2 files changed, 15 insertions, 4 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index d1e22c730c7..4a388d29570 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,11 @@
+2010-04-17  Eli Zaretskii  <eliz@gnu.org>
+
+        Fix a crash when an NSM character is inserted at BEGV.
+
+        * bidi.c (bidi_init_it): Fix initialization of bidi_it->prev.
+        (bidi_resolve_weak): Don't use prev.type_after_w1 if it is
+        NEUTRAL_B or UNKNOWN_BT.
+
 2010-04-16  Eli Zaretskii  <eliz@gnu.org>
 
         * xdisp.c (set_cursor_from_row): Don't consider possibility of
diff --git a/src/bidi.c b/src/bidi.c
index 0c8a3182510..d637ee0eeb5 100644
--- a/src/bidi.c
+++ b/src/bidi.c
@@ -976,10 +976,11 @@ bidi_init_it (EMACS_INT charpos, EMACS_INT bytepos, struct bidi_it *bidi_it)
   bidi_it->new_paragraph = 1;
   bidi_it->separator_limit = -1;
   bidi_it->type = NEUTRAL_B;
-  bidi_it->type_after_w1 = UNKNOWN_BT;
-  bidi_it->orig_type = UNKNOWN_BT;
+  bidi_it->type_after_w1 = NEUTRAL_B;
+  bidi_it->orig_type = NEUTRAL_B;
   bidi_it->prev_was_pdf = 0;
-  bidi_it->prev.type = bidi_it->prev.type_after_w1 = UNKNOWN_BT;
+  bidi_it->prev.type = bidi_it->prev.type_after_w1 =
+    bidi_it->prev.orig_type = UNKNOWN_BT;
   bidi_it->last_strong.type = bidi_it->last_strong.type_after_w1 =
     bidi_it->last_strong.orig_type = UNKNOWN_BT;
   bidi_it->next_for_neutral.charpos = -1;
@@ -1353,7 +1354,9 @@ bidi_resolve_weak (struct bidi_it *bidi_it)
              current level run, and thus not relevant to this NSM.
              This is why NSM gets the type_after_w1 of the previous
              character.  */
-          if (bidi_it->prev.type != UNKNOWN_BT)
+          if (bidi_it->prev.type_after_w1 != UNKNOWN_BT
+              /* if type_after_w1 is NEUTRAL_B, this NSM is at sor */
+              && bidi_it->prev.type_after_w1 != NEUTRAL_B)
             type = bidi_it->prev.type_after_w1;
           else if (bidi_it->sor == R2L)
             type = STRONG_R;