function clearStack is done

stack.c

@@ -10,24 +10,43 @@
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data)
 {
-
+StackNode *newNode = (StackNode *)malloc(sizeof(StackNode));
+if(newNode == NULL)
+  return NULL;
+newNode->data = data;
+newNode->next = stack;
+return newNode;
 }
 
 // Deletes the top element of the stack (latest added element) and releases its memory. (Pointer to data has to be
 // freed by caller.)
 StackNode *pop(StackNode *stack)
 {
+    if (stack == NULL)
+        return NULL;
 
+    StackNode *next = stack->next;
+    free(stack);
+    return next;
 }
 
 // Returns the data of the top element.
 void *top(StackNode *stack)
 {
-
+if (stack == NULL)
+  return NULL;
+return stack->data;
 }
 
 // Clears stack and releases all memory.
 void clearStack(StackNode *stack)
 {
+StackNode *current = stack;
 
+while (current != NULL)
+  {
+  StackNode *next = current->next;
+  free(current);
+  current = next;
+  }
 }

stack.h

@@ -10,13 +10,11 @@ The latest element is taken from the stack. */
 //TODO: passenden Datentyp als struct anlegen
 
 
-typedef struct Node{
-  int *data;
-  struct Node *next;
-
+typedef struct StackNode {
+    void *data;
+    struct StackNode *next;
 } StackNode;
 
-
 // Pushes data as pointer onto the stack.
 StackNode *push(StackNode *stack, void *data);