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.

2 files changed, 10 insertions, 2 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index f92eb7b85fc..696475c17e5 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,8 @@
+2013-11-16  Eli Zaretskii  <eliz@gnu.org>
+
+        * keymap.c (describe_map): Don't crash if PT is 1 both before and
+        after inserting the description string.  (Bug#15907)
+
 2013-11-15  Paul Eggert  <eggert@cs.ucla.edu>
 
         * data.c: Work around bogus GCC diagnostic about shift count.
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);
         }
     }