diff --git a/include/pocketpy/interpreter/vm.h b/include/pocketpy/interpreter/vm.h
index 903d5347..b25fcda7 100644
--- a/include/pocketpy/interpreter/vm.h
+++ b/include/pocketpy/interpreter/vm.h
@@ -12,8 +12,8 @@ typedef struct pk_TypeInfo{
     StrName name;
     Type base;
 
-    PyObject* obj;      // the type object itself
-    PyObject* module;   // the module where the type is defined
+    PyVar self;      // the type object itself
+    PyVar module;    // the module where the type is defined
     bool subclass_enabled;
 
     void (*dtor)(void*);
@@ -38,7 +38,7 @@ typedef struct pk_TypeInfo{
     py_CFunction on_end_subclass;   // for enum module
 } pk_TypeInfo;
 
-void pk_TypeInfo__ctor(pk_TypeInfo* self, StrName name, Type base, PyObject* obj, PyObject* module, bool subclass_enabled);
+void pk_TypeInfo__ctor(pk_TypeInfo* self, StrName name, Type base, PyObject* obj, const PyVar* module, bool subclass_enabled);
 void pk_TypeInfo__dtor(pk_TypeInfo* self);
 
 typedef struct pk_VM {
@@ -47,14 +47,14 @@ typedef struct pk_VM {
     pk_NameDict modules;
     c11_vector/*T=pk_TypeInfo*/ types;
 
-    PyObject* StopIteration;    // a special Exception class
-    PyObject* builtins;         // builtins module
-    PyObject* main;             // __main__ module
+    PyVar StopIteration;    // a special Exception class
+    PyVar builtins;         // builtins module
+    PyVar main;             // __main__ module
 
-    void (*_ceval_on_step)(struct pk_VM*, Frame*, Bytecode);
-    unsigned char* (*_import_file)(struct pk_VM*, const char*);
-    void (*_stdout)(struct pk_VM*, const char*);
-    void (*_stderr)(struct pk_VM*, const char*);
+    void (*_ceval_on_step)(Frame*, Bytecode);
+    unsigned char* (*_import_file)(const char*);
+    void (*_stdout)(const char*);
+    void (*_stderr)(const char*);
     
     // singleton objects
     PyVar True, False, None, NotImplemented, Ellipsis;
@@ -62,6 +62,8 @@ typedef struct pk_VM {
     py_Error* last_error;
     // last retval
     PyVar last_retval;
+    // registers
+    PyVar reg[8];
 
     PyObject* __curr_class;
     PyObject* __cached_object_new;
@@ -81,16 +83,15 @@ void pk_VM__push_frame(pk_VM* self, Frame* frame);
 void pk_VM__pop_frame(pk_VM* self);
 
 typedef enum pk_FrameResult{
-    RES_ERROR,
+    RES_RETURN,
     RES_CALL,
     RES_YIELD,
-    RES_RETURN
+    RES_ERROR,
 } pk_FrameResult;
 
 pk_FrameResult pk_VM__run_top_frame(pk_VM* self);
 
-Type pk_VM__new_type(pk_VM* self, const char* name, Type base, PyObject* module, bool subclass_enabled);
-PyObject* pk_VM__new_module(pk_VM* self, const char* name, const char* package);
+Type pk_VM__new_type(pk_VM* self, const char* name, Type base, const PyVar* module, bool subclass_enabled);
 
