RFR: 8360288: Shenandoah crash at size_given_klass in op_degenerated [v3]

[Aleksey Shipilev]

On Tue, 15 Jul 2025 20:28:19 GMT, William Kemper <wkemper at openjdk.org> wrote:

>> Both degenerated and full GCs unload classes before reclaiming unmarked humongous objects. This may result in a null klass pointer dereference when reclaiming unmarked humongous objects. Prior to this change, the number of regions occupied by a humongous object was computed from the size of the object. To avoid using `oop::size` after class unloading on an unmarked object, Shenandoah now trashes the humongous start region followed by subsequent continuation regions.
>
> William Kemper has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Micro optimizations

Yeah, no big deal, just not a great commit message :)

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PR Comment: https://git.openjdk.org/jdk/pull/26256#issuecomment-3079715774