8296433: Encountered null CLD while loading shared lambda proxy class

[calvinccheung]

Please review this simple fix for calling load_shared_class(), which initializes class_loader_data prior to set_nest_host() in SystemDictionary::load_shared_lambda_proxy_class(). Otherwise, a null class_loader_data would be encountered in set_nest_host(); it would fail the added assertion in set_nest_host().

Passed tiers 1 and 2 testing on Oracle supported platforms.

---

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Issue

• JDK-8296433: Encountered null CLD while loading shared lambda proxy class

Reviewers

• Ioi Lam (@iklam - Reviewer)
• David Holmes (@dholmes-ora - Reviewer)

Reviewing

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[calvinccheung]

/label add hotspot-runtime

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[openjdk]

@calvinccheung
The hotspot-runtime label was successfully added.

[mlbridge]

Webrevs

• 00: Full (80e2f877)

[iklam]

Looks good.

I think the reason that we've never crashed is because we return at line 431:

jdk/src/hotspot/share/classfile/classLoaderData.cpp

Lines 420 to 432 in 1169dc0

	void ClassLoaderData::record_dependency(const Klass* k) {
	assert(k != NULL, "invariant");
	ClassLoaderData * const from_cld = this;
	ClassLoaderData * const to_cld = k->class_loader_data();
	// Do not need to record dependency if the dependency is to a class whose
	// class loader data is never freed. (i.e. the dependency's class loader
	// is one of the three builtin class loaders and the dependency's class
	// loader data has a ClassLoader holder, not a Class holder.)
	if (to_cld->is_permanent_class_loader_data()) {
	return;
	}

CDS only supports lambda proxy classes for the built-in loaders. So when we call ClassLoaderData::record_dependency with a NULL this, the this pointer is never dereferenced (at least for our current C++ compilers).

Anyway, passing a NULL this is undefined behavior, so it's good to get rid of it.

[openjdk]

@calvinccheung 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:

8296433: Encountered null CLD while loading shared lambda proxy class

Reviewed-by: iklam, dholmes

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 5 new commits pushed to the master branch:

• 1169dc0: 8296447: RISC-V: Make the operands order of vrsub_vx/vrsub_vi consistent with RVV 1.0 spec
• 4c80dff: 8296435: RISC-V: Small refactoring for increment/decrement
• 47d2c7b: 8295376: Improve debug agent virtual thread performance when no debugger is attached
• 76790ad: 8295673: Deprecate and disable legacy parallel class loading workaround for non-parallel-capable class loaders
• b6738c1: 8295663: Rephrase introduction to testing.md

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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[dholmes-ora]

Looks good!

Thanks

[calvinccheung]

Thanks Ioi and David.

/integrate

[openjdk]

Going to push as commit d04d656.
Since your change was applied there have been 9 commits pushed to the master branch:

• 74f2b16: 8295303: cleanup debug agent's confusing use of EI_GC_FINISH
• 0ee25de: 8296504: Memory leak in G1PLABAllocator::PLABData
• dd5d4df: 8295658: G1: Refactor G1SegmentedArray to indicate that it is an allocator
• cf65605: 8296445: C++ syntax error in jdwpTransport.h
• 1169dc0: 8296447: RISC-V: Make the operands order of vrsub_vx/vrsub_vi consistent with RVV 1.0 spec
• 4c80dff: 8296435: RISC-V: Small refactoring for increment/decrement
• 47d2c7b: 8295376: Improve debug agent virtual thread performance when no debugger is attached
• 76790ad: 8295673: Deprecate and disable legacy parallel class loading workaround for non-parallel-capable class loaders
• b6738c1: 8295663: Rephrase introduction to testing.md

Your commit was automatically rebased without conflicts.

[openjdk]

@calvinccheung Pushed as commit d04d656.

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