RFR: 8358537: (bf) JavaNioAccess::getBufferAddress bypasses direct buffer MemorySession state check

[Brian Burkhalter]

On Tue, 3 Jun 2025 21:39:54 GMT, Jorn Vernee <jvernee at openjdk.org> wrote:

>> Add package-scope `long java.nio.Buffer::address()` to simply return the value of the `address` instance variable; use this method in `JavaNioAccess::getBufferAddress`.
>
> test/jdk/java/nio/channels/etc/MemorySegments.java line 61:
> 
>> 59:      */
>> 60:     static Stream<Supplier<Arena>> arenaSuppliers() {
>> 61:         return Stream.of(Arena::global, Arena::ofAuto, Arena::ofConfined);
> 
> Why is using a shared arena causing the UOE to be thrown? I'd think that would be triggered by the use of heap buffers, but shared arena is for off-heap memory.

I thin it's running into this method in DirectBufferX:

    public long address() {
        MemorySessionImpl session = session();
        if (session != null) {
            if (session.ownerThread() == null && session.isCloseable()) {
                throw new UnsupportedOperationException("ByteBuffer derived from closeable shared sessions not supported");
            }

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PR Review Comment: https://git.openjdk.org/jdk/pull/25631#discussion_r2125050873