bug#6401:

[Eli Zaretskii]

> From: Glenn Morris <rgm@gnu.org>
> Cc: tim@tenkan.org,  6401@debbugs.gnu.org
> Date: Tue, 22 Nov 2011 12:29:58 -0500
> 
> Eli Zaretskii wrote:
> 
> >> 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?
> 
> I'm ignorant of all this. What do child processes of Emacs need these
> variables for? Can you give me one example of something I might want to
> run inside an emacs M-x shell buffer that needs to know EMACSDATA? It's
> not set in shells spawned by a GNU/Linux build.

Consider the case when the user sets this in the parent shell.  Then a
sub-shell will inherit it, and so will a sub-Emacs.

Don't know if this is the problems with ns, though.