> guix package -I local
glibc-utf8-locales	2.26.105-g0890d5379c	out	/gnu/store/3k6hl20c3b7big8ngrsl6mj9k8xav99d-glibc-utf8-locales-2.26.105-g0890d5379c

> guix package -I emacs
emacs	25.3	out	/gnu/store/y335nx4r08m6kg0yrna7spfwr4s05n36-emacs-25.3

How do I check which glibc Emacs is using?
I can think of `ldd emacs` but... Where is ldd? :p

A more general question: How do I find to which non-installed package a
filename belongs?

If Emacs happens to be using glibc 2.25, how could such a sitution occur
in the first place?  Why is glibc 2.25 needed at all?

-- 
Pierre Neidhardt