From 10b81c59c3dc8e66f1a61e58edcac5b12fd39922 Mon Sep 17 00:00:00 2001
From: simonm <unknown>
Date: Fri, 26 Feb 1999 17:46:09 +0000
Subject: [PATCH] [project @ 1999-02-26 17:46:04 by simonm] Fix a bug in weak
pointer support: if finalize is called on a weak pointer, then a DEAD_WEAK
object could appear on the weak pointer list.
To avoid needing to double-link this list, add a link field to
DEAD_WEAK objects, and remove them from the list at garbage collection
time.
---
ghc/includes/Closures.h | 7 ++++++-
ghc/rts/GC.c | 12 +++++++++++-
ghc/rts/PrimOps.hc | 13 ++++++++-----
3 files changed, 25 insertions(+), 7 deletions(-)
diff --git a/ghc/includes/Closures.h b/ghc/includes/Closures.h
index 23446c457c4d..76aeecc5680c 100644
--- a/ghc/includes/Closures.h
+++ b/ghc/includes/Closures.h
@@ -1,5 +1,5 @@
/* ----------------------------------------------------------------------------
- * $Id: Closures.h,v 1.9 1999/02/19 18:26:04 sewardj Exp $
+ * $Id: Closures.h,v 1.10 1999/02/26 17:46:04 simonm Exp $
*
* (c) The GHC Team, 1998-1999
*
@@ -265,6 +265,11 @@ typedef struct _StgWeak { /* Weak v */
struct _StgWeak *link;
} StgWeak;
+typedef struct _StgDeadWeak { /* Weak v */
+ StgHeader header;
+ struct _StgWeak *link;
+} StgDeadWeak;
+
/* Dynamic stack frames - these have a liveness mask in the object
* itself, rather than in the info table. Useful for generic heap
* check code.
diff --git a/ghc/rts/GC.c b/ghc/rts/GC.c
index 71048a16f90e..64108c9b4d3e 100644
--- a/ghc/rts/GC.c
+++ b/ghc/rts/GC.c
@@ -1,5 +1,5 @@
/* -----------------------------------------------------------------------------
- * $Id: GC.c,v 1.44 1999/02/26 13:36:12 simonm Exp $
+ * $Id: GC.c,v 1.45 1999/02/26 17:46:08 simonm Exp $
*
* (c) The GHC Team 1998-1999
*
@@ -758,6 +758,16 @@ traverse_weak_ptr_list(void)
w = (StgWeak *)((StgEvacuated *)w)->evacuee;
*last_w = w;
}
+
+ /* There might be a DEAD_WEAK on the list if finalizeWeak# was
+ * called on a live weak pointer object. Just remove it.
+ */
+ if (w->header.info == &DEAD_WEAK_info) {
+ next_w = ((StgDeadWeak *)w)->link;
+ *last_w = next_w;
+ continue;
+ }
+
ASSERT(get_itbl(w)->type == WEAK);
/* Now, check whether the key is reachable.
diff --git a/ghc/rts/PrimOps.hc b/ghc/rts/PrimOps.hc
index 33e2d2332d75..37af75ff9264 100644
--- a/ghc/rts/PrimOps.hc
+++ b/ghc/rts/PrimOps.hc
@@ -1,5 +1,5 @@
/* -----------------------------------------------------------------------------
- * $Id: PrimOps.hc,v 1.17 1999/02/26 12:46:48 simonm Exp $
+ * $Id: PrimOps.hc,v 1.18 1999/02/26 17:46:09 simonm Exp $
*
* (c) The GHC Team, 1998-1999
*
@@ -348,10 +348,11 @@ FN_(finalizzeWeakzh_fast)
{
/* R1.p = weak ptr
*/
- StgWeak *w;
+ StgDeadWeak *w;
+ StgClosure *f;
FB_
TICK_RET_UNBOXED_TUP(0);
- w = (StgWeak *)R1.p;
+ w = (StgDeadWeak *)R1.p;
/* already dead? */
if (w->header.info == &DEAD_WEAK_info) {
@@ -360,12 +361,14 @@ FN_(finalizzeWeakzh_fast)
/* kill it */
w->header.info = &DEAD_WEAK_info;
+ f = ((StgWeak *)w)->finalizer;
+ w->link = ((StgWeak *)w)->link;
/* return the finalizer */
- if (w->finalizer == &NO_FINALIZER_closure) {
+ if (f == &NO_FINALIZER_closure) {
RET_NP(0,&NO_FINALIZER_closure);
} else {
- RET_NP(1,w->finalizer);
+ RET_NP(1,f);
}
FE_
}
--
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