From 87912786af9125d062babe2497fc4cb664728eda Mon Sep 17 00:00:00 2001
From: Roberto Ierusalimschy <roberto@inf.puc-rio.br>
Date: Sat, 24 Sep 2011 18:12:01 -0300
Subject: [PATCH] dead objects are not collectable.

---
 lgc.c     | 7 ++++---
 lobject.h | 8 +++++---
 ltable.c  | 4 ++--
 3 files changed, 11 insertions(+), 8 deletions(-)

diff --git a/lgc.c b/lgc.c
index 89cdd2c5..1c741a4a 100644
--- a/lgc.c
+++ b/lgc.c
@@ -100,12 +100,13 @@ static void reallymarkobject (global_State *g, GCObject *o);
 
 
 /*
-** mark a table entry as dead (therefore removing it from the table)
+** if key is not marked, mark its entry as dead (therefore removing it
+** from the table)
 */
 static void removeentry (Node *n) {
   lua_assert(ttisnil(gval(n)));
-  if (iscollectable(gkey(n)))
-    setdeadvalue(gkey(n));  /* dead key; remove it */
+  if (valiswhite(gkey(n)))
+    setdeadvalue(gkey(n));  /* unused and unmarked key; remove it */
 }
 
 
diff --git a/lobject.h b/lobject.h
index 2e660b62..1f32e50f 100644
--- a/lobject.h
+++ b/lobject.h
@@ -1,5 +1,5 @@
 /*
-** $Id: lobject.h,v 2.60 2011/06/13 14:13:06 roberto Exp roberto $
+** $Id: lobject.h,v 2.61 2011/07/04 20:29:02 roberto Exp roberto $
 ** Type definitions for Lua objects
 ** See Copyright Notice in lua.h
 */
@@ -132,7 +132,7 @@ typedef struct lua_TValue TValue;
 #define ttislcf(o)		checktag((o), LUA_TLCF)
 #define ttisuserdata(o)		checktag((o), ctb(LUA_TUSERDATA))
 #define ttisthread(o)		checktag((o), ctb(LUA_TTHREAD))
-#define ttisdeadkey(o)		checktag((o), ctb(LUA_TDEADKEY))
+#define ttisdeadkey(o)		checktag((o), LUA_TDEADKEY)
 
 #define ttisequal(o1,o2)	(rttype(o1) == rttype(o2))
 
@@ -151,6 +151,8 @@ typedef struct lua_TValue TValue;
 #define hvalue(o)	check_exp(ttistable(o), &val_(o).gc->h)
 #define bvalue(o)	check_exp(ttisboolean(o), val_(o).b)
 #define thvalue(o)	check_exp(ttisthread(o), &val_(o).gc->th)
+/* a dead value may get the 'gc' field, but cannot access its contents */
+#define deadvalue(o)	check_exp(ttisdeadkey(o), cast(void *, val_(o).gc))
 
 #define l_isfalse(o)	(ttisnil(o) || (ttisboolean(o) && bvalue(o) == 0))
 
@@ -224,7 +226,7 @@ typedef struct lua_TValue TValue;
     val_(io).gc=cast(GCObject *, (x)); settt_(io, ctb(LUA_TPROTO)); \
     checkliveness(G(L),io); }
 
-#define setdeadvalue(obj)	settt_(obj, ctb(LUA_TDEADKEY))
+#define setdeadvalue(obj)	settt_(obj, LUA_TDEADKEY)
 
 
 
diff --git a/ltable.c b/ltable.c
index 2ac57a07..f6b765d4 100644
--- a/ltable.c
+++ b/ltable.c
@@ -1,5 +1,5 @@
 /*
-** $Id: ltable.c,v 2.62 2011/08/17 20:26:47 roberto Exp roberto $
+** $Id: ltable.c,v 2.63 2011/09/15 17:09:02 roberto Exp roberto $
 ** Lua tables (hash)
 ** See Copyright Notice in lua.h
 */
@@ -152,7 +152,7 @@ static int findindex (lua_State *L, Table *t, StkId key) {
       /* key may be dead already, but it is ok to use it in `next' */
       if (luaV_rawequalobj(gkey(n), key) ||
             (ttisdeadkey(gkey(n)) && iscollectable(key) &&
-             gcvalue(gkey(n)) == gcvalue(key))) {
+             deadvalue(gkey(n)) == gcvalue(key))) {
         i = cast_int(n - gnode(t, 0));  /* key index in hash table */
         /* hash elements are numbered after array ones */
         return i + t->sizearray;