Re: localename: Fix gettext test failures on mingw

[Bruno Haible]

Hi Eli,

> LC_MESSAGES means nothing on MS-Windows, so why does Gnulib need to
> "fix" something that is not supported by the runtime library?

On native Windows, LC_MESSAGES is indeed not defined by the runtime
library, but by Gnulib: it's defined in gnulib's <locale.h> replacement [1]
and supported by gnulib's 'setlocale' module.

Why do we do this?
1. Because LC_MESSAGES is defined by POSIX, and one of Gnulib's goals is
   to emulate POSIX APIs, as far as it makes sense.
2. Because LC_MESSAGES is essential for GNU gettext.

> Applications that want to be portable to MinGW and use LC_MESSAGES
> should make sure the related code is either ifdef'ed out on MS-Windows
> or does something reasonable "by other means".

... where "other means" include using Gnulib's 'locale' and 'setlocale'
modules.

> Proliferating the illusion that LC_MESSAGES are supported on
> MS-Windows is IMO not a good idea.

Why not? It's a good "illusion". It's an "illusion" that allows GNU gettext
to work on native Windows.

This kind of "illusion" is the basis of the POSIX emulation part of Gnulib. [2]

> > 2018-11-23  Bruno Haible  <address@hidden>
> > 
> >     localename: Fix gettext test failures on mingw.
> >     * lib/localename.c (gl_locale_name_posix): Convert the result of
> >     gl_locale_name_environ to XPG syntax.
> 
> I no longer remember the details, but wouldn't such conversion get in
> the way of calling 'setlocale'?  The MS-Windows runtime library
> implementation doesn't understand the XPG syntax, AFAIR, so it will
> generally fail.

Correct. Programs should not call 'setlocale' with the result of
'gl_locale_name_posix'. This follows from the documentation of
'gl_locale_name_posix' in localename.h.

Programs that call 'setlocale' and want to consider locale names given
by environment variables usually do so by calling
   setlocale (LC_something, "");

Bruno

[1] https://www.gnu.org/software/gnulib/manual/html_node/locale_002eh.html
[2] 
https://www.gnu.org/software/gnulib/manual/html_node/Various-Kinds-of-Modules.html#Support-for-ISO-C-or-POSIX-functions_002e