bug#6401:

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: tim@tenkan.org,  6401@debbugs.gnu.org
> Date: Tue, 22 Nov 2011 02:49:30 -0500
> 
> Why does a --with-ns build actually need to set these env-vars for child
> processes?
> Could they specifically be unset in spawned M-x shells?

How will Emacs know that these variables weren't set by the parent
shell?

> Similar to the suggestion in emacs-devel, could configure unset
> $EMACSDATA if $EMACS is set (which indicates it is running from an Emacs
> shell)? Under what circusmtances would one want to set EMACSDATA when
> building Emacs?

Building Emacs is just one use case, even if we find a solution for
it.  The problem is much broader: Emacs running as a child of another
Emacs gets EMACSDATA etc. variables that could well point to a wrong
place, because they were set by a different Emacs version.