diff --git a/module/fib.cpp b/module/fib.cpp
index 41c1449..80b4220 100644
--- a/module/fib.cpp
+++ b/module/fib.cpp
@@ -37,7 +37,7 @@ var quick_fib(var* args, usize size, gc* ngc) {
     return var::num(res);
 }
 
-u32 ghost_for_test;
+const auto ghost_for_test = "ghost_for_test";
 
 void ghost_for_test_destructor(void* ptr) {
     std::cout << "ghost_for_test::destructor (0x";
@@ -49,7 +49,7 @@ void ghost_for_test_destructor(void* ptr) {
 
 var create_new_ghost(var* args, usize size, gc* ngc) {
     var res = ngc->alloc(vm_obj);
-    res.obj().set(ghost_for_test, new u32, &ngc->global_ghost_type_table);
+    res.obj().set(ghost_for_test, ghost_for_test_destructor, new u32);
     return res;
 }
 
@@ -87,14 +87,6 @@ module_func_info func_tbl[] = {
 
 }
 
-extern "C" module_func_info* get(ghost_register_table* table) {
-    if (table->exists("fib_for_test")) {
-        nasal_fib_module::ghost_for_test = table->get_ghost_type_index("fib_for_test");
-        return nasal_fib_module::func_tbl;
-    }
-    nasal_fib_module::ghost_for_test = table->register_ghost_type(
-        "fib_for_test",
-        nasal_fib_module::ghost_for_test_destructor
-    );
+extern "C" module_func_info* get() {
     return nasal_fib_module::func_tbl;
 }
\ No newline at end of file
diff --git a/module/keyboard.cpp b/module/keyboard.cpp
index 18f0368..04a830d 100644
--- a/module/keyboard.cpp
+++ b/module/keyboard.cpp
@@ -99,6 +99,6 @@ module_func_info func_tbl[]={
     {nullptr,nullptr}
 };
 
-extern "C" module_func_info* get(ghost_register_table* table) {
+extern "C" module_func_info* get() {
     return func_tbl;
 }
\ No newline at end of file
diff --git a/module/matrix.cpp b/module/matrix.cpp
index 8d1f582..e293837 100644
--- a/module/matrix.cpp
+++ b/module/matrix.cpp
@@ -291,6 +291,6 @@ module_func_info func_tbl[]={
     {nullptr,nullptr}
 };
 
-extern "C" module_func_info* get(ghost_register_table* table) {
+extern "C" module_func_info* get() {
     return func_tbl;
 }
\ No newline at end of file
diff --git a/module/nasocket.cpp b/module/nasocket.cpp
index 5fffe8b..71b95c8 100644
--- a/module/nasocket.cpp
+++ b/module/nasocket.cpp
@@ -209,6 +209,6 @@ module_func_info func_tbl[]={
     {nullptr,nullptr}
 };
 
-extern "C" module_func_info* get(ghost_register_table* table) {
+extern "C" module_func_info* get() {
     return func_tbl;
 }
\ No newline at end of file
diff --git a/src/nasal_builtin.cpp b/src/nasal_builtin.cpp
index 60ec19e..1047b6a 100644
--- a/src/nasal_builtin.cpp
+++ b/src/nasal_builtin.cpp
@@ -444,13 +444,13 @@ var builtin_open(var* local, gc& ngc) {
         return nas_err("open", "failed to open file <"+name.str()+">");
     }
     var ret = ngc.alloc(vm_obj);
-    ret.obj().set(ngc.global_ghost_type_table.ghost_file, res, &ngc.global_ghost_type_table);
+    ret.obj().set("file", filehandle_destructor, res);
     return ret;
 }
 
