[foreign-memaccess] RFR: 8253025: Add support for registering a segment with a Cleaner [v2]

[Maurizio Cimadamore]

On Fri, 11 Sep 2020 15:08:11 GMT, Paul Sandoz <psandoz at openjdk.org> wrote:

>> Maurizio Cimadamore has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Addressed review comments
>>   Beefed up test
>
> test/jdk/java/foreign/TestCleaner.java line 97:
> 
>> 95:     enum SegmentFunction implements Function<MemorySegment, MemorySegment> {
>> 96:         IDENTITY(Function.identity()),
>> 97:         CLOSE(s -> { s.close(); return s; }),
> 
> Won't that just skip cleaner registration, making the test redundant for that case? I guess for this case it should be
> called after registration?

Not really - note that the function is called after registration:
MemorySegment segment = makeSegment(segmentState);
        // register cleaners before
        for (int i = 0 ; i < n ; i++) {
            segment.registerCleaner(cleanerFactory.get());
        }
        segment = segmentFunction.apply(segment); // <-------------------------
So, the test here is useful: it tests that the cleaner registered before close() can't really call the cleanup action
multiple times if the segment has also been closed explicitly.

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PR: https://git.openjdk.java.net/panama-foreign/pull/320