RFR: JDK-8211241: Missing obj equals in TemplateTable::fast_aldc

Daniel D. Daugherty daniel.daugherty at oracle.com
Thu Sep 27 20:37:01 UTC 2018

On 9/27/18 4:33 PM, Roman Kennke wrote:
> Included hotspot-runtime-dev because it's an interpreter bug, excluded
> hotspot-compiler dev, and also here's all the links:
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8211241

Thanks for adding the direct bug link.

> Webrev:
> http://cr.openjdk.java.net/~rkennke/JDK-8211241/webrev.00/
> It's never been quite clear to me where to put interpreter bugs.
> hotspot/runtime in Jira and hotspot-runtime-dev on mailing lists? Is
> that right?

Yes, the interpreter is owned by the Runtime team.


> Thanks, Roman
>> TemplateTable::fast_aldc compares the just-loaded reference with
>> Universe::the_null_sentinel. If it really is that null-sentinel, we may
>> get a false negative (with GCs like Shenandoah that allow both
>> from-space and to-space copies of an object to be around), and thus skip
>> NULL-ing the ref. In other words, it would allow to get
>> the-null-sentinel out into the wild as oop which can cause subtle and
>> not-so-subtle bugs.
>> Fix is easy, call cmpoop() which re-routes through GC-interface for GCs
>> that need it:
>> http://cr.openjdk.java.net/~rkennke/JDK-8211241/webrev.00/
>> Testing: hotspot/jtreg:tier1
>> Ok?
>> Roman

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