 #ifdef __cplusplus
 }
diff --git a/include/pocketpy/interpreter/vm.hpp b/include/pocketpy/interpreter/vm.hpp
deleted file mode 100644
index 0eef3b5f..00000000
--- a/include/pocketpy/interpreter/vm.hpp
+++ /dev/null
@@ -1,719 +0,0 @@
-#pragma once
-
-#include "pocketpy/objects/object.h"
-#include "pocketpy/objects/base.h"
-#include "pocketpy/objects/dict.hpp"
-#include "pocketpy/objects/error.hpp"
-#include "pocketpy/objects/builtins.hpp"
-#include "pocketpy/interpreter/gc.h"
-#include "pocketpy/interpreter/frame.h"
-#include "pocketpy/interpreter/profiler.hpp"
-
-#include <typeindex>
-
-namespace pkpy {
-
-/* Stack manipulation macros */
-// https://github.com/python/cpython/blob/3.9/Python/ceval.c#L1123
-#define TOP() (s_data.sp[-1])
-#define SECOND() (s_data.sp[-2])
-#define THIRD() (s_data.sp[-3])
-#define STACK_SHRINK(n) (s_data.sp -= (n))
-#define PUSH(v) (*s_data.sp++ = (v))
-#define PUSH_NULL() memset(s_data.sp++, 0, sizeof(PyVar))
-#define POP() (--s_data.sp)
-#define POPX() (*--s_data.sp)
-#define STACK_VIEW(n) (ArgsView(s_data.sp - (n), s_data.sp))
-
-typedef PyVar (*BinaryFuncC)(VM*, PyVar, PyVar);
-typedef void (*RegisterFunc)(VM*, PyObject*, PyObject*);
-
-#if PK_ENABLE_PROFILER
-struct NextBreakpoint {
-    int callstack_size;
-    int lineno;
-    bool should_step_into;
-
-    NextBreakpoint() : callstack_size(0) {}
-
-    NextBreakpoint(int callstack_size, int lineno, bool should_step_into) :
-        callstack_size(callstack_size), lineno(lineno), should_step_into(should_step_into) {}
-
-    void _step(VM* vm);
-
-    bool empty() const { return callstack_size == 0; }
-};
-#endif
-
-struct PyTypeInfo {
-    struct Vt {
-        void (*_dtor)(void*);
-        void (*_gc_mark)(void*, VM*);
-
-        Vt() : _dtor(nullptr), _gc_mark(nullptr) {}
-
-        operator bool () const { return _dtor || _gc_mark; }
-
-        template <typename T>
-        inline static Vt get() {
-            static_assert(std::is_same_v<T, std::decay_t<T>>);
-            Vt vt;
-            if constexpr(!std::is_trivially_destructible_v<T>) {
-                vt._dtor = [](void* p) {
-                    ((T*)p)->~T();
-                };
-            }
-            if constexpr(has_gc_marker<T>::value) {
-                vt._gc_mark = [](void* p, VM* vm) {
-                    ((T*)p)->_gc_mark(vm);
-                };
-            }
-            return vt;
-        }
-    };
-
-    PyObject* obj;  // never be garbage collected
-    Type base;
-    PyObject* mod;  // never be garbage collected
-    StrName name;
-    bool subclass_enabled;
-    Vt vt;
-
-    PyTypeInfo(PyObject* obj, Type base, PyObject* mod, StrName name, bool subclass_enabled, Vt vt = {}) :
-        obj(obj), base(base), mod(mod), name(name), subclass_enabled(subclass_enabled), vt(vt) {}
-
-    vector<StrName> annotated_fields;
-
-    // unary operators
-    Str (*m__repr__)(VM* vm, PyVar) = nullptr;
-    Str (*m__str__)(VM* vm, PyVar) = nullptr;
-    i64 (*m__hash__)(VM* vm, PyVar) = nullptr;
-    i64 (*m__len__)(VM* vm, PyVar) = nullptr;
-    PyVar (*m__iter__)(VM* vm, PyVar) = nullptr;
-    unsigned (*op__next__)(VM* vm, PyVar) = nullptr;
-    PyVar (*m__neg__)(VM* vm, PyVar) = nullptr;
-    PyVar (*m__invert__)(VM* vm, PyVar) = nullptr;
-
-    BinaryFuncC m__eq__ = nullptr;
-    BinaryFuncC m__lt__ = nullptr;
-    BinaryFuncC m__le__ = nullptr;
-    BinaryFuncC m__gt__ = nullptr;
-    BinaryFuncC m__ge__ = nullptr;
-    BinaryFuncC m__contains__ = nullptr;
-
-    // binary operators
-    BinaryFuncC m__add__ = nullptr;
-    BinaryFuncC m__sub__ = nullptr;
-    BinaryFuncC m__mul__ = nullptr;
-    BinaryFuncC m__truediv__ = nullptr;
-    BinaryFuncC m__floordiv__ = nullptr;
-    BinaryFuncC m__mod__ = nullptr;
-    BinaryFuncC m__pow__ = nullptr;
-    BinaryFuncC m__matmul__ = nullptr;
-
-    BinaryFuncC m__lshift__ = nullptr;
-    BinaryFuncC m__rshift__ = nullptr;
-    BinaryFuncC m__and__ = nullptr;
-    BinaryFuncC m__or__ = nullptr;
-    BinaryFuncC m__xor__ = nullptr;
-
-    // indexer
-    PyVar (*m__getitem__)(VM* vm, PyVar, PyVar) = nullptr;
-    void (*m__setitem__)(VM* vm, PyVar, PyVar, PyVar) = nullptr;
-    void (*m__delitem__)(VM* vm, PyVar, PyVar) = nullptr;
-
-    // attributes
-    void (*m__setattr__)(VM* vm, PyVar, StrName, PyVar) = nullptr;
-    PyVar (*m__getattr__)(VM* vm, PyVar, StrName) = nullptr;
-    bool (*m__delattr__)(VM* vm, PyVar, StrName) = nullptr;
-
-    // backdoors
-    void (*on_end_subclass)(VM* vm, PyTypeInfo*) = nullptr;
-};
-
-struct ImportContext {
-    PK_ALWAYS_PASS_BY_POINTER(ImportContext)
-
-    vector<Str> pending;
-    vector<bool> pending_is_init;  // a.k.a __init__.py
-
-    ImportContext() {}
-
-    struct Temp {
-        PK_ALWAYS_PASS_BY_POINTER(Temp)
-
-        ImportContext* ctx;
-
-        Temp(ImportContext* ctx, Str name, bool is_init) : ctx(ctx) {
-            ctx->pending.push_back(name);
-            ctx->pending_is_init.push_back(is_init);
-        }
-
-        ~Temp() {
-            ctx->pending.pop_back();
-            ctx->pending_is_init.pop_back();
-        }
-    };
-
-    Temp scope(Str name, bool is_init) { return {this, name, is_init}; }
-};
-
-class VM {
-    PK_ALWAYS_PASS_BY_POINTER(VM)
-
-    VM* vm;  // self reference to simplify code
-
-public:
-    pk_ManagedHeap heap;
-    Frame* top_frame;
-    vector<PyTypeInfo> _all_types;
-
-    pk_NameDict _modules;                       // loaded modules
-    small_map<StrName, Str> _lazy_modules;      // lazy loaded modules
-
-    struct {
-        PyObject* error;
-        vector<ArgsView> s_view;
-    } __c;
-
-    PyObject* StopIteration;  // a special Exception class
-    PyObject* builtins;
-    PyObject* _main;
-
-    // typeid -> Type
-    small_map<std::type_index, Type> _cxx_typeid_map;
-    // this is for repr() recursion detection (no need to mark)
-    vector<PyObject*> _repr_recursion_set;
-
-    ImportContext __import_context;
-    PyObject* __last_exception;
-    PyObject* __curr_class;
-    PyVar __cached_object_new;
-    FuncDecl_ __dynamic_func_decl;
-    PyVar __vectorcall_buffer[PK_MAX_CO_VARNAMES];
-
-#if PK_ENABLE_PROFILER
-    LineProfiler* _profiler = nullptr;
-    NextBreakpoint _next_breakpoint;
-#endif
-
-    void (*_ceval_on_step)(VM*, Frame*, Bytecode bc);
-    void (*_stdout)(const char*, int);
-    void (*_stderr)(const char*, int);
-    unsigned char* (*_import_handler)(const char*, int*);
-
-    // for quick access
-    constexpr static Type tp_object = Type(1), tp_type = Type(2);
-    constexpr static Type tp_int = Type(3), tp_float = Type(4), tp_bool = Type(5),
-                          tp_str = Type(6);
-    constexpr static Type tp_list = Type(7), tp_tuple = Type(8);
-    constexpr static Type tp_slice = Type(9), tp_range = Type(10), tp_module = Type(11);
-    constexpr static Type tp_function = Type(12), tp_native_func = Type(13), tp_bound_method = Type(14);
-    constexpr static Type tp_super = Type(15), tp_exception = Type(16), tp_bytes = Type(17), tp_mappingproxy = Type(18);
-    constexpr static Type tp_dict = Type(19), tp_property = Type(20), tp_star_wrapper = Type(21);
-    constexpr static Type tp_staticmethod = Type(22), tp_classmethod = Type(23);
-    constexpr static Type tp_none_type = Type(24), tp_not_implemented_type = Type(25);
-    constexpr static Type tp_ellipsis = Type(26);
-
-    PyVar True;
-    PyVar False;
-    PyVar None;
-    PyVar NotImplemented;
-    PyVar Ellipsis;
-
-    const bool enable_os;
-
-    // put s_data at the end of VM struct to improve cache locality
-    ValueStack s_data;
-
-    VM(bool enable_os = true);
-
-    // clang-format off
-#if PK_REGION("Python Equivalents")
-    Str py_str(PyVar obj);                              // x -> str(x)
-    Str py_repr(PyVar obj);                             // x -> repr(x)
-    Str py_json(PyVar obj);                             // x -> json.dumps(x)
-
-    PyVar py_iter(PyVar obj);                           // x -> iter(x)
-    PyVar py_next(PyVar);                               // x -> next(x)
-    PyVar _py_next(const PyTypeInfo*, PyVar);           // x -> next(x) with type info cache
-    PyObject* py_import(Str path, bool throw_err=true); // x -> __import__(x)
-    PyVar py_negate(PyVar obj);                         // x -> -x
-
-    List py_list(PyVar);                                // x -> list(x)
-    bool py_callable(PyVar obj);                        // x -> callable(x)
-    bool py_bool(PyVar obj){                            // x -> bool(x)
-        if(obj.type == tp_bool) return (bool)obj.extra;
-        return __py_bool_non_trivial(obj);
-    }
-    i64 py_hash(PyVar obj);                             // x -> hash(x)
-
-    bool py_eq(PyVar lhs, PyVar rhs);                   // (lhs, rhs) -> lhs == rhs
-    bool py_lt(PyVar lhs, PyVar rhs);                   // (lhs, rhs) -> lhs < rhs
-    bool py_le(PyVar lhs, PyVar rhs);                   // (lhs, rhs) -> lhs <= rhs
-    bool py_gt(PyVar lhs, PyVar rhs);                   // (lhs, rhs) -> lhs > rhs
-    bool py_ge(PyVar lhs, PyVar rhs);                   // (lhs, rhs) -> lhs >= rhs
-    bool py_ne(PyVar lhs, PyVar rhs){                   // (lhs, rhs) -> lhs != rhs
-        return !py_eq(lhs, rhs);
-    }
-
-    PyVar py_op(const char* name);                 // (name) -> operator.name
-
-    void py_exec(const char*, PyVar, PyVar);       // exec(source, globals, locals)
-    PyVar py_eval(const char*, PyVar, PyVar);      // eval(source, globals, locals)
-#endif
-
-#if PK_REGION("Utility Methods")
-    ArgsView cast_array_view(PyVar obj);
-    void set_main_argv(int argc, char** argv);
-    i64 normalized_index(i64 index, int size);
-    Str disassemble(CodeObject* co);
-    void parse_int_slice(const Slice& s, int length, int& start, int& stop, int& step);
-    void obj_gc_mark(PyVar obj) { if(obj.is_ptr) __obj_gc_mark(obj._obj); }
-    void obj_gc_mark(PyObject* p) { if(p) __obj_gc_mark(p); }
-#endif
-
-#if PK_REGION("Name Lookup Methods")
-    PyVar* find_name_in_mro(Type cls, StrName name);
-    PyVar get_unbound_method(PyVar obj, StrName name, PyVar* self, bool throw_err=true, bool fallback=false);
-    PyVar getattr(PyVar obj, StrName name, bool throw_err=true);
-    void delattr(PyVar obj, StrName name);
-    void setattr(PyVar obj, StrName name, PyVar value);
-#endif
-
-#if PK_REGION("Source Execution Methods")
-    CodeObject* compile(std::string_view source, const Str& filename, CompileMode mode, bool unknown_global_scope=false);
-    Str precompile(std::string_view source, const Str& filename, CompileMode mode);
-    PyVar exec(std::string_view source, Str filename, CompileMode mode, PyObject* _module=nullptr);
-    PyVar exec(std::string_view source);
-    PyVar eval(std::string_view source);
-
-    template<typename ...Args>
-    PyVar _exec(Args&&... args){
-        callstack.emplace(s_data.sp, std::forward<Args>(args)...);
-        return __run_top_frame();
-    }
-#endif
-
-#if PK_REGION("Invocation Methods")
-    PyVar vectorcall(int ARGC, int KWARGC=0, bool op_call=false);
-
-    template<typename... Args>
-    PyVar call(PyVar callable, Args&&... args){
-        PUSH(callable); PUSH_NULL();
-        __push_varargs(args...);
-        return vectorcall(sizeof...(args));
-    }
-
-    template<typename... Args>
-    PyVar call_method(PyVar self, PyVar callable, Args&&... args){
-        PUSH(callable); PUSH(self);
-        __push_varargs(args...);
-        return vectorcall(sizeof...(args));
-    }
-
-    template<typename... Args>
-    PyVar call_method(PyVar self, StrName name, Args&&... args){
-        PyVar callable = get_unbound_method(self, name, &self);
-        return call_method(self, callable, args...);
-    }
-#endif
-
-#if PK_REGION("Logging Methods")
-    virtual void stdout_write(const Str& s){ _stdout(s.c_str(), s.size); }
-    virtual void stderr_write(const Str& s){ _stderr(s.c_str(), s.size); }
-#endif
-
-#if PK_REGION("Magic Bindings")
-    void bind__repr__(Type type, Str (*f)(VM*, PyVar));
-    void bind__str__(Type type, Str (*f)(VM*, PyVar));
-    void bind__iter__(Type type, PyVar (*f)(VM*, PyVar));
-
-    void bind__next__(Type type, unsigned (*f)(VM*, PyVar));
-    [[deprecated]] void bind__next__(Type type, PyVar (*f)(VM*, PyVar));
-    void bind__neg__(Type type, PyVar (*f)(VM*, PyVar));
-    void bind__invert__(Type type, PyVar (*f)(VM*, PyVar));
-    void bind__hash__(Type type, i64 (*f)(VM* vm, PyVar));
-    void bind__len__(Type type, i64 (*f)(VM* vm, PyVar));
-
-    void bind__eq__(Type type, BinaryFuncC f);
-    void bind__lt__(Type type, BinaryFuncC f);
-    void bind__le__(Type type, BinaryFuncC f);
-    void bind__gt__(Type type, BinaryFuncC f);
-    void bind__ge__(Type type, BinaryFuncC f);
-    void bind__contains__(Type type, BinaryFuncC f);
-
-    void bind__add__(Type type, BinaryFuncC f);
-    void bind__sub__(Type type, BinaryFuncC f);
-    void bind__mul__(Type type, BinaryFuncC f);
-    void bind__truediv__(Type type, BinaryFuncC f);
-    void bind__floordiv__(Type type, BinaryFuncC f);
-    void bind__mod__(Type type, BinaryFuncC f);
-    void bind__pow__(Type type, BinaryFuncC f);
-    void bind__matmul__(Type type, BinaryFuncC f);
-
-    void bind__lshift__(Type type, BinaryFuncC f);
-    void bind__rshift__(Type type, BinaryFuncC f);
-    void bind__and__(Type type, BinaryFuncC f);
-    void bind__or__(Type type, BinaryFuncC f);
-    void bind__xor__(Type type, BinaryFuncC f);
-
-    void bind__getitem__(Type type, PyVar (*f)(VM*, PyVar, PyVar));
-    void bind__setitem__(Type type, void (*f)(VM*, PyVar, PyVar, PyVar));
-    void bind__delitem__(Type type, void (*f)(VM*, PyVar, PyVar));
-#endif
-
-#if PK_REGION("General Bindings")
-    PyObject* bind_func(PyObject* obj, StrName name, int argc, NativeFuncC fn, any userdata={}, BindType bt=BindType_FUNCTION);
-    PyObject* bind_func(Type type, StrName name, int argc, NativeFuncC fn, any userdata={}, BindType bt=BindType_FUNCTION){
-        return bind_func(_t(type), name, argc, fn, std::move(userdata), bt);
-    }
-    PyObject* bind_property(PyObject*, const char*, NativeFuncC fget, NativeFuncC fset=nullptr);
-    template<typename T, typename F, bool ReadOnly=false>
-    PyObject* bind_field(PyObject*, const char*, F T::*);
-
-    PyObject* bind(PyObject*, const char*, NativeFuncC, any userdata={}, BindType bt=BindType_FUNCTION);
-    template<typename Ret, typename... Params>
-    PyObject* bind(PyObject*, const char*, Ret(*)(Params...), BindType bt=BindType_FUNCTION);
-    template<typename Ret, typename T, typename... Params>
-    PyObject* bind(PyObject*, const char*, Ret(T::*)(Params...), BindType bt=BindType_FUNCTION);
-
-    PyObject* bind(PyObject*, const char*, const char*, NativeFuncC, any userdata={}, BindType bt=BindType_FUNCTION);
-    template<typename Ret, typename... Params>
-    PyObject* bind(PyObject*, const char*, const char*, Ret(*)(Params...), BindType bt=BindType_FUNCTION);
-    template<typename Ret, typename T, typename... Params>
-    PyObject* bind(PyObject*, const char*, const char*, Ret(T::*)(Params...), BindType bt=BindType_FUNCTION);
-#endif
-
-#if PK_REGION("Error Reporting Methods")
-    [[noreturn]] void _error(PyVar);
-    [[noreturn]] void StackOverflowError() { __builtin_error("StackOverflowError"); }
-    [[noreturn]] void IOError(const Str& msg) { __builtin_error("IOError", msg); }
-    [[noreturn]] void NotImplementedError(){ __builtin_error("NotImplementedError"); }
-    [[noreturn]] void TypeError(const Str& msg){ __builtin_error("TypeError", msg); }
-    [[noreturn]] void TypeError(Type expected, Type actual) { TypeError("expected " + _type_name(vm, expected).escape() + ", got " + _type_name(vm, actual).escape()); }
-    [[noreturn]] void IndexError(const Str& msg){ __builtin_error("IndexError", msg); }
-    [[noreturn]] void ValueError(const Str& msg){ __builtin_error("ValueError", msg); }
-    [[noreturn]] void RuntimeError(const Str& msg){ __builtin_error("RuntimeError", msg); }
-    [[noreturn]] void ZeroDivisionError(const Str& msg){ __builtin_error("ZeroDivisionError", msg); }
-    [[noreturn]] void ZeroDivisionError(){ __builtin_error("ZeroDivisionError", "division by zero"); }
-    [[noreturn]] void NameError(StrName name){ __builtin_error("NameError", _S("name ", name.escape() + " is not defined")); }
-    [[noreturn]] void UnboundLocalError(StrName name){ __builtin_error("UnboundLocalError", _S("local variable ", name.escape() + " referenced before assignment")); }
-    [[noreturn]] void KeyError(PyVar obj){ __builtin_error("KeyError", obj); }
-    [[noreturn]] void ImportError(const Str& msg){ __builtin_error("ImportError", msg); }
-    [[noreturn]] void AssertionError(const Str& msg){ __builtin_error("AssertionError", msg); }
-    [[noreturn]] void AssertionError(){ __builtin_error("AssertionError"); }
-    [[noreturn]] void BinaryOptError(const char* op, PyVar _0, PyVar _1);
-    [[noreturn]] void AttributeError(PyVar obj, StrName name);
-    [[noreturn]] void AttributeError(const Str& msg){ __builtin_error("AttributeError", msg); }
-#endif
-
-#if PK_REGION("Type Checking Methods")
-    bool isinstance(PyVar obj, Type base);
-    bool issubclass(Type cls, Type base);
-    void check_type(PyVar obj, Type type){ if(!is_type(obj, type)) TypeError(type, _tp(obj)); }
-    void check_compatible_type(PyVar obj, Type type){ if(!isinstance(obj, type)) TypeError(type, _tp(obj)); }
-
-    Type _tp(PyVar obj){ return obj.type; }
-    const PyTypeInfo* _tp_info(PyVar obj) { return &_all_types[_tp(obj)]; }
-    const PyTypeInfo* _tp_info(Type type) { return &_all_types[type]; }
-    PyObject* _t(PyVar obj){ return _all_types[_tp(obj)].obj; }
-    PyObject* _t(Type type){ return _all_types[type].obj; }
-#endif
-
-#if PK_REGION("User Type Registration")
-    PyObject* new_module(Str name, Str package="");
-    PyObject* new_type_object(PyObject* mod, StrName name, Type base, bool subclass_enabled, PyTypeInfo::Vt vt={});
-
-    template<typename T>
-    PyObject* new_type_object(PyObject* mod, StrName name, Type base, bool subclass_enabled){
-        return new_type_object(mod, name, base, subclass_enabled, PyTypeInfo::Vt::get<T>());
-    }
-
-    template<typename T>
-    Type _tp_user(){ return _find_type_in_cxx_typeid_map<T>(); }
-    template<typename T>
-    bool is_user_type(PyVar obj){ return _tp(obj) == _tp_user<T>(); }
-
-    // template<typename T>
-    // PyObject* register_user_class(PyObject*, StrName, RegisterFunc, Type base=tp_object, bool subclass_enabled=false);
-    // template<typename T>
-    // PyObject* register_user_class(PyObject*, StrName, Type base=tp_object, bool subclass_enabled=false);
-
-    // template<typename T, typename ...Args>
-    // PyVar new_user_object(Args&&... args){
-    //     return new_object<T>(_tp_user<T>(), std::forward<Args>(args)...);
-    // }
-
-    template<typename T, typename ...Args>
-    PyVar new_object(Type type, Args&&... args){
-        static_assert(!is_sso_v<T>);
-        static_assert(std::is_same_v<T, std::decay_t<T>>);
-        PyObject* p = pk_ManagedHeap__new(&heap, type, py_sizeof<T>, true);
-        new (PyObject__value_ptr(p)) T(std::forward<Args>(args)...);
-        // backdoor for important builtin types
-        if constexpr(std::is_same_v<T, DummyInstance>
-            || std::is_same_v<T, Type>
-            || std::is_same_v<T, DummyModule>) {
-            p->_attr = pk_NameDict__new();
-        }
-        return PyVar__fromobj(p);
-    }
-
-    template<typename T, typename ...Args>
-    PyVar new_object_no_gc(Type type, Args&&... args){
-        static_assert(!is_sso_v<T>);
-        static_assert(std::is_same_v<T, std::decay_t<T>>);
-        PyObject* p = pk_ManagedHeap__new(&heap, type, py_sizeof<T>, true);
-        new (PyObject__value_ptr(p)) T(std::forward<Args>(args)...);
-        // backdoor for important builtin types
-        if constexpr(std::is_same_v<T, DummyInstance>
-            || std::is_same_v<T, Type>
-            || std::is_same_v<T, DummyModule>) {
-            p->_attr = pk_NameDict__new();
-        }
-        return PyVar__fromobj(p);
-    }
-#endif
-
-    template <typename T>
-    Type _find_type_in_cxx_typeid_map() {
-        auto it = _cxx_typeid_map.try_get(typeid(T));
-        if(it == nullptr) PK_FATAL_ERROR("T not found in cxx_typeid_map\n")
-        return *it;
-    }
-    /********** old heap op **********/
-    struct HeapScopeLock {
-        PK_ALWAYS_PASS_BY_POINTER(HeapScopeLock)
-        pk_ManagedHeap* heap;
-        HeapScopeLock(pk_ManagedHeap* heap) : heap(heap) { pk_ManagedHeap__push_lock(heap);}
-        ~HeapScopeLock() { pk_ManagedHeap__pop_lock(heap); }
-    };
-    HeapScopeLock gc_scope_lock(){ return {&heap}; }
-    /********** private **********/
-    virtual ~VM();
-
-#if PK_DEBUG_CEVAL_STEP
-    void __log_s_data(const char* title = nullptr);
-#endif
-    PyVar __py_exec_internal(const CodeObject* code, PyVar globals, PyVar locals);
-    void __breakpoint();
-    PyVar __format_object(PyVar, Str);
-    PyVar __run_top_frame();
-    void __pop_frame();
-    PyVar __py_generator(Frame* frame, ArgsView buffer);
-    void __op_unpack_sequence(uint16_t arg);
-    void __prepare_py_call(PyVar*, ArgsView, ArgsView, const FuncDecl*);
-    void __unpack_as_list(ArgsView args, List& list);
-    void __unpack_as_dict(ArgsView args, Dict& dict);
-    [[noreturn]] void __raise_exc(bool re_raise = false);
-    [[noreturn]] void __builtin_error(StrName type);
-    [[noreturn]] void __builtin_error(StrName type, PyVar arg);
-    [[noreturn]] void __builtin_error(StrName type, const Str& msg);
-    [[noreturn]] void __compile_error(Error* err);
-    void __init_builtin_types();
-    void __post_init_builtin_types();
-    void __push_varargs() {}
-    void __push_varargs(PyVar _0) { PUSH(_0); }
-    void __push_varargs(PyVar _0, PyVar _1) {
-        PUSH(_0);
-        PUSH(_1);
-    }
-    void __push_varargs(PyVar _0, PyVar _1, PyVar _2) {
-        PUSH(_0);
-        PUSH(_1);
-        PUSH(_2);
-    }
-    void __push_varargs(PyVar _0, PyVar _1, PyVar _2, PyVar _3) {
-        PUSH(_0);
-        PUSH(_1);
-        PUSH(_2);
-        PUSH(_3);
-    }
-    PyVar __pack_next_retval(unsigned);
-    PyVar __minmax_reduce(bool (VM::*op)(PyVar, PyVar), PyVar args, PyVar key);
-    bool __py_bool_non_trivial(PyVar);
-    void __obj_gc_mark(PyObject*);
-    void __stack_gc_mark(PyVar* begin, PyVar* end);
-    void* __stack_alloc(int size);
-};
-
-template <typename T>
-constexpr inline bool is_immutable_v =
-    is_integral_v<T> || is_floating_point_v<T> || std::is_same_v<T, Str> || std::is_same_v<T, Tuple> ||
-    std::is_same_v<T, Bytes> || std::is_same_v<T, bool> || std::is_same_v<T, Range> || std::is_same_v<T, Slice> ||
-    std::is_pointer_v<T> || std::is_enum_v<T>;
-
-template<typename T> constexpr Type _tp_builtin() { return Type(); }
-template<> constexpr Type _tp_builtin<Str>() { return VM::tp_str; }
-template<> constexpr Type _tp_builtin<List>() { return VM::tp_list; }
-template<> constexpr Type _tp_builtin<Tuple>() { return VM::tp_tuple; }
-template<> constexpr Type _tp_builtin<Function>() { return VM::tp_function; }
-template<> constexpr Type _tp_builtin<NativeFunc>() { return VM::tp_native_func; }
-template<> constexpr Type _tp_builtin<BoundMethod>() { return VM::tp_bound_method; }
-template<> constexpr Type _tp_builtin<Range>() { return VM::tp_range; }
-template<> constexpr Type _tp_builtin<Slice>() { return VM::tp_slice; }
-template<> constexpr Type _tp_builtin<Exception>() { return VM::tp_exception; }
-template<> constexpr Type _tp_builtin<Bytes>() { return VM::tp_bytes; }
-template<> constexpr Type _tp_builtin<MappingProxy>() { return VM::tp_mappingproxy; }
-template<> constexpr Type _tp_builtin<Dict>() { return VM::tp_dict; }
-template<> constexpr Type _tp_builtin<Property>() { return VM::tp_property; }
-template<> constexpr Type _tp_builtin<StarWrapper>() { return VM::tp_star_wrapper; }
-template<> constexpr Type _tp_builtin<StaticMethod>() { return VM::tp_staticmethod; }
-template<> constexpr Type _tp_builtin<ClassMethod>() { return VM::tp_classmethod; }
-
-// clang-format on
-
-template <typename __T>
-PyVar py_var(VM* vm, __T&& value) {
-    using T = std::decay_t<__T>;
-
-    static_assert(!std::is_same_v<T, PyVar>, "py_var(VM*, PyVar) is not allowed");
-
-    if constexpr(std::is_same_v<T, const char*> || std::is_same_v<T, std::string> ||
-                 std::is_same_v<T, std::string_view>) {
-        // str (shortcuts)
-        return VAR(Str(std::forward<__T>(value)));
-    } else if constexpr(std::is_same_v<T, NoReturn>) {
-        // NoneType
-        return vm->None;
-    } else if constexpr(std::is_same_v<T, bool>) {
-        // bool
-        return value ? vm->True : vm->False;
-    } else if constexpr(is_integral_v<T>) {
-        // int
-        ::PyVar retval;
-        retval.type = tp_int;
-        retval.is_ptr = false;
-        retval._i64 = (i64)value;
-        return retval;
-    } else if constexpr(is_floating_point_v<T>) {
-        // float
-        ::PyVar retval;
-        retval.type = tp_float;
-        retval.is_ptr = false;
-        retval._f64 = (f64)value;
-        return retval;
-    } else if constexpr(std::is_pointer_v<T>) {
-        return from_void_p(vm, (void*)value);
-    } else {
-        constexpr Type const_type = _tp_builtin<T>();
-        if constexpr((bool)const_type) {
-            if constexpr(is_sso_v<T>)
-                return PyVar(const_type, value);
-            else
-                return vm->new_object<T>(const_type, std::forward<__T>(value));
-        } else {
-            Type type = vm->_find_type_in_cxx_typeid_map<T>();
-            if constexpr(is_sso_v<T>)
-                return PyVar(type, value);
-            else
-                return vm->new_object<T>(type, std::forward<__T>(value));
-        }
-    }
-}
-
-// fast path for bool if py_var<> cannot be inlined
-inline PyVar py_var(VM* vm, bool value) { return value ? vm->True : vm->False; }
-
-template <typename __T, bool with_check>
-__T _py_cast__internal(VM* vm, PyVar obj) {
-    static_assert(!std::is_rvalue_reference_v<__T>, "rvalue reference is not allowed");
-    using T = std::decay_t<__T>;
-    static_assert(!(is_sso_v<T> && std::is_reference_v<__T>), "SSO types cannot be reference");
-
-    if constexpr(std::is_same_v<T, const char*> || std::is_same_v<T, CString>) {
-        static_assert(!std::is_reference_v<__T>);
-        // str (shortcuts)
-        if(is_none(obj)) return nullptr;
-        if constexpr(with_check) vm->check_type(obj, vm->tp_str);
-        return PK_OBJ_GET(Str, obj).c_str();
-    } else if constexpr(std::is_same_v<T, bool>) {
-        static_assert(!std::is_reference_v<__T>);
-        // bool
-        if constexpr(with_check) {
-            if(obj.type != tp_bool){
-                vm->TypeError("expected 'bool', got " + _type_name(vm, vm->_tp(obj)).escape());
-            }
-        }
-        return (bool)obj.extra;
-    } else if constexpr(is_integral_v<T>) {
-        static_assert(!std::is_reference_v<__T>);
-        // int
-        if constexpr(with_check) {
-            if(!is_int(obj)) vm->TypeError("expected 'int', got " + _type_name(vm, vm->_tp(obj)).escape());
-        }
-        return (T)obj._i64;
-    } else if constexpr(is_floating_point_v<T>) {
-        static_assert(!std::is_reference_v<__T>);
-        if(is_float(obj)) return (T)obj._f64;
-        if(is_int(obj)) return (T)obj._i64;
-        vm->TypeError("expected 'int' or 'float', got " + _type_name(vm, vm->_tp(obj)).escape());
-        return 0.0f;
-    } else if constexpr(std::is_enum_v<T>) {
-        static_assert(!std::is_reference_v<__T>);
-        return (__T)_py_cast__internal<i64, with_check>(vm, obj);
-    } else if constexpr(std::is_pointer_v<T>) {
-        static_assert(!std::is_reference_v<__T>);
-        return to_void_p<T>(vm, obj);
-    } else {
-        constexpr Type const_type = _tp_builtin<T>();
-        if constexpr((bool)const_type) {
-            if constexpr(with_check) {
-                if constexpr(std::is_same_v<T, Exception>) {
-                    // Exception is `subclass_enabled`
-                    vm->check_compatible_type(obj, const_type);
-                } else {
-                    vm->check_type(obj, const_type);
-                }
-            }
-            return PK_OBJ_GET(T, obj);
-        } else {
-            if constexpr(with_check) {
-                Type type = vm->_find_type_in_cxx_typeid_map<T>();
-                vm->check_compatible_type(obj, type);
-            }
-            return PK_OBJ_GET(T, obj);
-        }
-    }
-}
-
-template <typename __T>
-__T py_cast(VM* vm, PyVar obj) {
-    return _py_cast__internal<__T, true>(vm, obj);
-}
-
-template <typename __T>
-__T _py_cast(VM* vm, PyVar obj) {
-    return _py_cast__internal<__T, false>(vm, obj);
-}
-
-// template <typename T>
-// PyObject*
-//     VM::register_user_class(PyObject* mod, StrName name, RegisterFunc _register, Type base, bool subclass_enabled) {
-//     PyObject* type = new_type_object(mod, name, base, subclass_enabled, PyTypeInfo::Vt::get<T>());
-//     mod->attr().set(name, type);
-//     _cxx_typeid_map.insert(typeid(T), type->as<Type>());
-//     _register(this, mod, type);
-//     if(!type->attr().contains(__new__)) {
-//         if constexpr(std::is_default_constructible_v<T>) {
-//             bind_func(type, __new__, -1, [](VM* vm, ArgsView args) {
-//                 Type cls_t = args[0]->as<Type>();
-//                 return vm->new_object<T>(cls_t);
-//             });
-//         } else {
-//             bind_func(type, __new__, -1, [](VM* vm, ArgsView args) {
-//                 vm->NotImplementedError();
-//                 return vm->None;
-//             });
-//         }
-//     }
-//     return type;
-// }
-
-// template <typename T>
-// PyObject* VM::register_user_class(PyObject* mod, StrName name, Type base, bool subclass_enabled) {
-//     return register_user_class<T>(mod, name, &T::_register, base, subclass_enabled);
-// }
-
-}  // namespace pkpy
diff --git a/include/pocketpy/objects/base.h b/include/pocketpy/objects/base.h
index 834b6633..e6a28aa2 100644
--- a/include/pocketpy/objects/base.h
+++ b/include/pocketpy/objects/base.h
@@ -43,7 +43,7 @@ static const Type tp_object = {1}, tp_type = {2};
 static const Type tp_int = {3}, tp_float = {4}, tp_bool = {5}, tp_str = {6};
 static const Type tp_list = {7}, tp_tuple = {8};
 static const Type tp_slice = {9}, tp_range = {10}, tp_module = {11};
-static const Type tp_function = {12}, tp_native_func = {13}, tp_bound_method = {14};
+static const Type tp_function = {12}, tp_nativefunc = {13}, tp_bound_method = {14};
 static const Type tp_super = {15}, tp_exception = {16}, tp_bytes = {17}, tp_mappingproxy = {18};
 static const Type tp_dict = {19}, tp_property = {20}, tp_star_wrapper = {21};
 static const Type tp_staticmethod = {22}, tp_classmethod = {23};
diff --git a/include/pocketpy/objects/codeobject.h b/include/pocketpy/objects/codeobject.h
index eab24093..34904c50 100644
--- a/include/pocketpy/objects/codeobject.h
+++ b/include/pocketpy/objects/codeobject.h
@@ -8,6 +8,7 @@
 #include "pocketpy/objects/base.h"
 #include "pocketpy/objects/sourcedata.h"
 #include "pocketpy/common/refcount.h"
+#include "pocketpy/pocketpy.h"
 
