(use giflib)

;; when slurp-gif is used the second time, you get:
;; Error: (slurp-gif) Failed to read from given file

(for-each
 (lambda (arg)
   (let ((gif (open-gif arg)))
     (slurp-gif gif)
     (printf "~a: ~ax~a\n" arg (gif-width gif) (gif-height gif))
     ;; problematic, but only in combination with slurp-gif
     (close-gif gif)))
 (command-line-arguments))

;; usage: ./giffail foo.gif bar.gif