Fix bidi_explicit_dir_char undefined behavior

* bidi.c (bidi_explicit_dir_char): Avoid subscript error when
argument is BIDI_EOB.  This can happen in bidi_level_of_next_char.

2 files changed, 9 insertions, 0 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 017b8f15e3b..3b2c9a6777f 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,5 +1,9 @@
 2015-02-09  Paul Eggert  <eggert@cs.ucla.edu>
 
+        Fix bidi_explicit_dir_char undefined behavior
+        * bidi.c (bidi_explicit_dir_char): Avoid subscript error when
+        argument is BIDI_EOB.  This can happen in bidi_level_of_next_char.
+
         Better distinguish infinite from invalid times
         * editfns.c (check_time_validity): New function.
         (decode_time_components): Return int, not bool.
diff --git a/src/bidi.c b/src/bidi.c
index cbc1820c2a5..e5e08c6a252 100644
--- a/src/bidi.c
+++ b/src/bidi.c
@@ -1799,6 +1799,11 @@ bidi_explicit_dir_char (int ch)
 
   if (!bidi_initialized)
     emacs_abort ();
+  if (ch < 0)
+    {
+      eassert (ch == BIDI_EOB);
+      return false;
+    }
   ch_type = (bidi_type_t) XINT (CHAR_TABLE_REF (bidi_type_table, ch));
   return (ch_type == LRE || ch_type == LRO
           || ch_type == RLE || ch_type == RLO