RFR JDK-8181425: Reflection API defend against issues with internal VM derived value type

[Mandy Chung]

> On Jun 21, 2017, at 1:25 AM, Maurizio Cimadamore <maurizio.cimadamore at oracle.com> wrote:
> 
> That's great - thanks Mandy. One last thing (which can also be addressed as a followup changeset) - it seems like the:
> 
> MinimalValueTypes_1_0.classHasValueType
> 
> method is basically just an heavy alias for the new 'isValueCapable' predicate - which also attempts to load the class. I wonder if we wouldn't be better off simply using the predicate, which seems less heavy as it doesn't strictly require generation/loading of DVT. Although I can imagine that if a client calls that method, he'll be interested in the DVT anyway.
> 

I had similar question and wonder if this is needed at all.  If one wants to load DVT, it can call getValueTypeClass instead.  I think we should simply remove it.

ValueType::classHasValueType is not used.  Should this be replaced with isValueCapable?  Is there a case no DVT defined for VCC (which would be the case classHasValueType would return false for VCC) but I suspect not?


> That said, from an API perspective, having one method instead of two slightly different one is better, so we should aim for it, I think.
> 

Agree.

> [but, as I said before, the changeset you have looks good enough to be pushed - so it's up to you whether you wanna try it now or later, ok? ]
> 

I will make this change once we agree what to do for ValueType::classHasValueType.

I’ll be traveling to Hong Kong tomorrow.  I don’t want to push something and not available.  I may push next Monday.

Mandy

> Thanks
> Maurizio
> 
> 
> 
> On 21/06/17 03:26, Mandy Chung wrote:
>>> On Jun 20, 2017, at 4:19 PM, Maurizio Cimadamore <maurizio.cimadamore at oracle.com> wrote:
>>> 
>>> The new version looks good - I wonder if we should add a dual method called isValueCapable(Class<?>) and use that for the assertion check? The method would look at the class, retrieve the @VCC annotation and return true if one such annotation exists.
>>> 
>>> As things stand, it is possible to pass classes to the loadValueClassType that are not VCC but which fail to trigger the assertion check.
>>> 
>>> Probably a nitpick - but since we're tweaking in this area…
>>> 
>> I added the isValueCapable method and made further clean up that I think
>> MinimalValueTypes_1_0 Valueclass is clearer.
>> 
>> http://cr.openjdk.java.net/~mchung/valhalla/webrevs/8181425/webrev.01/index.html
>> 
>> Mandy
>