* alloc.c (free_save_value): New function.

(safe_alloca_unwind): Use it.
* lisp.h (free_save_value): New prototype.
* editfns.c (save_excursion_save): Use Lisp_Misc_Save_Value.
Add comment.
(save_excursion_restore): Adjust to match saved data structure.
Use free_save_value to offload some work from GC.  Drop obsolete
#if 0 code.

4 files changed, 61 insertions, 48 deletions

diff --git a/src/ChangeLog b/src/ChangeLog
index 0808dad2c93..035ef88c485 100644
--- a/src/ChangeLog
+++ b/src/ChangeLog
@@ -1,3 +1,14 @@
+2012-12-03  Dmitry Antipov  <dmantipov@yandex.ru>
+
+        * alloc.c (free_save_value): New function.
+        (safe_alloca_unwind): Use it.
+        * lisp.h (free_save_value): New prototype.
+        * editfns.c (save_excursion_save): Use Lisp_Misc_Save_Value.
+        Add comment.
+        (save_excursion_restore): Adjust to match saved data structure.
+        Use free_save_value to offload some work from GC.  Drop obsolete
+        #if 0 code.
+
 2012-12-03  Chong Yidong  <cyd@gnu.org>
 
         * fileio.c (Vauto_save_list_file_name): Doc fix.
diff --git a/src/alloc.c b/src/alloc.c
index e504b3d93ec..0f105f87207 100644
--- a/src/alloc.c
+++ b/src/alloc.c
@@ -826,12 +826,7 @@ xstrdup (const char *s)
 Lisp_Object
 safe_alloca_unwind (Lisp_Object arg)
 {
-  register struct Lisp_Save_Value *p = XSAVE_VALUE (arg);
-
-  p->dogc = 0;
-  xfree (p->pointer);
-  p->pointer = 0;
-  free_misc (arg);
+  free_save_value (arg);
   return Qnil;
 }
 
@@ -3365,6 +3360,19 @@ make_save_value (void *pointer, ptrdiff_t integer)
   return val;
 }
 
+/* Free a Lisp_Misc_Save_Value object.  */
+
+void
+free_save_value (Lisp_Object save)
+{
+  register struct Lisp_Save_Value *p = XSAVE_VALUE (save);
+
+  p->dogc = 0;
+  xfree (p->pointer);
+  p->pointer = NULL;
+  free_misc (save);
+}
+
 /* Return a Lisp_Misc_Overlay object with specified START, END and PLIST.  */
 
 Lisp_Object
diff --git a/src/editfns.c b/src/editfns.c
index 8122ffdd0d4..390ce21bbca 100644
--- a/src/editfns.c
+++ b/src/editfns.c
@@ -813,38 +813,43 @@ This function does not move point.  */)
                               Qnil, Qt, Qnil);
 }
 
-
+/* Save current buffer state for `save-excursion' special form.
+   We (ab)use Lisp_Misc_Save_Value to allow explicit free and so
+   offload some work from GC.  */
+
 Lisp_Object
 save_excursion_save (void)
 {
-  bool visible = (XBUFFER (XWINDOW (selected_window)->buffer)
-                  == current_buffer);
+  Lisp_Object save, *data = xmalloc (word_size * 4);
+
+  data[0] = Fpoint_marker ();
   /* Do not copy the mark if it points to nowhere.  */
-  Lisp_Object mark = (XMARKER (BVAR (current_buffer, mark))->buffer
-                      ? Fcopy_marker (BVAR (current_buffer, mark), Qnil)
-                      : Qnil);
-
-  return Fcons (Fpoint_marker (),
-                Fcons (mark,
-                       Fcons (visible ? Qt : Qnil,
-                              Fcons (BVAR (current_buffer, mark_active),
-                                     selected_window))));
+  data[1] = (XMARKER (BVAR (current_buffer, mark))->buffer
+             ? Fcopy_marker (BVAR (current_buffer, mark), Qnil)
+             : Qnil);
+  /* Selected window if current buffer is shown in it, nil otherwise.  */
+  data[2] = ((XBUFFER (XWINDOW (selected_window)->buffer) == current_buffer)
+             ? selected_window : Qnil);
+  data[3] = BVAR (current_buffer, mark_active);
+
+  save = make_save_value (data, 4);
+  XSAVE_VALUE (save)->dogc = 1;
+  return save;
 }
 
