nestmates spec open issues

David Holmes david.holmes at
Tue Oct 31 01:45:39 UTC 2017

Hi John,

On 26/10/2017 2:03 PM, John Rose wrote:
> On Oct 25, 2017, at 8:54 PM, David Holmes <david.holmes at> wrote:
>> Though I still feel uncomfortable lying about the nest-host. I don't see what usecases would be served by doing that. Other than informational uses, I can't see a reason to actually identify the nest-host which would not be impacted by lying about that identity. The only truly useful query is for nestmate access and that doesn't need to expose the identity of the nest-host and conservatively rejects access if anything goes wrong.
> I'm sympathetic to this, but that implies that getNestHost should return null
> rather than this for a non-nesty class.  I think it's more valuable that getNestHost
> return 'this' for non-nesty classes, and therefore also for broken-nest classes.

Ok. The JVMS is proposed to state:

"A class or interface without a NestHost attribute belongs to the nest 
hosted by itself."

That covers top-level classes and all types compiled with an earlier 
version of javac. If we consider a class with an unresolvable, or 
otherwise invalid, NestHost attribute, as-if it had no NestHost 
attribute, then returning "this" is the natural response for that case.

>> Bottom line for my personal preferences:
>> - hasNestMateAccess: never throws, always returns true or false
> Yes!


>> - getNestHost(): throw if the host isn't there or else a membership validation check fails
> See above.

getNestHost() won't throw, as above.

Suggestion: also add getValidatedNestHost() that can throw?

>> - getNestMembers(): throw if any nest member isn't there or a membership validation check fails
> As I said before, I don't mind this choice.  Especially if we have hasNestMateAccess.

Okay. getNestMembers() will throw.

Now the question is what to throw? Dan's spec change for the access 
checking allows resolution/linkage errors (and VME) to pass through, and 
specifies IllegalAccessError for an invalid nest membership claim. The 
IAE makes sense in the context of an access check - though could also be 

But in the context of the reflection API, getNestMembers or 
getValidatedNestHost, IllegalAccessError doesn't really make sense - 
we're not trying to access anything. ICCE seems more fitting there.


>> Cheers,
>> David

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