messing around with the stack

#include <stdio.h>
#include <stdarg.h>


struct intfarm {
    int a;
    int b;
};

static void             (*hackptr) ();
static struct intfarm   farm;

static void hack    (int, ...);
static void hackdbg (char *, size_t);
static void hackfarm(struct intfarm);

void
hack(int foo, ...)
{
    int bar, baz;
    va_list v;

    va_start (v, foo);
    bar = va_arg (v, int);
    baz = va_arg (v, int);
    printf ("foo: %d, bar: %d, baz: %d\n", foo, bar, baz);
    printf ("&foo: %p, &bar: %p, &baz: %p\n", &foo, &bar, &baz);
    hackdbg ((char *)(&foo), sizeof foo);
    hackdbg ((char *)(&bar), sizeof bar);
    hackdbg ((char *)(&baz), sizeof baz);

}

void
hackfarm (struct intfarm f)
{
    printf ("&f.a: %p, &f.b: %p\n", &(f.a), &(f.b));
}

void
hackdbg (char *data, size_t len)
{
    size_t i;

    for (i= 0; i < len; i ++)
      {
        printf ("%02x ", data[i] & 0xff);
      }
    printf ("\n");
}

int
main()
{
    farm.a = 7;
    farm.b = 16;
    hackptr = hackdbg;

    hackptr (&farm, sizeof farm);

    hackptr = hack;

    hackptr (3, farm);

    return 0;
}