* guardians.c (scm_guardian_zombify): Separate scanning for

zombies from marking the pairs of the free list.

diff --git a/libguile/guardians.c b/libguile/guardians.c
index 3dd28a2..2bfdf6c 100644 (file)
--- a/libguile/guardians.c
+++ b/libguile/guardians.c
@@ -1,4 +1,4 @@
-/*     Copyright (C) 1998 Free Software Foundation, Inc.
+/*     Copyright (C) 1998, 1999 Free Software Foundation, Inc.
  * 
  * This program is free software; you can redistribute it and/or modify
  * it under the terms of the GNU General Public License as published by
@@ -184,60 +184,35 @@ scm_guardian_zombify ()
      of this list, so they'll be processed properly.  */
   for (g = first_live_guardian; g; g = g->next)
     {
-      /* Loop through the live list and
-        1. move unmarked objects to the zombies tconc
-        2. mark the live tconc.  */
+      /* Scan the live list for unmarked objects, and move them to the
+         zombies tconc.  */
       SCM tconc_tail = g->live.tail;
-      SCM prev_pair = SCM_BOOL_F;
+      SCM *prev_ptr = &g->live.head;
       SCM pair = g->live.head;
+
       while (pair != tconc_tail)
        {
          SCM next_pair = SCM_CDR (pair);
 
-         /* Since next_pair is never assigned to, and since pair is
-            always set to next_pair at the end of the loop, we know
-            that this loop always reaches every pair in the tconc
-            once, except the tail.
-
-            At each iteration, we either throw the pair out of the
-            live list, or we mark it.  And when we edit a pair's CDR,
-            we make sure to preserve its mark bit.  So when this loop
-            terminates, all pairs left in the live tconc (except the
-            tail) have been marked.
-
-            Whenever we throw out a pair, we always relink the tconc,
-            so the tconc list structure is valid at the end of every
-            iteration.  */
-
          if (SCM_NMARKEDP (SCM_CAR (pair)))
            {
              /* got you, zombie! */
 
              /* out of the live list! */
-             if (SCM_FALSEP (prev_pair))
-               g->live.head = next_pair;
-             else
-               {
-                 SCM_SETCDR (prev_pair, next_pair);
-                 /* Don't lose the mark bit!  */
-                 SCM_SETGCMARK (prev_pair);
-               }
+             *prev_ptr = next_pair;
 
              /* to the zombie list! */
              TCONC_IN (g->zombies, SCM_CAR (pair), pair);
            }
          else
-           {
-             SCM_SETGCMARK (pair);
-             prev_pair = pair;
-           }
+           prev_ptr = SCM_CDRLOC (pair);
 
          pair = next_pair;
        }
-      
-      /* Mark the tconc's tail cell.  All the other pairs in the tconc
-         are already marked.  */
-      SCM_SETGCMARK (tconc_tail);
+
+      /* Mark the cells of the live list.  */
+      for (pair = g->live.head; SCM_NIMP (pair); pair = SCM_GCCDR (pair))
+       SCM_SETGCMARK (pair);
 
       /* Bring the zombies back from the dead.  */
       scm_gc_mark (g->zombies.head);