Implementación de pilas en C

Stack.c

#include <stdio.h>
#include <stdlib.h>

int size_stack = 7;

void print_stack(int *stack, int *top)
{
    int i;
    for(i = 0; i < *top; i++) printf(" %i ", *(stack + i));
}

void push(int *stack, int *top, int val)
{
    *top += 1;
    if (*top > size_stack)
    {
        printf("Stack Overflow!");
        exit(0);
    }
    *(stack + (*top - 1)) = val;
}

void pop(int *top)
{
    *top -= 1;
    if (*top < 0)
    {
        printf("Stack Underflow!");
        exit(0);
    }
}

void main()
{
    int *stack, *top;

    stack = (int*)malloc(sizeof(int) * size_stack);
    top = (int*)malloc(sizeof(int));
    *top = 0;

    push(stack, top, 15);
    push(stack, top, 6);
    push(stack, top, 2);
    push(stack, top, 9);
    pop(top);
    print_stack(stack, top);
}