Discard killed buffers from deleted window and frame objects.

This reduces an amount of references to killed buffers and
helps GC to reclaim them faster.
* alloc.c (discard_killed_buffers): New function.
(mark_object): Use it for deleted windows and frames.
(mark_object): If symbol's value is set up for a killed buffer
or deleted frame, restore it's global binding.
* data.c (swap_in_global_binding): Add GC notice.
(swap_in_symval_forwarding): Use convenient set_blv_where.
* window.c (wset_next_buffers, wset_prev_buffers): Move ...
* window.h: ... to here.

1 files changed, 5 insertions, 3 deletions

diff --git a/src/data.c b/src/data.c
index 4678ac1208c..d894ac71a65 100644
--- a/src/data.c
+++ b/src/data.c
@@ -948,8 +948,10 @@ store_symval_forwarding (union Lisp_Fwd *valcontents, register Lisp_Object newva
     }
 }
 
-/* Set up SYMBOL to refer to its global binding.
-   This makes it safe to alter the status of other bindings.  */
+/* Set up SYMBOL to refer to its global binding.  This makes it safe
+   to alter the status of other bindings.  BEWARE: this may be called
+   during the mark phase of GC, where we assume that Lisp_Object slots
+   of BLV are marked after this function has changed them.  */
 
 void
 swap_in_global_binding (struct Lisp_Symbol *symbol)
@@ -1008,7 +1010,7 @@ swap_in_symval_forwarding (struct Lisp_Symbol *symbol, struct Lisp_Buffer_Local_
         else
           {
             tem1 = assq_no_quit (var, BVAR (current_buffer, local_var_alist));
-            XSETBUFFER (blv->where, current_buffer);
+            set_blv_where (blv, Fcurrent_buffer ());
           }
       }
       if (!(blv->found = !NILP (tem1)))