Re: master 28bf387: Tweak Fdirectory_append for efficiency

[Eli Zaretskii]

> From: Lars Ingebrigtsen <larsi@gnus.org>
> Cc: emacs-devel@gnu.org
> Date: Sat, 24 Jul 2021 18:29:11 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Isn't SCHARS (arg) == SBYTES (arg) true for any unibyte string, even
> > one that includes non-ASCII characters?
> 
> Yes, indeed.  I'll get fixing...

I actually don't understand the call to make_multibyte_string in that
loop, either.  Can you tell why you needed to convert unibyte strings?
In any case, make_multibyte_string will not convert as you intended,
because you call it with the identical last two arguments, which is
only valid for all-ASCII strings.