diff --git a/nasal_codegen.h b/nasal_codegen.h
index 1a7553d..de7c33f 100644
--- a/nasal_codegen.h
+++ b/nasal_codegen.h
@@ -12,7 +12,7 @@ enum op_code
     op_pushstr,
     op_newvec,op_newhash,op_newfunc,
     op_vecapp,op_hashapp,
-    op_para,op_defpara,op_dynpara,op_entry,
+    op_para,op_defpara,op_dynpara,
     op_unot,op_usub,
     op_add,op_sub,op_mul,op_div,op_lnk,
     op_addeq,op_subeq,op_muleq,op_diveq,op_lnkeq,op_meq,
@@ -62,7 +62,6 @@ struct
     {op_para,        "para  "},
     {op_defpara,     "deflt "},
     {op_dynpara,     "dyn   "},
-    {op_entry,       "entry "},
     {op_unot,        "not   "},
     {op_usub,        "usub  "},
     {op_add,         "add   "},
@@ -275,6 +274,7 @@ void nasal_codegen::hash_gen(nasal_ast& ast)
 
 void nasal_codegen::function_gen(nasal_ast& ast)
 {
+    int newfunc_label=exec_code.size();
     gen(op_newfunc,0);
 
     nasal_ast& ref_arg=ast.get_children()[0];
@@ -302,7 +302,7 @@ void nasal_codegen::function_gen(nasal_ast& ast)
             gen(op_dynpara,string_table[str]);
         }
     }
-    gen(op_entry,exec_code.size()+2);
+    exec_code[newfunc_label].index=exec_code.size()+1;
     int ptr=exec_code.size();
     gen(op_jmp,0);
     nasal_ast& block=ast.get_children()[1];
diff --git a/nasal_gc.h b/nasal_gc.h
index d2f3e9f..cce4955 100644
--- a/nasal_gc.h
+++ b/nasal_gc.h
@@ -148,7 +148,6 @@ nasal_vec::~nasal_vec()
     int size=elems.size();
     for(int i=0;i<size;++i)
         gc.del_reference(elems[i]);
-    elems.clear();
     return;
 }
 void nasal_vec::add_elem(nasal_val* value_address)
@@ -227,7 +226,6 @@ nasal_hash::~nasal_hash()
 {
     for(auto iter=elems.begin();iter!=elems.end();++iter)
         gc.del_reference(iter->second);
-    elems.clear();
     return;
 }
 void nasal_hash::add_elem(std::string key,nasal_val* value_address)
@@ -441,7 +439,6 @@ nasal_scop::~nasal_scop()
 {
     for(auto i=elems.begin();i!=elems.end();++i)
         gc.del_reference(i->second);
-    elems.clear();
     return;
 }
 void nasal_scop::add_new_value(int key,nasal_val* value_address)
@@ -468,8 +465,6 @@ nasal_val** nasal_scop::get_mem_address(int key)
 }
 void nasal_scop::set_closure(nasal_scop& tmp)
 {
-    for(auto i=elems.begin();i!=elems.end();++i)
-        gc.del_reference(i->second);
     elems=tmp.elems;
     for(auto i=elems.begin();i!=elems.end();++i)
         gc.add_reference(i->second);
@@ -617,7 +612,6 @@ nasal_gc::~nasal_gc()
         delete memory[i];
     while(!free_space.empty())
         free_space.pop();
-    memory.clear();
     return;
 }
 void nasal_gc::clear()
diff --git a/nasal_vm.h b/nasal_vm.h
index c7a9f80..a2abfbc 100644
--- a/nasal_vm.h
+++ b/nasal_vm.h
@@ -7,6 +7,7 @@ class nasal_vm
 private:
     nasal_val* zero_addr;          // reserved address of nasal_val,type vm_num, 0
     nasal_val* one_addr;           // reserved address of nasal_val,type vm_num, 1
+    nasal_val* nil_addr;           // reserved address of nasal_val,type vm_nil
     bool main_loop_break_mark;     // when mark is false,break the main loop
     int ptr;                       // program counter
     int me_index;                  // this is the index of "me" in string_table
@@ -45,7 +46,6 @@ private:
     void opr_para();
     void opr_defpara();
     void opr_dynpara();
-    void opr_entry();
     void opr_unot();
     void opr_usub();
     void opr_add();
@@ -182,7 +182,8 @@ void nasal_vm::opr_pushzero()
 }
 void nasal_vm::opr_pushnil()
 {
-    *(++val_stack_top)=gc.gc_alloc(vm_nil);
+    *(++val_stack_top)=nil_addr;
+    gc.add_reference(nil_addr);
     return;
 }
 void nasal_vm::opr_pushstr()
@@ -206,6 +207,7 @@ void nasal_vm::opr_newfunc()
 {
     nasal_val* val_addr=gc.gc_alloc(vm_func);
     nasal_val* local_scope_top=local_scope_stack.top();
+    val_addr->get_func().set_entry(exec_code[ptr].index);
     if(local_scope_top)
         val_addr->get_func().set_closure_addr(local_scope_top);
     else
@@ -215,14 +217,12 @@ void nasal_vm::opr_newfunc()
 }
 void nasal_vm::opr_vecapp()
 {
-    nasal_val* val_addr=*val_stack_top--;
-    (*val_stack_top)->get_vector().add_elem(val_addr);
+    (*val_stack_top)->get_vector().add_elem(*val_stack_top--);
     return;
 }
 void nasal_vm::opr_hashapp()
 {
-    nasal_val* val_addr=*val_stack_top--;
-    (*val_stack_top)->get_hash().add_elem(string_table[exec_code[ptr].index],val_addr);
+    (*val_stack_top)->get_hash().add_elem(string_table[exec_code[ptr].index],*val_stack_top--);
     return;
 }
 void nasal_vm::opr_para()
@@ -232,8 +232,7 @@ void nasal_vm::opr_para()
 }
 void nasal_vm::opr_defpara()
 {
-    nasal_val* val_addr=*val_stack_top--;
-    (*val_stack_top)->get_func().add_para(exec_code[ptr].index,val_addr);
+    (*val_stack_top)->get_func().add_para(exec_code[ptr].index,*val_stack_top--);
     return;
 }
 void nasal_vm::opr_dynpara()
@@ -241,11 +240,6 @@ void nasal_vm::opr_dynpara()
     (*val_stack_top)->get_func().add_para(exec_code[ptr].index,NULL,true);
     return;
 }
-void nasal_vm::opr_entry()
-{
-    (*val_stack_top)->get_func().set_entry(exec_code[ptr].index);
-    return;
-}
 void nasal_vm::opr_unot()
 {
     nasal_val* val_addr=*val_stack_top;
@@ -1099,6 +1093,8 @@ void nasal_vm::run(std::vector<std::string>& strs,std::vector<double>& nums,std:
     zero_addr->set_number(0);
     one_addr=gc.gc_alloc(vm_num);
     one_addr->set_number(1);
+    nil_addr=gc.gc_alloc(vm_nil);
+
     builtin_use_string_table.clear();
     for(int i=0;i<string_table.size();++i)
     {
@@ -1124,7 +1120,6 @@ void nasal_vm::run(std::vector<std::string>& strs,std::vector<double>& nums,std:
         &nasal_vm::opr_para,
         &nasal_vm::opr_defpara,
         &nasal_vm::opr_dynpara,
-        &nasal_vm::opr_entry,
         &nasal_vm::opr_unot,
         &nasal_vm::opr_usub,
         &nasal_vm::opr_add,