func (i *specialsIter) unlinkAndNext() *special {
	cur := i.s
	i.s = cur.next
	*i.pprev = i.s
	return cur
}

// freeSpecial performs any cleanup on special s and deallocates it.
// s must already be unlinked from the specials list.
func freeSpecial(s *special, p unsafe.Pointer, size uintptr) {
	switch s.kind {
	case _KindSpecialFinalizer:
		sf := (*specialfinalizer)(unsafe.Pointer(s))