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* guardians.c (scm_guardian_zombify): Don't set marks manually ---

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use the macros.  (Thanks to Michael Livshin.)
This commit is contained in:
Jim Blandy 1999-07-19 18:45:57 +00:00
parent 6d8500ad76
commit 55b7e0bd82
1 changed files with 33 additions and 12 deletions
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45
libguile/guardians.c
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@ -176,12 +176,17 @@ void
scm_guardian_zombify () scm_guardian_zombify ()
{ {
guardian_t *g; guardian_t *g;
/* Note that new guardians may be stuck on the end of the live
guardian list as we run this loop. As we move unmarked objects
to the zombie list and mark them, we may find some guarded
guardians. The guardian mark function will stick them on the end
of this list, so they'll be processed properly. */
for (g = first_live_guardian; g; g = g->next) for (g = first_live_guardian; g; g = g->next)
{ {
/* Loop through the live list and /* Loop through the live list and
1. move unmarked objects to the zombies tconc 1. move unmarked objects to the zombies tconc
2. mark the live tconc. 2. mark the live tconc. */
*/
SCM tconc_tail = g->live.tail; SCM tconc_tail = g->live.tail;
SCM prev_pair = SCM_BOOL_F; SCM prev_pair = SCM_BOOL_F;
SCM pair = g->live.head; SCM pair = g->live.head;
@ -189,6 +194,21 @@ scm_guardian_zombify ()
{ {
SCM next_pair = SCM_CDR (pair); 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))) if (SCM_NMARKEDP (SCM_CAR (pair)))
{ {
/* got you, zombie! */ /* got you, zombie! */
@ -197,28 +217,29 @@ scm_guardian_zombify ()
if (SCM_FALSEP (prev_pair)) if (SCM_FALSEP (prev_pair))
g->live.head = next_pair; g->live.head = next_pair;
else else
/* mark previous pair */ {
SCM_SETCDR (prev_pair, next_pair | 1); SCM_SETCDR (prev_pair, next_pair);
/* Don't lose the mark bit! */
SCM_SETGCMARK (prev_pair);
}
/* to the zombie list! */ /* to the zombie list! */
TCONC_IN (g->zombies, SCM_CAR (pair), pair); TCONC_IN (g->zombies, SCM_CAR (pair), pair);
} }
else else
{ {
if (SCM_NFALSEP (prev_pair)) SCM_SETGCMARK (pair);
/* mark previous pair */
SCM_SETCDR (prev_pair, pair | 1);
prev_pair = pair; prev_pair = pair;
} }
pair = next_pair; pair = next_pair;
} }
if (SCM_NFALSEP (prev_pair))
/* mark previous pair */
SCM_SETCDR (prev_pair, pair | 1);
/* mark live list tail */
SCM_SETOR_CDR (tconc_tail, 1);
/* Mark the tconc's tail cell. All the other pairs in the tconc
are already marked. */
SCM_SETGCMARK (tconc_tail);
/* Bring the zombies back from the dead. */
scm_gc_mark (g->zombies.head); scm_gc_mark (g->zombies.head);
} }
} }