 #ifdef __cplusplus
 extern "C" {
@@ -16,12 +17,6 @@ extern "C" {
 #define BC_NOARG        0
 #define BC_KEEPLINE     -1
 
-typedef enum BindType {
-    BindType_FUNCTION,
-    BindType_STATICMETHOD,
-    BindType_CLASSMETHOD,
-} BindType;
-
 typedef enum FuncType {
     FuncType_UNSET,
     FuncType_NORMAL,
diff --git a/include/pocketpy/objects/object.h b/include/pocketpy/objects/object.h
index a906df06..04f39fca 100644
--- a/include/pocketpy/objects/object.h
+++ b/include/pocketpy/objects/object.h
@@ -22,9 +22,10 @@ static_assert(sizeof(PyObject) <= 16, "!(sizeof(PyObject) <= 16)");
 #define PK_OBJ_SIZEOF(T)            (sizeof(T) + 16)
 
 PyObject* PyObject__new(Type type, int size);
-void PyObject__delete(pk_VM* vm, PyObject* self);
+void PyObject__delete(PyObject* self);
 
 PK_INLINE PyVar PyVar__fromobj(PyObject* obj){
+    if(!obj) return PY_NULL;
     PyVar retval = {
         .type = obj->type,
         .is_ptr = true,
diff --git a/include/pocketpy/pocketpy.h b/include/pocketpy/pocketpy.h
index 4531bb89..c58680f1 100644
--- a/include/pocketpy/pocketpy.h
+++ b/include/pocketpy/pocketpy.h
@@ -1,3 +1,5 @@
+#pragma once
+
 #include "stdint.h"
 #include "stdbool.h"
 
@@ -10,8 +12,17 @@ typedef struct PyVar PyVar;
 typedef struct pk_VM pk_VM;
 typedef struct py_Error py_Error;
 
+typedef enum BindType {
+    BindType_FUNCTION,
+    BindType_STATICMETHOD,
+    BindType_CLASSMETHOD,
+} BindType;
+
 typedef int (*py_CFunction)(const PyVar*, int);
 
+typedef uint16_t StrName;
+typedef int16_t Type;
+
 extern pk_VM* pk_current_vm;
 
 void py_initialize();
@@ -25,20 +36,34 @@ py_Error* py_eval_simple(const char*, PyVar*);
 void py_Error__print(const py_Error*);
 void py_Error__delete(py_Error*);
 
-
-bool py_eq(const PyVar*, const PyVar*);
-bool py_le(const PyVar*, const PyVar*);
-int64_t py_hash(const PyVar*);
-
+int py_eq(const PyVar*, const PyVar*);
+int py_le(const PyVar*, const PyVar*);
+int py_hash(const PyVar*, int64_t* out);
 
 /* py_var */
-void py_newint(PyVar*, int64_t);
-void py_newfloat(PyVar*, double);
-void py_newbool(PyVar*, bool);
-void py_newstr(PyVar*, const char*);
-void py_newstr2(PyVar*, const char*, int);
-void py_newbytes(PyVar*, const uint8_t*, int);
-void py_newnone(PyVar*);
+void py_new_int(PyVar*, int64_t);
+void py_new_float(PyVar*, double);
+void py_new_bool(PyVar*, bool);
+void py_new_str(PyVar*, const char*);
+void py_new_strn(PyVar*, const char*, int);
+void py_new_fstr(PyVar*, const char*, ...);
+void py_new_bytes(PyVar*, const uint8_t*, int);
+void py_new_none(PyVar*);
+void py_new_null(PyVar*);
+
+// new style decl-based function
+void py_new_function(PyVar*, py_CFunction, const char* sig, BindType bt);
+void py_new_function2(PyVar*, py_CFunction, const char* sig, BindType bt, const char* docstring, const PyVar* userdata);
+// old style argc-based function
+void py_new_nativefunc(PyVar*, py_CFunction, int argc, BindType bt);
+void py_new_nativefunc2(PyVar*, py_CFunction, int argc, BindType bt, const char* docstring, const PyVar* userdata);
+
+int py_setattr(PyVar* self, StrName name, const PyVar* val);
+
+PyVar py_new_module(const char* name);
+PyVar pk_new_module(const char* name, const char* package);
+
+// Type pk_new_type
 
 #define py_isnull(self) ((self)->type == 0)
 
diff --git a/src/interpreter/vm.c b/src/interpreter/vm.c
index b0089607..29c4816c 100644
--- a/src/interpreter/vm.c
+++ b/src/interpreter/vm.c
@@ -1,28 +1,28 @@
 #include "pocketpy/interpreter/vm.h"
 #include "pocketpy/common/memorypool.h"
 
-static unsigned char* pk_default_import_file(pk_VM* vm, const char* path){
+static unsigned char* pk_default_import_file(const char* path){
     return NULL;
 }
 
-static void pk_default_stdout(pk_VM* vm, const char* s){
+static void pk_default_stdout(const char* s){
     fprintf(stdout, "%s", s);
     fflush(stdout);
 }
 
-static void pk_default_stderr(pk_VM* vm, const char* s){
+static void pk_default_stderr(const char* s){
     fprintf(stderr, "%s", s);
     fflush(stderr);
 }
 
-void pk_TypeInfo__ctor(pk_TypeInfo *self, StrName name, Type base, PyObject* obj, PyObject* module, bool subclass_enabled){
+void pk_TypeInfo__ctor(pk_TypeInfo *self, StrName name, Type base, PyObject* obj, const PyVar* module, bool subclass_enabled){
     memset(self, 0, sizeof(pk_TypeInfo));
     
     self->name = name;
     self->base = base;
 
-    self->obj = obj;
-    self->module = module;
+    self->self = PyVar__fromobj(obj);
+    self->module = module ? *module : PY_NULL;
     self->subclass_enabled = subclass_enabled;
 
     c11_vector__ctor(&self->annotated_fields, sizeof(StrName));
@@ -32,22 +32,35 @@ void pk_TypeInfo__dtor(pk_TypeInfo *self){
     c11_vector__dtor(&self->annotated_fields);
 }
 
+static int _hello(const PyVar* args, int argc){
+    return 0;
+}
+
+static void do_builtin_bindings(){
+    pk_VM* vm = pk_current_vm;
+
+    py_new_nativefunc(&vm->reg[0], _hello, 2, BindType_FUNCTION);
+    py_setattr(&vm->builtins, pk_StrName__map("hello"), &vm->reg[0]);
+}
+
 void pk_VM__ctor(pk_VM* self){
     self->top_frame = NULL;
 
     pk_NameDict__ctor(&self->modules);
     c11_vector__ctor(&self->types, sizeof(pk_TypeInfo));
 
-    self->StopIteration = NULL;
-    self->builtins = NULL;
-    self->main = NULL;
+    self->StopIteration = PY_NULL;
+    self->builtins = PY_NULL;
+    self->main = PY_NULL;
 
     self->_ceval_on_step = NULL;
     self->_import_file = pk_default_import_file;
     self->_stdout = pk_default_stdout;
     self->_stderr = pk_default_stderr;
 
-    self->__last_exception = NULL;
+    self->last_error = NULL;
+    self->last_retval = PY_NULL;
+
     self->__curr_class = NULL;
     self->__cached_object_new = NULL;
     self->__dynamic_func_decl = NULL;
@@ -92,7 +105,7 @@ void pk_VM__ctor(pk_VM* self){
     validate(tp_module, pk_VM__new_type(self, "module", tp_object, NULL, false));
 
     validate(tp_function, pk_VM__new_type(self, "function", tp_object, NULL, false));
-    validate(tp_native_func, pk_VM__new_type(self, "native_func", tp_object, NULL, false));
+    validate(tp_nativefunc, pk_VM__new_type(self, "nativefunc", tp_object, NULL, false));
     validate(tp_bound_method, pk_VM__new_type(self, "bound_method", tp_object, NULL, false));
 
     validate(tp_super, pk_VM__new_type(self, "super", tp_object, NULL, false));
@@ -118,8 +131,8 @@ void pk_VM__ctor(pk_VM* self){
     validate(tp_stop_iteration, pk_VM__new_type(self, "StopIteration", tp_exception, NULL, false));
     #undef validate
 
