On Fri, 1 Jan 2016 21:22:54 -0800
Paul Eggert <eggert@cs.ucla.edu> wrote:

> Ouch, good point. I missed the possibility of a unibyte encoding where
> not all bytes are valid unibyte characters. I installed the attached
> additional patch to fix this, and to test for the bug I recently
> introduced here.

Thanks, I see that it is good idea, but I propose minor change for your
fix.  Perhaps, it will be what you want.