Re: Exception safety: how to assign std::string when strong guarantee is needed?

How would you assign one std::string to another, when you need to have
the "strong guarantee", with respect to exception safety?
It seems to me that the following five attempts only offer the basic
guarantee:
void Foo( const std::string & string1, std::string & string2 ) {
  // Attempt 1. operator=
  string2 = string1;
  // Attempt 2. Copy-and-swap.
  std::string(string1).swap(string2);
  // Attempt 3. Copy-and-swap (non-member).
  std::string temp(string1);
  swap(string2, temp);
  // Attempt 4. assign.
  string2.assign(string1);
  // Attempt 5. assign iterator-range.
  string2.assign(string1.begin(), string1.end());
}