 var builtin_close(var* local, gc& ngc) {
     var fd = local[1];
-    if (!fd.objchk(ngc.global_ghost_type_table.ghost_file)) {
+    if (!fd.objchk("file")) {
         return nas_err("close", "not a valid filehandle");
     }
     fd.obj().clear();
@@ -461,7 +461,7 @@ var builtin_read(var* local, gc& ngc) {
     var fd = local[1];
     var buf = local[2];
     var len = local[3];
-    if (!fd.objchk(ngc.global_ghost_type_table.ghost_file)) {
+    if (!fd.objchk("file")) {
         return nas_err("read", "not a valid filehandle");
     }
     if (buf.type!=vm_str || buf.val.gcobj->unmut) {
@@ -487,7 +487,7 @@ var builtin_read(var* local, gc& ngc) {
 var builtin_write(var* local, gc& ngc) {
     var fd = local[1];
     var str = local[2];
-    if (!fd.objchk(ngc.global_ghost_type_table.ghost_file)) {
+    if (!fd.objchk("file")) {
         return nas_err("write", "not a valid filehandle");
     }
     if (str.type!=vm_str) {
@@ -500,7 +500,7 @@ var builtin_seek(var* local, gc& ngc) {
     var fd = local[1];
     var pos = local[2];
     var whence = local[3];
-    if (!fd.objchk(ngc.global_ghost_type_table.ghost_file)) {
+    if (!fd.objchk("file")) {
         return nas_err("seek", "not a valid filehandle");
     }
     return var::num((f64)fseek((FILE*)fd.obj().ptr, pos.num(), whence.num()));
@@ -508,7 +508,7 @@ var builtin_seek(var* local, gc& ngc) {
 
 var builtin_tell(var* local, gc& ngc) {
     var fd = local[1];
-    if (!fd.objchk(ngc.global_ghost_type_table.ghost_file)) {
+    if (!fd.objchk("file")) {
         return nas_err("tell", "not a valid filehandle");
     }
     return var::num((f64)ftell((FILE*)fd.obj().ptr));
@@ -516,7 +516,7 @@ var builtin_tell(var* local, gc& ngc) {
 
 var builtin_readln(var* local, gc& ngc) {
     var fd = local[1];
-    if (!fd.objchk(ngc.global_ghost_type_table.ghost_file)) {
+    if (!fd.objchk("file")) {
         return nas_err("readln", "not a valid filehandle");
     }
     var str = ngc.alloc(vm_str);
@@ -564,7 +564,7 @@ var builtin_stat(var* local, gc& ngc) {
 
 var builtin_eof(var* local, gc& ngc) {
     var fd = local[1];
-    if (!fd.objchk(ngc.global_ghost_type_table.ghost_file)) {
+    if (!fd.objchk("file")) {
         return nas_err("readln", "not a valid filehandle");
     }
     return var::num((f64)feof((FILE*)fd.obj().ptr));
@@ -646,13 +646,13 @@ var builtin_opendir(var* local, gc& ngc) {
     }
 #endif
     var ret = ngc.alloc(vm_obj);
-    ret.obj().set(ngc.global_ghost_type_table.ghost_dir, p, &ngc.global_ghost_type_table);
+    ret.obj().set("dir", dir_entry_destructor, p);
     return ret;
 }
 
 var builtin_readdir(var* local, gc& ngc) {
     var handle = local[1];
-    if (!handle.objchk(ngc.global_ghost_type_table.ghost_dir)) {
+    if (!handle.objchk("dir")) {
         return nas_err("readdir", "not a valid dir handle");
     }
 #ifdef _MSC_VER
@@ -669,7 +669,7 @@ var builtin_readdir(var* local, gc& ngc) {
 
 var builtin_closedir(var* local, gc& ngc) {
     var handle = local[1];
-    if (!handle.objchk(ngc.global_ghost_type_table.ghost_dir)) {
+    if (!handle.objchk("dir")) {
         return nas_err("closedir", "not a valid dir handle");
     }
     handle.obj().clear();
@@ -733,7 +733,7 @@ var builtin_dlopen(var* local, gc& ngc) {
     }
     var ret = ngc.temp = ngc.alloc(vm_hash);
     var lib = ngc.alloc(vm_obj);
-    lib.obj().set(ngc.global_ghost_type_table.ghost_dylib, ptr, &ngc.global_ghost_type_table);
+    lib.obj().set("dylib", dylib_destructor, ptr);
     ret.hash().elems["lib"] = lib;
 
