should not manipulate NULL pointers (even without accessing them)

lfunc.c

@@ -1,5 +1,5 @@
 /*
-** $Id: lfunc.c,v 2.11 2005/05/05 20:47:02 roberto Exp roberto $
+** $Id: lfunc.c,v 2.12 2005/12/22 16:19:56 roberto Exp roberto $
 ** Auxiliary functions to manipulate prototypes and closures
 ** See Copyright Notice in lua.h
 */
@@ -55,7 +55,7 @@ UpVal *luaF_findupval (lua_State *L, StkId level) {
   GCObject **pp = &L->openupval;
   UpVal *p;
   UpVal *uv;
-  while ((p = ngcotouv(*pp)) != NULL && p->v >= level) {
+  while (*pp != NULL && (p = ngcotouv(*pp))->v >= level) {
     lua_assert(p->v != &p->u.value);
     if (p->v == level) {  /* found a corresponding upvalue? */
       if (isdead(g, obj2gco(p)))  /* is it dead? */
@@ -96,7 +96,7 @@ void luaF_freeupval (lua_State *L, UpVal *uv) {
 void luaF_close (lua_State *L, StkId level) {
   UpVal *uv;
   global_State *g = G(L);
-  while ((uv = ngcotouv(L->openupval)) != NULL && uv->v >= level) {
+  while (L->openupval != NULL && (uv = ngcotouv(L->openupval))->v >= level) {
     GCObject *o = obj2gco(uv);
     lua_assert(!isblack(o) && uv->v != &uv->u.value);
     L->openupval = uv->next;  /* remove from `open' list */

lstate.h

@@ -1,5 +1,5 @@
 /*
-** $Id: lstate.h,v 2.26 2006/08/15 19:59:20 roberto Exp roberto $
+** $Id: lstate.h,v 2.27 2006/09/19 13:57:50 roberto Exp roberto $
 ** Global State
 ** See Copyright Notice in lua.h
 */
@@ -156,8 +156,7 @@ union GCObject {
 #define gco2h(o)	check_exp((o)->gch.tt == LUA_TTABLE, &((o)->h))
 #define gco2p(o)	check_exp((o)->gch.tt == LUA_TPROTO, &((o)->p))
 #define gco2uv(o)	check_exp((o)->gch.tt == LUA_TUPVAL, &((o)->uv))
-#define ngcotouv(o) \
-	check_exp((o) == NULL || (o)->gch.tt == LUA_TUPVAL, &((o)->uv))
+#define ngcotouv(o)	check_exp((o)->gch.tt == LUA_TUPVAL, &((o)->uv))
 #define gco2th(o)	check_exp((o)->gch.tt == LUA_TTHREAD, &((o)->th))
 
 /* macro to convert any Lua object into a GCObject */