/*
** $Id: trash.cc 625 2007-03-23 05:50:52Z phf $
**
** Example of "accidental" trashing of stuff on the stack.
*/

#include <iostream>
#include <iomanip>

using std::cout;
using std::endl;
using std::hex;

// It's a bad idea to return a pointer or a reference to
// a local variable, something that got put on the stack
// by the compiler. Here are two functions that do just
// that, much to their detriment...

int* bla()
{
  int a = 0xAFFEAFFE;
  int *p = &a;
  return p;
}

int& blu()
{
  int a = 0xCAFEBABE;
  int &r = a;
  return r;
}

// Here's another, unrelated function that uses some
// stack space for a local string. It's going to trash
// the values bla() or blu() left on the stack before.

void argh()
{
  char s[] = "Peter!";
}

// And here is how it all works out... Enjoy! :-)

int main()
{
  cout << hex;
  int *x = bla();
  cout << "*x: " << *x << endl;
  argh();
  cout << "*x: " << *x << endl;
  int &y = blu();
  cout << "y: " << y << endl;
  argh();
  cout << "y: " << y << endl;
}

// Famous last words: I tried the "trashing" on several machines.
// On my OS X laptop, parts of "a" get trashed, you can still see
// a few bytes from the old patterns. On ugradx.cs.jhu.edu all of
// "a" gets trashed. On qube.cs.jhu.edu "a" gets trashed right
// away, i.e. even the first print right after bla() or blu() is
// trashed already. Fascinating. :-)