1 files changed, 104 insertions, 59 deletions

diff --git a/src/fns.c b/src/fns.c
index 9621361653e..9ac0bbadf70 100644
--- a/src/fns.c
+++ b/src/fns.c
@@ -3440,6 +3440,7 @@ static unsigned sxhash_string P_ ((unsigned char *, int));
 static unsigned sxhash_list P_ ((Lisp_Object, int));
 static unsigned sxhash_vector P_ ((Lisp_Object, int));
 static unsigned sxhash_bool_vector P_ ((Lisp_Object));
+static int sweep_weak_table P_ ((struct Lisp_Hash_Table *, int));
 
 
 
@@ -4022,6 +4023,86 @@ hash_clear (h)
                            Weak Hash Tables
  ************************************************************************/
 
+/* Sweep weak hash table H.  REMOVE_ENTRIES_P non-zero means remove
+   entries from the table that don't survive the current GC.
+   REMOVE_ENTRIES_P zero means mark entries that are in use.  Value is
+   non-zero if anything was marked.  */
+
+static int
+sweep_weak_table (h, remove_entries_p)
+     struct Lisp_Hash_Table *h;
+     int remove_entries_p;
+{
+  int bucket, n, marked;
+  
+  n = XVECTOR (h->index)->size & ~ARRAY_MARK_FLAG;
+  marked = 0;
+  
+  for (bucket = 0; bucket < n; ++bucket)
+    {
+      Lisp_Object idx, prev;
+
+      /* Follow collision chain, removing entries that
+         don't survive this garbage collection.  */
+      idx = HASH_INDEX (h, bucket);
+      prev = Qnil;
+      while (!GC_NILP (idx))
+        {
+          int remove_p;
+          int i = XFASTINT (idx);
+          Lisp_Object next;
+
+          if (EQ (h->weak, Qkey))
+            remove_p = !survives_gc_p (HASH_KEY (h, i));
+          else if (EQ (h->weak, Qvalue))
+            remove_p = !survives_gc_p (HASH_VALUE (h, i));
+          else if (EQ (h->weak, Qt))
+            remove_p = (!survives_gc_p (HASH_KEY (h, i))
+                        || !survives_gc_p (HASH_VALUE (h, i)));
+          else
+            abort ();
+                      
+          next = HASH_NEXT (h, i);
+
+          if (remove_entries_p)
+            {
+              if (remove_p)
+                {
+                  /* Take out of collision chain.  */
+                  if (GC_NILP (prev))
+                    HASH_INDEX (h, i) = next;
+                  else
+                    HASH_NEXT (h, XFASTINT (prev)) = next;
+                  
+                  /* Add to free list.  */
+                  HASH_NEXT (h, i) = h->next_free;
+                  h->next_free = idx;
+                  
+                  /* Clear key, value, and hash.  */
+                  HASH_KEY (h, i) = HASH_VALUE (h, i) = Qnil;
+                  HASH_HASH (h, i) = Qnil;
+                  
+                  h->count = make_number (XFASTINT (h->count) - 1);
+                }
+            }
+          else
+            {
+              if (!remove_p)
+                {
+                  /* Make sure key and value survive.  */
+                  mark_object (&HASH_KEY (h, i));
+                  mark_object (&HASH_VALUE (h, i));
+                  marked = 1;
+                }
+            }
+
+          idx = next;
+        }
+    }
+
+  return marked;
+}
+
 /* Remove elements from weak hash tables that don't survive the
    current garbage collection.  Remove weak tables that don't survive
    from Vweak_hash_tables.  Called from gc_sweep.  */
@@ -4030,8 +4111,29 @@ void
 sweep_weak_hash_tables ()
 {
   Lisp_Object table;
-  struct Lisp_Hash_Table *h = 0, *prev;
+  struct Lisp_Hash_Table *h, *prev;
+  int marked;
+
+  /* Mark all keys and values that are in use.  Keep on marking until
+     there is no more change.  This is necessary for cases like
+     value-weak table A containing an entry X -> Y, where Y is used in a
+     key-weak table B, Z -> Y.  If B comes after A in the list of weak
+     tables, X -> Y might be removed from A, although when looking at B
+     one finds that it shouldn't.  */
+  do
+    {
+      marked = 0;
+      for (table = Vweak_hash_tables; !GC_NILP (table); table = h->next_weak)
+        {
+          h = XHASH_TABLE (table);
+          if (h->size & ARRAY_MARK_FLAG)
+            marked |= sweep_weak_table (h, 0);
+        }
+    }
+  while (marked);
 
+  /* Remove tables and entries that aren't used.  */
+  prev = NULL;
   for (table = Vweak_hash_tables; !GC_NILP (table); table = h->next_weak)
     {
       prev = h;
@@ -4040,64 +4142,7 @@ sweep_weak_hash_tables ()
       if (h->size & ARRAY_MARK_FLAG)
         {
           if (XFASTINT (h->count) > 0)
-            {
-              int bucket, n;
-
-              n = XVECTOR (h->index)->size & ~ARRAY_MARK_FLAG;
-              for (bucket = 0; bucket < n; ++bucket)
-                {
-                  Lisp_Object idx, prev;
-
-                  /* Follow collision chain, removing entries that
-                     don't survive this garbage collection.  */
-                  idx = HASH_INDEX (h, bucket);
-                  prev = Qnil;
-                  while (!GC_NILP (idx))
-                    {
-                      int remove_p;
-                      int i = XFASTINT (idx);
-                      Lisp_Object next;
-
-                      if (EQ (h->weak, Qkey))
-                        remove_p = !survives_gc_p (HASH_KEY (h, i));
-                      else if (EQ (h->weak, Qvalue))
-                        remove_p = !survives_gc_p (HASH_VALUE (h, i));
-                      else if (EQ (h->weak, Qt))
-                        remove_p = (!survives_gc_p (HASH_KEY (h, i))
-                                    || !survives_gc_p (HASH_VALUE (h, i)));
-                      else
-                        abort ();
-                      
-                      next = HASH_NEXT (h, i);
-                      if (remove_p)
-                        {
-                          /* Take out of collision chain.  */
-                          if (GC_NILP (prev))
-                            HASH_INDEX (h, i) = next;
-                          else
-                            HASH_NEXT (h, XFASTINT (prev)) = next;
-
-                          /* Add to free list.  */
-                          HASH_NEXT (h, i) = h->next_free;
-                          h->next_free = idx;
-
-                          /* Clear key, value, and hash.  */
-                          HASH_KEY (h, i) = HASH_VALUE (h, i) = Qnil;
-                          HASH_HASH (h, i) = Qnil;
-
-                          h->count = make_number (XFASTINT (h->count) - 1);
-                        }
-                      else
-                        {
-                          /* Make sure key and value survive.  */
-                          mark_object (&HASH_KEY (h, i));
-                          mark_object (&HASH_VALUE (h, i));
-                        }
-
-                      idx = next;
-                    }
-                }
-            }
+            sweep_weak_table (h, 1);
         }
       else
         {