-    self->StopIteration = c11__at(pk_TypeInfo, &self->types, tp_stop_iteration)->obj;
-    self->builtins = pk_VM__new_module(self, "builtins", NULL);
+    self->StopIteration = c11__at(pk_TypeInfo, &self->types, tp_stop_iteration)->self;
+    self->builtins = py_new_module("builtins");
     
     /* Setup Public Builtin Types */
     Type public_types[] = {
@@ -134,13 +147,13 @@ void pk_VM__ctor(pk_VM* self){
     for(int i=0; i<PK_ARRAY_COUNT(public_types); i++){
         Type t = public_types[i];
         pk_TypeInfo* ti = c11__at(pk_TypeInfo, &self->types, t);
-        pk_NameDict__set(self->builtins->dict, ti->name, PyVar__fromobj(ti->obj));
+        pk_NameDict__set(self->builtins._obj->dict, ti->name, ti->self);
     }
-    pk_NameDict__set(self->builtins->dict, pk_StrName__map("NotImplemented"), self->NotImplemented);
+    pk_NameDict__set(self->builtins._obj->dict, pk_StrName__map("NotImplemented"), self->NotImplemented);
 
     /* Do Buildin Bindings*/
-    // TODO: ...
-    self->main = pk_VM__new_module(self, "__main__", NULL);
+    do_builtin_bindings();
+    self->main = py_new_module("__main__");
 }
 
 void pk_VM__dtor(pk_VM* self){
@@ -170,7 +183,7 @@ pk_FrameResult pk_VM__run_top_frame(pk_VM* self){
     return RES_RETURN;
 }
 
