Avoid infinite loop in redisplay when header-line-format is invalid

* src/xdisp.c (handle_invisible_prop): Avoid inflooping when the
string has an invalid %-construct in it and is displayed as part
of mode-line or header-line.  (Bug#26586)

1 files changed, 2 insertions, 1 deletions

diff --git a/src/xdisp.c b/src/xdisp.c
index 58b5ca2f018..3e6a3078cea 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -4318,7 +4318,8 @@ handle_invisible_prop (struct it *it)
                       bidi_move_to_visually_next (&it->bidi_it);
                     }
                   while (oldpos <= it->bidi_it.charpos
-                         && it->bidi_it.charpos < endpos);
+                         && it->bidi_it.charpos < endpos
+                         && it->bidi_it.charpos < it->bidi_it.string.schars);
 
                   IT_STRING_CHARPOS (*it) = it->bidi_it.charpos;
                   IT_STRING_BYTEPOS (*it) = it->bidi_it.bytepos;