- friend XBT_PUBLIC void intrusive_ptr_release(simgrid::s4u::Io* i);
- friend XBT_PUBLIC void intrusive_ptr_add_ref(simgrid::s4u::Io* i);
- friend simgrid::s4u::Storage; // Factory of IOs
+#ifndef DOXYGEN
+ friend Disk; // Factory of IOs
+ friend Storage; // Factory of IOs
+
+ ~Io() override = default;
+#endif