-Type pk_VM__new_type(pk_VM* self, const char* name, Type base, PyObject* module, bool subclass_enabled){
+Type pk_VM__new_type(pk_VM* self, const char* name, Type base, const PyVar* module, bool subclass_enabled){
     Type type = self->types.count;
     pk_TypeInfo* ti = c11_vector__emplace(&self->types);
     PyObject* typeobj = pk_ManagedHeap__gcnew(&self->heap, tp_type, PK_OBJ_SIZEOF(Type));
diff --git a/src/interpreter/vm.cpp b/src/interpreter/vm.cpp
deleted file mode 100644
index 5354229e..00000000
--- a/src/interpreter/vm.cpp
+++ /dev/null
@@ -1,1973 +0,0 @@
-#include "pocketpy/interpreter/vm.hpp"
-#include "pocketpy/common/memorypool.h"
-#include "pocketpy/interpreter/frame.h"
-#include "pocketpy/objects/base.h"
-#include "pocketpy/objects/codeobject.h"
-#include "pocketpy/objects/public.h"
-
-#include <cstddef>
-#include <iostream>
-#include <cmath>
-#include <stdexcept>
-
-#if PK_DEBUG_CEVAL_STEP
-#include <map>
-#endif
-
-const static char* OP_NAMES[] = {
-#define OPCODE(name) #name,
-#include "pocketpy/xmacros/opcodes.h"
-#undef OPCODE
-};
-
-namespace pkpy {
-
-struct JsonSerializer {
-    VM* vm;
-    PyVar root;
-    SStream ss;
-
-    JsonSerializer(VM* vm, PyVar root) : vm(vm), root(root) {}
-
-    template <typename T>
-    void write_array(T& arr) {
-        ss << '[';
-        for(int i = 0; i < arr.size(); i++) {
-            if(i != 0) ss << ", ";
-            write_object(arr[i]);
-        }
-        ss << ']';
-    }
-
-    void write_dict(Dict& dict) {
-        ss << '{';
-        bool first = true;
-        dict.apply([&](PyVar k, PyVar v) {
-            if(!first) ss << ", ";
-            first = false;
-            if(!is_type(k, VM::tp_str)) {
-                vm->TypeError(_S("json keys must be string, got ", _type_name(vm, vm->_tp(k))));
-            }
-            ss << _CAST(Str&, k).escape('"') << ": ";
-            write_object(v);
-        });
-        ss << '}';
-    }
-
-    void write_object(PyVar obj) {
-        Type obj_t = vm->_tp(obj);
-        if(is_none(obj)) {
-            ss << "null";
-        } else if(obj_t == vm->tp_int) {
-            ss << _CAST(i64, obj);
-        } else if(obj_t == vm->tp_float) {
-            f64 val = _CAST(f64, obj);
-            if(std::isinf(val) || std::isnan(val)) vm->ValueError("cannot jsonify 'nan' or 'inf'");
-            ss << val;
-        } else if(obj_t == vm->tp_bool) {
-            ss << (obj.extra ? "true" : "false");
-        } else if(obj_t == vm->tp_str) {
-            ss << _CAST(Str&, obj).escape('"');
-        } else if(obj_t == vm->tp_list) {
-            write_array<List>(_CAST(List&, obj));
-        } else if(obj_t == vm->tp_tuple) {
-            write_array<Tuple>(_CAST(Tuple&, obj));
-        } else if(obj_t == vm->tp_dict) {
-            write_dict(_CAST(Dict&, obj));
-        } else {
-            vm->TypeError(_S("unrecognized type ", _type_name(vm, obj_t).escape()));
-        }
-    }
-
-    Str serialize() {
-        auto _lock = vm->gc_scope_lock();
-        write_object(root);
-        return ss.str();
-    }
-};
-
-VM::VM(bool enable_os) : enable_os(enable_os) {
-    pkpy_g.vm = (pk_VM*)this;    // setup the current VM
-    Pools_initialize();
-    pk_StrName__initialize();
-
-    pk_ManagedHeap__ctor(&heap, (pk_VM*)this);
-
-    static ::PyObject __true_obj = {tp_bool, false, false, NULL};
-    static ::PyObject __false_obj = {tp_bool, false, false, NULL};
-    static ::PyObject __none_obj = {tp_none_type, false, false, NULL};
-    static ::PyObject __not_implemented_obj = {tp_not_implemented_type, false, false, NULL};
-    static ::PyObject __ellipsis_obj = {tp_ellipsis, false, false, NULL};
-
-    /* Must be heap objects to support `==` and `is` and `is not` */
-    True.type = tp_bool; True.is_ptr = true; True.extra = 1; True._obj = &__true_obj;
-    False.type = tp_bool; False.is_ptr = true; False.extra = 0; False._obj = &__false_obj;
-    None.type = tp_none_type; None.is_ptr = true; None._obj = &__none_obj;
-    NotImplemented.type = tp_not_implemented_type; NotImplemented.is_ptr = true; NotImplemented._obj = &__not_implemented_obj;
-    Ellipsis.type = tp_ellipsis; Ellipsis.is_ptr = true; Ellipsis._obj = &__ellipsis_obj;
-    
-    this->vm = this;
-    this->__c.error = nullptr;
-    _ceval_on_step = nullptr;
-    _stdout = [](const char* buf, int size) {
-        std::cout.write(buf, size);
-    };
-    _stderr = [](const char* buf, int size) {
-        std::cerr.write(buf, size);
-    };
-    builtins = nullptr;
-    _main = nullptr;
-    __last_exception = nullptr;
-    _import_handler = [](const char* name, int* out_size) -> unsigned char* {
-        return nullptr;
-    };
-    __init_builtin_types();
-}
-
-Str VM::py_str(PyVar obj) {
-    const PyTypeInfo* ti = _tp_info(obj);
-    if(ti->m__str__) return ti->m__str__(this, obj);
-    PyVar self;
-    PyVar f = get_unbound_method(obj, __str__, &self, false);
-    if(self.type) {
-        PyVar retval = call_method(self, f);
-        if(!is_type(retval, tp_str)) { throw std::runtime_error("object.__str__ must return str"); }
-        return PK_OBJ_GET(Str, retval);
-    }
-    return py_repr(obj);
-}
-
-Str VM::py_repr(PyVar obj) {
-    const PyTypeInfo* ti = _tp_info(obj);
-    if(ti->m__repr__) return ti->m__repr__(this, obj);
-    PyVar retval = call_method(obj, __repr__);
-    if(!is_type(retval, tp_str)) { throw std::runtime_error("object.__repr__ must return str"); }
-    return PK_OBJ_GET(Str, retval);
-}
-
-Str VM::py_json(PyVar obj) {
-    JsonSerializer j(this, obj);
-    return j.serialize();
-}
-
-PyVar VM::py_iter(PyVar obj) {
-    const PyTypeInfo* ti = _tp_info(obj);
-    if(ti->m__iter__) return ti->m__iter__(this, obj);
-    PyVar self;
-    PyVar iter_f = get_unbound_method(obj, __iter__, &self, false);
-    if(self.type) return call_method(self, iter_f);
-    TypeError(_type_name(vm, _tp(obj)).escape() + " object is not iterable");
-    return nullptr;
-}
-
-ArgsView VM::cast_array_view(PyVar obj) {
-    if(is_type(obj, VM::tp_list)) {
-        List& list = PK_OBJ_GET(List, obj);
-        return ArgsView(list.begin(), list.end());
-    } else if(is_type(obj, VM::tp_tuple)) {
-        Tuple& tuple = PK_OBJ_GET(Tuple, obj);
-        return ArgsView(tuple.begin(), tuple.end());
-    }
-    TypeError(_S("expected list or tuple, got ", _type_name(this, _tp(obj)).escape()));
-}
-
-void VM::set_main_argv(int argc, char** argv) {
-    PyVar mod = vm->_modules["sys"];
-    List argv_(argc);
-    for(int i = 0; i < argc; i++)
-        argv_[i] = VAR(std::string_view(argv[i]));
-    mod->attr().set("argv", VAR(std::move(argv_)));
-}
-
-PyVar* VM::find_name_in_mro(Type cls, StrName name) {
-    PyVar* val;
-    do {
-        val = _t(cls)->attr().try_get_2(name);
-        if(val != nullptr) return val;
-        cls = _all_types[cls].base;
-        if(!cls) break;
-    } while(true);
-    return nullptr;
-}
-
-bool VM::isinstance(PyVar obj, Type base) { return issubclass(_tp(obj), base); }
-
-bool VM::issubclass(Type cls, Type base) {
-    do {
-        if(cls == base) return true;
-        Type next = _all_types[cls].base;
-        if(!next) break;
-        cls = next;
-    } while(true);
-    return false;
-}
-
-PyVar VM::exec(std::string_view source, Str filename, CompileMode mode, PyObject* _module) {
-    if(_module == nullptr) _module = _main;
-    CodeObject* code = NULL;
-    try {
-#if PK_DEBUG_PRECOMPILED_EXEC == 1
-        Str precompiled = vm->precompile(source, filename, mode);
-        source = precompiled.sv();
-#endif
-        code = compile(source, filename, mode);
-        PyVar retval = _exec(code, _module);
-        CodeObject__delete(code);
-        return retval;
-    } catch(TopLevelException e) {
-        stderr_write(e.summary() + "\n");
-    } catch(const std::exception& e) {
-        Str msg = "An std::exception occurred! It could be a bug.\n";
-        msg = msg + e.what() + "\n";
-        stderr_write(msg);
-    } catch(NeedMoreLines) { throw; } catch(...) {
-        Str msg = "An unknown exception occurred! It could be a bug. Please report it to @blueloveTH on GitHub.\n";
-        stderr_write(msg);
-    }
-    CodeObject__delete(code);
-    while(top_frame) __pop_frame(); // this changes s_data.sp, it must put before ValueStack__clear();
-    ValueStack__clear(&s_data);
-    return nullptr;
-}
-
-PyVar VM::exec(std::string_view source) { return exec(source, "main.py", EXEC_MODE); }
-
-PyVar VM::eval(std::string_view source) { return exec(source, "<eval>", EVAL_MODE); }
-
-PyObject* VM::new_type_object(PyObject* mod, StrName name, Type base, bool subclass_enabled, PyTypeInfo::Vt vt) {
-    PyObject* obj = new_object_no_gc<Type>(tp_type, Type(_all_types.size())).get();
-    const PyTypeInfo& base_info = _all_types[base];
-    if(!base_info.subclass_enabled) {
-        Str error = _S("type ", base_info.name.escape(), " is not `subclass_enabled`");
-        throw std::runtime_error(error.c_str());
-    }
-    if(base_info.vt) {
-        if(vt) {
-            Str error = _S("type ", base_info.name.escape(), " has a custom vtable, cannot override");
-            throw std::runtime_error(error.c_str());
-        } else {
-            // promote base vt to its subclass
-            vt = base_info.vt;
-        }
-    }
-    _all_types.emplace_back(obj, base, mod, name, subclass_enabled, vt);
-    return obj;
-}
-
-bool VM::py_eq(PyVar lhs, PyVar rhs) {
-    if(is_int(lhs) && is_int(rhs)) return lhs._i64 == rhs._i64;
-    const PyTypeInfo* ti = _tp_info(lhs);
-    PyVar res;
-    if(ti->m__eq__) {
-        res = ti->m__eq__(this, lhs, rhs);
-        if(!is_not_implemented(res)) return res.extra;
-    }
-    res = call_method(lhs, __eq__, rhs);
-    if(!is_not_implemented(res)) return res.extra;
-
-    ti = _tp_info(rhs);
-    if(ti->m__eq__) {
-        res = ti->m__eq__(this, rhs, lhs);
-        if(!is_not_implemented(res)) return res.extra;
-    }
-    res = call_method(rhs, __eq__, lhs);
-    if(!is_not_implemented(res)) return res.extra;
-    return false;
-}
-
-PyVar VM::py_op(std::string_view name) {
-    // TODO: cache the result
-    return py_import("operator")->attr()[StrName::get(name)];
-}
-
-i64 VM::normalized_index(i64 index, int size) {
-    if(index < 0) index += size;
-    if(index < 0 || index >= size) { IndexError(std::to_string(index) + " not in [0, " + std::to_string(size) + ")"); }
-    return index;
-}
-
-PyVar VM::_py_next(const PyTypeInfo* ti, PyVar obj) {
-    if(ti->op__next__) {
-        unsigned n = ti->op__next__(this, obj);
-        return __pack_next_retval(n);
-    }
-    return call_method(obj, __next__);
-}
-
-PyVar VM::py_next(PyVar obj) {
-    const PyTypeInfo* ti = _tp_info(obj);
-    return _py_next(ti, obj);
-}
-
-bool VM::py_callable(PyVar obj) {
-    Type cls = vm->_tp(obj);
-    switch(cls) {
-        case VM::tp_function: return true;
-        case VM::tp_native_func: return true;
-        case VM::tp_bound_method: return true;
-        case VM::tp_type: return true;
-    }
-    return vm->find_name_in_mro(cls, __call__) != nullptr;
-}
-
-PyVar VM::__minmax_reduce(bool (VM::*op)(PyVar, PyVar), PyVar args, PyVar key) {
-    auto _lock = gc_scope_lock();
-    const Tuple& args_tuple = PK_OBJ_GET(Tuple, args);  // from *args, it must be a tuple
-    if(is_none(key) && args_tuple.size() == 2) {
-        // fast path
-        PyVar a = args_tuple[0];
-        PyVar b = args_tuple[1];
-        return (this->*op)(a, b) ? a : b;
-    }
-
-    if(args_tuple.size() == 0) TypeError("expected at least 1 argument, got 0");
-
-    ArgsView view;
-    if(args_tuple.size() == 1) {
-        view = cast_array_view(args_tuple[0]);
-    } else {
-        view = ArgsView(args_tuple);
-    }
-
-    if(view.empty()) ValueError("arg is an empty sequence");
-    PyVar res = view[0];
-
-    if(is_none(key)) {
-        for(int i = 1; i < view.size(); i++) {
-            if((this->*op)(view[i], res)) res = view[i];
-        }
-    } else {
-        auto _lock = gc_scope_lock();
-        for(int i = 1; i < view.size(); i++) {
-            PyVar a = call(key, view[i]);
-            PyVar b = call(key, res);
-            if((this->*op)(a, b)) res = view[i];
-        }
-    }
-    return res;
-}
-
-PyObject* VM::py_import(Str path, bool throw_err) {
-    if(path.empty()) vm->ValueError("empty module name");
-    static auto f_join = [](const vector<std::string_view>& cpnts) {
-        SStream ss;
-        for(int i = 0; i < cpnts.size(); i++) {
-            if(i != 0) ss << ".";
-            ss << cpnts[i];
-        }
-        return ss.str();
-    };
-
-    if(path[0] == '.') {
-        if(__import_context.pending.empty()) { ImportError("relative import outside of package"); }
-        Str curr_path = __import_context.pending.back();
-        bool curr_is_init = __import_context.pending_is_init.back();
-        // convert relative path to absolute path
-        vector<std::string_view> cpnts = curr_path.split('.');
-        int prefix = 0;  // how many dots in the prefix
-        for(int i = 0; i < path.length(); i++) {
-            if(path[i] == '.')
-                prefix++;
-            else
-                break;
-        }
-        if(prefix > cpnts.size()) ImportError("attempted relative import beyond top-level package");
-        path = path.substr(prefix);  // remove prefix
-        for(int i = (int)curr_is_init; i < prefix; i++)
-            cpnts.pop_back();
-        if(!path.empty()) cpnts.push_back(path.sv());
-        path = f_join(cpnts);
-    }
-
-    assert(path.begin()[0] != '.' && path.end()[-1] != '.');
-
-    // check existing module
-    StrName name(path);
-    PyVar ext_mod = _modules.try_get(name);
-    if(ext_mod) return ext_mod.get();
-
-    vector<std::string_view> path_cpnts = path.split('.');
-    // check circular import
-    if(__import_context.pending.size() > 128) { ImportError("maximum recursion depth exceeded while importing"); }
-
-    // try import
-    Str filename = path.replace('.', PK_PLATFORM_SEP) + ".py";
-    Str source;
-    bool is_init = false;
-    auto it = _lazy_modules.try_get(name);
-    if(it == nullptr) {
-        int out_size;
-        unsigned char* out = _import_handler(filename.c_str(), &out_size);
-        if(out == nullptr) {
-            filename = path.replace('.', PK_PLATFORM_SEP).str() + PK_PLATFORM_SEP + "__init__.py";
-            is_init = true;
-            out = _import_handler(filename.c_str(), &out_size);
-        }
-        if(out == nullptr) {
-            if(throw_err)
-                ImportError(_S("module ", path.escape(), " not found"));
-            else
-                return nullptr;
-        }
-        assert(out_size >= 0);
-        source = Str(std::string_view((char*)out, out_size));
-        std::free(out);
-    } else {
-        source = *it;
-        // _lazy_modules.erase(it);  // no need to erase
-    }
-    auto _ = __import_context.scope(path, is_init);
-    Str name_cpnt = path_cpnts.back();
-    path_cpnts.pop_back();
-    PyObject* new_mod = new_module(name_cpnt, f_join(path_cpnts));
-    CodeObject* code = compile(source, filename, EXEC_MODE);
-    _exec(code, new_mod);
-    CodeObject__delete(code);
-    return new_mod;
-}
-
-VM::~VM() {
-    PK_DECREF(__dynamic_func_decl);
-    // destroy all objects
-    pk_ManagedHeap__dtor(&heap);
-    pk_NameDict__dtor(&_modules);
-    // clear everything
-    while(top_frame) __pop_frame(); // this changes s_data.sp, it must put before ValueStack__clear();
-    ValueStack__clear(&s_data);
-    _all_types.clear();
-    _lazy_modules.clear();
-}
-
-PyVar VM::py_negate(PyVar obj) {
-    const PyTypeInfo* ti = _tp_info(obj);
-    if(ti->m__neg__) return ti->m__neg__(this, obj);
-    return call_method(obj, __neg__);
-}
-
-bool VM::__py_bool_non_trivial(PyVar obj) {
-    if(is_none(obj)) return false;
-    if(is_int(obj)) return _CAST(i64, obj) != 0;
-    if(is_float(obj)) return _CAST(f64, obj) != 0.0;
-    PyVar self;
-    PyVar len_f = get_unbound_method(obj, __len__, &self, false);
-    if(self) {
-        PyVar ret = call_method(self, len_f);
-        return CAST(i64, ret) != 0;
-    }
-    return true;
-}
-
-void VM::__obj_gc_mark(PyObject* obj) {
-    if(obj->gc_marked) return;
-    obj->gc_marked = true;
-    const PyTypeInfo* ti = _tp_info(obj->type);
-    if(ti->vt._gc_mark) ti->vt._gc_mark(obj->_value_ptr(), this);
-    if(obj->is_attr_valid()) {
-        obj->attr().apply([](StrName _, PyVar obj, void* userdata) {
-            VM* vm = (VM*)userdata;
-            if(obj.is_ptr) vm->__obj_gc_mark((obj).get());
-        }, vm);
-    }
-}
-
-void VM::__stack_gc_mark(PyVar* begin, PyVar* end) {
-    for(PyVar* it = begin; it != end; it++) {
-        if(it->is_ptr) {
-            __obj_gc_mark(it->get());
-        }
-    }
-}
-
-List VM::py_list(PyVar it) {
-    auto _lock = gc_scope_lock();
-    it = py_iter(it);
-    List list;
-    const PyTypeInfo* info = _tp_info(it);
-    PyVar obj = _py_next(info, it);
-    while(obj != StopIteration) {
-        list.push_back(obj);
-        obj = _py_next(info, it);
-    }
-    return list;
-}
-
-void VM::parse_int_slice(const Slice& s, int length, int& start, int& stop, int& step) {
-    auto clip = [](int value, int min, int max) {
-        if(value < min) return min;
-        if(value > max) return max;
-        return value;
-    };
-    if(is_none(s.step))
-        step = 1;
-    else
-        step = CAST(int, s.step);
-    if(step == 0) ValueError("slice step cannot be zero");
-    if(step > 0) {
-        if(is_none(s.start)) {
-            start = 0;
-        } else {
-            start = CAST(int, s.start);
-            if(start < 0) start += length;
-            start = clip(start, 0, length);
-        }
-        if(is_none(s.stop)) {
-            stop = length;
-        } else {
-            stop = CAST(int, s.stop);
-            if(stop < 0) stop += length;
-            stop = clip(stop, 0, length);
-        }
-    } else {
-        if(is_none(s.start)) {
-            start = length - 1;
