  584:     {