bug#55870: GNU Emacs 26.3, Select All(C-x h) does not work

[Eli Zaretskii]

> Cc: larsi@gnus.org, 55870@debbugs.gnu.org
> From: Bruce <brucelam1982pi@anche.no>
> Date: Sun, 17 Jul 2022 10:38:25 +0800
> 
> (default-value 'selection-coding-system)
> 
> reports: nil

Maybe this is the reason.  Po Lu, what data-type do we use on X to put
data into the clipboard when the user presses M-w?

> What functions do emacs call after I press Meta-w?

There are too many of them to mention here.  In general, Emacs saves
the text on the kill-ring and also puts it into the X clipboard.