RFR: JDK-81518: Could not parse core image with JSnap.

[Yasumasa Suenaga]

Hi all,

When I use `jhsdb jsnap` to get PerfCounter from core images, I encountered NPE: 
------------- 
Exception in thread "main" java.lang.NullPointerException 
        at sun.jvm.hotspot.tools.JSnap.run(JSnap.java:45) 
        at sun.jvm.hotspot.tools.Tool.startInternal(Tool.java:260) 
        at sun.jvm.hotspot.tools.Tool.start(Tool.java:223) 
        at sun.jvm.hotspot.tools.Tool.execute(Tool.java:118) 
        at sun.jvm.hotspot.tools.JSnap.main(JSnap.java:67) 
        at sun.jvm.hotspot.SALauncher.runJSNAP(SALauncher.java:352) 
        at sun.jvm.hotspot.SALauncher.main(SALauncher.java:404) 
------------- 

PerfMemory::destroy() clears all members which are used in JSnap. 
Thus NPE is occurred. 

I uploaded webrev for this issue.
Could you review it?

  http://cr.openjdk.java.net/~ysuenaga/JDK-8151815/webrev.00/

I cannot access JPRT.
So I need a Sponsor.


Thanks,

Yasumasa