I updated my Guix installation and user profile yesterday, and 
since then Emacs has started crashing. I've attached the output of 
running "emacs -Q".

I'm using my own branch of Guix that is based on 
089a2c51ff4d4d8ddd180001b25535019c0d35c0, but I haven't modified 
Emacs. As a workaround I am now using emacs-no-x-toolkit, which 
does not have this problem.

The output claims that it's a GTK bug, but I have not experienced 
it before today.