step5-internals-impact.c

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

typedef struct int_node IntNode;
struct internals {
    IntNode* top;
};

// ...

IntStack* new_stack()
{
    IntStack* this = malloc(sizeof (IntStack));
    this->_internals = malloc(sizeof (struct internals));
    this->_internals->top = NULL;
    // Function pointer assignments
    return this;
}

// ...

void push(IntStack* this, int value)
{
    IntNode* pushed = malloc(sizeof (IntNode));
    pushed->value = value;
    pushed->next = this->_internals->top; // top is not tied directly to this anymore
    this->_internals->top = pushed;
}

// ...