[Nestmates] RFR: 8187768 and 8189940 - nest host resolution and exceptions

David Holmes david.holmes at oracle.com
Mon Oct 30 01:24:12 UTC 2017

On 27/10/2017 6:04 PM, David Holmes wrote:
> Combined webrev: http://cr.openjdk.java.net/~dholmes/8187768/webrev/
> bug: https://bugs.openjdk.java.net/browse/JDK-8187768
> 8187768: [Nestmates] Improve exception information related to 
> bad/missing nest-host class
> This work implements the latest specification proposal for nest-host 
> resolution and validation exceptions:
> http://cr.openjdk.java.net/~dlsmith/nestmates.html
> and also provides better diagnostic information for the exceptions that 
> occur. Key features:
> - instanceKlass::nest_host():
>    - passes through most resolution related exceptions
>    - replaces NoClassDefFoundError with a  new NCDFE with the original 
> as the cause and a message "Unable to load nest-host class of %s" to 
> give context to the exception
>    - throws IllegalAccessError when nest membership validation fails (as 
> per updated spec) with appropriate error message

I realized that nest_host() should only throw IllegalAccessError when 
called from has_nestmate_access_to(). I'll address that when adding the 
reflection API support.


> - Reflection::verify_field_access can now more obviously result in 
> pending exceptions
> - All callers of Reflection::verify_field_access watch for pending 
> exceptions and don't replace them with their own IllegalAccessErrors.
> - runtime/Nestmates/membership tests have been completely rewritten to 
> test updated spec - including the need to test for failures in the 
> calling class's nest-host resolution and in the target class's nest-host 
> resolution.
> While working here I rediscovered the Xcomp problem where the JIT tries 
> to load a nest-host class when not allowed to:
> bug: https://bugs.openjdk.java.net/browse/JDK-8189940
> 8189940:  [Nestmates] VM Compiler thread needs to load nest-host class!
> The fix here was to check in InstanceKlass::nest_host() if we are on a 
> thread that can't call java, and that we may have to load a nest-host 
> class. In that case we return NULL, causing has_nestmate_access_to to 
> return false, it's callers post IllegalAccessError and the JIT sees that 
> failure and falls back to going through the interpreter to complete its 
> work.
> runtime/Nestmates tests all pass in normal and Xcomp mode now.
> Thanks,
> David

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