Pile & File en C

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


typedef struct stack 
{ 
    int data[100]; 
    int size; 
} s_stack; 

void init(s_stack* stack) 
{ 
  stack->size = 0; 
} 

void push(s_stack* stack, int elem) 
{ 
  if (stack->size < 100) 
    stack->data[stack->size++] = elem; 
  else 
    printf("la stack est pleine\n"); 
} 

int pop(s_stack* stack) 
{ 
  if (stack->size > 0) 
    return stack->data[--stack->size]; 
  else 
  { 
    printf("la stack est déjà vide...\n"); 
    return -1; 
  } 
} 

int main() 
{ 
  s_stack* stack = malloc(sizeof (s_stack)); 

  init(stack); 

  printf("push : 5\n"); 
  push(stack, 5); 

  printf("push : 10\n"); 
  push(stack, 10); 

  printf("push : 15\n"); 
  push(stack, 15); 

  printf("taille de la stack : %d\n", stack->size); 

  printf("pop : %d\n", pop(stack)); 
  printf("pop : %d\n", pop(stack)); 
  printf("pop : %d\n", pop(stack)); 

  printf("taille de la stack : %d\n", stack->size); 
  printf("pop : %d\n", pop(stack)); 

  free(stack); 

  return 0; 
}