RFR: CODETOOLS-7902944: JMH: Avoid direct weak references in Blackhole.consume(Object) [v2]

[Aleksey Shipilev]

> CODETOOLS-7901867 wrapped the stored object reference with a `WeakReference`. This unfortunately fails with Value Type boxes that throw the exceptions like:
> 
> 
> java.lang.IllegalArgumentException: cannot reference a primitive type: org.openjdk.PrimitiveClasses$Value
> at java.base/java.lang.ref.Reference.<init>(Reference.java:495)
> at java.base/java.lang.ref.Reference.<init>(Reference.java:489)
> at java.base/java.lang.ref.WeakReference.<init>(WeakReference.java:62)
> at org.openjdk.jmh.infra.Blackhole.consumeFull(Blackhole.java:515)
> at org.openjdk.jmh.infra.Blackhole.consume(Blackhole.java:315)
> at org.openjdk.jmh_generated.PrimitiveClasses_test_jmhTest.test_avgt_jmhStub(PrimitiveClasses_test_jmhTest.java:190)
> at org.openjdk.jmh_generated.PrimitiveClasses_test_jmhTest.test_AverageTime(PrimitiveClasses_test_jmhTest.java:152)
> at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
> at java.base/jdk.internal.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:78)
> at java.base/jdk.internal.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
> at java.base/java.lang.reflect.Method.invoke(Method.java:568)
> at org.openjdk.jmh.runner.BenchmarkHandler$BenchmarkTask.call(BenchmarkHandler.java:470)
> at org.openjdk.jmh.runner.BenchmarkHandler$BenchmarkTask.call(BenchmarkHandler.java:453)
> at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
> at java.base/java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:515)
> at java.base/java.util.concurrent.FutureTask.run(FutureTask.java:264)
> at java.base/java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1135)
> at java.base/java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:635)
> at java.base/java.lang.Thread.run(Thread.java:831)
> 
> 
> Wrapping in `WeakReference` is not reliable anyway, so it might make more sense to drop it.

Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:

  Wrap with Holder

-------------

Changes:
  - all: https://git.openjdk.java.net/jmh/pull/42/files
  - new: https://git.openjdk.java.net/jmh/pull/42/files/d1d15846..7011be4f

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jmh&pr=42&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jmh&pr=42&range=00-01

  Stats: 11 lines in 1 file changed: 9 ins; 0 del; 2 mod
  Patch: https://git.openjdk.java.net/jmh/pull/42.diff
  Fetch: git fetch https://git.openjdk.java.net/jmh pull/42/head:pull/42

PR: https://git.openjdk.java.net/jmh/pull/42