8313323: javac -g on a java file which uses unnamed variable leads to ClassFormatError when launching that class

[lahodaj]

When unnamed (_) variables are present, and javac emits the LocalVariableTable (and potentially the LocalVariableTypeTable), it includes the unnamed variable in the table. As the variable does not have a name, the table contains an empty name, which is not allowed by the spec, see [1], [2], [3].

The proposed solution is to simply not include the unnamed variables in these tables, by not adding them to the internal Code.varBuffer.

[1] https://docs.oracle.com/javase/specs/jvms/se20/html/jvms-4.html#jvms-4.2.2
[2] https://docs.oracle.com/javase/specs/jvms/se20/html/jvms-4.html#jvms-4.7.13
[3] https://docs.oracle.com/javase/specs/jvms/se20/html/jvms-4.html#jvms-4.7.14

---

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Issue

• JDK-8313323: javac -g on a java file which uses unnamed variable leads to ClassFormatError when launching that class (Bug - P3)

Reviewers

• Vicente Romero (@vicente-romero-oracle - Reviewer)

Reviewing

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• 00: Full (d4af6167)

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[vicente-romero-oracle]

looks good

[openjdk]

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

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

8313323: javac -g on a java file which uses unnamed variable leads to ClassFormatError when launching that class

Reviewed-by: vromero

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At the time when this comment was updated there had been 395 new commits pushed to the master branch:

• 2f7c65e: 8303427: Fixpath confused if unix root contains "/jdk"
• e9e0c56: 8314319: LogCompilation doesn't reset lateInlining when it encounters a failure.
• 56b8db1: 8258970: Disabled JPasswordField foreground color is wrong with GTK LAF
• 0d4cadb: 8315195: RISC-V: Update hwprobe query for new extensions
• b4f7069: 8315446: G1: Remove unused G1AllocRegion::attempt_allocation
• cf02cf3: 8315098: Improve URLEncodeDecode microbenchmark
• c32e340: 8315321: [aix] os::attempt_reserve_memory_at must map at the requested address or fail
• 42f5b9e: 8315436: HttpsServer does not send TLS alerts
• 033f311: 8315069: Relativize extended_sp in interpreter frames
• c2e01eb: 8313983: jmod create --target-platform should replace existing ModuleTarget attribute
• ... and 385 more: https://git.openjdk.org/jdk/compare/47c4b992b44a5ce120aa4fe9e01279d4c52bca0a...master

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.

➡️ To integrate this PR with the above commit message to the master branch, type /integrate in a new comment.

[lahodaj]

/integrate

[lahodaj]

/backport jdk21u

[openjdk]

Going to push as commit adfc1d6.
Since your change was applied there have been 401 commits pushed to the master branch:

• 2dc930d: 8314997: Missing optimization opportunities due to missing try_clean_mem_phi() calls
• ab12c5d: 8315549: CITime misreports code/total nmethod sizes
• ba8d5c2: 8315582: Exclude compiler/codecache/CodeCacheFullCountTest.java with Xcomp
• 75d4ac2: 8311775: [TEST] duplicate verifyHeapDump in several tests
• 4f90aba: 8311585: Add JRadioButtonMenuItem to bug8031573.java
• 2a11bc4: 8314837: 5 compiled/codecache tests ignore VM flags
• 2f7c65e: 8303427: Fixpath confused if unix root contains "/jdk"
• e9e0c56: 8314319: LogCompilation doesn't reset lateInlining when it encounters a failure.
• 56b8db1: 8258970: Disabled JPasswordField foreground color is wrong with GTK LAF
• 0d4cadb: 8315195: RISC-V: Update hwprobe query for new extensions
• ... and 391 more: https://git.openjdk.org/jdk/compare/47c4b992b44a5ce120aa4fe9e01279d4c52bca0a...master

Your commit was automatically rebased without conflicts.

[openjdk]

@lahodaj Pushed as commit adfc1d6.

💡 You may see a message that your pull request was closed with unmerged commits. This can be safely ignored.

[openjdk]

@lahodaj the backport was successfully created on the branch lahodaj-backport-adfc1d6c in my personal fork of openjdk/jdk21u. To create a pull request with this backport targeting openjdk/jdk21u:master, just click the following link:

➡️ Create pull request

The title of the pull request is automatically filled in correctly and below you find a suggestion for the pull request body:

Hi all,

This pull request contains a backport of commit adfc1d6c from the openjdk/jdk repository.

The commit being backported was authored by Jan Lahoda on 4 Sep 2023 and was reviewed by Vicente Romero.

Thanks!

If you need to update the source branch of the pull then run the following commands in a local clone of your personal fork of openjdk/jdk21u:

$ git fetch https://github.com/openjdk-bots/jdk21u.git lahodaj-backport-adfc1d6c:lahodaj-backport-adfc1d6c
$ git checkout lahodaj-backport-adfc1d6c
# make changes
$ git add paths/to/changed/files
$ git commit --message 'Describe additional changes made'
$ git push https://github.com/openjdk-bots/jdk21u.git lahodaj-backport-adfc1d6c