[9] RFR (XS): 8169000: Define reference reachability more precisely in java.lang.ref package

[Zoltán Majó]

Hi Peter,


On 11/11/2016 04:33 PM, Peter Levart wrote:
> [...]
> I think the wording could be even less specific about "detecting" the 
> reachability of the reference object. For example:
>
> ... If a registered reference becomes unreachable itself, then it 
> *may* never be enqueued.
>
>
> In addition, the situations that describe when the reference *may* not 
> be enqueued could be expanded. For example:
>
> ... If a registered reference ceases to be strongly reachable itself, 
> then it *may* never be enqueued.
>

thank you for the suggestion and for the example program!

Here is the updated webrev with the updated text:

http://cr.openjdk.java.net/~zmajo/8169000/webrev.01/

Does that look reasonable to you?

Thank you!

Best regards,


Zoltan

>
> The following modified test shows this situation:
>
>
> public class WeaklyReachablePhantomReference {
>
>     static ReferenceQueue<Object> rq = new ReferenceQueue<>();
>     static WeakReference<PhantomReference<Object>> weakRefRef;
>
>     public static void main(final String[] args) throws Exception {
>         weakRefRef = new WeakReference<>(
>             new PhantomReference<>(
>                 new Object(),
>                 rq
>             )
>         );
>         // <- here
>         System.gc();
>         Reference rmRef = rq.remove(1000);
>         if (rmRef == null) {
>             System.out.println("PhantomReference NOT enqueued");
>         } else {
>             System.out.println("PhantomReference enqueued");
>         }
>     }
> }
>
>
> At "<-- here" the PhantomReference object becomes weakly reachable 
> while its referent becomes phantom reachable and this is enough for 
> PhantomReference to not be enqueued.
>
>
> Regards, Peter
>