tests/malloc: fail if allocation count does not match

If we can't allocate the same amount of buffers in the second run,
fail the test. This indicates that not all buffers have been properly
freed.

tests/malloc/main.c

@@ -47,7 +47,7 @@ struct node {
 
 static uint32_t total = 0;
 
-static void fill_memory(struct node *head)
+static uint32_t fill_memory(struct node *head)
 {
     uint32_t allocations = 0;
 
@@ -70,6 +70,8 @@ static void fill_memory(struct node *head)
     }
 
     printf("Allocations count: %"PRIu32"\n", allocations);
+
+    return allocations;
 }
 
 static void free_memory(struct node *head)
@@ -102,6 +104,8 @@ static void free_memory(struct node *head)
 
 int main(void)
 {
+    uint32_t allocations = 0;
+
     printf("CHUNK_SIZE: %"PRIu32"\n", (uint32_t)CHUNK_SIZE);
     printf("NUMBER_OF_TESTS: %d\n", NUMBER_OF_TESTS);
 
@@ -110,8 +114,16 @@ int main(void)
         struct node *head = malloc(sizeof(struct node));
         total += sizeof(struct node);
 
-        fill_memory(head);
+        uint32_t new_allocations = fill_memory(head);
         free_memory(head);
+
+        /* test if all memory was freed/can be allocated again */
+        if (allocations == 0) {
+            allocations = new_allocations;
+        } else if (allocations != new_allocations) {
+            puts("[FAILED]");
+            return -1;
+        }
     }
 
     puts("[SUCCESS]");