diff --git i/src/.gdbinit w/src/.gdbinit
index cc06b2e11c..0ebf07f0f7 100644
--- i/src/.gdbinit
+++ w/src/.gdbinit
@@ -1264,6 +1264,35 @@ commands
 end
 
 
+watch selected_window
+set $selwindow_watch = $bpnum
+commands $selwindow_watch
+  bt
+end
+disable $selwindow_watch
+
+# this one never happens, I think
+break xdisp.c:13929 if !WINDOWP(selected_window)
+
+break xdisp.c:13929 if WINDOWP(selected_window)
+commands
+  silent
+  enable $selwindow_watch
+  continue
+end
+set $enable_selwindow_watch = $bpnum
+disable $enable_selwindow_watch
+printf "selected window watch enabler = %d\n", $enable_selwindow_watch
+
+break xdisp.c:13939 if !NILP(w->contents)
+commands
+  silent
+  disable $selwindow_watch
+  continue
+end
+
+break xdisp.c:13939 if NILP(w->contents)
+
 # Put the Python code at the end of .gdbinit so that if GDB does not
 # support Python, GDB will do all the above initializations before
 # reporting an error.