Re: Reachable killed buffers

[Dmitry Antipov <dmantipov@yandex.ru>]

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On 09/10/2012 05:25 PM, Stefan Monnier wrote:

> Hmm... how can we find those?  I guess we could handle it during GC when
> we mark the BLV.
[...skip...]
> I think here as well the problem is how to find those windows, and again
> I think the easiest is to do it during GC.

Like this?

Dmitry


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=== modified file 'src/alloc.c'
--- src/alloc.c	2012-09-07 07:24:08 +0000
+++ src/alloc.c	2012-09-10 15:04:15 +0000
@@ -6009,6 +6009,12 @@
 	    {
 	      struct window *w = (struct window *) ptr;
 
+	      /* Lisp code removes killed buffers from buffer lists
+		 of live windows.  For dead windows, we do it here
+		 in attempt to help GC to reclaim killed buffers.  */
+	      if (!WINDOW_VALID_P (obj))
+		window_drain_buffer_lists (w);
+
 	      mark_vectorlike (ptr);
 	      /* Mark glyphs for leaf windows.  Marking window
 		 matrices is sufficient because frame matrices
@@ -6081,10 +6087,10 @@
 	  case SYMBOL_LOCALIZED:
 	    {
 	      struct Lisp_Buffer_Local_Value *blv = SYMBOL_BLV (ptr);
-	      /* If the value is forwarded to a buffer or keyboard field,
-		 these are marked when we see the corresponding object.
-		 And if it's forwarded to a C variable, either it's not
-		 a Lisp_Object var, or it's staticpro'd already.  */
+	      /* If the value is set up for a killed buffer or deleted
+		 frame, restore it's global binding.  */
+	      if (orphaned_local_binding (blv))
+		swap_in_global_binding (ptr);
 	      mark_object (blv->where);
 	      mark_object (blv->valcell);
 	      mark_object (blv->defcell);

=== modified file 'src/data.c'
--- src/data.c	2012-09-09 16:06:33 +0000
+++ src/data.c	2012-09-10 15:11:42 +0000
@@ -1020,7 +1020,18 @@
 	store_symval_forwarding (blv->fwd, blv_value (blv), NULL);
     }
 }
-\f
+
+/* True if binding is set up for a killed buffer or deleted frame.  */
+
+bool
+orphaned_local_binding (struct Lisp_Buffer_Local_Value *blv)
+{
+  Lisp_Object where = blv->where;
+
+  return ((BUFFERP (where) && NILP (BVAR (XBUFFER (where), name)))
+	  || (FRAMEP (where) && !FRAME_LIVE_P (XFRAME (where))));
+}
+
 /* Find the value of a symbol, returning Qunbound if it's not bound.
    This is helpful for code which just wants to get a variable's value
    if it has one, without signaling an error.

=== modified file 'src/lisp.h'
--- src/lisp.h	2012-09-10 01:17:23 +0000
+++ src/lisp.h	2012-09-10 14:26:18 +0000
@@ -2615,6 +2615,7 @@
 extern void set_internal (Lisp_Object, Lisp_Object, Lisp_Object, bool);
 extern void syms_of_data (void);
 extern void init_data (void);
+extern bool orphaned_local_binding (struct Lisp_Buffer_Local_Value *);
 extern void swap_in_global_binding (struct Lisp_Symbol *);
 
 /* Defined in cmds.c */

=== modified file 'src/window.c'
--- src/window.c	2012-09-05 07:18:46 +0000
+++ src/window.c	2012-09-10 14:59:00 +0000
@@ -3002,7 +3002,42 @@
   FOR_EACH_FRAME (tail, frame)
     window_loop (REPLACE_BUFFER_IN_WINDOWS_SAFELY, buffer, 1, frame);
 }
-\f
+
+/* Change alist started at ALISTPTR so it doesn't contains an items whose
+   car is a killed buffer.  */
+
+static inline void
+delete_killed_buffers (Lisp_Object *alistptr)
+{
+  Lisp_Object tail, prev, buffer;
+
+  eassert (alistptr != NULL);
+  for (tail = *alistptr, prev = Qnil; CONSP (tail); tail = XCDR (tail))
+    {
+      buffer = CAR (XCAR (tail));
+      CHECK_BUFFER (buffer);
+      if (NILP (BVAR (XBUFFER (buffer), name)))
+	{
+	  if (NILP (prev))
+	    *alistptr = XCDR (tail);
+	  else
+	    XSETCDR (prev, XCDR (tail));
+	}
+      else
+	prev = tail;
+    }
+}
+
+/* Delete killed buffers from both W's window lists.  Called during GC
+   for dead windows only.  */
+
+void
+window_drain_buffer_lists (struct window *w)
+{
+  delete_killed_buffers (&w->prev_buffers);
+  delete_killed_buffers (&w->next_buffers);
+}
+
 /* If *ROWS or *COLS are too small a size for FRAME, set them to the
    minimum allowable size.  */
 

=== modified file 'src/window.h'
--- src/window.h	2012-09-05 17:05:32 +0000
+++ src/window.h	2012-09-10 14:59:27 +0000
@@ -978,6 +978,7 @@
 extern void temp_output_buffer_show (Lisp_Object);
 extern void replace_buffer_in_windows (Lisp_Object);
 extern void replace_buffer_in_windows_safely (Lisp_Object);
+extern void window_drain_buffer_lists (struct window *);
 extern void init_window_once (void);
 extern void init_window (void);
 extern void syms_of_window (void);