RFR: 8369642: [ubsan] nmethod::nmethod null pointer passed as argument 2 to memcpy

[Matthias Baesken]

On Mon, 13 Oct 2025 23:56:20 GMT, Chad Rakoczy <duke at openjdk.org> wrote:

> [JDK-8316694](https://bugs.openjdk.org/browse/JDK-8316694) introduced a counter so that the nmethod immutable data can be shared between relocated nmethods to eliminate an unnecessary copy. The counter is aligned in memory so that must be taken into account when calculating the amount of memory used by the counter

This fixes the ubsan - issue reported !

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Marked as reviewed by mbaesken (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/27778#pullrequestreview-3335149901