#include <stdio.h>

/* based on your knowledge of stack frames, what would
   I have to type to get executable code into the input
   string and overwrite f's return address with that
   code's start address? */

char * gets(char * s)
{ int len = 0;
  while (1)
  { char c = getchar();
    if (c == EOF)
    { if (len == 0)
        return NULL;
      else
        break; }
    if (c == '\n')
      break;
    s[len] = c;
    len += 1; }
  s[len] = 0;
  return s; }

void f()
{ int a = 1234;
  char input[16];
  int b = 9876;
                  // this is so we can see how much padding the compiler inserts
  printf("     %u %u %u\n", & b, input, & a);
  printf("  %d '%s' %d\n", a, input, b);
  gets(input);
  printf("  %d '%s' %d\n", a, input, b); }

int main()
{ printf("one\n");
  f();
  printf("\ntwo\n");
  f();
  printf("\nthree\n");
  f();
  printf("\nfour\n");
  f();
  printf("\nfive\n"); }