boost::lexical_cast wrong output

The C++ standard does not specify how a Boolean is stored in memory, only that there are two possible values: true and false. Now, on your machine, I presume these are stored, respectively, as 1 and 0. The compiler is allowed to make assumptions, and in particular it's allowed to assume that these are going to be the only two values stored in a Boolean.

Thus, when boost::lexical_cast sees a Boolean, it runs code that probably looks something like this (after optimization)

// Gross oversimplification
std::string lexical_cast(bool value) {
  char res = '0' + (int)value;
  return std::string(1, res);
}

If value is 0 or 1, this works fine and does what you want. However, you put a 71 into it. So we add the ASCII code of '0' (48) to 71 and get 119, the ASCII code of 'w'.

Now, I'm not a C++ standard expert, but I would guess that storing a non-standard value into a Boolean with memcpy is undefined behavior. At the very least, your code is non-portable. Perhaps someone more versed in the standard can fill in the holes in my knowledge as far as that's concerned.