(lambda (features)
      (flet ((enable (x)
               (pushnew x features))
             (disable (x)
               (setf features (remove x features))))
        ;; Threading support, available only on x86/x86-64 Linux, x86 Solaris
        ;; and x86 Mac OS X (experimental).
        (enable :sb-thread)
        (enable :sb-doc)
        (enable :sb-package-locks)
        (enable :sb-unicode)
        (enable :sb-source-locations)))