RFR 8156073 : 2-slot LiveStackFrame locals (long and double) are incorrect

Mandy Chung mandy.chung at oracle.com
Tue Aug 23 04:30:21 UTC 2016

Hi Brent,

> On Aug 17, 2016, at 1:05 PM, Brent Christian <brent.christian at oracle.com> wrote:
> Hi,
> Please review this StackWalker fix in hotspot for 8156073, "2-slot LiveStackFrame locals (long and double) are incorrect"
> Bug: https://bugs.openjdk.java.net/browse/JDK-8156073
> Webrev: http://cr.openjdk.java.net/~bchristi/8156073/webrev.01/

This looks a good stop-gap fix that will allow further experiments of using LiveStackFrame. The new test has long lines that should be wrapped.

> On 08/17/2016 02:28 PM, Frederic Parain wrote:
>> Another question: is it guaranteed that an unused slot from
>> a pair-slot is always zero? This is not written in the JVM spec,
>> and I don't remember that the JVM zeroes unused slots.
> Interesting.  I've only seen zeros in my testing of locally-declared longs.  (How does other VM code account for unused local slots?).

We need to follow up this issue to understand what the interpreter and compiler do for this unused slot and whether it’s always zero out.

We should file JBS issue to follow it up separately.


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