+/* Restore saved buffer before leaving `save-excursion' special form.  */
+
 Lisp_Object
 save_excursion_restore (Lisp_Object info)
 {
-  Lisp_Object tem, tem1, omark, nmark;
+  Lisp_Object tem, tem1, omark, nmark, *data = XSAVE_VALUE (info)->pointer;
   struct gcpro gcpro1, gcpro2, gcpro3;
-  bool visible_p;
 
-  tem = Fmarker_buffer (XCAR (info));
-  /* If buffer being returned to is now deleted, avoid error */
-  /* Otherwise could get error here while unwinding to top level
-     and crash */
-  /* In that case, Fmarker_buffer returns nil now.  */
+  tem = Fmarker_buffer (data[0]);
+  /* If we're unwinding to top level, saved buffer may be deleted.  This
+     means that all of its markers are unchained and so tem is nil.  */
   if (NILP (tem))
-    return Qnil;
+    goto out;
 
   omark = nmark = Qnil;
   GCPRO3 (info, omark, nmark);
@@ -852,13 +857,12 @@ save_excursion_restore (Lisp_Object info)
   Fset_buffer (tem);
 
   /* Point marker.  */
-  tem = XCAR (info);
+  tem = data[0];
   Fgoto_char (tem);
   unchain_marker (XMARKER (tem));
 
   /* Mark marker.  */
-  info = XCDR (info);
-  tem = XCAR (info);
+  tem = data[1];
   omark = Fmarker_position (BVAR (current_buffer, mark));
   if (NILP (tem))
     unchain_marker (XMARKER (BVAR (current_buffer, mark)));
@@ -869,23 +873,8 @@ save_excursion_restore (Lisp_Object info)
       unchain_marker (XMARKER (tem));
     }
 
-  /* visible */
-  info = XCDR (info);
-  visible_p = !NILP (XCAR (info));
-
-#if 0 /* We used to make the current buffer visible in the selected window
-         if that was true previously.  That avoids some anomalies.
-         But it creates others, and it wasn't documented, and it is simpler
-         and cleaner never to alter the window/buffer connections.  */
-  tem1 = Fcar (tem);
-  if (!NILP (tem1)
-      && current_buffer != XBUFFER (XWINDOW (selected_window)->buffer))
-    Fswitch_to_buffer (Fcurrent_buffer (), Qnil);
-#endif /* 0 */
-
-  /* Mark active */
-  info = XCDR (info);
-  tem = XCAR (info);
+  /* Mark active.  */
+  tem = data[3];
   tem1 = BVAR (current_buffer, mark_active);
   bset_mark_active (current_buffer, tem);
 
@@ -909,8 +898,8 @@ save_excursion_restore (Lisp_Object info)
   /* If buffer was visible in a window, and a different window was
      selected, and the old selected window is still showing this
      buffer, restore point in that window.  */
-  tem = XCDR (info);
-  if (visible_p
+  tem = data[2];
+  if (WINDOWP (tem)
       && !EQ (tem, selected_window)
       && (tem1 = XWINDOW (tem)->buffer,
           (/* Window is live...  */
@@ -920,6 +909,10 @@ save_excursion_restore (Lisp_Object info)
     Fset_window_point (tem, make_number (PT));
 
   UNGCPRO;
+
+ out:
+
+  free_save_value (info);
   return Qnil;
 }
 
diff --git a/src/lisp.h b/src/lisp.h
index 419176d06c8..4dae66eec96 100644
--- a/src/lisp.h
+++ b/src/lisp.h
@@ -2963,6 +2963,7 @@ extern Lisp_Object make_float (double);
 extern void display_malloc_warning (void);
 extern ptrdiff_t inhibit_garbage_collection (void);
 extern Lisp_Object make_save_value (void *, ptrdiff_t);
+extern void free_save_value (Lisp_Object);
 extern Lisp_Object build_overlay (Lisp_Object, Lisp_Object, Lisp_Object);
 extern void free_marker (Lisp_Object);
 extern void free_cons (struct Lisp_Cons *);