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

int main() {
    unsigned long long stack_var = 0x21;
    fprintf(stderr, "Allocating 3 buffers.\n");
    char *a = malloc(9);
    char *b = malloc(9);
    char *c = malloc(9);
    strcpy(a, "AAAAAAAA");
    strcpy(b, "BBBBBBBB");
    strcpy(c, "CCCCCCCC");
    fprintf(stderr, "1st malloc(9) %p points to %s\n", a, a);
    fprintf(stderr, "2nd malloc(9) %p points to %s\n", b, b);
    fprintf(stderr, "3rd malloc(9) %p points to %s\n", c, c);

    fprintf(stderr, "Freeing the first one %p.\n", a);
    free(a);
    fprintf(stderr, "Then freeing another one %p.\n", b);
    free(b);
    fprintf(stderr, "Freeing the first one %p again.\n", a);
    free(a);

    fprintf(stderr, "Allocating 4 buffers.\n");
    unsigned long long *d = malloc(9);
    *d = (unsigned long long) (((char*)&stack_var) - sizeof(d));
    fprintf(stderr, "4nd malloc(9) %p points to %p\n", d, &d);
    char *e = malloc(9);
    strcpy(e, "EEEEEEEE");
    fprintf(stderr, "5nd malloc(9) %p points to %s\n", e, e);
    char *f = malloc(9);
    strcpy(f, "FFFFFFFF");
    fprintf(stderr, "6rd malloc(9) %p points to %s\n", f, f);
    char *g = malloc(9);
    strcpy(g, "GGGGGGGG");
    fprintf(stderr, "7th malloc(9) %p points to %s\n", g, g);
}