-        } else {
-            start = CAST(int, s.start);
-            if(start < 0) start += length;
-            start = clip(start, -1, length - 1);
-        }
-        if(is_none(s.stop)) {
-            stop = -1;
-        } else {
-            stop = CAST(int, s.stop);
-            if(stop < 0) stop += length;
-            stop = clip(stop, -1, length - 1);
-        }
-    }
-}
-
-i64 VM::py_hash(PyVar obj) {
-    // https://docs.python.org/3.10/reference/datamodel.html#object.__hash__
-    const PyTypeInfo* ti = _tp_info(obj);
-    if(ti->m__hash__) return ti->m__hash__(this, obj);
-
-    PyVar self;
-    PyVar f = get_unbound_method(obj, __hash__, &self, false);
-    if(f) {
-        PyVar ret = call_method(self, f);
-        return CAST(i64, ret);
-    }
-    // if it is trivial `object`, return PK_BITS
-    if(ti == &_all_types[tp_object]) return obj.hash();
-    // otherwise, we check if it has a custom __eq__ other than object.__eq__
-    bool has_custom_eq = false;
-    if(ti->m__eq__)
-        has_custom_eq = true;
-    else {
-        f = get_unbound_method(obj, __eq__, &self, false);
-        PyVar base_eq = _t(tp_object)->attr()[__eq__];
-        has_custom_eq = !PyVar__IS_OP(&f, &base_eq);
-    }
-    if(has_custom_eq) {
-        TypeError(_S("unhashable type: ", ti->name.escape()));
-    } else {
-        return obj.hash();
-    }
-}
-
-PyVar VM::__py_exec_internal(const CodeObject* code, PyVar globals, PyVar locals) {
-    Frame* frame = nullptr;
-    if(!callstack.empty()) frame = &callstack.top();
-
-    // fast path
-    if(frame && is_none(globals) && is_none(locals)) {
-        return vm->_exec(code, frame->_module, frame->_callable, frame->_locals);
-    }
-
-    auto _lock = gc_scope_lock();  // for safety
-
-    PyObject* globals_obj = nullptr;
-    Dict* globals_dict = nullptr;
-
-    NameDict* locals_closure = nullptr;
-    Dict* locals_dict = nullptr;
-
-    if(is_none(globals)){
-        globals_obj = frame ? frame->_module: _main;
-    } else {
-        if(is_type(globals, VM::tp_mappingproxy)) {
-            globals_obj = PK_OBJ_GET(MappingProxy, globals).obj;
-        } else {
-            check_compatible_type(globals, VM::tp_dict);
-            // make a temporary object and copy globals into it
-            globals_obj = new_object<DummyInstance>(VM::tp_object).get();
-            globals_dict = &PK_OBJ_GET(Dict, globals);
-            globals_dict->apply([&](PyVar k, PyVar v) {
-                globals_obj->attr().set(CAST(Str&, k), v);
-            });
-        }
-    }
-
-    PyVar retval = nullptr;
-
-    if(is_none(locals)) {
-        retval = vm->_exec(code, globals_obj);  // only globals
-    } else {
-        check_compatible_type(locals, VM::tp_dict);
-        locals_dict = &PK_OBJ_GET(Dict, locals);
-        locals_closure = new NameDict();
-        locals_dict->apply([&](PyVar k, PyVar v) {
-            locals_closure->set(CAST(Str&, k), v);
-        });
-        PyObject* _callable =
-            new_object<Function>(tp_function, __dynamic_func_decl, globals_obj, nullptr, locals_closure).get();
-        retval = vm->_exec(code, globals_obj, _callable, vm->s_data.sp);
-    }
-
-    if(globals_dict) {
-        globals_dict->clear();
-        for(auto [k, v]: globals_obj->attr().items()){
-            globals_dict->set(vm, VAR(k.sv()), v);
-        }
-    }
-
-    if(locals_dict) {
-        locals_dict->clear();
-        for(auto [k, v]: locals_closure->items()){
-            locals_dict->set(vm, VAR(k.sv()), v);
-        }
-    }
-    return retval;
-}
-
-void VM::py_exec(std::string_view source, PyVar globals, PyVar locals) {
-    CodeObject* code = vm->compile(source, "<exec>", EXEC_MODE, true);
-    __py_exec_internal(code, globals, locals);
-    CodeObject__delete(code);
-}
-
-PyVar VM::py_eval(std::string_view source, PyVar globals, PyVar locals) {
-    CodeObject* code = vm->compile(source, "<eval>", EVAL_MODE, true);
-    PyVar retval = __py_exec_internal(code, globals, locals);
-    CodeObject__delete(code);
-    return retval;
-}
-
-PyVar VM::__format_object(PyVar obj, Str spec) {
-    if(spec.empty()) return VAR(py_str(obj));
-    char type;
-    switch(spec.end()[-1]) {
-        case 'f':
-        case 'd':
-        case 's':
-            type = spec.end()[-1];
-            spec = spec.slice(0, spec.length() - 1);
-            break;
-        default: type = ' '; break;
-    }
-
-    char pad_c = ' ';
-    for(char c: std::string_view("0-=*#@!~")) {
-        if(spec[0] == c) {
-            pad_c = c;
-            spec = spec.substr(1);
-            break;
-        }
-    }
-    char align;
-    if(spec[0] == '^') {
-        align = '^';
-        spec = spec.substr(1);
-    } else if(spec[0] == '>') {
-        align = '>';
-        spec = spec.substr(1);
-    } else if(spec[0] == '<') {
-        align = '<';
-        spec = spec.substr(1);
-    } else {
-        if(is_int(obj) || is_float(obj))
-            align = '>';
-        else
-            align = '<';
-    }
-
-    int dot = spec.index(".");
-    int width, precision;
-    try {
-        if(dot >= 0) {
-            if(dot == 0) {
-                width = -1;
-            } else {
-                width = std::stoi(spec.slice(0, dot).str());
-            }
-            precision = std::stoi(spec.slice(dot + 1).str());
-        } else {
-            width = std::stoi(spec.str());
-            precision = -1;
-        }
-    } catch(...) { ValueError("invalid format specifer"); }
-
-    if(type != 'f' && dot >= 0) ValueError("precision not allowed in the format specifier");
-    Str ret;
-    if(type == 'f') {
-        f64 val = CAST(f64, obj);
-        if(precision < 0) precision = 6;
-        SStream ss;
-        ss.setprecision(precision);
-        ss << val;
-        ret = ss.str();
-    } else if(type == 'd') {
-        ret = std::to_string(CAST(i64, obj));
-    } else if(type == 's') {
-        ret = CAST(Str&, obj);
-    } else {
-        ret = py_str(obj);
-    }
-    if(width != -1 && width > ret.length()) {
-        int pad = width - ret.length();
-        if(align == '>' || align == '<') {
-            std::string padding(pad, pad_c);
-            if(align == '>')
-                ret = padding.c_str() + ret;
-            else
-                ret = ret + padding.c_str();
-        } else {  // ^
-            int pad_left = pad / 2;
-            int pad_right = pad - pad_left;
-            std::string padding_left(pad_left, pad_c);
-            std::string padding_right(pad_right, pad_c);
-            ret = padding_left.c_str() + ret + padding_right.c_str();
-        }
-    }
-    return VAR(ret);
-}
-
-PyObject* VM::new_module(Str name, Str package) {
-    PyObject* obj = new_object_no_gc<DummyModule>(tp_module).get();
-    obj->attr().set(__name__, VAR(name));
-    obj->attr().set(__package__, VAR(package));
-    // convert to fullname
-    if(!package.empty()) name = package + "." + name;
-    obj->attr().set(__path__, VAR(name));
-
-    // we do not allow override in order to avoid memory leak
-    // it is because Module objects are not garbage collected
-    if(_modules.contains(name)) { throw std::runtime_error(_S("module ", name.escape(), " already exists").str()); }
-    // set it into _modules
-    _modules.set(name, obj);
-    return obj;
-}
-
-static std::string _opcode_argstr(VM* vm, int i, Bytecode byte, const CodeObject* co) {
-    SStream ss;
-    if(Bytecode__is_forward_jump(&byte)){
-        std::string argStr = std::to_string((int16_t)byte.arg);
-        ss << (i64)(int16_t)byte.arg;
-        ss << " (to " << (i64)((int16_t)byte.arg + i) << ")";
-        return ss.str().str();
-    }
-    ss << (i64)byte.arg;
-    switch(byte.op) {
-        case OP_LOAD_CONST:
-        case OP_FORMAT_STRING:
-        case OP_IMPORT_PATH: {
-            PyVar obj = c11__getitem(PyVar, &co->consts, byte.arg);
-            if(vm != nullptr) ss << " (" << vm->py_repr(obj) << ")";
-            break;
-        }
-        case OP_LOAD_NAME:
-        case OP_LOAD_GLOBAL:
-        case OP_LOAD_NONLOCAL:
-        case OP_STORE_GLOBAL:
-        case OP_LOAD_ATTR:
-        case OP_LOAD_METHOD:
-        case OP_STORE_ATTR:
-        case OP_DELETE_ATTR:
-        case OP_BEGIN_CLASS:
-        case OP_GOTO:
-        case OP_DELETE_GLOBAL:
-        case OP_STORE_CLASS_ATTR:
-        case OP_FOR_ITER_STORE_GLOBAL: ss << " (" << StrName(byte.arg).sv() << ")"; break;
-        case OP_LOAD_FAST:
-        case OP_STORE_FAST:
-        case OP_DELETE_FAST:
-        case OP_FOR_ITER_STORE_FAST:
-        case OP_LOAD_SUBSCR_FAST:
-        case OP_STORE_SUBSCR_FAST:{
-            StrName name = c11__getitem(StrName, &co->varnames, byte.arg);
-            ss << " (" << name.sv() << ")";
-            break;
-        }
-        case OP_LOAD_FUNCTION: {
-            const FuncDecl* decl = c11__getitem(FuncDecl*, &co->func_decls, byte.arg);
-            ss << " (" << pkpy_Str__data(&decl->code->name) << ")";
-            break;
-        }
-    }
-    return ss.str().str();
-}
-
-Str VM::disassemble(CodeObject* co) {
-    auto pad = [](const Str& s, const int n) {
-        if(s.length() >= n) return s.slice(0, n);
-        return s + std::string(n - s.length(), ' ');
-    };
-
-    vector<int> jumpTargets;
-    for(int i=0; i<co->codes.count; i++) {
-        Bytecode* bc = c11__at(Bytecode, &co->codes, i);
-        if(Bytecode__is_forward_jump(bc)) {
-            jumpTargets.push_back((int16_t)bc->arg + i);
-        }
-    }
-    SStream ss;
-    int prev_line = -1;
-    for(int i = 0; i < co->codes.count; i++) {
-        Bytecode byte = c11__getitem(Bytecode, &co->codes, i);
-        BytecodeEx ex = c11__getitem(BytecodeEx, &co->codes_ex, i);
-        Str line = std::to_string(ex.lineno);
-        if(ex.lineno == prev_line)
-            line = "";
-        else {
-            if(prev_line != -1) ss << "\n";
-            prev_line = ex.lineno;
-        }
-
-        std::string pointer;
-        if(jumpTargets.contains(i)) {
-            pointer = "-> ";
-        } else {
-            pointer = "   ";
-        }
-        ss << pad(line, 8) << pointer << pad(std::to_string(i), 3);
-        std::string bc_name(OP_NAMES[byte.op]);
-        if(ex.is_virtual) bc_name += '*';
-        ss << " " << pad(bc_name, 25) << " ";
-        std::string argStr = _opcode_argstr(this, i, byte, co);
-        ss << argStr;
-        if(i != co->codes.count - 1) ss << '\n';
-    }
-
-    c11_vector__foreach(FuncDecl*, &co->func_decls, it) {
-        FuncDecl* decl = *it;
-        ss << "\n\n"
-           << "Disassembly of " << pkpy_Str__data(&decl->code->name) << ":\n";
-        ss << disassemble(decl->code);
-    }
-    ss << "\n";
-    return Str(ss.str());
-}
-
-#if PK_DEBUG_CEVAL_STEP
-void VM::__log_s_data(const char* title) {
-    if(_main == nullptr) return;
-    if(callstack.empty()) return;
-    SStream ss;
-    if(title) ss << title << " | ";
-    std::map<PyVar*, int> sp_bases;
-    callstack.apply([&](Frame& f) {
-        assert(f._sp_base != nullptr);
-        sp_bases[f._sp_base] += 1;
-    });
-    Frame* frame = &callstack.top();
-    int line = frame->curr_lineno();
-    ss << pkpy_Str__data(&frame->co->name) << ":" << line << " [";
-    for(PyVar* p = s_data.begin(); p != s_data.end(); p++) {
-        ss << std::string(sp_bases[p], '|');
-        if(sp_bases[p] > 0) ss << " ";
-        if(!(*p))
-            ss << "NULL";
-        else {
-            switch(p->type) {
-                case tp_none_type: ss << "None"; break;
-                case tp_int: ss << _CAST(i64, *p); break;
-                case tp_float: ss << _CAST(f64, *p); break;
-                case tp_bool: ss << (p->extra ? "True" : "False"); break;
-                case tp_str: ss << _CAST(Str, *p).escape(); break;
-                case tp_function: ss << pkpy_Str__data(&p->obj_get<Function>().decl->code->name) << "()"; break;
-                case tp_type: ss << "<class " + _type_name(this, p->obj_get<Type>()).escape() + ">"; break;
-                case tp_list: ss << "list(size=" << p->obj_get<List>().size() << ")"; break;
-                case tp_tuple: ss << "tuple(size=" << p->obj_get<Tuple>().size() << ")"; break;
-                default: ss << "(" << _type_name(this, p->type) << ")"; break;
-            }
-        }
-        ss << ", ";
-    }
-    std::string output = ss.str().str();
-    if(!s_data.empty()) {
-        output.pop_back();
-        output.pop_back();
-    }
-    output.push_back(']');
-    Bytecode byte = *frame->_ip;
-    std::cout << output << " " << OP_NAMES[byte.op] << " " << _opcode_argstr(nullptr, frame->ip(), byte, frame->co)
-              << std::endl;
-}
-#endif
-
-void VM::__init_builtin_types() {
-    _all_types.emplace_back(nullptr, Type(), nullptr, "", false);  // 0 is not used
-    _all_types.emplace_back(new_object_no_gc<Type>(tp_type, tp_object).get(), Type(), nullptr, "object", true);
-    _all_types.emplace_back(new_object_no_gc<Type>(tp_type, tp_type).get(), tp_object, nullptr, "type", false);
-
-    auto validate = [](Type type, PyObject* ret) {
-        Type ret_t = ret->as<Type>();
-        if(ret_t != type) exit(-3);
-    };
-
-    validate(tp_int, new_type_object(nullptr, "int", tp_object, false));
-    validate(tp_float, new_type_object(nullptr, "float", tp_object, false));
-    validate(tp_bool, new_type_object(nullptr, "bool", tp_object, false));
-
-    validate(tp_str, new_type_object<Str>(nullptr, "str", tp_object, false));
-    validate(tp_list, new_type_object<List>(nullptr, "list", tp_object, false));
-    validate(tp_tuple, new_type_object<Tuple>(nullptr, "tuple", tp_object, false));
-
-    validate(tp_slice, new_type_object<Slice>(nullptr, "slice", tp_object, false));
-    validate(tp_range, new_type_object<Range>(nullptr, "range", tp_object, false));
-    validate(tp_module, new_type_object<DummyModule>(nullptr, "module", tp_object, false));
-    validate(tp_function, new_type_object<Function>(nullptr, "function", tp_object, false));
-    validate(tp_native_func, new_type_object<NativeFunc>(nullptr, "native_func", tp_object, false));
-    validate(tp_bound_method, new_type_object<BoundMethod>(nullptr, "bound_method", tp_object, false));
-
-    validate(tp_super, new_type_object<Super>(nullptr, "super", tp_object, false));
-    validate(tp_exception, new_type_object<Exception>(nullptr, "Exception", tp_object, true));
-    validate(tp_bytes, new_type_object<Bytes>(nullptr, "bytes", tp_object, false));
-    validate(tp_mappingproxy, new_type_object<MappingProxy>(nullptr, "mappingproxy", tp_object, false));
-    validate(tp_dict, new_type_object<Dict>(nullptr, "dict", tp_object, true));
-    validate(tp_property, new_type_object<Property>(nullptr, "property", tp_object, false));
-    validate(tp_star_wrapper, new_type_object<StarWrapper>(nullptr, "_star_wrapper", tp_object, false));
-
-    validate(tp_staticmethod, new_type_object<StaticMethod>(nullptr, "staticmethod", tp_object, false));
-    validate(tp_classmethod, new_type_object<ClassMethod>(nullptr, "classmethod", tp_object, false));
-
-    validate(tp_none_type, new_type_object(nullptr, "NoneType", tp_object, false));
-    validate(tp_not_implemented_type, new_type_object(nullptr, "NotImplementedType", tp_object, false));
-    validate(tp_ellipsis, new_type_object(nullptr, "ellipsis", tp_object, false));
-
-    validate(::tp_op_call, new_type_object(nullptr, "__op_call", tp_object, false));
-    validate(::tp_op_yield, new_type_object(nullptr, "__op_yield", tp_object, false));
-
-    // SyntaxError and IndentationError must be created here
-    PyObject* SyntaxError = new_type_object(nullptr, "SyntaxError", tp_exception, true);
-    PyObject* IndentationError = new_type_object(nullptr, "IndentationError", SyntaxError->as<Type>(), true);
-    this->StopIteration = new_type_object(nullptr, "StopIteration", tp_exception, true);
-
-    this->builtins = new_module("builtins");
-
-    // setup public types
-    builtins->attr().set("type", _t(tp_type));
-    builtins->attr().set("object", _t(tp_object));
-    builtins->attr().set("bool", _t(tp_bool));
-    builtins->attr().set("int", _t(tp_int));
-    builtins->attr().set("float", _t(tp_float));
-    builtins->attr().set("str", _t(tp_str));
-    builtins->attr().set("list", _t(tp_list));
-    builtins->attr().set("tuple", _t(tp_tuple));
-    builtins->attr().set("range", _t(tp_range));
-    builtins->attr().set("bytes", _t(tp_bytes));
-    builtins->attr().set("dict", _t(tp_dict));
-    builtins->attr().set("property", _t(tp_property));
-    builtins->attr().set("StopIteration", StopIteration);
-    builtins->attr().set("NotImplemented", NotImplemented);
-    builtins->attr().set("slice", _t(tp_slice));
-    builtins->attr().set("Exception", _t(tp_exception));
-    builtins->attr().set("SyntaxError", SyntaxError);
-    builtins->attr().set("IndentationError", IndentationError);
-
-    __post_init_builtin_types();
-    this->_main = new_module("__main__");
-}
-
-void VM::__unpack_as_list(ArgsView args, List& list) {
-    auto _lock = gc_scope_lock();
-    for(PyVar obj: args) {
-        if(is_type(obj, tp_star_wrapper)) {
-            const StarWrapper& w = _CAST(StarWrapper&, obj);
-            // maybe this check should be done in the compile time
-            if(w.level != 1) TypeError("expected level 1 star wrapper");
-            PyVar _0 = py_iter(w.obj);
-            const PyTypeInfo* info = _tp_info(_0);
-            PyVar _1 = _py_next(info, _0);
-            while(_1 != StopIteration) {
-                list.push_back(_1);
-                _1 = _py_next(info, _0);
-            }
-        } else {
-            list.push_back(obj);
-        }
-    }
-}
-
-void VM::__unpack_as_dict(ArgsView args, Dict& dict) {
-    auto _lock = gc_scope_lock();
-    for(PyVar obj: args) {
-        if(is_type(obj, tp_star_wrapper)) {
-            const StarWrapper& w = _CAST(StarWrapper&, obj);
-            // maybe this check should be done in the compile time
-            if(w.level != 2) TypeError("expected level 2 star wrapper");