 #ifdef _WIN32
@@ -745,14 +745,14 @@ var builtin_dlopen(var* local, gc& ngc) {
         return nas_err("dlopen", "cannot find <get> function");
     }
     // get function pointer by name
-    module_func_info* tbl = ((get_func_ptr)func)(&ngc.global_ghost_type_table);
+    module_func_info* tbl = ((get_func_ptr)func)();
     if (!tbl) {
         return nas_err("dlopen", "failed to get module functions");
     }
     for(u32 i = 0; tbl[i].name; ++i) {
         void* p = (void*)tbl[i].fd;
         var tmp = ngc.alloc(vm_obj);
-        tmp.obj().set(ngc.global_ghost_type_table.ghost_faddr, p, &ngc.global_ghost_type_table);
+        tmp.obj().set("faddr", func_addr_destructor, p);
         ret.hash().elems[tbl[i].name] = tmp;
     }
 
@@ -762,7 +762,7 @@ var builtin_dlopen(var* local, gc& ngc) {
 
 var builtin_dlclose(var* local, gc& ngc) {
     var libptr = local[1];
-    if (!libptr.objchk(ngc.global_ghost_type_table.ghost_dylib)) {
+    if (!libptr.objchk("dylib")) {
         return nas_err("dlclose", "\"lib\" is not a valid dynamic lib");
     }
     libptr.obj().clear();
@@ -772,7 +772,7 @@ var builtin_dlclose(var* local, gc& ngc) {
 var builtin_dlcallv(var* local, gc& ngc) {
     var fp = local[1];
     var args = local[2];
-    if (!fp.objchk(ngc.global_ghost_type_table.ghost_faddr)) {
+    if (!fp.objchk("faddr")) {
         return nas_err("dlcall", "\"ptr\" is not a valid function pointer");
     }
     auto& vec = args.vec().elems;
@@ -781,7 +781,7 @@ var builtin_dlcallv(var* local, gc& ngc) {
 
 var builtin_dlcall(var* local, gc& ngc) {
     var fp = local[1];
-    if (!fp.objchk(ngc.global_ghost_type_table.ghost_faddr)) {
+    if (!fp.objchk("faddr")) {
         return nas_err("dlcall", "\"ptr\" is not a valid function pointer");
     }
 
diff --git a/src/nasal_dbg.h b/src/nasal_dbg.h
index 7f466e4..f4c645a 100644
--- a/src/nasal_dbg.h
+++ b/src/nasal_dbg.h
@@ -141,9 +141,11 @@ private:
     u32 bk_line;
     error src;
 
+private:
     debug_prof_data data;
     bool do_profiling;
 
+private:
     std::vector<std::string> parse(const std::string&);
     u16 file_index(const std::string&) const;
     void err();
diff --git a/src/nasal_gc.cpp b/src/nasal_gc.cpp
index b99fe96..b7b9882 100644
--- a/src/nasal_gc.cpp
+++ b/src/nasal_gc.cpp
@@ -123,18 +123,22 @@ void nas_func::clear() {
 }
 
 void nas_ghost::set(
-    usize ghost_type, void* ghost_pointer, ghost_register_table* table) {
-    type = ghost_type;
+    const std::string& ghost_type_name,
+    destructor destructor_pointer,
+    void* ghost_pointer) {
+    type_name = ghost_type_name;
+    dtor_ptr = destructor_pointer;
     ptr = ghost_pointer;
-    ghost_type_table = table;
 }
 
 void nas_ghost::clear() {
-    if (!ptr) {
+    if (!ptr || !dtor_ptr) {
         return;
     }
-    ghost_type_table->destructor(type)(ptr);
+    dtor_ptr(ptr);
+    type_name = "";
     ptr = nullptr;
+    dtor_ptr = nullptr;
 }
 
 std::ostream& operator<<(std::ostream& out, const nas_ghost& ghost) {
@@ -268,8 +272,8 @@ std::ostream& operator<<(std::ostream& out, var& ref) {
     return out;
 }
 
