span> that translates to the ML
value <span class=font-it>v</span>.</p><p>IDL pointers of kind <span class=machine><span class=font-tt>ptr</span></span> are mapped to a <span class=machine><span class=font-tt>Com.opaque</span></span> type.
This is an abstract type that encapsulates the C pointer without
attempting to convert it to an ML data structure.</p><p>IDL pointers of kind <span class=machine><span class=font-tt>ignore</span></span> denote struct fields and function
parameters that need not be exposed