RFR: 7093328: JVMTI: jvmtiPrimitiveFieldCallback always report 0's for static primitives

[Daniel D. Daugherty]

On 8/29/12 8:16 AM, Daniel D. Daugherty wrote:
> Logistics issue: This review request went out to OpenJDK alias, but
> I think this webrev is not accessible outside of Oracle. The webrev
> should be publicly accessible when the review is public. However,
> in this case, this is a one line fix so IMHO you could get away with
> a context diff in the suggested fix of the bug report.
>
> On 8/29/12 1:24 AM, Rickard Bäckman wrote:
>> Hi all,
>>
>> can I get a couple of reviews for the following bug fix:
>>
>> http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=7093328
>> webrev: http://rbackman.se.oracle.com/~rbackman/7093328/
>>
>> Thanks
>> /R
>
> Thumbs up.
>
> src/share/vm/prims/jvmtiTagMap.cpp
>     No content comments.
>
>     This is a perfect example of how casting can bite you. :-)
>
>     The buggy line:
>
>     1165     address addr = (address)k + offset;
>
>     dates back to the original implementation of this function:
>
>     src/share/vm/prims/SCCS/s.jvmtiTagMap.cpp
>     D 1.47 05/08/22 20:30:26 ab23780 77 76  01476/01330/01852
>     MRs:
>     COMMENTS:
>     6195957: further clean-up and caching of field maps
>
>     In the buggy code, a value is copied from the instanceKlass
>     at the offset instead of from the Java mirror. If the value
>     copied from the instanceKlass happened to match the expected
>     value, then that was pure luck.
>
>     The bug report claims that this last "worked" in 6u26. I suspect
>     that "working" is defined as returning a non-zero value.
>
> Dan

Rickard,

Very nice find:

> I did some research (archeology), the change that introduced this:
>
> changeset:   2223:c7f3d0b4570f
> user:        never
> date:        Fri Mar 18 16:00:34 2011 -0700
> summary:     7017732: move static fields into Class to prepare for perm ten removal

I had forgotten that static fields moved from the instanceKlass
into Class. The original code from 2005 did indeed work as expected
way back then. In fact, there were three such uses in jvmtiTagMap.cpp
back then and it looks like the other two uses were updated to use
the Java mirror and one was missed.

Dan