[foreign] RFR: 8229857: scope inference on pointer to pointer is not friendly

[Henry Jen]

Hi,

Please review a webrev[1] that change the scope of dereferenced Pointer to unchecked instead of using the scope of containing Pointer.

A Pointer to a pointer is storing the address of target pointer in the containing Pointer, where the scope is not necessary related. A Pointer instance with address allocated from Java land will have a Scope, but an address obtained from the native code doesn’t(as the runtime would not know, only developer can know).

In cases where a Java allocated Pointer was send to native side and receive back, it’s possible to implement some scope inference to maintaining a table(limited or complete) for Pointers passed into native side. Otherwise, when a Pointer is used only on Java side, the scope is always there.

This webrev does not implement a scope inference mechanism, but rather provide an API for developer to explicitly assign a Scope that developer believe the Pointer should have if the Pointer doesn’t have one already.

This webrev also move the UNCHECKED into Scope, and use null value for now. I believe UNCHECKED scope should be different from global scope as it should be very limited and not allowing any allocation from it. Basically, an Pointer with UNCHECKED scope is just an address.

Thoughts?

Cheers,
Henry

[1] http://cr.openjdk.java.net/~henryjen/panama/8229857/0/webrev