8361363: ShenandoahAsserts::print_obj() does not work for forwarded objects and UseCompactObjectHeaders

[vish-chan]

Backport of:

JDK-8361363 - ShenandoahAsserts::print_obj() does not work for forwarded objects and UseCompactObjectHeaders
This change fixes Shenandoah’s print_obj() so it correctly prints forwarded objects when compact object headers are enabled, instead of crashing by reading an invalid klass from the forwarding pointer.

Risk is Low as this is a clean backport and the changes are in diagnostic code.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• JDK-8361363 needs maintainer approval

Issue

• JDK-8361363: ShenandoahAsserts::print_obj() does not work for forwarded objects and UseCompactObjectHeaders (Bug - P4 - Approved)

Reviewing

Using git

Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk25u-dev.git pull/28/head:pull/28
$ git checkout pull/28

Update a local copy of the PR:
$ git checkout pull/28
$ git pull https://git.openjdk.org/jdk25u-dev.git pull/28/head

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Checkout this PR locally:
$ git pr checkout 28

View PR using the GUI difftool:
$ git pr show -t 28

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Download this PR as a diff file:
https://git.openjdk.org/jdk25u-dev/pull/28.diff

Using Webrev

Link to Webrev Comment

[bridgekeeper]

👋 Welcome back vish-chan! A progress list of the required criteria for merging this PR into master will be added to the body of your pull request. There are additional pull request commands available for use with this pull request.

[openjdk]

@vish-chan This change now passes all automated pre-integration checks.

ℹ️ This project also has non-automated pre-integration requirements. Please see the file CONTRIBUTING.md for details.

After integration, the commit message for the final commit will be:

8361363: ShenandoahAsserts::print_obj() does not work for forwarded objects and UseCompactObjectHeaders

You can use pull request commands such as /summary, /contributor and /issue to adjust it as needed.

At the time when this comment was updated there had been 3 new commits pushed to the master branch:

• a3b1fb8: 8371316: Adjust assertion (GC pause time cannot be smaller than the sum of each phase) in G1GCPhaseTimes::print
• 082ecfa: 8370393: Cleanup handling of ancient Windows versions from GetJavaProperties java_props_md
• 5696531: 8343474: [updates] Customize README.md to specifics of update project

Please see this link for an up-to-date comparison between the source branch of this pull request and the master branch.
As there are no conflicts, your changes will automatically be rebased on top of these commits when integrating. If you prefer to avoid this automatic rebasing, please check the documentation for the /integrate command for further details.

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[openjdk]

This backport pull request has now been updated with issue from the original commit.

[openjdk]

⚠️ @vish-chan This change is now ready for you to apply for maintainer approval. This can be done directly in each associated issue or by using the /approval command.

[vish-chan]

/approval request for backport of JDK-8361363 which fixes Shenandoah’s print_obj() so it correctly prints forwarded objects when compact object headers are enabled, instead of crashing by reading an invalid klass from the forwarding pointer.
Risk is Low as this is a clean backport and the changes are in diagnostic code.

[mlbridge]

Webrevs

• 00: Full (a955fe37)

[openjdk]

@vish-chan
8361363: The approval request has been created successfully.

[vish-chan]

/integrate

[openjdk]

@vish-chan
Your change (at version a955fe3) is now ready to be sponsored by a Committer.

[phohensee]

/sponsor

[openjdk]

Going to push as commit 2121b3b.
Since your change was applied there have been 3 commits pushed to the master branch:

• a3b1fb8: 8371316: Adjust assertion (GC pause time cannot be smaller than the sum of each phase) in G1GCPhaseTimes::print
• 082ecfa: 8370393: Cleanup handling of ancient Windows versions from GetJavaProperties java_props_md
• 5696531: 8343474: [updates] Customize README.md to specifics of update project

Your commit was automatically rebased without conflicts.

[openjdk]

@phohensee @vish-chan Pushed as commit 2121b3b.

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