-            const Dict& other = CAST(Dict&, w.obj);
-            dict.update(this, other);
-        } else {
-            const Tuple& t = CAST(Tuple&, obj);
-            if(t.size() != 2) TypeError("expected tuple of length 2");
-            dict.set(this, t[0], t[1]);
-        }
-    }
-}
-
-void VM::__prepare_py_call(PyVar* buffer, ArgsView args, ArgsView kwargs, const FuncDecl* decl) {
-    const CodeObject* co = decl->code;
-    int decl_argc = decl->args.count;
-
-    if(args.size() < decl_argc) {
-        vm->TypeError(_S(pkpy_Str__data(&co->name), "() takes ", decl_argc, " positional arguments but ", args.size(), " were given"));
-    }
-
-    int i = 0;
-    // prepare args
-    std::memset(buffer, 0, co->nlocals * sizeof(PyVar));
-    c11_vector__foreach(int, &decl->args, index) {
-        buffer[*index] = args[i++];
-    }
-    // prepare kwdefaults
-    c11_vector__foreach(FuncDeclKwArg, &decl->kwargs, kv) {
-        buffer[kv->index] = kv->value;
-    }
-
-    // handle *args
-    if(decl->starred_arg != -1) {
-        ArgsView vargs(args.begin() + i, args.end());
-        buffer[decl->starred_arg] = VAR(vargs.to_tuple());
-        i += vargs.size();
-    } else {
-        // kwdefaults override
-        c11_vector__foreach(FuncDeclKwArg, &decl->kwargs, kv) {
-            if(i >= args.size()) break;
-            buffer[kv->index] = args[i++];
-        }
-        if(i < args.size()) TypeError(_S("too many arguments", " (", pkpy_Str__data(&decl->code->name), ')'));
-    }
-
-    PyVar vkwargs;
-    if(decl->starred_kwarg != -1) {
-        vkwargs = VAR(Dict());
-        buffer[decl->starred_kwarg] = vkwargs;
-    } else {
-        vkwargs = nullptr;
-    }
-
-    for(int j = 0; j < kwargs.size(); j += 2) {
-        StrName key(_CAST(uint16_t, kwargs[j]));
-        int index = c11_smallmap_n2i__get(&decl->kw_to_index, key.index, -1);
-        // if key is an explicit key, set as local variable
-        if(index >= 0) {
-            buffer[index] = kwargs[j + 1];
-        } else {
-            // otherwise, set as **kwargs if possible
-            if(!vkwargs) {
-                TypeError(_S(key.escape(), " is an invalid keyword argument for ", pkpy_Str__data(&co->name), "()"));
-            } else {
-                Dict& dict = _CAST(Dict&, vkwargs);
-                dict.set(this, VAR(key.sv()), kwargs[j + 1]);
-            }
-        }
-    }
-}
-
-PyVar VM::vectorcall(int ARGC, int KWARGC, bool op_call) {
-    PyVar* p1 = (PyVar*)(s_data.sp - KWARGC * 2);
-    PyVar* p0 = p1 - ARGC - 2;
-    // [callable, <self>, args..., kwargs...]
-    //      ^p0                    ^p1      ^_sp
-    PyVar callable = p1[-ARGC - 2];
-    Type callable_t = _tp(callable);
-
-    // handle boundmethod, do a patch
-    if(callable_t == tp_bound_method) {
-        assert(!p0[1]);
-        BoundMethod& bm = PK_OBJ_GET(BoundMethod, callable);
-        callable = bm.func;  // get unbound method
-        callable_t = _tp(callable);
-        p1[-(ARGC + 2)] = bm.func;
-        p1[-(ARGC + 1)] = bm.self;
-        // [unbound, self, args..., kwargs...]
-    }
-
-    ArgsView args((!p0[1]) ? (p0 + 2) : (p0 + 1), p1);
-    ArgsView kwargs(p1, s_data.sp);
-
-    PyVar* _base = args.begin();
-
-    if(callable_t == tp_function) {
-        /*****************_py_call*****************/
-        // check stack overflow
-        if(s_data.sp > s_data.end) StackOverflowError();
-
-        const Function& fn = PK_OBJ_GET(Function, callable);
-        const CodeObject* co = fn.decl->code;
-
-        switch(fn.decl->type) {
-            case FuncType_NORMAL:
-                __prepare_py_call(__vectorcall_buffer, args, kwargs, fn.decl);
-                // copy buffer back to stack
-                s_data.sp = (_base + co->nlocals);
-                for(int j = 0; j < co->nlocals; j++)
-                    _base[j] = __vectorcall_buffer[j];
-                break;
-            case FuncType_SIMPLE:
-                if(args.size() != fn.decl->args.count){
-                    TypeError(pk_format(
-                        "{} takes {} positional arguments but {} were given",
-                        &co->name, fn.decl->args.count, args.size()
-                    ));
-                }
-                if(!kwargs.empty()){
-                    TypeError(pk_format("{} takes no keyword arguments", &co->name));
-                }
-                // [callable, <self>, args..., local_vars...]
-                //      ^p0                    ^p1      ^_sp
-                s_data.sp = (_base + co->nlocals);
-                // initialize local variables to PY_NULL
-                std::memset(p1, 0, (char*)s_data.sp - (char*)p1);
-                break;
-            case FuncType_EMPTY:
-                if(args.size() != fn.decl->args.count){
-                    TypeError(pk_format(
-                        "{} takes {} positional arguments but {} were given",
-                        &co->name, fn.decl->args.count, args.size()
-                    ));
-                }
-                if(!kwargs.empty()){
-                    TypeError(pk_format("{} takes no keyword arguments", &co->name));
-                }
-                s_data.sp = p0;
-                return None;
-            case FuncType_GENERATOR:
-                __prepare_py_call(__vectorcall_buffer, args, kwargs, fn.decl);
-                s_data.sp = p0;
-                callstack.emplace(nullptr, co, fn._module, callable.get(), nullptr);
-                return __py_generator(callstack.popx(),
-                                      ArgsView(__vectorcall_buffer, __vectorcall_buffer + co->nlocals));
-            default: PK_UNREACHABLE()
-        };
-
-        // simple or normal
-        callstack.emplace(p0, co, fn._module, callable.get(), args.begin());
-        if(op_call) return PY_OP_CALL;
-        return __run_top_frame();
-        /*****************_py_call*****************/
-    }
-
-    if(callable_t == tp_native_func) {
-        const auto& f = PK_OBJ_GET(NativeFunc, callable);
-        PyVar ret;
-        if(f.decl != nullptr) {
-            int co_nlocals = f.decl->code->nlocals;
-            __prepare_py_call(__vectorcall_buffer, args, kwargs, f.decl);
-            // copy buffer back to stack
-            s_data.sp = (_base + co_nlocals);
-            for(int j = 0; j < co_nlocals; j++)
-                _base[j] = __vectorcall_buffer[j];
-            ret = f.call(vm, ArgsView(s_data.sp - co_nlocals, s_data.sp));
-        } else {
-            if(f.argc != -1) {
-                if(KWARGC != 0)
-                    TypeError(
-                        "old-style native_func does not accept keyword arguments. If you want to skip this check, specify `argc` to -1");
-                if(args.size() != f.argc) { vm->TypeError(_S("expected ", f.argc, " arguments, got ", args.size())); }
-            }
-            ret = f.call(this, args);
-        }
-        s_data.sp = (p0);
-        return ret;
-    }
-
-    if(callable_t == tp_type) {
-        // [type, NULL, args..., kwargs...]
-        PyVar new_f = *find_name_in_mro(PK_OBJ_GET(Type, callable), __new__);
-        PyVar obj;
-        assert(new_f && (!p0[1]));
-        if(PyVar__IS_OP(&new_f, &__cached_object_new)) {
-            // fast path for object.__new__
-            obj = vm->new_object<DummyInstance>(PK_OBJ_GET(Type, callable));
-        } else {
-            PUSH(new_f);
-            PUSH_NULL();
-            PUSH(callable);  // cls
-            for(PyVar o: args)
-                PUSH(o);
-            for(PyVar o: kwargs)
-                PUSH(o);
-            // if obj is not an instance of `cls`, the behavior is undefined
-            obj = vectorcall(ARGC + 1, KWARGC);
-        }
-
-        // __init__
-        PyVar self;
-        callable = get_unbound_method(obj, __init__, &self, false);
-        if(callable) {
-            callable_t = _tp(callable);
-            // replace `NULL` with `self`
-            p1[-(ARGC + 2)] = callable;
-            p1[-(ARGC + 1)] = self;
-            // [init_f, self, args..., kwargs...]
-            vectorcall(ARGC, KWARGC);
-            // We just discard the return value of `__init__`
-            // in cpython it raises a TypeError if the return value is not None
-        } else {
-            // manually reset the stack
-            s_data.sp = (p0);
-        }
-        return obj;
-    }
-
-    // handle `__call__` overload
-    PyVar self;
-    PyVar call_f = get_unbound_method(callable, __call__, &self, false);
-    if(self) {
-        p1[-(ARGC + 2)] = call_f;
-        p1[-(ARGC + 1)] = self;
-        // [call_f, self, args..., kwargs...]
-        return vectorcall(ARGC, KWARGC, op_call);
-    }
-    TypeError(_type_name(vm, callable_t).escape() + " object is not callable");
-}
-
-void VM::delattr(PyVar _0, StrName _name) {
-    const PyTypeInfo* ti = _tp_info(_0);
-    if(ti->m__delattr__ && ti->m__delattr__(this, _0, _name)) return;
-    if(is_tagged(_0) || !_0->is_attr_valid()) TypeError("cannot delete attribute");
-    if(!_0->attr().del(_name)) AttributeError(_0, _name);
-}
-
-// https://docs.python.org/3/howto/descriptor.html#invocation-from-an-instance
-PyVar VM::getattr(PyVar obj, StrName name, bool throw_err) {
-    Type objtype(0);
-    // handle super() proxy
-    if(is_type(obj, tp_super)) {
-        const Super& super = PK_OBJ_GET(Super, obj);
-        obj = super.first;
-        objtype = super.second;
-    } else {
-        objtype = _tp(obj);
-    }
-    PyVar* cls_var = find_name_in_mro(objtype, name);
-    if(cls_var != nullptr) {
-        // handle descriptor
-        if(is_type(*cls_var, tp_property)) {
-            const Property& prop = PK_OBJ_GET(Property, *cls_var);
-            return call(prop.getter, obj);
-        }
-    }
-    // handle instance __dict__
-    if(!is_tagged(obj) && obj->is_attr_valid()) {
-        PyVar* val;
-        if(obj.type == tp_type) {
-            val = find_name_in_mro(PK_OBJ_GET(Type, obj), name);
-            if(val != nullptr) {
-                if(is_tagged(*val)) return *val;
-                if(val->type == tp_staticmethod) return PK_OBJ_GET(StaticMethod, *val).func;
-                if(val->type == tp_classmethod) return VAR(BoundMethod(obj, PK_OBJ_GET(ClassMethod, *val).func));
-                return *val;
-            }
-        } else {
-            val = obj->attr().try_get_2_likely_found(name);
-            if(val != nullptr) return *val;
-        }
-    }
-    if(cls_var != nullptr) {
-        // bound method is non-data descriptor
-        if(!is_tagged(*cls_var)) {
-            switch(cls_var->type) {
-                case tp_function: return VAR(BoundMethod(obj, *cls_var));
-                case tp_native_func: return VAR(BoundMethod(obj, *cls_var));
-                case tp_staticmethod: return PK_OBJ_GET(StaticMethod, *cls_var).func;
-                case tp_classmethod: return VAR(BoundMethod(_t(objtype), PK_OBJ_GET(ClassMethod, *cls_var).func));
-            }
-        }
-        return *cls_var;
-    }
-
-    const PyTypeInfo* ti = &_all_types[objtype];
-    if(ti->m__getattr__) {
-        PyVar ret = ti->m__getattr__(this, obj, name);
-        if(ret) return ret;
-    }
-
-    if(throw_err) AttributeError(obj, name);
-    return nullptr;
-}
-
-// used by OP_LOAD_METHOD
-// try to load a unbound method (fallback to `getattr` if not found)
-PyVar VM::get_unbound_method(PyVar obj, StrName name, PyVar* self, bool throw_err, bool fallback) {
-    self->set_null();
-    Type objtype(0);
-    // handle super() proxy
-    if(is_type(obj, tp_super)) {
-        const Super& super = PK_OBJ_GET(Super, obj);
-        obj = super.first;
-        objtype = super.second;
-    } else {
-        objtype = _tp(obj);
-    }
-    PyVar* cls_var = find_name_in_mro(objtype, name);
-
-    if(fallback) {
-        if(cls_var != nullptr) {
-            // handle descriptor
-            if(is_type(*cls_var, tp_property)) {
-                const Property& prop = PK_OBJ_GET(Property, *cls_var);
-                return call(prop.getter, obj);
-            }
-        }
-        // handle instance __dict__
-        if(!is_tagged(obj) && obj->is_attr_valid()) {
-            PyVar* val;
-            if(obj.type == tp_type) {
-                val = find_name_in_mro(PK_OBJ_GET(Type, obj), name);
-                if(val != nullptr) {
-                    if(is_tagged(*val)) return *val;
-                    if(val->type == tp_staticmethod) return PK_OBJ_GET(StaticMethod, *val).func;
-                    if(val->type == tp_classmethod) return VAR(BoundMethod(obj, PK_OBJ_GET(ClassMethod, *val).func));
-                    return *val;
-                }
-            } else {
-                val = obj->attr().try_get_2_likely_found(name);
-                if(val != nullptr) return *val;
-            }
-        }
-    }
-
-    if(cls_var != nullptr) {
-        if(!is_tagged(*cls_var)) {
-            switch(cls_var->type) {
-                case tp_function: *self = obj; break;
-                case tp_native_func: *self = obj; break;
-                case tp_staticmethod: self->set_null(); return PK_OBJ_GET(StaticMethod, *cls_var).func;
-                case tp_classmethod: *self = _t(objtype); return PK_OBJ_GET(ClassMethod, *cls_var).func;
-            }
-        }
-        return *cls_var;
-    }
-
-    const PyTypeInfo* ti = &_all_types[objtype];
-    if(fallback && ti->m__getattr__) {
-        PyVar ret = ti->m__getattr__(this, obj, name);
-        if(ret) return ret;
-    }
-
-    if(throw_err) AttributeError(obj, name);
-    return nullptr;
-}
-
-void VM::setattr(PyVar obj, StrName name, PyVar value) {
-    Type objtype(0);
-    // handle super() proxy
-    if(is_type(obj, tp_super)) {
-        Super& super = PK_OBJ_GET(Super, obj);
-        obj = super.first;
-        objtype = super.second;
-    } else {
-        objtype = _tp(obj);
-    }
-    PyVar* cls_var = find_name_in_mro(objtype, name);
-    if(cls_var != nullptr) {
-        // handle descriptor
-        if(is_type(*cls_var, tp_property)) {
-            const Property& prop = _CAST(Property&, *cls_var);
-            if(!is_none(prop.setter)) {
-                call(prop.setter, obj, value);
-            } else {
-                TypeError(_S("readonly attribute: ", name.escape()));
-            }
-            return;
-        }
-    }
-
-    const PyTypeInfo* ti = &_all_types[objtype];
-    if(ti->m__setattr__) {
-        ti->m__setattr__(this, obj, name, value);
-        return;
-    }
-
-    // handle instance __dict__
-    if(is_tagged(obj) || !obj->is_attr_valid()) TypeError("cannot set attribute");
-    obj->attr().set(name, value);
-}
-
-PyObject* VM::bind_func(PyObject* obj, StrName name, int argc, NativeFuncC fn, any userdata, BindType bt) {
-    PyObject* nf = new_object<NativeFunc>(tp_native_func, fn, argc, std::move(userdata)).get();
-    switch(bt) {
-        case BindType_FUNCTION: break;
-        case BindType_STATICMETHOD: nf = new_object<StaticMethod>(tp_staticmethod, nf).get(); break;
-        case BindType_CLASSMETHOD: nf = new_object<ClassMethod>(tp_classmethod, nf).get(); break;
-    }
-    if(obj != nullptr) obj->attr().set(name, nf);
-    return nf;
-}
-
-PyObject* VM::bind(PyObject* obj, const char* sig, NativeFuncC fn, any userdata, BindType bt) {
-    return bind(obj, sig, nullptr, fn, std::move(userdata), bt);
-}
-
-PyObject* VM::bind(PyObject* obj, const char* sig, const char* docstring, NativeFuncC fn, any userdata, BindType bt) {
-    char buffer[256];
-    int length = snprintf(buffer, sizeof(buffer), "def %s : pass", sig);
-    std::string_view source(buffer, length);
-    // fn(a, b, *c, d=1) -> None
-    CodeObject* code = compile(source, "<bind>", EXEC_MODE);
-    assert(code->func_decls.count == 1);
-    FuncDecl_ decl = c11__getitem(FuncDecl_, &code->func_decls, 0);
-    c11_vector__clear(&code->func_decls);   // move decl
-    CodeObject__delete(code);   // may leak if exception occurs
-    decl->docstring = docstring;
-    PyObject* f_obj = new_object<NativeFunc>(tp_native_func, fn, decl, std::move(userdata)).get();
-
-    switch(bt) {
-        case BindType_STATICMETHOD: f_obj = new_object<StaticMethod>(tp_staticmethod, f_obj).get(); break;
-        case BindType_CLASSMETHOD: f_obj = new_object<ClassMethod>(tp_classmethod, f_obj).get(); break;
-        case BindType_FUNCTION: break;
-    }
-    if(obj != nullptr){
-        StrName name = pkpy_Str__data(&decl->code->name);
-        obj->attr().set(name, f_obj);
-    }
-    return f_obj;
-}
-
-PyObject* VM::bind_property(PyObject* obj, const char* name, NativeFuncC fget, NativeFuncC fset) {
-    assert(is_type(obj, tp_type));
-    std::string_view name_sv(name);
-    int pos = name_sv.find(':');
-    if(pos > 0) name_sv = name_sv.substr(0, pos);
-    PyVar _0 = new_object<NativeFunc>(tp_native_func, fget, 1);
-    PyVar _1 = vm->None;
-    if(fset != nullptr) _1 = new_object<NativeFunc>(tp_native_func, fset, 2);
-    PyObject* prop = new_object<Property>(tp_property, _0, _1).get();
-    obj->attr().set(StrName(name_sv), prop);
-    return prop;
-}
-
-void VM::__builtin_error(StrName type) { _error(call(builtins->attr()[type])); }
-
-void VM::__builtin_error(StrName type, PyVar arg) { _error(call(builtins->attr()[type], arg)); }
-
-void VM::__builtin_error(StrName type, const Str& msg) { __builtin_error(type, VAR(msg)); }
-
-void VM::BinaryOptError(const char* op, PyVar _0, PyVar _1) {
-    StrName name_0 = _type_name(vm, _tp(_0));
-    StrName name_1 = _type_name(vm, _tp(_1));
-    TypeError(_S("unsupported operand type(s) for ", op, ": ", name_0.escape(), " and ", name_1.escape()));
-}
-
-void VM::AttributeError(PyVar obj, StrName name) {
-    if(isinstance(obj, vm->tp_type)) {
-        __builtin_error(
-            "AttributeError",
-            _S("type object ", _type_name(vm, PK_OBJ_GET(Type, obj)).escape(), " has no attribute ", name.escape()));
-    } else {
-        __builtin_error("AttributeError",
