RFR: 8357919: Arena::allocate returns segments with address zero if the segment length is zero after JDK-8345687

[Maurizio Cimadamore]

On Wed, 28 May 2025 09:06:57 GMT, Per Minborg <pminborg at openjdk.org> wrote:

> After https://bugs.openjdk.org/browse/JDK-8345687 was integrated, zero-length segments always have an address of zero. This may cause problems in certain native methods that can receive segments and/or buffers derived from segments.
> 
> This PR also guards for overflow for extremely large allocation requests.

Very good catch -- and good thing you added more tests! In the PR I linked, it seems that a test has been added for this case -- but sadly that test doesn't check for `address() != 0` -- you have now fixed that -- thanks.

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Marked as reviewed by mcimadamore (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/25485#pullrequestreview-2874495380