think I read somewhere that it's unspecified. An implementation isn't required to document what the behaviour is, but there must be some behaviour. So that would mean, comparing any two pointers is still legal, but doesn't neccessarily yield a total order. Does that mean, that we still have to get a consistent result, when comparing the same two pointers twice? The general case would be: Does invoking the same unspecified behaviour twice within an application always yield the same result?