auto_ptr conversion derived to base

Hello,

I get differing results for the following code on differing platforms.
Could someone please advise if what I have written is legal? I found a
reference to an older document that seems to intimate that this might
be ok. (Look right at the end)...
http://www.awprofessional.com/content/images/020163371X/autoptrupdate/auto_ptr_update.html

TIA,

Peter Dulimov.
[email address is my first name followed by the first two letters of my
surname at
resmedA dot comB dot auC, without capitals.]

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#include <memory>
#include <iostream>
#include <ostream>
#include <fstream>
#include <iomanip>

class Test
{
  std::auto_ptr<std::ostream> m_pOs;

public:
  Test(std::auto_ptr<std::ostream> o) : m_pOs(o)
  {
    *m_pOs << "Hello" << std::endl;
  }

private:
  Test(const Test& other);
  const Test& operator=(const Test& rhs);
};

int main(int argc, char* argv[])
{
  Test question(std::auto_ptr<std::ofstream>(new
std::ofstream("file")));

  return 0;
}

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