-                        _S(_type_name(vm, _tp(obj)).escape(), " object has no attribute ", name.escape()));
-    }
-}
-
-void VM::_error(PyVar e_obj) {
-    assert(isinstance(e_obj, tp_exception));
-    Exception& e = PK_OBJ_GET(Exception, e_obj);
-    if(callstack.empty()) {
-        e.is_re = false;
-        __last_exception = e_obj.get();
-        throw TopLevelException(this, &e);
-    }
-    PUSH(e_obj);
-    __raise_exc();
-}
-
-void VM::__raise_exc(bool re_raise) {
-    Frame* frame = &callstack.top();
-    Exception& e = PK_OBJ_GET(Exception, (PyVar&)s_data.sp[-1]);
-    if(!re_raise) {
-        e._ip_on_error = frame->ip();
-        e._code_on_error = (void*)frame->co;
-    }
-    int next_ip = frame->prepare_jump_exception_handler(&s_data);
-
-    int actual_ip = frame->ip();
-    if(e._ip_on_error >= 0 && e._code_on_error == (void*)frame->co) actual_ip = e._ip_on_error;
-    int current_line = c11__at(BytecodeEx, &frame->co->codes_ex, actual_ip)->lineno;
-    const char* current_f_name = pkpy_Str__data(&frame->co->name);  // current function name
-    if(frame->_callable == nullptr) current_f_name = "";            // not in a function
-    e.stpush(frame->co->src, current_line, nullptr, current_f_name);
-
-    if(next_ip >= 0) {
-        throw InternalException(InternalExceptionType::Handled, next_ip);
-    } else {
-        throw InternalException(InternalExceptionType::Unhandled);
-    }
-}
-
-StrName _type_name(VM* vm, Type type) { return vm->_all_types[type].name; }
-
-void VM::bind__getitem__(Type type, PyVar (*f)(VM*, PyVar, PyVar)) {
-    _all_types[type].m__getitem__ = f;
-    bind_func(
-        type,
-        __getitem__,
-        2,
-        [](VM* vm, ArgsView args) {
-            return lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0], args[1]);
-        },
-        f);
-}
-
-void VM::bind__setitem__(Type type, void (*f)(VM*, PyVar, PyVar, PyVar)) {
-    _all_types[type].m__setitem__ = f;
-    bind_func(
-        type,
-        __setitem__,
-        3,
-        [](VM* vm, ArgsView args) {
-            lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0], args[1], args[2]);
-            return vm->None;
-        },
-        f);
-}
-
-void VM::bind__delitem__(Type type, void (*f)(VM*, PyVar, PyVar)) {
-    _all_types[type].m__delitem__ = f;
-    bind_func(
-        type,
-        __delitem__,
-        2,
-        [](VM* vm, ArgsView args) {
-            lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0], args[1]);
-            return vm->None;
-        },
-        f);
-}
-
-PyVar VM::__pack_next_retval(unsigned n) {
-    if(n == 0) return StopIteration;
-    if(n == 1) return *--s_data.sp;
-    ArgsView view(s_data.sp - n, s_data.sp);
-    PyVar retval = VAR(view.to_tuple());
-    s_data.sp -= n;
-    return retval;
-}
-
-void VM::bind__next__(Type type, unsigned (*f)(VM*, PyVar)) {
-    _all_types[type].op__next__ = f;
-    bind_func(
-        type,
-        __next__,
-        1,
-        [](VM* vm, ArgsView args) {
-            int n = lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0]);
-            return vm->__pack_next_retval(n);
-        },
-        f);
-}
-
-void VM::bind__next__(Type type, PyVar (*f)(VM*, PyVar)) {
-    bind_func(
-        type,
-        __next__,
-        1,
-        [](VM* vm, ArgsView args) {
-            auto f = lambda_get_userdata<PyVar (*)(VM*, PyVar)>(args.begin());
-            return f(vm, args[0]);
-        },
-        f);
-}
-
-#define BIND_UNARY_SPECIAL(name)                                                                                       \
-    void VM::bind##name(Type type, PyVar (*f)(VM*, PyVar)) {                                                           \
-        _all_types[type].m##name = f;                                                                                  \
-        bind_func(                                                                                                     \
-            type,                                                                                                      \
-            name,                                                                                                      \
-            1,                                                                                                         \
-            [](VM* vm, ArgsView args) {                                                                                \
-                return lambda_get_userdata<PyVar (*)(VM*, PyVar)>(args.begin())(vm, args[0]);                          \
-            },                                                                                                         \
-            f);                                                                                                        \
-    }
-BIND_UNARY_SPECIAL(__iter__)
-BIND_UNARY_SPECIAL(__neg__)
-BIND_UNARY_SPECIAL(__invert__)
-#undef BIND_UNARY_SPECIAL
-
-void VM::bind__str__(Type type, Str (*f)(VM*, PyVar)) {
-    _all_types[type].m__str__ = f;
-    bind_func(
-        type,
-        __str__,
-        1,
-        [](VM* vm, ArgsView args) {
-            Str s = lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0]);
-            return VAR(s);
-        },
-        f);
-}
-
-void VM::bind__repr__(Type type, Str (*f)(VM*, PyVar)) {
-    _all_types[type].m__repr__ = f;
-    bind_func(
-        type,
-        __repr__,
-        1,
-        [](VM* vm, ArgsView args) {
-            Str s = lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0]);
-            return VAR(s);
-        },
-        f);
-}
-
-void VM::bind__hash__(Type type, i64 (*f)(VM*, PyVar)) {
-    _all_types[type].m__hash__ = f;
-    bind_func(
-        type,
-        __hash__,
-        1,
-        [](VM* vm, ArgsView args) {
-            i64 ret = lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0]);
-            return VAR(ret);
-        },
-        f);
-}
-
-void VM::bind__len__(Type type, i64 (*f)(VM*, PyVar)) {
-    _all_types[type].m__len__ = f;
-    bind_func(
-        type,
-        __len__,
-        1,
-        [](VM* vm, ArgsView args) {
-            i64 ret = lambda_get_userdata<decltype(f)>(args.begin())(vm, args[0]);
-            return VAR(ret);
-        },
-        f);
-}
-
-#define BIND_BINARY_SPECIAL(name)                                                                                      \
-    void VM::bind##name(Type type, BinaryFuncC f) {                                                                    \
-        _all_types[type].m##name = f;                                                                                  \
-        bind_func(                                                                                                     \
-            type,                                                                                                      \
-            name,                                                                                                      \
-            2,                                                                                                         \
-            [](VM* vm, ArgsView args) {                                                                                \
-                return lambda_get_userdata<BinaryFuncC>(args.begin())(vm, args[0], args[1]);                           \
-            },                                                                                                         \
-            f);                                                                                                        \
-    }
-
-BIND_BINARY_SPECIAL(__eq__)
-BIND_BINARY_SPECIAL(__lt__)
-BIND_BINARY_SPECIAL(__le__)
-BIND_BINARY_SPECIAL(__gt__)
-BIND_BINARY_SPECIAL(__ge__)
-BIND_BINARY_SPECIAL(__contains__)
-
-BIND_BINARY_SPECIAL(__add__)
-BIND_BINARY_SPECIAL(__sub__)
-BIND_BINARY_SPECIAL(__mul__)
-BIND_BINARY_SPECIAL(__truediv__)
-BIND_BINARY_SPECIAL(__floordiv__)
-BIND_BINARY_SPECIAL(__mod__)
-BIND_BINARY_SPECIAL(__pow__)
-BIND_BINARY_SPECIAL(__matmul__)
-
-BIND_BINARY_SPECIAL(__lshift__)
-BIND_BINARY_SPECIAL(__rshift__)
-BIND_BINARY_SPECIAL(__and__)
-BIND_BINARY_SPECIAL(__or__)
-BIND_BINARY_SPECIAL(__xor__)
-
-#undef BIND_BINARY_SPECIAL
-
-#if PK_ENABLE_PROFILER
-void NextBreakpoint::_step(VM* vm) {
-    int curr_callstack_size = vm->callstack.size();
-    int curr_lineno = vm->callstack.top().curr_lineno();
-    if(should_step_into) {
-        if(curr_callstack_size != callstack_size || curr_lineno != lineno) { vm->__breakpoint(); }
-    } else {
-        if(curr_callstack_size == callstack_size) {
-            if(curr_lineno != lineno) vm->__breakpoint();
-        } else if(curr_callstack_size < callstack_size) {
-            // returning
-            vm->__breakpoint();
-        }
-    }
-}
-#endif
-
-void VM::__pop_frame() {
-    assert(top_frame);
-    s_data.sp = top_frame->p0;
-    // callstack.pop()
-    Frame* p = top_frame;
-    top_frame = p->f_back;
-    Frame__delete(p);
-
-#if PK_ENABLE_PROFILER
-    if(!_next_breakpoint.empty() && callstack.size() < _next_breakpoint.callstack_size) {
-        _next_breakpoint = NextBreakpoint();
-    }
-#endif
-}
-
-void VM::__breakpoint() {
-#if PK_ENABLE_PROFILER
-    _next_breakpoint = NextBreakpoint();
-
-    bool show_where = false;
-    bool show_headers = true;
-
-    while(true) {
-        vector<LinkedFrame*> frames;
-        LinkedFrame* lf = callstack._tail;
-        while(lf != nullptr) {
-            frames.push_back(lf);
-            lf = lf->f_back;
-            if(frames.size() >= 4) break;
-        }
-
-        if(show_headers) {
-            for(int i = frames.size() - 1; i >= 0; i--) {
-                if(!show_where && i != 0) continue;
-
-                SStream ss;
-                Frame* frame = &frames[i]->frame;
-                int lineno = frame->curr_lineno();
-                ss << "File \"" << frame->co->src.filename() << "\", line " << lineno;
-                if(frame->_callable) {
-                    ss << ", in ";
-                    ss << frame->_callable->as<Function>().decl->code->name;
-                }
-                ss << '\n';
-                ss << "-> " << frame->co->src->get_line(lineno) << '\n';
-                stdout_write(ss.str());
-            }
-            show_headers = false;
-        }
-
-        vm->stdout_write("(Pdb) ");
-        Frame* frame_0 = &frames[0]->frame;
-
-        std::string line;
-        if(!std::getline(std::cin, line)) {
-            stdout_write("--KeyboardInterrupt--\n");
-            continue;
-        }
-
-        if(line == "h" || line == "help") {
-            stdout_write("h, help: show this help message\n");
-            stdout_write("q, quit: exit the debugger\n");
-            stdout_write("n, next: execute next line\n");
-            stdout_write("s, step: step into\n");
-            stdout_write("w, where: show current stack frame\n");
-            stdout_write("c, continue: continue execution\n");
-            stdout_write("a, args: show local variables\n");
-            stdout_write("p, print <expr>: evaluate expression\n");
-            stdout_write("l, list: show lines around current line\n");
-            stderr_write("ll, longlist: show all lines\n");
-            stdout_write("!: execute statement\n");
-            continue;
-        }
-        if(line == "q" || line == "quit") { vm->RuntimeError("pdb quit"); }
-        if(line == "n" || line == "next") {
-            vm->_next_breakpoint = NextBreakpoint(vm->callstack.size(), frame_0->curr_lineno(), false);
-            break;
-        }
-        if(line == "s" || line == "step") {
-            vm->_next_breakpoint = NextBreakpoint(vm->callstack.size(), frame_0->curr_lineno(), true);
-            break;
-        }
-        if(line == "w" || line == "where") {
-            show_where = !show_where;
-            show_headers = true;
-            continue;
-        }
-        if(line == "c" || line == "continue") break;
-        if(line == "a" || line == "args") {
-            int i = 0;
-            for(PyVar obj: frame_0->_locals) {
-                if(obj == PY_NULL) continue;
-                StrName name = frame_0->co->varnames[i++];
-                stdout_write(_S(name.sv(), " = ", vm->py_repr(obj), '\n'));
-            }
-            continue;
-        }
-
-        bool is_list = line == "l" || line == "list";
-        bool is_longlist = line == "ll" || line == "longlist";
-
-        if(is_list || is_longlist) {
-            if(frame_0->co->src->is_precompiled) continue;
-            int lineno = frame_0->curr_lineno();
-            int start, end;
-
-            if(is_list) {
-                int max_line = frame_0->co->src->line_starts.size() + 1;
-                start = (std::max)(1, lineno - 5);
-                end = (std::min)(max_line, lineno + 5);
-            } else {
-                start = frame_0->co->start_line;
-                end = frame_0->co->end_line;
-                if(start == -1 || end == -1) continue;
-            }
-
-            SStream ss;
-            int max_width = std::to_string(end).size();
-            for(int i = start; i <= end; i++) {
-                int spaces = max_width - std::to_string(i).size();
-                ss << std::string(spaces, ' ') << std::to_string(i);
-                if(i == lineno)
-                    ss << "  -> ";
-                else
-                    ss << "     ";
-                ss << frame_0->co->src->get_line(i) << '\n';
-            }
-            stdout_write(ss.str());
-            continue;
-        }
-
-        int space = line.find_first_of(' ');
-        if(space != -1) {
-            std::string cmd = line.substr(0, space);
-            std::string arg = line.substr(space + 1);
-            if(arg.empty()) continue;  // ignore empty command
-            if(cmd == "p" || cmd == "print") {
-                CodeObject* code = compile(arg, "<stdin>", EVAL_MODE, true);
-                PyVar retval = vm->_exec(code, frame_0->_module, frame_0->_callable, frame_0->_locals);
-                CodeObject__delete(code);
-                stdout_write(vm->py_repr(retval));
-                stdout_write("\n");
-            } else if(cmd == "!") {
-                CodeObject* code = compile(arg, "<stdin>", EXEC_MODE, true);
-                vm->_exec(code, frame_0->_module, frame_0->_callable, frame_0->_locals);
-                CodeObject__delete(code);
-            }
-            continue;
-        }
-    }
-#endif
-}
-
-PyVar PyObject::attr(StrName name) const{
-    return attr()[name];
-}
-
-/**************************************************************************/
-void Function::_gc_mark(VM* vm) const {
-    FuncDecl__gc_mark(decl);
-    if(_closure) {
-        _closure->apply([](StrName _, PyVar obj, void* userdata) {
-            VM* vm = (VM*)userdata;
-            vm->obj_gc_mark(obj);
-        }, vm);
-    }
-}
-
-void NativeFunc::_gc_mark(VM* vm) const {
-    if(decl){
-        FuncDecl__gc_mark(decl);
-    }
-}
-
-extern "C"{
-    void FuncDecl__gc_mark(const FuncDecl *self){
-        VM* vm = (VM*)pkpy_g.vm;
-        CodeObject__gc_mark(self->code);
-        c11_vector__foreach(FuncDeclKwArg, &self->kwargs, kv) {
-            vm->obj_gc_mark(kv->value);
-        }
-    }
-
-    void CodeObject__gc_mark(const CodeObject* self) {
-        VM* vm = (VM*)pkpy_g.vm;
-        c11_vector__foreach(PyVar, &self->consts, v) {
-            vm->obj_gc_mark(*v);
-        }
-        c11_vector__foreach(FuncDecl*, &self->func_decls, decl) {
-            FuncDecl__gc_mark(*decl);
-        }
-    }
-}
-
-void List::_gc_mark(VM* vm) const {
-    for(PyVar obj: *this)
-        vm->obj_gc_mark(obj);
-}
-
-void Tuple::_gc_mark(VM* vm) const {
-    for(PyVar obj: *this)
-        vm->obj_gc_mark(obj);
-}
-
-void MappingProxy::_gc_mark(VM* vm) const { vm->__obj_gc_mark(obj); }
-
-void BoundMethod::_gc_mark(VM* vm) const {
-    vm->obj_gc_mark(func);
-    vm->obj_gc_mark(self);
-}
-
-void StarWrapper::_gc_mark(VM* vm) const { vm->obj_gc_mark(obj); }
-
-void StaticMethod::_gc_mark(VM* vm) const { vm->obj_gc_mark(func); }
-
-void ClassMethod::_gc_mark(VM* vm) const { vm->obj_gc_mark(func); }
-
-void Property::_gc_mark(VM* vm) const {
-    vm->obj_gc_mark(getter);
-    vm->obj_gc_mark(setter);
-}
-
-void Slice::_gc_mark(VM* vm) const {
-    vm->obj_gc_mark(start);
-    vm->obj_gc_mark(stop);
-    vm->obj_gc_mark(step);
-}
-
-void Super::_gc_mark(VM* vm) const { vm->obj_gc_mark(first); }
-
-void Frame::_gc_mark(VM* vm) const {
-    vm->obj_gc_mark(_module);
-    CodeObject__gc_mark(co);
-    // Frame could be stored in a generator, so mark _callable for safety
-    vm->obj_gc_mark(_callable);
-}
-
-extern "C"{
-    void pk_ManagedHeap__mark(pk_ManagedHeap* self){
-        VM* vm = (VM*)self->vm;
-        for(int i=0; i<self->no_gc.count; i++){
-            PyObject* obj = c11__getitem(PyObject*, &self->no_gc, i);
-            vm->__obj_gc_mark(obj);
-        }
-        vm->callstack.apply([vm](Frame& frame) {
-            frame._gc_mark(vm);
-        });
-        vm->obj_gc_mark(vm->__last_exception);
-        vm->obj_gc_mark(vm->__curr_class);
-        vm->obj_gc_mark(vm->__c.error);
-        vm->__stack_gc_mark((PyVar*)vm->s_data.begin, (PyVar*)vm->s_data.end);
-        if(self->_gc_marker_ex) self->_gc_marker_ex((pk_VM*)vm);
-    }
-
-    void pk_ManagedHeap__delete_obj(pk_ManagedHeap* self, ::PyObject* __obj){
-        PyObject* obj = (PyObject*)__obj;
-        const PyTypeInfo* ti = ((VM*)(self->vm))->_tp_info(obj->type);
-        if(ti->vt._dtor) ti->vt._dtor(obj->_value_ptr());
-        if (obj->_attr)
-            c11_vector__dtor(obj->_attr);
-        delete obj->_attr;  // delete __dict__ if exists
-        if(obj->gc_is_large){
-            std::free(obj);
-        }else{
-            PoolObject_dealloc(obj);
-        }
-    }
-}
-
-void Dict::_gc_mark(VM* vm) const {
-    apply([vm](PyVar k, PyVar v) {
-        vm->obj_gc_mark(k);
-        vm->obj_gc_mark(v);
-    });
-}
-
-}  // namespace pkpy