RFR: JDK-8163808 fix vtable assertion and logging for older classfiles

Lois Foltan lois.foltan at oracle.com
Fri Aug 12 15:56:13 UTC 2016

On 8/12/2016 11:47 AM, Karen Kinnear wrote:
> Lois,
> Thank you for the review and the question.
> The new overriding rules were fixed for JDK-4766230 in JDK7 based on discussions between
> Alex Buckley, David Holmes, Vladimir Ivanov and myself. Today we would have modified the specification
> to clarify how the fix applies to the different classfile versions - at the time we left the old classfile versions
> obeying the previous version of the JVMS. And yes, that was explicitly the overriding rule (JVMS 5.4.5 Overriding) - i.e. does my
> class method override an inherited class method - and so it depends on the classfile version of the current
> class which we are processing and for whom we are calculating the overriding rules.
> The classfile-version specific logic for this was added in 2009. This fix does not change the logic for inheritance
> and overriding at all. What it does change is the vtable pre-calculation of expected size for older classfiles to
> match the usage logic, so simply an internal inconsistency fix.

Got it, thanks for the explanation!

> thanks,
> Karen
>> On Aug 12, 2016, at 10:11 AM, Lois Foltan <lois.foltan at oracle.com> wrote:
>> Hi Karen,
>> Looks good.  For my clarification, it doesn't matter what the version of the supers are?  The transitive over-ride behavior is only governed by the version of the current class whose vtable is being constructed, correct?
>> Thanks,
>> Lois
>> On 8/11/2016 5:07 PM, Karen Kinnear wrote:
>>> Please review:
>>> https://bugs.openjdk.java.net/browse/JDK-8163808
>>> http://cr.openjdk.java.net/~acorn/8163808.hs/webrev
>>> Bug: For classfiles before class file version 51, JVMS did not support transitive over-ride behavior.
>>> Implementation needed to check this in three places, not just one. Vtable size calculation is only exact
>>> for later classfile versions.
>>> Also fixed vtable logging output - since the method name-and-sig printing was changed to also print
>>> the holder’s class name, we do not need to print the holder’s class name separately - it was printing twice.
>>> Testing: linux-x64-slowdebug
>>> rbt hs-nightly-runtime.js
>>> jck vm,lang, api.java.lang
>>> small invocation tests
>>> thanks,
>>> Karen

More information about the hotspot-runtime-dev mailing list