diff --git a/include/unicstl_config.h b/include/unicstl_config.h
index 994abb7..451f88c 100644
--- a/include/unicstl_config.h
+++ b/include/unicstl_config.h
@@ -27,7 +27,8 @@
  * @brief debug 
  * 
  */
-#define NDEBUG
+#define NDEBUG       // assert disable
+
 #define UNICSTL_DEBUG
 
 #ifdef UNICSTL_DEBUG
diff --git a/src/stack.c b/src/stack.c
index 544fb73..1e346b8 100644
--- a/src/stack.c
+++ b/src/stack.c
@@ -300,6 +300,9 @@ static bool stack_init(struct _stack* self, uint32_t obj_size)
 
 const void* stack_iter_next(struct _iterator* iter)
 {
+    assert(iter != NULL);
+    assert(iter->parent != NULL);
+
     stack_t self = (stack_t)iter->parent;
     void *obj = self->_head->obj + self->_iter._cur * self->_obj_size;
     self->_iter._cur += 1;
@@ -308,8 +311,10 @@ const void* stack_iter_next(struct _iterator* iter)
 
 bool stack_iter_hasnext(struct _iterator* iter)
 {
-    stack_t self = (stack_t)iter->parent;
+    assert(iter != NULL);
+    assert(iter->parent != NULL);
 
+    stack_t self = (stack_t)iter->parent;
     if(self->_iter._cur < self->size(self))
     {
         return true;
@@ -320,15 +325,11 @@ bool stack_iter_hasnext(struct _iterator* iter)
 iterator_t stack_iter(struct _stack* self)
 {
     assert(self != NULL);
-    if (self == NULL)
-    {
-        return NULL;
-    }
+    self->_iter.parent = self;
     self->_iter._cur = 0;
     return &self->_iter;
 }
 
-
 static bool stack_init2(struct _stack* self, uint32_t obj_size, uint32_t capacity)
 {
     assert(self != NULL);
diff --git a/test/test_stack.c b/test/test_stack.c
index 98caa98..c8376e2 100644
--- a/test/test_stack.c
+++ b/test/test_stack.c
@@ -440,6 +440,44 @@ static void test_stack2_struct(void)
     TEST_ASSERT_NULL(stack);
 }
 
+static void test_stack2_iter(void)
+{
+    uint32_t i = 0;
+    int data[] = { 1,2,3,4,5,6,7,8,9,10 };
+    int temp = 0;
+    uint32_t len = sizeof(data) / sizeof(data[0]);
+    uint32_t capacity = len;
+
+    stack_t stack = NULL;
+    stack = stack_new2(sizeof(int), capacity);
+    TEST_ASSERT_NOT_NULL(stack);
+    stack->print_obj = print_num;
+
+    TEST_ASSERT_FALSE(stack->peek(stack, &temp));
+    TEST_ASSERT_TRUE(stack->clear(stack));
+    for (i = 0; i < len; i++)
+    {
+        TEST_ASSERT_TRUE(stack->push(stack, &data[i]));
+        TEST_ASSERT_EQUAL_INT(i + 1, stack->size(stack));
+
+        TEST_ASSERT_TRUE(stack->peek(stack, &temp));
+        TEST_ASSERT_EQUAL_INT(data[i], temp);
+    }
+
+    iterator_t iter = stack->iter(stack);
+    TEST_ASSERT_NOT_NULL(iter);
+    i = 0;
+    while(iter->hasnext(iter))
+    {
+        temp = *(int *)iter->next(iter);
+        printf("%d ", temp);
+        TEST_ASSERT_EQUAL_INT(data[len - 1 - i], temp);
+        i++;
+    }
+    stack_free(&stack);
+    TEST_ASSERT_NULL(stack);
+}
+
 void test_stack(void)
 {
     UnitySetTestFile(__FILE__);
@@ -454,4 +492,6 @@ void test_stack(void)
 
     RUN_TEST(test_stack2_num);
     RUN_TEST(test_stack2_struct);
+
+    RUN_TEST(test_stack2_iter);
 }