g++ and aliasing bools

[Neil Booth]

Mark Mitchell wrote:-

> OK, I like this argument.  *I* find it convincing, at least. :-)

[...]

> So, after the branch, let's have a patch to do this.

Great; I think that Joe's "proof" should go in as a comment; both to
explain the ideas and subtleties behind the code, but also so we can
point at it and extract a similar argument from anyone who wants to
tighten the logic in future.

Neil.