RFR (S) 8073532: jmap -heap fails after generation array removal

[Mikael Gerdin]

Hi all,

Please review this small fix to an issue introduced by JDK-8061802.

The API in the SA is pretty strange, but a "Field" object basically only 
encodes the type and offset of a non-static field, so to get what the 
field points to you must supply "this.addr", which is the base address 
of the containing object.

An alternate fix could have been to call getAddress(addr), but a quick 
look at the other usages of AddressField seems to suggest that 
getValue(addr) is the preferred way.

Webrev: http://cr.openjdk.java.net/~mgerdin/8073532/webrev.0/
Bug: https://bugs.openjdk.java.net/browse/JDK-8073532

Testing:
Ran jdk/test/sun/tools/jmap/heapconfig/JMapHeapConfigTest.java with 
-XX:+UseSerialGC before/after fix.
Ran "jmap -heap" and inspected the output to verify that the correct 
output is produced with the fix applied:
== Before fix ==
Heap Usage:
Exception in thread "main" java.lang.reflect.InvocationTargetException
         at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
         at 
sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
         at 
sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
         at java.lang.reflect.Method.invoke(Method.java:498)
         at sun.tools.jmap.JMap.runTool(JMap.java:201)
         at sun.tools.jmap.JMap.main(JMap.java:130)
Caused by: sun.jvm.hotspot.types.WrongTypeException
         at 
sun.jvm.hotspot.types.basic.BasicField.getAddress(BasicField.java:246)
         at 
sun.jvm.hotspot.types.basic.BasicFieldWrapper.getAddress(BasicFieldWrapper.java:131)
         at 
sun.jvm.hotspot.memory.GenCollectedHeap.getGen(GenCollectedHeap.java:79)
         at sun.jvm.hotspot.tools.HeapSummary.run(HeapSummary.java:89)
         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.HeapSummary.main(HeapSummary.java:49)
         ... 6 more

== With fix ==
Heap Usage:
New Generation (Eden + 1 Survivor Space):
    capacity = 157941760 (150.625MB)
    used     = 14044472 (13.393852233886719MB)
    free     = 143897288 (137.23114776611328MB)
    8.892184055692427% used
Eden Space:
    capacity = 140443648 (133.9375MB)
    used     = 14044472 (13.393852233886719MB)
    free     = 126399176 (120.54364776611328MB)
    10.000076329546781% used
 From Space:
    capacity = 17498112 (16.6875MB)
    used     = 0 (0.0MB)
    free     = 17498112 (16.6875MB)
    0.0% used
To Space:
    capacity = 17498112 (16.6875MB)
    used     = 0 (0.0MB)
    free     = 17498112 (16.6875MB)
    0.0% used
tenured generation:
    capacity = 350945280 (334.6875MB)
    used     = 0 (0.0MB)
    free     = 350945280 (334.6875MB)
    0.0% used

/Mikael