main: Avoid a crash with crossing event handling

We are reusing the GtkCrossingData struct for multiple
calls here, so we need to make sure that the targets
stay alive from beginning to end.

Fixes: #3090

1 files changed, 5 insertions, 2 deletions

diff --git a/gtk/gtkmain.c b/gtk/gtkmain.c
index a517a0e6e7..23c61cd270 100644
--- a/gtk/gtkmain.c
+++ b/gtk/gtkmain.c
@@ -1335,9 +1335,9 @@ gtk_synthesize_crossing_events (GtkRoot         *toplevel,
 
   crossing.type = crossing_type;
   crossing.mode = mode;
-  crossing.old_target = old_target;
+  crossing.old_target = old_target ? g_object_ref (old_target) : NULL;
   crossing.old_descendent = NULL;
-  crossing.new_target = new_target;
+  crossing.new_target = new_target ? g_object_ref (new_target) : NULL;
   crossing.new_descendent = NULL;
   crossing.drop = drop;
 
@@ -1417,6 +1417,9 @@ gtk_synthesize_crossing_events (GtkRoot         *toplevel,
         gtk_widget_set_state_flags (widget, GTK_STATE_FLAG_PRELIGHT, FALSE);
     }
 
+  g_clear_object (&crossing.old_target);
+  g_clear_object (&crossing.new_target);
+
   gtk_widget_stack_clear (&target_array);
 }