Introduce the destructor

step3-destructor.c

/* int_stack.h */

//...
// Other function declarations
void delete_stack(IntStack** stack);

/* main.c */
#include "int_stack.h"

//...

int main()
{
    //...
    delete_stack(&stack);
    return 0;
}

/* int_stack.c */
#include "int_stack.h"

//...

void delete_stack(IntStack** stack)
{
    while (!is_empty_stack(*stack)) {
        pop_stack(*stack);
    }
    free(*stack); *stack = NULL;
}