diff --git a/src/ceval.h b/src/ceval.h
index ee884bfb..995bb5c0 100644
--- a/src/ceval.h
+++ b/src/ceval.h
@@ -141,7 +141,6 @@ __NEXT_STEP:;
         _0 = vm->builtins->attr().try_get(_name);
         if(_0 != nullptr) { PUSH(_0); DISPATCH(); }
         vm->NameError(_name);
-        DISPATCH();
     } DISPATCH();
     TARGET(LOAD_GLOBAL)
         heap._auto_collect();
diff --git a/src/compiler.h b/src/compiler.h
index 06a81c51..b528ec5b 100644
--- a/src/compiler.h
+++ b/src/compiler.h
@@ -707,8 +707,8 @@ __SUBSCR_END:
                 // stack size is n+1
                 Expr_ val = ctx()->s_expr.popx();
                 val->emit(ctx());
-                for(int i=1; i<n; i++) ctx()->emit(OP_DUP_TOP, BC_NOARG, BC_KEEPLINE);
-                for(int i=0; i<n; i++){
+                for(int j=1; j<n; j++) ctx()->emit(OP_DUP_TOP, BC_NOARG, BC_KEEPLINE);
+                for(int j=0; j<n; j++){
                     auto e = ctx()->s_expr.popx();
                     if(e->is_starred()) SyntaxError();
                     bool ok = e->emit_store(ctx());
diff --git a/src/expr.h b/src/expr.h
index d779ecf8..c0958549 100644
--- a/src/expr.h
+++ b/src/expr.h
@@ -28,10 +28,16 @@ struct Expr{
     bool is_starred() const { return star_level() > 0; }
 
     // for OP_DELETE_XXX
-    [[nodiscard]] virtual bool emit_del(CodeEmitContext* ctx) { return false; }
+    [[nodiscard]] virtual bool emit_del(CodeEmitContext* ctx) {
+        PK_UNUSED(ctx);
+        return false;
+    }
 
     // for OP_STORE_XXX
-    [[nodiscard]] virtual bool emit_store(CodeEmitContext* ctx) { return false; }
+    [[nodiscard]] virtual bool emit_store(CodeEmitContext* ctx) {
+        PK_UNUSED(ctx);
+        return false;
+    }
 };
 
 struct CodeEmitContext{
diff --git a/src/vm.h b/src/vm.h
index d5590d21..e3070bf8 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -962,6 +962,7 @@ inline PyObject* VM::format(Str spec, PyObject* obj){
         }
     }catch(...){
         ValueError("invalid format specifer");
+        UNREACHABLE();
     }
 
     if(type != 'f' && dot >= 0) ValueError("precision not allowed in the format specifier");
@@ -1307,18 +1308,18 @@ inline PyObject* VM::vectorcall(int ARGC, int KWARGC, bool op_call){
             vkwargs = nullptr;
         }
 
-        for(int i=0; i<kwargs.size(); i+=2){
-            StrName key(CAST(int, kwargs[i]));
+        for(int j=0; j<kwargs.size(); j+=2){
+            StrName key(CAST(int, kwargs[j]));
             int index = co->varnames_inv.try_get(key);
             if(index < 0){
                 if(vkwargs == nullptr){
                     TypeError(fmt(key.escape(), " is an invalid keyword argument for ", co->name, "()"));
                 }else{
                     Dict& dict = _CAST(Dict&, vkwargs);
-                    dict.set(VAR(key.sv()), kwargs[i+1]);
+                    dict.set(VAR(key.sv()), kwargs[j+1]);
                 }
             }else{
-                buffer[index] = kwargs[i+1];
+                buffer[index] = kwargs[j+1];
             }
         }
         
@@ -1332,7 +1333,7 @@ inline PyObject* VM::vectorcall(int ARGC, int KWARGC, bool op_call){
 
         // copy buffer back to stack
         s_data.reset(args.begin());
-        for(int i=0; i<co_nlocals; i++) PUSH(buffer[i]);
+        for(int j=0; j<co_nlocals; j++) PUSH(buffer[j]);
         callstack.emplace(&s_data, p0, co, fn._module, callable, FastLocals(co, args.begin()));
         if(op_call) return PY_OP_CALL;
         return _run_top_frame();
@@ -1357,8 +1358,8 @@ inline PyObject* VM::vectorcall(int ARGC, int KWARGC, bool op_call){
             PUSH(new_f);
             PUSH(PY_NULL);
             PUSH(callable);    // cls
-            for(PyObject* obj: args) PUSH(obj);
-            for(PyObject* obj: kwargs) PUSH(obj);
+            for(PyObject* o: args) PUSH(o);
+            for(PyObject* o: kwargs) PUSH(o);
             // if obj is not an instance of callable, the behavior is undefined
             obj = vectorcall(ARGC+1, KWARGC);
         }