Field 'Proto.is_vararg' uses only one bit

So that the other bits can be used for other purposes.

lcode.c

@@ -1849,7 +1849,7 @@ void luaK_finish (FuncState *fs) {
     lua_assert(i == 0 || isOT(*(pc - 1)) == isIT(*pc));
     switch (GET_OPCODE(*pc)) {
       case OP_RETURN0: case OP_RETURN1: {
-        if (!(fs->needclose || p->is_vararg))
+        if (!(fs->needclose || (p->flag & PF_ISVARARG)))
           break;  /* no extra work */
         /* else use OP_RETURN to do the extra work */
         SET_OPCODE(*pc, OP_RETURN);
@@ -1857,7 +1857,7 @@ void luaK_finish (FuncState *fs) {
       case OP_RETURN: case OP_TAILCALL: {
         if (fs->needclose)
           SETARG_k(*pc, 1);  /* signal that it needs to close */
-        if (p->is_vararg)
+        if (p->flag & PF_ISVARARG)
           SETARG_C(*pc, p->numparams + 1);  /* signal that it is vararg */
         break;
       }

ldebug.c

@@ -182,7 +182,7 @@ static const char *upvalname (const Proto *p, int uv) {
 
 
 static const char *findvararg (CallInfo *ci, int n, StkId *pos) {
-  if (clLvalue(s2v(ci->func.p))->p->is_vararg) {
+  if (clLvalue(s2v(ci->func.p))->p->flag & PF_ISVARARG) {
     int nextra = ci->u.l.nextraargs;
     if (n >= -nextra) {  /* 'n' is negative */
       *pos = ci->func.p - nextra - (n + 1);
@@ -301,7 +301,7 @@ static void collectvalidlines (lua_State *L, Closure *f) {
     sethvalue2s(L, L->top.p, t);  /* push it on stack */
     api_incr_top(L);
     setbtvalue(&v);  /* boolean 'true' to be the value of all indices */
-    if (!p->is_vararg)  /* regular function? */
+    if (!(p->flag & PF_ISVARARG))  /* regular function? */
       i = 0;  /* consider all instructions */
     else {  /* vararg function */
       lua_assert(GET_OPCODE(p->code[0]) == OP_VARARGPREP);
@@ -344,7 +344,7 @@ static int auxgetinfo (lua_State *L, const char *what, lua_Debug *ar,
           ar->nparams = 0;
         }
         else {
-          ar->isvararg = f->l.p->is_vararg;
+          ar->isvararg = f->l.p->flag & PF_ISVARARG;
           ar->nparams = f->l.p->numparams;
         }
         break;
@@ -878,7 +878,7 @@ int luaG_tracecall (lua_State *L) {
   Proto *p = ci_func(ci)->p;
   ci->u.l.trap = 1;  /* ensure hooks will be checked */
   if (ci->u.l.savedpc == p->code) {  /* first instruction (not resuming)? */
-    if (p->is_vararg)
+    if (p->flag & PF_ISVARARG)
       return 0;  /* hooks will start at VARARGPREP instruction */
     else if (!(ci->callstatus & CIST_HOOKYIELD))  /* not yieded? */
       luaD_hookcall(L, ci);  /* check 'call' hook */

ldo.c

@@ -391,7 +391,7 @@ static void rethook (lua_State *L, CallInfo *ci, int nres) {
     int ftransfer;
     if (isLua(ci)) {
       Proto *p = ci_func(ci)->p;
-      if (p->is_vararg)
+      if (p->flag & PF_ISVARARG)
         delta = ci->u.l.nextraargs + p->numparams + 1;
     }
     ci->func.p += delta;  /* if vararg, back to virtual 'func' */

ldump.c

@@ -224,7 +224,7 @@ static void dumpFunction (DumpState *D, const Proto *f) {
   dumpInt(D, f->linedefined);
   dumpInt(D, f->lastlinedefined);
   dumpByte(D, f->numparams);
-  dumpByte(D, f->is_vararg);
+  dumpByte(D, f->flag);
   dumpByte(D, f->maxstacksize);
   dumpCode(D, f);
   dumpConstants(D, f);

lfunc.c

@@ -253,7 +253,7 @@ Proto *luaF_newproto (lua_State *L) {
   f->upvalues = NULL;
   f->sizeupvalues = 0;
   f->numparams = 0;
-  f->is_vararg = 0;
+  f->flag = 0;
   f->maxstacksize = 0;
   f->locvars = NULL;
   f->sizelocvars = 0;

lobject.h

@@ -544,13 +544,20 @@ typedef struct AbsLineInfo {
   int line;
 } AbsLineInfo;
 
+
+/*
+** Flags in Prototypes
+*/
+#define PF_ISVARARG	1
+
+
 /*
 ** Function Prototypes
 */
 typedef struct Proto {
   CommonHeader;
   lu_byte numparams;  /* number of fixed (named) parameters */
-  lu_byte is_vararg;
+  lu_byte flag;
   lu_byte maxstacksize;  /* number of registers needed by this function */
   int sizeupvalues;  /* size of 'upvalues' */
   int sizek;  /* size of 'k' */

lparser.c

@@ -959,7 +959,7 @@ static void constructor (LexState *ls, expdesc *t) {
 
 
 static void setvararg (FuncState *fs, int nparams) {
-  fs->f->is_vararg = 1;
+  fs->f->flag |= PF_ISVARARG;
   luaK_codeABC(fs, OP_VARARGPREP, nparams, 0, 0);
 }
 
@@ -1177,7 +1177,7 @@ static void simpleexp (LexState *ls, expdesc *v) {
     }
     case TK_DOTS: {  /* vararg */
       FuncState *fs = ls->fs;
-      check_condition(ls, fs->f->is_vararg,
+      check_condition(ls, fs->f->flag & PF_ISVARARG,
                       "cannot use '...' outside a vararg function");
       init_exp(v, VVARARG, luaK_codeABC(fs, OP_VARARG, 0, 0, 1));
       break;

lundump.c

@@ -287,7 +287,7 @@ static void loadFunction (LoadState *S, Proto *f) {
   f->linedefined = loadInt(S);
   f->lastlinedefined = loadInt(S);
   f->numparams = loadByte(S);
-  f->is_vararg = loadByte(S);
+  f->flag = loadByte(S) & PF_ISVARARG;  /* keep only the meaningful flags */
   f->maxstacksize = loadByte(S);
   loadCode(S, f);
   loadConstants(S, f);