/* http://csapp.cs.cmu.edu/
 * Figure 3.26 Code illustrating use of pointers in C.
 */

struct str { /* Example structure */
    int t;
    char v;
};

union uni { /* Example union */
    int t;
    char v;
} u;

int g=15;

void fun(int *xp)
{
    void (*f)(int*) = fun;	/* f is a function pointer */

    /* Allocate structure on stack */
    struct str s = {1,'a'}; 	/* Initialize structure */

    /* Allocate union from heap */
    union uni *up = (union uni *)malloc(sizeof(union uni));

    /* Locally declared array */
    int *ip[2] = {xp, &g};

    up->v = s.v+1;

    printf("ip     = %p, *ip      = %p, **ip     = %d\n",
           ip, *ip, **ip);
    printf("ip+1   = %p, ip[1]    = %p, *ip[1]  = %d\n",
           ip+1, ip[1], *ip[1]);
    printf("&s.v   = %p, s.v      = '%c'\n", &s.v, s.v);
    printf("&up->v = %p, up->v    = '%c'\n", &up->v, up->v);
    printf("f      = %p\n", f);
    if (--(*xp) > 0)
        f(xp);		/* Recursive call of fun */
}

int test()
{ 
    int x=2;
    fun(&x);
    return x;
}