bug#22392: Emacs OS X GUI doesn't set locale

[Random832 <random832@fastmail.com>]

On Fri, Feb 5, 2016, at 04:21, Eli Zaretskii wrote:
> You can set LANG in the program's environment even if you don't launch
> subprocesses, just to have the relevant libc routines adjust their
> defaults.  In fact, that's why Emacs does that in the first place.
> 
> I'm asking why don't the programs you allude to do that already.  If
> they do, then setting LANG in Emacs, and passing that to those
> programs as result, might interfere with what those programs already
> do.

Because they don't need it. Because they don't use LANG at all,
internally or otherwise. Because they use Core Foundation instead of
libc for localization. (Though, for applications we do not have the
source code for, I don't know how we can say for sure that they don't
set LANG - the only way to find out if a process has set an environment
variable is to examine its subprocesses with ps -E.)

If mac gui applications used LANG, then the GUI *would* set them when
launching applications, and we wouldn't be having this discussion.

Emacs is in a fundamentally different category from most gui
applications (and in the same category as terminal emulators) because it
launches BSD-subsystem programs which use libc functions for
localization. It's therefore arguably responsible for providing
appropriate environment locale values for those BSD-subsystem programs.
Most applications *don't* launch BSD-subsystem programs as subprocesses.
Emacs (and e.g. other text editors, such as Vim, which also sets LANG in
os_mac_conv.c:mac_lang_init) and terminal emulators are exceptions to
this.

Half of the *point* of this is to make sure subprocesses (like ispell,
or sort, or a shell in m-x terminal, etc) get the proper locale.