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bug#12745: crash in bidi_pop_it during (idle) redisplay


From: Eli Zaretskii
Subject: bug#12745: crash in bidi_pop_it during (idle) redisplay
Date: Sat, 03 Nov 2012 11:31:54 +0200

> Date: Wed, 31 Oct 2012 17:46:48 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: alptekin.aker@gmail.com, 12745@debbugs.gnu.org
> 
> I will meanwhile fix init_from_display_pos, because it's certainly
> looks broken, and could well be the root cause for this.

Now done in revision 110767 on the emacs-24 branch.  Will appear on
the trunk on the next merge.  The patch is below, FYI.

=== modified file 'src/xdisp.c'
--- src/xdisp.c 2012-10-20 21:30:51 +0000
+++ src/xdisp.c 2012-11-03 09:25:34 +0000
@@ -928,6 +928,7 @@ static enum move_it_result
        move_it_in_display_line_to (struct it *, ptrdiff_t, int,
                                   enum move_operation_enum);
 void move_it_vertically_backward (struct it *, int);
+static void get_visually_first_element (struct it *);
 static void init_to_row_start (struct it *, struct window *,
                                struct glyph_row *);
 static int init_to_row_end (struct it *, struct window *,
@@ -3113,6 +3114,40 @@ init_from_display_pos (struct it *it, st
       eassert (STRINGP (it->string));
       it->current.string_pos = pos->string_pos;
       it->method = GET_FROM_STRING;
+      it->end_charpos = SCHARS (it->string);
+      /* Set up the bidi iterator for this overlay string.  */
+      if (it->bidi_p)
+       {
+         it->bidi_it.string.lstring = it->string;
+         it->bidi_it.string.s = NULL;
+         it->bidi_it.string.schars = SCHARS (it->string);
+         it->bidi_it.string.bufpos = it->overlay_strings_charpos;
+         it->bidi_it.string.from_disp_str = it->string_from_display_prop_p;
+         it->bidi_it.string.unibyte = !it->multibyte_p;
+         bidi_init_it (IT_STRING_CHARPOS (*it), IT_STRING_BYTEPOS (*it),
+                       FRAME_WINDOW_P (it->f), &it->bidi_it);
+
+         /* Synchronize the state of the bidi iterator with
+            pos->string_pos.  For any string position other than
+            zero, this will be done automagically when we resume
+            iteration over the string and get_visually_first_element
+            is called.  But if string_pos is zero, and the string is
+            to be reordered for display, we need to resync manually,
+            since it could be that the iteration state recorded in
+            pos ended at string_pos of 0 moving backwards in string.  */
+         if (CHARPOS (pos->string_pos) == 0)
+           {
+             get_visually_first_element (it);
+             if (IT_STRING_CHARPOS (*it) != 0)
+               do {
+                 /* Paranoia.  */
+                 eassert (it->bidi_it.charpos < it->bidi_it.string.schars);
+                 bidi_move_to_visually_next (&it->bidi_it);
+               } while (it->bidi_it.charpos != 0);
+           }
+         eassert (IT_STRING_CHARPOS (*it) == it->bidi_it.charpos
+                  && IT_STRING_BYTEPOS (*it) == it->bidi_it.bytepos);
+       }
     }
 
   if (CHARPOS (pos->string_pos) >= 0)
@@ -3122,6 +3157,9 @@ init_from_display_pos (struct it *it, st
         IT should already be filled with that string.  */
       it->current.string_pos = pos->string_pos;
       eassert (STRINGP (it->string));
+      if (it->bidi_p)
+       bidi_init_it (IT_STRING_CHARPOS (*it), IT_STRING_BYTEPOS (*it),
+                     FRAME_WINDOW_P (it->f), &it->bidi_it);
     }
 
   /* Restore position in display vector translations, control






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