Empty the bidi cache "stack" when it->sp is zeroed.

Solves crashes due to overflow of bidi cache stack.
Make sure cache is saved and restored around all temporary iterations.

 src/dispnew.c (buffer_posn_from_coords): Save and restore the bidi
 cache around display iteration.
 src/window.c (Fwindow_end, window_scroll_pixel_based)
 (displayed_window_lines, Frecenter): Save and restore the bidi
 cache around display iteration.
 src/bidi.c (bidi_unshelve_cache): Ensure we have enough space before
 restoring the shelved cache.
 (bidi_cache_ensure_space): Don't assume the required size is just
 one BIDI_CACHE_CHUNK away.
 src/xdisp.c (back_to_previous_visible_line_start, reseat_1)
 (init_iterator): Empty the bidi cache "stack".

1 files changed, 36 insertions, 9 deletions

diff --git a/src/window.c b/src/window.c
index 4dbee41c5f4..094cfcfbda3 100644
--- a/src/window.c
+++ b/src/window.c
@@ -1162,6 +1162,7 @@ if it isn't already recorded.  */)
       struct text_pos startp;
       struct it it;
       struct buffer *old_buffer = NULL;
+      void *itdata = NULL;
 
       /* Cannot use Fvertical_motion because that function doesn't
          cope with variable-height lines.  */
@@ -1183,11 +1184,13 @@ if it isn't already recorded.  */)
       else
         SET_TEXT_POS_FROM_MARKER (startp, w->start);
 
+      itdata = bidi_shelve_cache ();
       start_display (&it, w, startp);
       move_it_vertically (&it, window_box_height (w));
       if (it.current_y < it.last_visible_y)
         move_it_past_eol (&it);
       value = make_number (IT_CHARPOS (it));
+      bidi_unshelve_cache (itdata);
 
       if (old_buffer)
         set_buffer_internal (old_buffer);
@@ -4736,6 +4739,7 @@ window_scroll_pixel_based (Lisp_Object window, int n, int whole, int noerror)
   /* True if we fiddled the window vscroll field without really scrolling.  */
   int vscrolled = 0;
   int x, y, rtop, rbot, rowh, vpos;
+  void *itdata = NULL;
 
   SET_TEXT_POS_FROM_MARKER (start, w->start);
 
@@ -4746,6 +4750,7 @@ window_scroll_pixel_based (Lisp_Object window, int n, int whole, int noerror)
 
   if (!pos_visible_p (w, PT, &x, &y, &rtop, &rbot, &rowh, &vpos))
     {
+      itdata = bidi_shelve_cache ();
       /* Move backward half the height of the window.  Performance note:
          vmotion used here is about 10% faster, but would give wrong
          results for variable height lines.  */
@@ -4766,6 +4771,7 @@ window_scroll_pixel_based (Lisp_Object window, int n, int whole, int noerror)
         }
 
       start = it.current.pos;
+      bidi_unshelve_cache (itdata);
     }
   else if (auto_window_vscroll_p)
     {
@@ -4828,6 +4834,7 @@ window_scroll_pixel_based (Lisp_Object window, int n, int whole, int noerror)
       Fset_window_vscroll (window, make_number (0), Qt);
     }
 
+  itdata = bidi_shelve_cache ();
   /* If scroll_preserve_screen_position is non-nil, we try to set
      point in the same window line as it is now, so get that line.  */
   if (!NILP (Vscroll_preserve_screen_position))
@@ -4906,12 +4913,16 @@ window_scroll_pixel_based (Lisp_Object window, int n, int whole, int noerror)
                             - it.current_y + it.max_ascent + it.max_descent);
               adjust_glyphs (it.f);
             }
-          else if (noerror)
-            return;
-          else if (n < 0)       /* could happen with empty buffers */
-            xsignal0 (Qbeginning_of_buffer);
           else
-            xsignal0 (Qend_of_buffer);
+            {
+              bidi_unshelve_cache (itdata);
+              if (noerror)
+                return;
+              else if (n < 0)   /* could happen with empty buffers */
+                xsignal0 (Qbeginning_of_buffer);
+              else
+                xsignal0 (Qend_of_buffer);
+            }
         }
       else
         {
@@ -4919,10 +4930,14 @@ window_scroll_pixel_based (Lisp_Object window, int n, int whole, int noerror)
             /* The first line was only partially visible, make it fully
                visible. */
             w->vscroll = 0;
-          else if (noerror)
-            return;
           else
-            xsignal0 (Qbeginning_of_buffer);
+            {
+              bidi_unshelve_cache (itdata);
+              if (noerror)
+                return;
+              else
+                xsignal0 (Qbeginning_of_buffer);
+            }
         }
 
       /* If control gets here, then we vscrolled.  */
@@ -5066,6 +5081,7 @@ window_scroll_pixel_based (Lisp_Object window, int n, int whole, int noerror)
             SET_PT_BOTH (charpos, bytepos);
         }
     }
+  bidi_unshelve_cache (itdata);
 }
 
 
@@ -5468,6 +5484,7 @@ displayed_window_lines (struct window *w)
   int height = window_box_height (w);
   struct buffer *old_buffer;
   int bottom_y;
+  void *itdata = NULL;
 
   if (XBUFFER (w->buffer) != current_buffer)
     {
@@ -5487,9 +5504,11 @@ displayed_window_lines (struct window *w)
   else
     SET_TEXT_POS_FROM_MARKER (start, w->start);
 
+  itdata = bidi_shelve_cache ();
   start_display (&it, w, start);
   move_it_vertically (&it, height);
   bottom_y = line_bottom_y (&it);
+  bidi_unshelve_cache (itdata);
 
   /* rms: On a non-window display,
      the value of it.vpos at the bottom of the screen
@@ -5588,12 +5607,14 @@ and redisplay normally--don't erase and redraw the frame.  */)
         {
           struct it it;
           struct text_pos pt;
+          void *itdata = bidi_shelve_cache ();
 
           SET_TEXT_POS (pt, PT, PT_BYTE);
           start_display (&it, w, pt);
           move_it_vertically_backward (&it, window_box_height (w) / 2);
           charpos = IT_CHARPOS (it);
           bytepos = IT_BYTEPOS (it);
+          bidi_unshelve_cache (itdata);
         }
       else if (iarg < 0)
         {
@@ -5602,6 +5623,7 @@ and redisplay normally--don't erase and redraw the frame.  */)
           int nlines = -iarg;
           int extra_line_spacing;
           int h = window_box_height (w);
+          void *itdata = bidi_shelve_cache ();
 
           iarg = - max (-iarg, this_scroll_margin);
 
@@ -5639,7 +5661,10 @@ and redisplay normally--don't erase and redraw the frame.  */)
               h -= nlines * (FRAME_LINE_HEIGHT (it.f) + extra_line_spacing);
             }
           if (h <= 0)
-            return Qnil;
+            {
+              bidi_unshelve_cache (itdata);
+              return Qnil;
+            }
 
           /* Now find the new top line (starting position) of the window.  */
           start_display (&it, w, pt);
@@ -5659,6 +5684,8 @@ and redisplay normally--don't erase and redraw the frame.  */)
 
           charpos = IT_CHARPOS (it);
           bytepos = IT_BYTEPOS (it);
+
+          bidi_unshelve_cache (itdata);
         }
       else
         {