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

[Paul Sandoz]

On Fri, 11 Sep 2020 15:59:46 GMT, Maurizio Cimadamore <mcimadamore at openjdk.org> wrote:

>> 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.

Oh, doh!, i missed the code above.

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