On 09.03.2017 11:47, Serhiy Storchaka wrote:
> 
> The SUPPORTED file from glibc is used for determining the default encoding  for locales that don't include it explicitly. For example en_IN uses UTF-8 rather than ISO8859-1.

No, the glibc locales don't say anything about default encodings
used in a locale:

http://manpages.ubuntu.com/manpages/wily/en/man5/locale.5.html

These encodings are just used for determining the default
set of locale.encoding variants to install on the system,
nothing more:

https://github.com/bminor/glibc/blob/73dfd088936b9237599e4ab737c7ae2ea7d710e1/localedata/Makefile#L204

glibc does have a locale.alias file:

https://github.com/bminor/glibc/blob/73dfd088936b9237599e4ab737c7ae2ea7d710e1/intl/locale.alias

which uses the X.org format, but this is completely out of
date and declared obsolete.

Serhiy: If you believe that there's anything authoritative about
the glibc SUPPORTED file in terms of defining the commonly
used encoding in a locale, please provide references. These
should also clarify why the glibc encoding is the correct one
compared to the X.org mapping.

It doesn't help, trying to interpret things into such build
files. We need a database that is being actively maintained
and has a track record of representing what people actually
use in their locales. The only one I know is the X.org one.