bug#65908: 29.1.50; Emacs 29 regresses on macOS

[Alan Third]

On Thu, Oct 05, 2023 at 08:02:41PM +0300, Eli Zaretskii wrote:
> > Date: Thu, 5 Oct 2023 17:33:56 +0100
> > From: Alan Third <alan@idiocy.org>
> > Cc: Gerd Möllmann <gerd.moellmann@gmail.com>,
> >     ccsmile2008@outlook.com, 65908@debbugs.gnu.org,
> >     gregory@heytings.org, stefankangas@gmail.com
> > 
> > On Thu, Oct 05, 2023 at 07:11:01PM +0300, Eli Zaretskii wrote:
> > > > From: Gerd Möllmann <gerd.moellmann@gmail.com>
> > > > Cc: Eli Zaretskii <eliz@gnu.org>,  gregory@heytings.org,
> > > >   65908@debbugs.gnu.org,  stefankangas@gmail.com,  
> > > > ccsmile2008@outlook.com
> > > > Date: Thu, 05 Oct 2023 15:18:42 +0200
> > > > 
> > > > I'd like to propose the attached patch for problem of invalid LANG
> > > > setting.  This simply falls back to "en_US.UTF-8" if LANG isn't valid,
> > > > or something valid can't be deduced from the locale.
> > > 
> > > Why is it reasonable to force the UTF-8 codeset as the fallback?
> > 
> > Both the macOS terminals I have access to use UTF-8 as their default,
> > and I'm not sure if they even let you change it. Therefore it seemed
> > reasonable to me that the default for Emacs should also be UTF-8.
> 
> Are you saying that macOS doesn't support non-UTF-8 encodings?

No, because of the slightly unusual way macOS works, where any
graphical application doesn't inherit much of an environment the
terminals have to set it up. I was just copying what the terminals do
by default. When I say I don't know if they let you change it, I mean
in their settings. You can change it in the shell and the locale
command here shows, for example:

# locale -a | grep en_GB
en_GB.ISO8859-1
en_GB.UTF-8
en_GB.US-ASCII
en_GB
en_GB.ISO8859-15

So we could skip the UTF-8 part if it's the wrong thing to do, but
since everything else in macOS is unicode aware, I suspect we should
keep it.

-- 
Alan Third