Add list helper without memory operations

Makefile

@@ -29,7 +29,7 @@ deps += $(LIB_OBJS:%.o=%.o.d)
 APPS := coop echo hello mqueues semaphore mutex cond \
         pipes pipes_small pipes_struct prodcons progress \
         rtsched suspend test64 timer timer_kill \
-        cpubench test_libc
+        cpubench test_utils
 
 # Output files for __link target
 IMAGE_BASE := $(BUILD_DIR)/image

app/test_libc.c → app/test_utils.c

@@ -1,11 +1,13 @@
-/* LibC Test Suite - Comprehensive tests for standard library functions.
+/* Utility Test Suite - Comprehensive tests for utilities and helpers.
  *
  * Current Coverage:
  * - vsnprintf/snprintf: Buffer overflow protection
  *   * C99 semantics, truncation behavior, ISR safety
  *   * Format specifiers: %s, %d, %u, %x, %p, %c, %%
  *   * Edge cases: size=0, size=1, truncation, null termination
  *
+ * - list operations: pushback node, remove node
+ *
  * Future Tests (Planned):
  * - String functions: strlen, strcmp, strcpy, strncpy, memcpy, memset
  * - Memory allocation: malloc, free, realloc
@@ -298,6 +300,81 @@ void test_mixed_formats(void)
     ASSERT_TEST(buf[test_strlen(buf)] == '\0', "Mixed format null termination");
 }
 
+/* Test 11: List node helpers behavior */
+void test_list_node_pushback_and_remove(void)
+{
+    list_node_t node1 = {0};
+    list_node_t node2 = {0};
+
+    node1.next = &node2; /* make node1 artificially “linked” */
+    list_t *list = list_create();
+
+    /* Check node push back normally - unlinked and linked */
+    list_pushback_node(list, &node1);
+    ASSERT_TEST(list_is_empty(list), "Linked node pushback fail");
+
+    node1.next = NULL;
+    list_pushback_node(list, &node1);
+    ASSERT_TEST(list->length == 1, "Unlinked node pushback success ");
+    ASSERT_TEST(list->head->next == &node1 && node1.next == list->tail,
+                "List consistent after pushback first node ");
+
+    /* Check node push back order */
+    node2.next = NULL;
+    list_pushback_node(list, &node2);
+    ASSERT_TEST(list->length == 2 && list->head->next == &node1 &&
+                    node1.next == &node2 && node2.next == list->tail,
+                "Insertion order preserved ");
+
+    /* Remove last node */
+    list_remove_node(list, &node2);
+    ASSERT_TEST(
+        list->length == 1 && node2.next == NULL && node1.next == list->tail,
+        "Removing last node must keep list structure consistent");
+
+    /* Remove non-existing node (second time) */
+    list_remove_node(list, &node2);
+    ASSERT_TEST(
+        list->length == 1 && node2.next == NULL && node1.next == list->tail,
+        "Removing non-existing node must not change the list");
+
+    /* Remove only node */
+    list_remove_node(list, &node1);
+    ASSERT_TEST(list->length == 0 && list->head->next == list->tail,
+                "Removing only node ");
+    ASSERT_TEST(list_is_empty(list), "Empty list check ");
+}
+
+/* Test 12: List helpers behavior */
+void test_list_pushback_and_remove(void)
+{
+    list_t *list = list_create();
+
+    int node1 = 1;
+    int node2 = 2;
+
+    /* Check node push back normally - unlinked and linked */
+    list_pushback(list, &node1);
+    ASSERT_TEST(list->length == 1 && *(int *) (list->head->next->data) == 1,
+                "Data push back into a new list ");
+
+    list_pushback(list, &node2);
+    ASSERT_TEST(
+        list->length == 2 && *(int *) (list->head->next->next->data) == 2,
+        "Second data pushback successful ");
+
+    /* Remove last node */
+    list_remove(list, list->head->next);
+    ASSERT_TEST(list->length == 1 && *(int *) (list->head->next->data) == 2,
+                "Remove first data ");
+
+    /* Remove non-existing node (second time) */
+    list_remove(list, list->head->next);
+    ASSERT_TEST(list->length == 0, "Unlinked node pushback success ");
+
+    ASSERT_TEST(list_is_empty(list), "Empty list check ");
+}
+
 void test_runner(void)
 {
     printf("\n=== LibC Test Suite ===\n");
@@ -314,6 +391,11 @@ void test_runner(void)
     test_isr_safety();
     test_mixed_formats();
 
+
+    printf("\n=== List Test Suite ===\n");
+    test_list_node_pushback_and_remove();
+    test_list_pushback_and_remove();
+
     printf("\n=== Test Summary ===\n");
     printf("Tests run:    %d\n", tests_run);
     printf("Tests passed: %d\n", tests_passed);

include/lib/list.h

@@ -78,6 +78,24 @@ static inline list_node_t *list_cnext(const list_t *list,
 
 /* Push and pop */
 
+/* Pushback list node into list without new node memory allocation */
+static inline void list_pushback_node(list_t *list, list_node_t *target)
+{
+    if (unlikely(!list || !target || target->next))
+        return;
+
+    target->next = list->tail;
+
+    /* Insert before tail sentinel */
+    list_node_t *prev = list->head;
+    while (prev->next != list->tail)
+        prev = prev->next;
+
+    prev->next = target;
+    list->length++;
+    return;
+}
+
 static inline list_node_t *list_pushback(list_t *list, void *data)
 {
     if (unlikely(!list))
@@ -88,15 +106,9 @@ static inline list_node_t *list_pushback(list_t *list, void *data)
         return NULL;
 
     node->data = data;
-    node->next = list->tail;
-
-    /* Insert before tail sentinel */
-    list_node_t *prev = list->head;
-    while (prev->next != list->tail)
-        prev = prev->next;
-    prev->next = node;
+    node->next = NULL;
 
-    list->length++;
+    list_pushback_node(list, node);
     return node;
 }
 
@@ -114,23 +126,35 @@ static inline void *list_pop(list_t *list)
     return data;
 }
 
-/* Remove a specific node; returns its data */
-static inline void *list_remove(list_t *list, list_node_t *target)
+/* Remove a node from list without freeing */
+static inline void list_remove_node(list_t *list, list_node_t *target)
 {
     if (unlikely(!list || !target || list_is_empty(list)))
-        return NULL;
+        return;
 
     list_node_t *prev = list->head;
     while (prev->next != list->tail && prev->next != target)
         prev = prev->next;
 
     if (unlikely(prev->next != target))
-        return NULL; /* node not found */
+        return; /* node not found */
 
     prev->next = target->next;
+    target->next = NULL;
+    list->length--;
+    return;
+}
+
+/* Remove a specific node; returns its data */
+static inline void *list_remove(list_t *list, list_node_t *target)
+{
+    if (unlikely(!list || !target || list_is_empty(list)))
+        return NULL;
+
+    list_remove_node(list, target);
+
     void *data = target->data;
     free(target);
-    list->length--;
     return data;
 }