diff --git a/c_bindings/pocketpy_c.cpp b/c_bindings/pocketpy_c.cpp
index 3126aed3..6abb7ef9 100644
--- a/c_bindings/pocketpy_c.cpp
+++ b/c_bindings/pocketpy_c.cpp
@@ -125,8 +125,8 @@ bool pkpy_clear_error(pkpy_vm* vm_handle, char** message) {
 }
 
 void gc_marker_ex(CVM* vm) {
-    for(PyObject* obj: *vm->c_data) if(obj!=nullptr) OBJ_MARK(obj);
-    if(vm->error != nullptr) OBJ_MARK(vm->error);
+    for(PyObject* obj: *vm->c_data) if(obj!=nullptr) PK_OBJ_MARK(obj);
+    if(vm->error != nullptr) PK_OBJ_MARK(vm->error);
 }
 
 static OutputHandler stdout_handler = nullptr;
diff --git a/src/codeobject.h b/src/codeobject.h
index 406b2d4f..67eaa817 100644
--- a/src/codeobject.h
+++ b/src/codeobject.h
@@ -161,7 +161,7 @@ struct CodeObject {
     std::vector<FuncDecl_> func_decls;
 
     void _gc_mark() const {
-        for(PyObject* v : consts) OBJ_MARK(v);
+        for(PyObject* v : consts) PK_OBJ_MARK(v);
         for(auto& decl: func_decls) decl->_gc_mark();
     }
 
diff --git a/src/dict.h b/src/dict.h
index a83fbdf3..8b8ada21 100644
--- a/src/dict.h
+++ b/src/dict.h
@@ -142,8 +142,8 @@ struct Dict{
     void _gc_mark() const{
         for(int i=0; i<_capacity; i++){
             if(_items[i].first == nullptr) continue;
-            OBJ_MARK(_items[i].first);
-            OBJ_MARK(_items[i].second);
+            PK_OBJ_MARK(_items[i].first);
+            PK_OBJ_MARK(_items[i].second);
         }
     }
 };
diff --git a/src/frame.h b/src/frame.h
index 42cde59c..3266a749 100644
--- a/src/frame.h
+++ b/src/frame.h
@@ -194,7 +194,7 @@ struct Frame {
     }
 
     void _gc_mark() const {
-        OBJ_MARK(_module);
+        PK_OBJ_MARK(_module);
         co->_gc_mark();
     }
 };
diff --git a/src/gc.h b/src/gc.h
index b247b295..38ba286c 100644
--- a/src/gc.h
+++ b/src/gc.h
@@ -128,7 +128,7 @@ struct ManagedHeap{
 
 inline void FuncDecl::_gc_mark() const{
     code->_gc_mark();
-    for(int i=0; i<kwargs.size(); i++) OBJ_MARK(kwargs[i].value);
+    for(int i=0; i<kwargs.size(); i++) PK_OBJ_MARK(kwargs[i].value);
 }
 
 }   // namespace pkpy
diff --git a/src/iter.h b/src/iter.h
index 97c02dc6..c7bad046 100644
--- a/src/iter.h
+++ b/src/iter.h
@@ -36,7 +36,7 @@ struct ArrayIter{
     ArrayIter(PyObject* ref, PyObject** begin, PyObject** end)
         : ref(ref), begin(begin), end(end), current(begin) {}
 
-    void _gc_mark() const{ OBJ_MARK(ref); }
+    void _gc_mark() const{ PK_OBJ_MARK(ref); }
 
     static void _register(VM* vm, PyObject* mod, PyObject* type){
         vm->_all_types[PK_OBJ_GET(Type, type)].subclass_enabled = false;
@@ -58,7 +58,7 @@ struct StringIter{
 
     StringIter(PyObject* ref) : ref(ref), str(&PK_OBJ_GET(Str, ref)), index(0) {}
 
-    void _gc_mark() const{ OBJ_MARK(ref); }
+    void _gc_mark() const{ PK_OBJ_MARK(ref); }
 
     static void _register(VM* vm, PyObject* mod, PyObject* type){
         vm->_all_types[PK_OBJ_GET(Type, type)].subclass_enabled = false;
@@ -85,7 +85,7 @@ struct Generator{
 
     void _gc_mark() const{
         frame._gc_mark();
-        for(PyObject* obj: s_backup) OBJ_MARK(obj);
+        for(PyObject* obj: s_backup) PK_OBJ_MARK(obj);
     }
 
     PyObject* next(VM* vm){
diff --git a/src/memory.h b/src/memory.h
index ec2d2893..85d0e357 100644
--- a/src/memory.h
+++ b/src/memory.h
@@ -168,6 +168,12 @@ struct MemoryPool{
         }
     };
 
+    MemoryPool() = default;
+    MemoryPool(const MemoryPool&) = delete;
+    MemoryPool& operator=(const MemoryPool&) = delete;
+    MemoryPool(MemoryPool&&) = delete;
+    MemoryPool& operator=(MemoryPool&&) = delete;
+
     DoubleLinkedList<Arena> _arenas;
     DoubleLinkedList<Arena> _empty_arenas;
 
diff --git a/src/obj.h b/src/obj.h
index 0fd24697..623c4c94 100644
--- a/src/obj.h
+++ b/src/obj.h
@@ -201,7 +201,7 @@ struct MappingProxy{
 
