Stack Implementation using Single Linked List

stack_list.c

#include <stdio.h>
#include <stdlib.h>
#include <assert.h>
#include "stack_list.h"

stack_t *Initialize()
{
  stack_t *top = NULL;
  return top;
}

int Empty(stack_t *top)
{
  return top == NULL;
}

void Push(stack_t **top, data_t data)
{
  // create new stack's node
  stack_t *NewNode = (stack_t*)malloc(sizeof(stack_t));
  assert(NewNode != NULL);
  NewNode->data = data;

  // push into stack and make new top
  NewNode->next = *top;
  *top = NewNode;
}

stack_t *Pop(stack_t **top, data_t *save)
{
  if(Empty(*top)) {
    printf("ERROR: Stack is empty. Can't pop.\n");
    return NULL;
  }

  // save the data
  *save = (**top).data;
  
  stack_t *temp = *top;
  *top = (**top).next;
  free(temp);
  
  return *top;
}

stack_list.h

#ifndef STACK_LIST_H
#define STACK_LIST_H

typedef ... data_t;

typedef struct StackNode {
  data_t data;
  struct StackNode *next;
} stack_t;

stack_t *Initialize();
int Empty(stack_t *top);
void Push(stack_t **top, data_t data);
stack_t *Pop(stack_t **top, data_t *save);

#endif