I wrote:
> Well, there aren't going to be any ASCII characters that produce 12
> bytes, and probably not any LATIN1 characters either, so I think we
> could assume that the shortest input character that could produce
> such a long output would be 3 bytes.
Ah sorry, I should have written BMP not LATIN1. Maybe it still holds
across that set, but I'm less sure.
regards, tom lane