RFR: 8278123: serviceability/dcmd/vm/ClassLoaderStatsTest.java failing with java.lang.AssertionError: Should have a hidden class

[Chris Plummer]

On Thu, 28 Apr 2022 00:49:03 GMT, Leonid Mesnik <lmesnik at openjdk.org> wrote:

>> test/hotspot/jtreg/serviceability/dcmd/vm/ClassLoaderStatsTest.java line 178:
>> 
>>> 176:     static {
>>> 177:         try {
>>> 178:             // Create a hidden class, keep reference in the case if GC happens
>> 
>> "Create a hidden class. Keep a reference in case a GC happens."
>> 
>> I hadn't noticed the original comment when first suggesting making the Class reference static. I wonder what was meant by "non-strong class".
>
> This line added by  8238358: Implementation of JEP 371: Hidden Classes which has many co-authors. Hope someone could provide an explanation during this review.
> 
> It might be possible that the goal was to verify that  VM.classloader_stats provide might provide info for non-reachable clasees. However it makes test to fragile, since can't block class unloading now.

Yes, that seems to be the case, and you are right that it is not something that is safe to assume.

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PR: https://git.openjdk.java.net/jdk/pull/8438