Protect against GCing of last_mouse_window

* src/window.c (last_mouse_window): New global var.  All static
instances removed, and all their uses replaced with this global
var.  This fixes a very unlikely bug where last_mouse_window was
GC’ed and a new window created in its place.  It also fixes several
places that assumed NIL_IS_ZERO without static_asserting it.
(init_window_once): Initialize the new var.

9 files changed, 10 insertions, 10 deletions

diff --git a/src/androidterm.c b/src/androidterm.c
index 688f254ee23..e0f66652300 100644
--- a/src/androidterm.c
+++ b/src/androidterm.c
@@ -1179,7 +1179,6 @@ handle_one_android_event (struct android_display_info *dpyinfo,
               && (f == XFRAME (selected_frame)
                   || !NILP (focus_follows_mouse)))
             {
-              static Lisp_Object last_mouse_window;
               Lisp_Object window
                 = window_from_coordinates (f, event->xmotion.x,
                                            event->xmotion.y, 0,
diff --git a/src/haikuterm.c b/src/haikuterm.c
index 7f02de2ca15..4a217c9e0e2 100644
--- a/src/haikuterm.c
+++ b/src/haikuterm.c
@@ -3562,7 +3562,6 @@ haiku_read_socket (struct terminal *terminal, struct input_event *hold_quit)
 
                 if (!NILP (Vmouse_autoselect_window))
                   {
-                    static Lisp_Object last_mouse_window;
                     Lisp_Object window = window_from_coordinates (f, b->x, b->y, 0, 0, 0, 0);
 
                     if (WINDOWP (window)
diff --git a/src/msdos.c b/src/msdos.c
index 95eb6453040..49403ba72f4 100644
--- a/src/msdos.c
+++ b/src/msdos.c
@@ -2677,8 +2677,6 @@ dos_rawgetc (void)
           /* Generate SELECT_WINDOW_EVENTs when needed.  */
           if (!NILP (Vmouse_autoselect_window))
             {
-              static Lisp_Object last_mouse_window;
-
               mouse_window = window_from_coordinates
                 (SELECTED_FRAME (), mouse_last_x, mouse_last_y, 0, 0, 0, 0);
               /* A window will be selected only when it is not
diff --git a/src/pgtkterm.c b/src/pgtkterm.c
index 2da1006b6f7..0f272bbeac8 100644
--- a/src/pgtkterm.c
+++ b/src/pgtkterm.c
@@ -5938,7 +5938,6 @@ motion_notify_event (GtkWidget *widget, GdkEvent *event,
              also when the target window is on another frame.  */
           && (f == XFRAME (selected_frame) || !NILP (focus_follows_mouse)))
         {
-          static Lisp_Object last_mouse_window;
           Lisp_Object window = window_from_coordinates
             (f, event->motion.x, event->motion.y, 0, false, false, false);
 
diff --git a/src/w32inevt.c b/src/w32inevt.c
index 1c80f7c6db7..b0e6b5a9286 100644
--- a/src/w32inevt.c
+++ b/src/w32inevt.c
@@ -467,7 +467,6 @@ do_mouse_event (MOUSE_EVENT_RECORD *event,
                 struct input_event *emacs_ev)
 {
   static DWORD button_state = 0;
-  static Lisp_Object last_mouse_window;
   DWORD but_change, mask, flags = event->dwEventFlags;
   int i;
 
diff --git a/src/w32term.c b/src/w32term.c
index cb7bc7e4540..5613ade01ce 100644
--- a/src/w32term.c
+++ b/src/w32term.c
@@ -5444,7 +5444,6 @@ w32_read_socket (struct terminal *terminal,
                       || (!NILP (focus_follows_mouse)
                           && !FRAME_NO_ACCEPT_FOCUS (f))))
                 {
-                  static Lisp_Object last_mouse_window;
                   Lisp_Object window = window_from_coordinates
                     (f, LOWORD (msg.msg.lParam), HIWORD (msg.msg.lParam), 0, 0, 0, 0);
 
diff --git a/src/window.c b/src/window.c
index 0ed1b53d866..330a95a716f 100644
--- a/src/window.c
+++ b/src/window.c
@@ -106,6 +106,9 @@ Lisp_Object minibuf_window;
    shown as the selected window when the minibuffer is selected.  */
 Lisp_Object minibuf_selected_window;
 
+/* Non-nil means it is the window containing the last mouse movement.  */
+Lisp_Object last_mouse_window;
+
 /* Incremented for each window created.  */
 static EMACS_INT sequence_number;
 
@@ -8778,6 +8781,8 @@ init_window_once (void)
 
   minibuf_selected_window = Qnil;
   staticpro (&minibuf_selected_window);
+  last_mouse_window = Qnil;
+  staticpro (&last_mouse_window);
   old_selected_window = Qnil;
   staticpro (&old_selected_window);
 
@@ -8796,6 +8801,7 @@ static void init_window_once_for_pdumper (void)
   PDUMPER_RESET_LV (selected_window, Qnil);
   PDUMPER_RESET_LV (Vwindow_list, Qnil);
   PDUMPER_RESET_LV (minibuf_selected_window, Qnil);
+  PDUMPER_RESET_LV (last_mouse_window, Qnil);
 
   /* Hack: if mode_line_in_non_selected_windows is true (which it may
      be, if we're restoring from a dump) the guts of
diff --git a/src/window.h b/src/window.h
index a48c370b198..2266fc7814c 100644
--- a/src/window.h
+++ b/src/window.h
@@ -1116,6 +1116,10 @@ extern Lisp_Object minibuf_window;
 
 extern Lisp_Object minibuf_selected_window;
 
+/* Non-nil means it is the window containing the last mouse movement.  */
+
+extern Lisp_Object last_mouse_window;
+
 extern Lisp_Object make_window (void);
 extern Lisp_Object window_from_coordinates (struct frame *, int, int,
                                             enum window_part *, bool, bool, bool);
diff --git a/src/xterm.c b/src/xterm.c
index fd61d5df91c..e024b36daf5 100644
--- a/src/xterm.c
+++ b/src/xterm.c
@@ -21291,8 +21291,6 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                 && (f == XFRAME (selected_frame)
                     || !NILP (focus_follows_mouse)))
               {
-                static Lisp_Object last_mouse_window;
-
                 if (xmotion.window != FRAME_X_WINDOW (f))
                   {
                     x_translate_coordinates (f, xmotion.x_root, xmotion.y_root,
@@ -23231,7 +23229,6 @@ handle_one_xevent (struct x_display_info *dpyinfo,
                       && (f == XFRAME (selected_frame)
                           || !NILP (focus_follows_mouse)))
                     {
-                      static Lisp_Object last_mouse_window;
                       Lisp_Object window = window_from_coordinates (f, ev.x, ev.y, 0, false, false,
                                                                     false);