Mark some data during drag-and-drop

It doesn't make sense to prevent the return frame or movement
frame from being deleted, but we should at least protect them
from garbage collection.

* src/alloc.c (garbage_collect): Call mark_xterm.
* src/xterm.c (x_dnd_begin_drag_and_drop)
(x_dnd_cleanup_drag_and_drop): Clear movement and return frames
upon DND completion.
(mark_xterm): Mark those frames.
* src/xterm.h: Update prototypes.

3 files changed, 35 insertions, 1 deletions

diff --git a/src/alloc.c b/src/alloc.c
index 6d91ec33585..733f7733fa9 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -6196,6 +6196,10 @@ garbage_collect (void)
   mark_fringe_data ();
 #endif
 
+#ifdef HAVE_X_WINDOWS
+  mark_xterm ();
+#endif
+
   /* Everything is now marked, except for the data in font caches,
      undo lists, and finalizers.  The first two are compacted by
      removing an items which aren't reachable otherwise.  */
diff --git a/src/xterm.c b/src/xterm.c
index 922aafbbdf1..b9a5355b415 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -3497,6 +3497,8 @@ x_dnd_cleanup_drag_and_drop (void *frame)
 #ifdef USE_GTK
   current_hold_quit = NULL;
 #endif
+  x_dnd_return_frame_object = NULL;
+  x_dnd_movement_frame = NULL;
 
   block_input ();
   /* Restore the old event mask.  */
@@ -9528,6 +9530,9 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
           if (x_dnd_use_toplevels)
             x_dnd_free_toplevels ();
 
+          x_dnd_return_frame_object = NULL;
+          x_dnd_movement_frame = NULL;
+
           FRAME_DISPLAY_INFO (f)->grabbed = 0;
 #ifdef USE_GTK
           current_hold_quit = NULL;
@@ -9546,6 +9551,7 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
 #ifdef USE_GTK
   current_hold_quit = NULL;
 #endif
+  x_dnd_movement_frame = NULL;
 
   /* Restore the old event mask.  */
   XSelectInput (FRAME_X_DISPLAY (f),
@@ -9554,14 +9560,18 @@ x_dnd_begin_drag_and_drop (struct frame *f, Time time, Atom xaction,
 
   unblock_input ();
 
-  if (x_dnd_return_frame == 3)
+  if (x_dnd_return_frame == 3
+      && FRAME_LIVE_P (x_dnd_return_frame_object))
     {
       x_dnd_return_frame_object->mouse_moved = true;
 
       XSETFRAME (action, x_dnd_return_frame_object);
+      x_dnd_return_frame_object = NULL;
       return action;
     }
 
+  x_dnd_return_frame_object = NULL;
+
   if (x_dnd_use_toplevels)
     x_dnd_free_toplevels ();
   FRAME_DISPLAY_INFO (f)->grabbed = 0;
@@ -23016,6 +23026,24 @@ init_xterm (void)
 #endif
 
 void
+mark_xterm (void)
+{
+  Lisp_Object val;
+
+  if (x_dnd_return_frame_object)
+    {
+      XSETFRAME (val, x_dnd_return_frame_object);
+      mark_object (val);
+    }
+
+  if (x_dnd_movement_frame)
+    {
+      XSETFRAME (val, x_dnd_movement_frame);
+      mark_object (val);
+    }
+}
+
+void
 syms_of_xterm (void)
 {
   x_error_message = NULL;
diff --git a/src/xterm.h b/src/xterm.h
index 79dee6a569c..4eb16d0c142 100644
--- a/src/xterm.h
+++ b/src/xterm.h
@@ -1557,6 +1557,8 @@ extern struct frame *x_dnd_frame;
 struct xi_device_t *xi_device_from_id (struct x_display_info *, int);
 #endif
 
+extern void mark_xterm (void);
+
 /* Is the frame embedded into another application? */
 
 #define FRAME_X_EMBEDDED_P(f) (FRAME_X_OUTPUT(f)->explicit_parent != 0)