CSR review for 8238358: Implementation of JEP 371: Hidden Classes

[Mandy Chung]

The javadoc and specdiff have been updated in place to reflect the 
recent discussion [1][2] to change the default of hidden classes that a 
hidden class may be unloaded even when the defining loader is reachable 
unless `ClassOption::STRONG` is specified such that the hidden class has 
the same strong relationship with its defining loader as the normal 
class has with its own defining loader.

javadoc/specdiff:
http://cr.openjdk.java.net/~mchung/valhalla/webrevs/hidden-classes/api/
http://cr.openjdk.java.net/~mchung/valhalla/webrevs/hidden-classes/specdiff/ 


JVMS 5.4.4 change:
http://cr.openjdk.java.net/~mchung/valhalla/webrevs/hidden-classes/Draft-JVMS-HiddenClasses.pdf 


Thanks
Mandy
[1] 
https://mail.openjdk.java.net/pipermail/valhalla-dev/2020-March/006889.html
[2] 
https://mail.openjdk.java.net/pipermail/valhalla-dev/2020-March/006911.html

On 3/9/20 2:00 PM, Mandy Chung wrote:
> Please review the CSR proposed for JEP 371 Hidden Classes [1].
>
> CSR:
>   https://bugs.openjdk.java.net/browse/JDK-8238359
>
> javadoc/specdiff:
> http://cr.openjdk.java.net/~mchung/valhalla/webrevs/hidden-classes/api/
> http://cr.openjdk.java.net/~mchung/valhalla/webrevs/hidden-classes/specdiff/ 
>
>
> JVMS 5.4.4 change:
> http://cr.openjdk.java.net/~mchung/valhalla/webrevs/hidden-classes/Draft-JVMS-HiddenClasses.pdf 
>
>
> A brief summary of the changes:
>
> 1. A new Lookup::defineHiddenClass method is the API to create a 
> hidden class.
> 2. A new Lookup.ClassOption enum class defines NESTMATE and WEAK 
> option that
>    can be specified when creating a hidden class.
> 3. A new Class::isHiddenClass method tests if a class is a hidden class.
> 4. Field::setXXX method will throw IAE on a final field of a hidden class
>    regardless of the value of the accessible flag.
> 5. Class::getNestMembers is updated not to throw any exception when it 
> fails
>    to validate the nest membership.  Instead this method will return all
>    members that are listed in `NestMembers` attribute if present and
>    determined to have the same nest host as this class.
>
> We uncovered a bug in Lookup::defineClass spec throws LinkageError and 
> intends
> to have the newly created class linked.  However, the implementation 
> in 14
> does not link the class.  A separate CSR proposes to update the 
> implementation
> to match the spec - please also review:
>    https://bugs.openjdk.java.net/browse/JDK-8240338
>
> This is tracked as a separate JBS issue JDK-8238195 that is fixed in 
> this patch.
>
> The code review will be posted separately.
>
> Thanks
> Mandy
> [1] https://openjdk.java.net/jeps/371
> [2] JDK-8230502 Add support in JVM TI and JDI for hidden classes
> [3] JDK-8219607 Add support in Graal and AOT for hidden and weak class
> [4] 
> https://mail.openjdk.java.net/pipermail/valhalla-dev/2020-March/006872.html
>