diff --git a/include/cubescript/cubescript.hh b/include/cubescript/cubescript.hh
index f5430d3..365d38e 100644
--- a/include/cubescript/cubescript.hh
+++ b/include/cubescript/cubescript.hh
@@ -345,8 +345,7 @@ struct OSTD_EXPORT CsState {
     CsMap<ostd::ConstCharRange, CsIdent *> idents;
     CsVector<CsIdent *> identmap;
 
-    CsIdentLink noalias;
-    CsIdentLink *p_callstack = &noalias;
+    CsIdentLink *p_callstack = nullptr;
 
     int identflags = 0;
     int nodebug = 0;
diff --git a/src/cs_vm.cc b/src/cs_vm.cc
index 904d664..d47e03d 100644
--- a/src/cs_vm.cc
+++ b/src/cs_vm.cc
@@ -66,34 +66,34 @@ bool CsStackState::gap() const {
 CsStackState cs_save_stack(CsState &cs) {
     CsIvar *dalias = static_cast<CsIvar *>(cs.identmap[DbgaliasIdx]);
     if (!dalias->get_value()) {
-        return CsStackState(nullptr, true);
+        return CsStackState(nullptr, !!cs.p_callstack);
     }
     int total = 0, depth = 0;
-    for (CsIdentLink *l = cs.p_callstack; l != &cs.noalias; l = l->next) {
+    for (CsIdentLink *l = cs.p_callstack; l; l = l->next) {
         total++;
     }
     if (!total) {
-        return CsStackState(nullptr, true);
+        return CsStackState(nullptr, false);
     }
     CsStackStateNode *st =
         new CsStackStateNode[ostd::min(total, dalias->get_value())];
     CsStackStateNode *ret = st, *nd = st;
     ++st;
-    for (CsIdentLink *l = cs.p_callstack; l != &cs.noalias; l = l->next) {
+    for (CsIdentLink *l = cs.p_callstack; l; l = l->next) {
         ++depth;
         if (depth < dalias->get_value()) {
             nd->id = l->id;
             nd->index = total - depth + 1;
-            if (l->next == &cs.noalias) {
+            if (!l->next) {
                 nd->next = nullptr;
             } else {
                 nd->next = st;
             }
             nd = st++;
-        } else if (l->next == &cs.noalias) {
+        } else if (!l->next) {
             nd->id = l->id;
             nd->index = 1;
-            nd->next = NULL;
+            nd->next = nullptr;
         }
     }
     return CsStackState(ret, total != dalias->get_value());
@@ -487,7 +487,7 @@ static inline CsAlias *cs_get_lookup_id(CsState &cs, ostd::Uint32 op) {
 
 static inline CsAlias *cs_get_lookuparg_id(CsState &cs, ostd::Uint32 op) {
     CsIdent *id = cs.identmap[op >> 8];
-    if (!(cs.p_callstack->usedargs & (1 << id->get_index()))) {
+    if (!cs_is_arg_used(cs, id)) {
         return nullptr;
     }
     return static_cast<CsAlias *>(id);
@@ -510,10 +510,7 @@ static inline int cs_get_lookupu_type(
                 if (id->get_flags() & CsIdfUnknown) {
                     break;
                 }
-                if (
-                    (id->get_index() < MaxArguments) &&
-                    !(cs.p_callstack->usedargs & (1 << id->get_index()))
-                ) {
+                if ((id->get_index() < MaxArguments) && !cs_is_arg_used(cs, id)) {
                     return CsIdUnknown;
                 }
                 return CsIdAlias;
@@ -655,13 +652,11 @@ static ostd::Uint32 *runcode(CsState &cs, ostd::Uint32 *code, CsValue &result) {
             case CsCodeDoArgs | CsRetString:
             case CsCodeDoArgs | CsRetInt:
             case CsCodeDoArgs | CsRetFloat:
-                if (cs.p_callstack != &cs.noalias) {
-                    cs_do_args(cs, [&]() {
-                        cs.run(args[--numargs].get_code(), result);
-                        force_arg(result, op & CsCodeRetMask);
-                    });
-                    continue;
-                }
+                cs_do_args(cs, [&]() {
+                    cs.run(args[--numargs].get_code(), result);
+                    force_arg(result, op & CsCodeRetMask);
+                });
+                continue;
             /* fallthrough */
             case CsCodeDo | CsRetNull:
             case CsCodeDo | CsRetString:
@@ -899,7 +894,7 @@ static ostd::Uint32 *runcode(CsState &cs, ostd::Uint32 *code, CsValue &result) {
                 continue;
             case CsCodeIdentArg: {
                 CsAlias *a = static_cast<CsAlias *>(cs.identmap[op >> 8]);
-                if (!(cs.p_callstack->usedargs & (1 << a->get_index()))) {
+                if (!cs_is_arg_used(cs, a)) {
                     CsValue nv;
                     CsAliasInternal::push_arg(
                         a, nv, cs.p_callstack->argstack[a->get_index()], false
@@ -919,10 +914,7 @@ static ostd::Uint32 *runcode(CsState &cs, ostd::Uint32 *code, CsValue &result) {
                 ) {
                     id = cs.new_ident(arg.get_strr());
                 }
-                if (
-                    id->get_index() < MaxArguments &&
-                    !(cs.p_callstack->usedargs & (1 << id->get_index()))
-                ) {
+                if ((id->get_index() < MaxArguments) && !cs_is_arg_used(cs, id)) {
                     CsValue nv;
                     CsAliasInternal::push_arg(
                         static_cast<CsAlias *>(id), nv,
@@ -1401,7 +1393,7 @@ static ostd::Uint32 *runcode(CsState &cs, ostd::Uint32 *code, CsValue &result) {
                 result.force_null();
                 CsIdent *id = cs.identmap[op >> 13];
                 int callargs = (op >> 8) & 0x1F, offset = numargs - callargs;
-                if (!(cs.p_callstack->usedargs & (1 << id->get_index()))) {
+                if (!cs_is_arg_used(cs, id)) {
                     numargs = offset;
                     force_arg(result, op & CsCodeRetMask);
                     continue;
@@ -1514,8 +1506,8 @@ noid:
                     case CsIdAlias: {
                         CsAlias *a = static_cast<CsAlias *>(id);
                         if (
-                            a->get_index() < MaxArguments &&
-                            !(cs.p_callstack->usedargs & (1 << a->get_index()))
+                            (a->get_index() < MaxArguments) &&
+                            !cs_is_arg_used(cs, a)
                         ) {
                             numargs = offset - 1;
                             force_arg(result, op & CsCodeRetMask);
@@ -1619,10 +1611,10 @@ void CsState::run(CsIdent *id, CsValueRange args, CsValue &ret) {
                 break;
             case CsIdentType::Alias: {
                 CsAlias *a = static_cast<CsAlias *>(id);
-                if (a->get_index() < MaxArguments) {
-                    if (!(p_callstack->usedargs & (1 << a->get_index()))) {
-                        break;
-                    }
+                if (
+                    (a->get_index() < MaxArguments) && !cs_is_arg_used(*this, a)
+                ) {
+                    break;
                 }
                 if (a->get_value().get_type() == CsValueType::Null) {
                     break;
diff --git a/src/cs_vm.hh b/src/cs_vm.hh
index 7bb8fd5..5997978 100644
--- a/src/cs_vm.hh
+++ b/src/cs_vm.hh
@@ -236,6 +236,13 @@ static inline void bcode_decr(ostd::Uint32 *bc) {
     }
 }
 
