+ ;; KLUDGE: The reason these clauses aren't directly parallel is
+ ;; that we need to use the internal CLASSOID structure ourselves,
+ ;; because we don't have CLASSes to work with until PCL is built.
+ ;; In the host, CLASSes have an approximately one-to-one
+ ;; correspondence with the target CLASSOIDs (as well as with the
+ ;; target CLASSes, modulo potential differences with respect to
+ ;; conditions).
+ #+sb-xc-host
+ (let ((old (class-of (find-classoid name)))
+ (new (class-of new-value)))
+ (unless (eq old new)
+ (bug "trying to change the metaclass of ~S from ~S to ~S in the ~
+ cross-compiler."
+ name (class-name old) (class-name new))))
+ #-sb-xc-host