-bool var::objchk(usize obj_type) {
-    return type==vm_obj && obj().type==obj_type && obj().ptr;
+bool var::objchk(const std::string& name) {
+    return type==vm_obj && obj().type_name==name && obj().ptr;
 }
 
 var var::none() {
diff --git a/src/nasal_gc.h b/src/nasal_gc.h
index 539104c..08529e4 100644
--- a/src/nasal_gc.h
+++ b/src/nasal_gc.h
@@ -93,7 +93,7 @@ public:
     // number and string can be translated to each other
     f64 tonum();
     std::string tostr();
-    bool objchk(usize);
+    bool objchk(const std::string&);
 
     // create new var object
     static var none();
@@ -185,77 +185,24 @@ void dir_entry_destructor(void*);
 void dylib_destructor(void*);
 void func_addr_destructor(void*);
 
-struct ghost_register_table {
-private:
-    using dtor=void (*)(void*);
-
-private:
-    std::unordered_map<std::string, usize> mapper;
-    std::vector<std::string> ghost_name;
-    std::vector<dtor> destructors;
-
-public:
-    // reserved ghost type only for native functions
-    usize ghost_file;
-    usize ghost_dir;
-    usize ghost_dylib;
-    usize ghost_faddr;
-
-public:
-    ghost_register_table() {
-        ghost_file = register_ghost_type("file", filehandle_destructor);
-        ghost_dir = register_ghost_type("dir", dir_entry_destructor);
-        ghost_dylib = register_ghost_type("dylib", dylib_destructor);
-        ghost_faddr = register_ghost_type("faddr", func_addr_destructor);
-    }
-
-    bool exists(const std::string& name) const {
-        return mapper.count(name);
-    }
-
-    usize get_ghost_type_index(const std::string& name) const {
-        return mapper.at(name);
-    }
-
-    const std::string& get_ghost_name(usize index) const {
-        return ghost_name.at(index);
-    }
-
-    usize register_ghost_type(const std::string& name, dtor ptr) {
-        if (mapper.count(name)) {
-            std::cerr << "nasal_gc.h: ghost_register_table::register_ghost_type: ";
-            std::cerr << "ghost type \"" << name << "\" already exists.\n";
-            std::exit(1);
-        }
-        auto res = destructors.size();
-        mapper[name] = res;
-        ghost_name.push_back(name);
-        destructors.push_back(ptr);
-        return res;
-    }
-
-    dtor destructor(usize index) {
-        return destructors.at(index);
-    }
-};
-
 struct nas_ghost {
+private:
+    using destructor=void (*)(void*);
+
 public:
-    usize type;
+    std::string type_name;
+    destructor dtor_ptr;
     void* ptr;
 
-private:
-    ghost_register_table* ghost_type_table;
-
 public:
-    nas_ghost(): type(0), ptr(nullptr), ghost_type_table(nullptr) {}
+    nas_ghost(): type_name(""), dtor_ptr(nullptr), ptr(nullptr) {}
     ~nas_ghost() {clear();}
-    void set(usize, void*, ghost_register_table*);
+    void set(const std::string&, destructor, void*);
     void clear();
 
 public:
     const std::string& get_ghost_name() const {
-        return ghost_type_table->get_ghost_name(type);
+        return type_name;
     }
 };
 
@@ -336,7 +283,6 @@ const var one = var::num(1);
 const var nil = var::nil();
 
 struct gc {
-    ghost_register_table global_ghost_type_table;
     /* main context temporary storage */
     context mctx;
 
@@ -433,4 +379,4 @@ struct module_func_info {
 };
 
 // module function "get" type
-typedef module_func_info* (*get_func_ptr)(ghost_register_table*);
+typedef module_func_info* (*get_func_ptr)();