Tag LUA_TUPVALTBC replaced by a flag

It is simpler to signal a to-be-closed upvalue with a boolean flag,
instead of using a different tag.

lfunc.c

@@ -59,14 +59,15 @@ void luaF_initupvals (lua_State *L, LClosure *cl) {
 
 
 /*
-** Create a new upvalue with the given tag at the given level,
+** Create a new upvalue at the given level, and link it to the list of
-** and link it to the list of open upvalues of 'L' after entry 'prev'.
+** open upvalues of 'L' after entry 'prev'.
 **/
-static UpVal *newupval (lua_State *L, int tag, StkId level, UpVal **prev) {
+static UpVal *newupval (lua_State *L, int tbc, StkId level, UpVal **prev) {
-  GCObject *o = luaC_newobj(L, tag, sizeof(UpVal));
+  GCObject *o = luaC_newobj(L, LUA_TUPVAL, sizeof(UpVal));
   UpVal *uv = gco2upv(o);
   UpVal *next = *prev;
   uv->v = s2v(level);  /* current value lives in the stack */
+  uv->tbc = tbc;
   uv->u.open.next = next;  /* link it to list of open upvalues */
   uv->u.open.previous = prev;
   if (next)
@@ -94,7 +95,7 @@ UpVal *luaF_findupval (lua_State *L, StkId level) {
     pp = &p->u.open.next;
   }
   /* not found: create a new upvalue after 'pp' */
-  return newupval(L, LUA_TUPVAL, level, pp);
+  return newupval(L, 0, level, pp);
 }
 
 
@@ -170,7 +171,7 @@ static int callclosemth (lua_State *L, StkId level, int status) {
 static void trynewtbcupval (lua_State *L, void *ud) {
   StkId level = cast(StkId, ud);
   lua_assert(L->openupval == NULL || uplevel(L->openupval) < level);
-  newupval(L, LUA_TUPVALTBC, level, &L->openupval);
+  newupval(L, 1, level, &L->openupval);
 }
 
 
@@ -204,7 +205,7 @@ int luaF_close (lua_State *L, StkId level, int status) {
   while ((uv = L->openupval) != NULL && uplevel(uv) >= level) {
     TValue *slot = &uv->u.value;  /* new position for value */
     lua_assert(uplevel(uv) < L->top);
-    if (uv->tt == LUA_TUPVALTBC && status != NOCLOSINGMETH) {
+    if (uv->tbc && status != NOCLOSINGMETH) {
       /* must run closing method, which may change the stack */
       ptrdiff_t levelrel = savestack(L, level);
       status = callclosemth(L, uplevel(uv), status);

lgc.c

@@ -273,8 +273,7 @@ static void reallymarkobject (global_State *g, GCObject *o) {
       gray2black(o);
       break;
     }
-    case LUA_TUPVAL:
+    case LUA_TUPVAL: {
-    case LUA_TUPVALTBC: {
       UpVal *uv = gco2upv(o);
       if (!upisopen(uv))  /* open upvalues are kept gray */
         gray2black(o);
@@ -571,7 +570,7 @@ static int traversethread (global_State *g, lua_State *th) {
   for (; o < th->top; o++)  /* mark live elements in the stack */
     markvalue(g, s2v(o));
   for (uv = th->openupval; uv != NULL; uv = uv->u.open.next) {
-    if (uv->tt == LUA_TUPVALTBC)  /* to be closed? */
+    if (uv->tbc)  /* to be closed? */
       markobject(g, uv);  /* cannot be collected */
   }
   if (g->gcstate == GCSatomic) {  /* final traversal? */
@@ -706,7 +705,6 @@ static void freeobj (lua_State *L, GCObject *o) {
       luaF_freeproto(L, gco2p(o));
       break;
     case LUA_TUPVAL:
-    case LUA_TUPVALTBC:
       freeupval(L, gco2upv(o));
       break;
     case LUA_TLCL:

lobject.h

@@ -568,6 +568,7 @@ typedef struct Proto {
 */
 typedef struct UpVal {
   CommonHeader;
+  lu_byte tbc;  /* true if it represents a to-be-closed variable */
   TValue *v;  /* points to stack or to its own value */
   union {
     struct {  /* (when open) */
@@ -579,9 +580,6 @@ typedef struct UpVal {
 } UpVal;
 
 
-/* variant for "To Be Closed" upvalues */
-#define LUA_TUPVALTBC	(LUA_TUPVAL | (1 << 4))
-
 
 #define ClosureHeader \
 	CommonHeader; lu_byte nupvalues; GCObject *gclist

lstate.h

@@ -335,8 +335,7 @@ union GCUnion {
 #define gco2t(o)  check_exp((o)->tt == LUA_TTABLE, &((cast_u(o))->h))
 #define gco2p(o)  check_exp((o)->tt == LUA_TPROTO, &((cast_u(o))->p))
 #define gco2th(o)  check_exp((o)->tt == LUA_TTHREAD, &((cast_u(o))->th))
-#define gco2upv(o)  \
+#define gco2upv(o)	check_exp((o)->tt == LUA_TUPVAL, &((cast_u(o))->upv))
-	check_exp(novariant((o)->tt) == LUA_TUPVAL, &((cast_u(o))->upv))
 
 
 /*

ltests.c

@@ -397,8 +397,7 @@ static void checkrefs (global_State *g, GCObject *o) {
       checkudata(g, gco2u(o));
       break;
     }
-    case LUA_TUPVAL:
+    case LUA_TUPVAL: {
-    case LUA_TUPVALTBC: {
       checkvalref(g, o, gco2upv(o)->v);
       break;
     }