+static inline bool cs_is_arg_used(CsState &cs, CsIdent *id) {
+    if (!cs.p_callstack) {
+        return true;
+    }
+    return cs.p_callstack->usedargs & (1 << id->get_index());
+}
+
 struct CsAliasInternal {
     static void push_arg(
         CsAlias *a, CsValue &v, CsIdentStack &st, bool um = true
@@ -284,7 +291,7 @@ struct CsAliasInternal {
     }
 
     static void set_arg(CsAlias *a, CsState &cs, CsValue &v) {
-        if (cs.p_callstack->usedargs & (1 << a->get_index())) {
+        if (cs_is_arg_used(cs, a)) {
             a->p_val = ostd::move(v);
             clean_code(a);
         } else {
@@ -323,6 +330,10 @@ struct CsAliasInternal {
 
 template<typename F>
 static void cs_do_args(CsState &cs, F body) {
+    if (!cs.p_callstack) {
+        body();
+        return;
+    }
     CsIdentStack argstack[MaxArguments];
     int argmask1 = cs.p_callstack->usedargs;
     for (int i = 0; argmask1; argmask1 >>= 1, ++i) {
diff --git a/src/cubescript.cc b/src/cubescript.cc
index 42209a4..0e83b75 100644
--- a/src/cubescript.cc
+++ b/src/cubescript.cc
@@ -255,11 +255,6 @@ void cs_init_lib_base(CsState &cs);
 CsState::CsState():
     p_callhook(), p_panicfunc(), p_out(&ostd::out), p_err(&ostd::err)
 {
-    noalias.id = nullptr;
-    noalias.next = nullptr;
-    noalias.usedargs = (1 << MaxArguments) - 1;
-    noalias.argstack = nullptr;
-
     /* default panic func */
     p_panicfunc = [this](ostd::ConstCharRange v, CsStackState) {
         get_err().writefln(
@@ -286,11 +281,7 @@ CsState::CsState():
     })->p_type = CsIdDo;
 
     new_command("doargs", "e", [this](CsValueRange args, CsValue &res) {
-        if (p_callstack != &noalias) {
-            cs_do_args(*this, [&]() { run(args[0].get_code(), res); });
-        } else {
-            run(args[0].get_code(), res);
-        }
+        cs_do_args(*this, [&]() { run(args[0].get_code(), res); });
     })->p_type = CsIdDoArgs;
 
     new_command("if", "tee", [this](CsValueRange args, CsValue &res) {
@@ -881,10 +872,7 @@ CsState::get_alias_val(ostd::ConstCharRange name) {
     if (!a) {
         return ostd::nothing;
     }
-    if (
-        (a->get_index() < MaxArguments) &&
-        !(p_callstack->usedargs & (1 << a->get_index()))
-    ) {
+    if ((a->get_index() < MaxArguments) && !cs_is_arg_used(*this, a)) {
         return ostd::nothing;
     }
     return ostd::move(a->get_value().get_str());