Stack Data Structure Linked based

#include <stdio.h>
#include <stdlib.h>
#define StackEntry int
typedef struct stacknode {
  StackEntry entry;
  struct stacknode *next;
}StackNode;
typedef struct stack {
  StackNode *top;
}Stack;

void CreateStack (Stack *ps) {
  ps->top = NULL;
}

void push (StackEntry e, Stack *ps) {
  StackNode *pn = (StackNode*) malloc(sizeof(StackNode));
  pn->entry = e;
  pn->next = ps->top;
  ps->top = pn;
}

void pop (StackEntry *pe, Stack *ps) {
  *pe = ps->top->entry;
  StackNode *pn = ps->top;
  ps->top = ps->top->next;
  free(pn);
  /*
   clear the StackNode (data) to the operating system,
   and the pointer still pointing to the same address
   */
}

void StackTop (StackEntry *pe, Stack *ps) {
  *pe = ps->top->entry;
}

int StackEmpty (Stack *ps) {
  return ps->top == NULL;
}

int StackFull (Stack *ps) {
  return 0;
}

int main() {

//  freopen("/home/hamoudi/Coding/DataStructures/LinkedStack/input.in", "r", stdin);

  Stack s;

  CreateStack(&s);

  StackEntry e;

  push(e, &s);

  return 0;
}