Fix bug #15907 with crashes due to after-change-functions.

 src/keymap.c (describe_map): Don't crash if PT is 1 both before and
 after inserting the description string.

1 files changed, 5 insertions, 2 deletions

diff --git a/src/keymap.c b/src/keymap.c
index 7a18cd5d983..562787ee8a5 100644
--- a/src/keymap.c
+++ b/src/keymap.c
@@ -3383,9 +3383,12 @@ describe_map (Lisp_Object map, Lisp_Object prefix,
 
       if (vect[i].shadowed)
         {
-          SET_PT (PT - 1);
+          ptrdiff_t pt = max (PT - 1, BEG);
+
+          SET_PT (pt);
           insert_string ("\n  (that binding is currently shadowed by another mode)");
-          SET_PT (PT + 1);
+          pt = min (PT + 1, Z);
+          SET_PT (pt);
         }
     }