void weak_shared(
    WP & first,
    SP & second
){
    const char * testfile = boost::archive::tmpnam(NULL);
    BOOST_REQUIRE(NULL != testfile);
    BOOST_CHECK(! first.expired());
    int firstm = first.lock()->m_x;
    int secondm = second->m_x;
    save2(testfile, first, second);

    // Clear the pointers, thereby destroying the objects they contain
    first.reset();
    second.reset();

    load2(testfile, first, second);
    BOOST_CHECK(! first.expired());

    // Check data member
    BOOST_CHECK(firstm == first.lock()->m_x);
    BOOST_CHECK(secondm == second->m_x);
    // Check pointer to vtable
    BOOST_CHECK(::dynamic_pointer_cast<Sub>(first.lock()));
    BOOST_CHECK(::dynamic_pointer_cast<Sub>(second));

    std::remove(testfile);
}
void save_and_load2(SP & first, SP & second)
{
    const char * testfile = boost::archive::tmpnam(NULL);
    BOOST_REQUIRE(NULL != testfile);

    save2(testfile, first, second);

    // Clear the pointers, thereby destroying the objects they contain
    first.reset();
    second.reset();

    load2(testfile, first, second);

    BOOST_CHECK(first == second);
    std::remove(testfile);
}