RFR: 8353835: Implement JEP 500: Prepare to Make Final Mean Final [v2]

[Volkan Yazici]

On Tue, 30 Sep 2025 08:08:09 GMT, Alan Bateman <alanb at openjdk.org> wrote:

>> test/hotspot/jtreg/runtime/jni/mutateFinals/MutateFinalsTest.java line 109:
>> 
>>> 107:         String instanceMethod = list1.get(rand.nextInt(list1.size()));
>>> 108:         String staticMethod = list2.get(rand.nextInt(list2.size()));
>>> 109:         return Stream.of(instanceMethod, staticMethod);
>> 
>> * What is the rationale for choosing a random `pairOf(instanceMutator, classMutator)`?
>> * Does "instance mutator gets followed by a class mutator" have any particular importance for the tests they are used?
>> 
>> I was looking at this argument supplier and thinking of `Collections.shuffle()` over a list containing all method names, preferably, multiple times.
>
> The comment in the test description has ".. to avoid starting a child VM to test every mutation method". I'll see if I can improve this comment to make it clearer, or maybe your comment is that the method source needs this comment too?
> 
> The context here is that the test is launching a VM with -Xcheck:jni to check that it terminates with a "FATAL ERROR in native method".  Doing this for each of 18 cases would be expensive, can be 30+ seconds on macOS systems with debug builds. To keep the test execution down, the test choses one JNI function that attempts to mutate a final instance field, and one JNI function that attempts to mutate a static final field. The ensures the instance + static implementations are tested on each run. There is template expansion, and all functions will get exercised with enough runs.

I was curious why in particular `instance+static`, but not, say, `static+instance`, or `static1+instance1+static2+static3+instance3`, etc. That is, does checking the static field *after* the instance field have any significance. But AFAIU from your explanation, it does not. I don't have any further remarks.

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PR Review Comment: https://git.openjdk.org/jdk/pull/25115#discussion_r2390371924