RFR: 8337981: ShenandoahHeap::is_in should check for alive regions

[Kelvin Nilsen]

On Fri, 18 Apr 2025 20:14:49 GMT, William Kemper <wkemper at openjdk.org> wrote:

> Need this to complete partial backport of related work in early change.

Thanks for backport

-------------

Marked as reviewed by kdnilsen (Committer).

PR Review: https://git.openjdk.org/shenandoah-jdk21u/pull/181#pullrequestreview-2779589256