 #define PK_OBJ_GET(T, obj) (((Py_<T>*)(obj))->_value)
 
-#define OBJ_MARK(obj) \
+#define PK_OBJ_MARK(obj) \
     if(!is_tagged(obj) && !(obj)->gc.marked) {                      \
         (obj)->gc.marked = true;                                    \
         (obj)->_obj_gc_mark();                                      \
@@ -212,7 +212,7 @@ inline void gc_mark_namedict(NameDict& t){
     if(t.size() == 0) return;
     for(uint16_t i=0; i<t._capacity; i++){
         if(t._items[i].first.empty()) continue;
-        OBJ_MARK(t._items[i].second);
+        PK_OBJ_MARK(t._items[i].second);
     }
 }
 
@@ -308,7 +308,7 @@ struct Py_<List> final: PyObject {
     Py_(Type type, const List& val): PyObject(type), _value(val) {}
 
     void _obj_gc_mark() override {
-        for(PyObject* obj: _value) OBJ_MARK(obj);
+        for(PyObject* obj: _value) PK_OBJ_MARK(obj);
     }
 };
 
@@ -319,7 +319,7 @@ struct Py_<Tuple> final: PyObject {
     Py_(Type type, const Tuple& val): PyObject(type), _value(val) {}
 
     void _obj_gc_mark() override {
-        for(PyObject* obj: _value) OBJ_MARK(obj);
+        for(PyObject* obj: _value) PK_OBJ_MARK(obj);
     }
 };
 
@@ -328,7 +328,7 @@ struct Py_<MappingProxy> final: PyObject {
     MappingProxy _value;
     Py_(Type type, MappingProxy val): PyObject(type), _value(val) {}
     void _obj_gc_mark() override {
-        OBJ_MARK(_value.obj);
+        PK_OBJ_MARK(_value.obj);
     }
 };
 
@@ -337,8 +337,8 @@ struct Py_<BoundMethod> final: PyObject {
     BoundMethod _value;
     Py_(Type type, BoundMethod val): PyObject(type), _value(val) {}
     void _obj_gc_mark() override {
-        OBJ_MARK(_value.self);
-        OBJ_MARK(_value.func);
+        PK_OBJ_MARK(_value.self);
+        PK_OBJ_MARK(_value.func);
     }
 };
 
@@ -347,7 +347,7 @@ struct Py_<StarWrapper> final: PyObject {
     StarWrapper _value;
     Py_(Type type, StarWrapper val): PyObject(type), _value(val) {}
     void _obj_gc_mark() override {
-        OBJ_MARK(_value.obj);
+        PK_OBJ_MARK(_value.obj);
     }
 };
 
@@ -356,8 +356,8 @@ struct Py_<Property> final: PyObject {
     Property _value;
     Py_(Type type, Property val): PyObject(type), _value(val) {}
     void _obj_gc_mark() override {
-        OBJ_MARK(_value.getter);
-        OBJ_MARK(_value.setter);
+        PK_OBJ_MARK(_value.getter);
+        PK_OBJ_MARK(_value.setter);
     }
 };
 
@@ -366,9 +366,9 @@ struct Py_<Slice> final: PyObject {
     Slice _value;
     Py_(Type type, Slice val): PyObject(type), _value(val) {}
     void _obj_gc_mark() override {
-        OBJ_MARK(_value.start);
-        OBJ_MARK(_value.stop);
-        OBJ_MARK(_value.step);
+        PK_OBJ_MARK(_value.start);
+        PK_OBJ_MARK(_value.stop);
+        PK_OBJ_MARK(_value.step);
     }
 };
 
@@ -380,7 +380,7 @@ struct Py_<Function> final: PyObject {
     }
     void _obj_gc_mark() override {
         _value.decl->_gc_mark();
-        if(_value._module != nullptr) OBJ_MARK(_value._module);
+        if(_value._module != nullptr) PK_OBJ_MARK(_value._module);
         if(_value._closure != nullptr) gc_mark_namedict(*_value._closure);
     }
 };
@@ -399,7 +399,7 @@ struct Py_<Super> final: PyObject {
     Super _value;
     Py_(Type type, Super val): PyObject(type), _value(val) {}
     void _obj_gc_mark() override {
-        OBJ_MARK(_value.first);
+        PK_OBJ_MARK(_value.first);
     }
 };
 
diff --git a/src/vm.h b/src/vm.h
index 3c804f09..8959d9fe 100644
--- a/src/vm.h
+++ b/src/vm.h
@@ -1529,11 +1529,11 @@ inline void VM::_error(Exception e){
 }
 
 inline void ManagedHeap::mark() {
-    for(PyObject* obj: _no_gc) OBJ_MARK(obj);
+    for(PyObject* obj: _no_gc) PK_OBJ_MARK(obj);
     for(auto& frame : vm->callstack.data()) frame._gc_mark();
-    for(PyObject* obj: vm->s_data) OBJ_MARK(obj);
+    for(PyObject* obj: vm->s_data) PK_OBJ_MARK(obj);
     if(_gc_marker_ex) _gc_marker_ex(vm);
-    if(vm->_last_exception) OBJ_MARK(vm->_last_exception);
+    if(vm->_last_exception) PK_OBJ_MARK(vm->_last_exception);
 }
 
 inline Str obj_type_name(VM *vm, Type type){