RFR: 8316994: Avoid modifying ClassLoader and Module objects during -Xshare:dump

[Calvin Cheung]

On Wed, 27 Sep 2023 05:05:31 GMT, Ioi Lam <iklam at openjdk.org> wrote:

> When dumping the module graph, we set some native pointers in `ClassLoader` and `Module` objects to null.
> 
> We used to modify the copies of these objects in the actual heap. This makes `InstanceKlass::class_loader_data()` return the wrong value inside `VM_PopulateDumpSharedSpace`.
> 
> Instead, this PR modifies the copies of the objects in the `ArchiveHeapWriter` buffer. This also means that the `HeapShared::restore_loader_data()` function is no longer needed.

LGTM

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Marked as reviewed by ccheung (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/15937#pullrequestreview-1647672353