Re: Can I easily install GNU Emacs 27.1.50 via Guix?

[Carlo Zancanaro]

Hi Simon,

On Fri, Dec 18 2020, zimoun wrote:
> Is your point that:
>
> ...

My point is: Guix manipulates environment variables in a way that 
can, and does, break "foreign" programs when Guix's programs 
launch "foreign" programs. We should consider this a bug. This bug 
might be hard, or even impossible, to resolve but we should 
consider it a bug nonetheless.

Lots of variables are safe to manipulate, like COLUMNS, or TERM, 
but some are dangerous, like GTK_PATH, XDG_DATA_DIRS, and 
LD_LIBRARY_PATH (among others). This isn't always a problem, but 
sometimes it is.

> However, on my machine running Guix on the top of Debian, I get:
>
> --8<---------------cut 
> here---------------start------------->8---
> guix environment --ad-hoc emacs grep coreutils --pure
> env | grep GTK_PATH
> /usr/bin/evince # Works!
>
> emacs -q -f shell
> sh-5.0$ env | grep GTK_PATH
> GTK_PATH=/gnu/store/v3rqcgz6chnmv2sg7lgf4s9kv2xyb5rl-gtk+-3.24.23/lib/gtk-3.0
> sh-5.0$ /usr/bin/evince
>
> (evince:21780): GLib-GIO-ERROR **: 11:24:25.706: No GSettings 
> schemas are installed on the system
> Trace/breakpoint trap
> sh-5.0$ unset GTK_PATH
> sh-5.0$ env | grep GTK_PATH
> sh-5.0$ /usr/bin/evince
>
> (evince:25064): GLib-GIO-ERROR **: 11:32:22.826: No GSettings 
> schemas are installed on the system
> Trace/breakpoint trap
> --8<---------------cut 
> here---------------end--------------->8---
>
> So the story seems more complicated than GTK_PATH. :-)

Did you try opening the print dialog in evince? If you did, then 
you should have seen different behaviour when GTK_PATH was set 
compared to when it wasn't. Namely, when GTK_PATH was set you 
should have seen some messages like this in your shell:

(evince:31345): Gtk-WARNING **: 22:26:55.204: 
/gnu/store/0vi459fa3b36b5xw8gkxmvfpqz48cyqr-gtk+-3.24.23/lib/gtk-3.0/3.0.0/printbackends/libprintbackend-cups.so: 
cannot open shared object file: Permission denied

The problem is that GTK_PATH is checked for libraries first, where 
it finds the above library and tries and fails to load it. It does 
not fall back to the default paths, but rather treats loading that 
library as having failed, and thus evince cannot print. When 
GTK_PATH is unset it checks the default locations, and 
successfully finds and loads the library, and thus evince can 
print.

Carlo