[Nestmates] Add a core reflection API to get nestmate information

[David Holmes]

Hi Peter,

On 17/11/2017 7:45 PM, Peter Levart wrote:
> Hi David,
> 
> On 11/16/2017 10:52 PM, David Holmes wrote:
>>>> John prefers to minimize exceptions for the Java API. :)
>>>
>>> Suppose that this is basic reflection API to get nestmate information 
>>> and that it will also be used for reflective access checks. For 
>>> example in jdk.internal.reflect.Reflection#verifyMemberAccess, which 
>>> is used 
>>
>> It isn't. The reflection API is purely for "external" use. Real access 
>> checks are performed in the same way as the VM access checks - as 
>> required - and will report the same exceptions in the same way.
>>
>> David 
> 
> Real access checks performed by bytecode(s), yes. But what about 
> reflective access checks - those performed by Method.invoke, 
> Field.[get|set], Constructor.newInstance? They will have to be revised 
> some day to include the nestmates. What facility should those methods 
> use to implement the checks (the guts of those checks is in 
> jdk.internal.reflect.Reflection#verifyMemberAccess).

Yes and the real nestmate access check for use by invoke etc has already 
been implemented in there.

http://hg.openjdk.java.net/valhalla/valhalla/file/df423aeaa8d1/src/java.base/share/classes/jdk/internal/reflect/Reflection.java

> Is the plan to have special internal native methods to facilitate that? 
> I don't quite understand why should a Class.isNestmateOf(Class) behave 
> any differently than real VM access check.

Purely because of the difference in exception handling. The view was 
that the reflection API should mostly "absorb" exceptions.

David

> Regards, Peter
>