diff --git a/demo/demo.c b/demo/demo.c
index cf1b127..d353d61 100644
--- a/demo/demo.c
+++ b/demo/demo.c
@@ -58,12 +58,12 @@ int main()
     printf("----- unicstl demo -----\n");
     // while (1)
     {
-        // demo_list();
+        demo_list();
         // demo_stack();
         // demo_deque();
         // demo_queue();
         // demo_tree();
-        demo_heap();
+        // demo_heap();
     }
 
     printf("----- unicstl ok -----\n");
diff --git a/demo/demo_heap.c b/demo/demo_heap.c
index 6cbd8c3..02cae81 100644
--- a/demo/demo_heap.c
+++ b/demo/demo_heap.c
@@ -78,7 +78,7 @@ void demo_heap_num(void)
     {
         printf("----- empty -----\n");
     }
-    heap_free(heap);
+    heap_free(&heap);
 }
 
 static void demo_heap_struct(void)
@@ -144,7 +144,7 @@ static void demo_heap_struct(void)
     {
         printf("----- empty -----\n");
     }
-    heap_free(heap);
+    heap_free(&heap);
 }
 
 void demo_heap(void)
diff --git a/demo/demo_queue.c b/demo/demo_queue.c
index bc65a26..68c2bd6 100644
--- a/demo/demo_queue.c
+++ b/demo/demo_queue.c
@@ -292,7 +292,7 @@ static void demo_queue_struct(void)
     queue->print(queue);
     printf("\n");
 
-    queue_free(queue);
+    queue_free(&queue);
 }
 
 
diff --git a/demo/demo_tree.c b/demo/demo_tree.c
index 9002cf2..7352716 100644
--- a/demo/demo_tree.c
+++ b/demo/demo_tree.c
@@ -141,7 +141,7 @@ void demo_avltree_num(void)
         printf("----- empty -----\n");
     }
 
-    tree_free(tree);
+    tree_free(&tree);
 }
 
 static bool tree_rb_check_color(struct _tree *self, struct _tree_node* root, int black_num, int black_num_expected)
@@ -326,7 +326,7 @@ void demo_rbtree_num(void)
         printf("----- empty -----\n");
     }
 #endif
-    tree_free(tree);
+    tree_free(&tree);
 }
 
 /**
@@ -458,7 +458,7 @@ void demo_rbtree_struct(void)
         printf("----- empty -----\n");
     }
 #endif
-    tree_free(tree);
+    tree_free(&tree);
 }
 
 void demo_tree(void)
diff --git a/include/deque.h b/include/deque.h
index 29a23b6..1533d4e 100644
--- a/include/deque.h
+++ b/include/deque.h
@@ -69,6 +69,6 @@ typedef struct _deque* deque_t;
 bool deque_init(struct _deque* self, uint32_t obj_size);
 
 deque_t deque_new(void);
-void deque_free(deque_t deque);
+void deque_free(deque_t* deque);
 
 #endif
diff --git a/include/heap.h b/include/heap.h
index 4b616e1..1196106 100644
--- a/include/heap.h
+++ b/include/heap.h
@@ -59,6 +59,6 @@ typedef struct _heap* heap_t;
 bool heap_init2(struct _heap* self, uint32_t obj_size, uint32_t capacity);
 
 heap_t heap_new(void);
-void heap_free(heap_t heap);
+void heap_free(heap_t* heap);
  
 #endif  // _HEAP_H_
diff --git a/include/list.h b/include/list.h
index 26e4a54..db10f9f 100644
--- a/include/list.h
+++ b/include/list.h
@@ -62,6 +62,6 @@ typedef struct _list* list_t;
 bool list_init2(struct _list* self, uint32_t obj_size, uint32_t capacity);
 
 list_t list_new(void);
-void list_free(list_t list);
+void list_free(list_t* list);
 
 #endif // _LIST_H_
diff --git a/include/queue.h b/include/queue.h
index 010e2b1..689c305 100644
--- a/include/queue.h
+++ b/include/queue.h
@@ -58,6 +58,6 @@ bool queue_init(struct _queue * queue, uint32_t obj_size);
 bool queue_init2(struct _queue * queue, uint32_t obj_size, uint32_t capacity);
 
 queue_t queue_new(void);
-void queue_free(queue_t queue);
+void queue_free(queue_t* queue);
 
