On Sat, Jun 4, 2016 at 1:55 PM, Eli Zaretskii <eliz@gnu.org> wrote:
> I would use
>
>   if (pos <= beg)
>     break;
>   DEC_BOTH (pos, pos_byte);

Oh yeah, that makes sense; parallels with the same check at the
beginning of the function. Full patch attached.