 #endif // _QUEUE_H_
diff --git a/include/tree.h b/include/tree.h
index 3a84075..92547a5 100644
--- a/include/tree.h
+++ b/include/tree.h
@@ -93,7 +93,7 @@ bool tree_avl_init(struct _tree *self, uint32_t obj_size);
 bool tree_rb_init(struct _tree *self, uint32_t obj_size);
 
 tree_t tree_new(void);
-void tree_free(tree_t tree);
+void tree_free(tree_t* tree);
 
 #endif // _TREE_H_
 
diff --git a/src/deque.c b/src/deque.c
index a51bea9..c0c13a3 100644
--- a/src/deque.c
+++ b/src/deque.c
@@ -333,11 +333,12 @@ deque_t deque_new(void)
     return (struct _deque*)malloc(sizeof(struct _deque));
 }
 
-void deque_free(deque_t deque)
+void deque_free(deque_t *deque)
 {
-    if(deque != NULL)
+    if(*deque != NULL)
     {
-        deque->destory(deque);
-        free(deque);
+        (*deque)->destory(*deque);
+        free(*deque);
     }
+    *deque = NULL;
 }
diff --git a/src/heap.c b/src/heap.c
index ec84537..8bf2f06 100644
--- a/src/heap.c
+++ b/src/heap.c
@@ -276,11 +276,12 @@ heap_t heap_new(void)
     return (struct _heap*)malloc(sizeof(struct _heap));
 }
 
-void heap_free(heap_t heap)
+void heap_free(heap_t* heap)
 {
-    if(heap)
+    if(*heap != NULL)
     {
-        heap->destory(heap);
-        free(heap);
+        (*heap)->destory(*heap);
+        free(*heap);
     }
+    heap = NULL;
 }
diff --git a/src/list.c b/src/list.c
index 5daed1f..93ce908 100644
--- a/src/list.c
+++ b/src/list.c
@@ -220,11 +220,12 @@ list_t list_new(void)
     return (struct _list*)malloc(sizeof(struct _list));
 }
 
-void list_free(list_t list)
+void list_free(list_t* list)
 {
-    if(list != NULL)
+    if(*list != NULL)
     {
-        list->destory(list);
-        free(list);
+        (*list)->destory(*list);
+        free(*list);
     }
+    list = NULL;
 }
diff --git a/src/queue.c b/src/queue.c
index 04709c3..b92c6a6 100644
--- a/src/queue.c
+++ b/src/queue.c
@@ -340,11 +340,12 @@ queue_t queue_new(void)
     return (struct _queue *)malloc(sizeof(struct _queue));
 }
 
-void queue_free(queue_t queue)
+void queue_free(queue_t* queue)
 {
-    if(queue != NULL)
+    if(*queue != NULL)
     {
-        queue->destory(queue);
-        free(queue);
+        (*queue)->destory(*queue);
+        free(*queue);
     }
+    queue = NULL;
 }
diff --git a/src/tree.c b/src/tree.c
index c3234a7..bdc4296 100644
--- a/src/tree.c
+++ b/src/tree.c
@@ -177,7 +177,7 @@ int32_t tree_height(struct _tree* self, struct _tree_node* root)
             count_cur_level++;
         }
     }
-    queue_free(queue);
+    queue_free(&queue);
     return height;
 #endif
 }
@@ -587,7 +587,7 @@ bool tree_clear(struct _tree* self)
         }
         tree_node_free(node);
     }
-    queue_free(queue);
+    queue_free(&queue);
     self->_root = NULL;
     self->_size = 0;
     return true;
@@ -928,7 +928,7 @@ void tree_breadth(struct _tree* self, struct _tree_node* root)
             self->print_obj(node->obj);
         }
     }
-    queue_free(queue);
+    queue_free(&queue);
 }
 
 static struct _tree_node* tree_find_min(struct _tree* self, struct _tree_node* root)
@@ -1532,12 +1532,12 @@ tree_t tree_new(void)
     return (struct _tree*)malloc(sizeof(struct _tree));
 }
 
-void tree_free(tree_t tree)
+void tree_free(tree_t* tree)
 {
-    if(tree != NULL)
+    if(*tree != NULL)
     {
-        tree->destory(tree);
-        free(tree);
+        (*tree)->destory(*tree);
+        free(*tree);
     }
+    tree = NULL;
 }
-          
\ No newline at end of file