8296007: crash in runtime/DefineClass/NullClassBytesTest.java

[dean-long]

This is a simple fix to Java_NullClassBytesTest_nativeDefineClass so that it returns the jclass as expected.

---

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Issue

• JDK-8296007: crash in runtime/DefineClass/NullClassBytesTest.java

Reviewers

• Daniel D. Daugherty (@dcubed-ojdk - Reviewer)
• David Holmes (@dholmes-ora - Reviewer)

Reviewing

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[bridgekeeper]

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[openjdk]

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• hotspot-runtime

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[mlbridge]

Webrevs

• 00: Full (794fcc98)

[dcubed-ojdk]

Thumbs up.

So did the callers of the function just assume there was
a return value? Why didn't this result in a linkage warning
or some other type of warning?

[openjdk]

@dean-long 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:

8296007: crash in runtime/DefineClass/NullClassBytesTest.java

Reviewed-by: dcubed, dholmes

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At the time when this comment was updated there had been 24 new commits pushed to the master branch:

• 4999f2c: 8156593: DataOutput.write(byte[],int,int) and its implementations do not specify index out bounds
• 8480f87: 8291974: PrivateCredentialPermission should not use local variable to enable debugging
• 590de37: 8284842: Update Unicode Data Files to Version 15.0.0
• 16744b3: 8256660: Disable DTLS 1.0
• f4d8c20: 8294729: [s390] Implement nmethod entry barriers
• 7e88209: 8295964: Move InstanceKlass::_misc_flags
• 91072ee: 5074006: Swing JOptionPane shows tag as a string after newline
• 274ea1d: 8295993: use K instead of 1024 in a couple of hotspot outputs
• 9b9be88: 8295125: os::signal should be os specific
• f8cc067: 8296087: Problem list headful tests which may fail on Linux VMs
• ... and 14 more: https://git.openjdk.org/jdk/compare/907d583376dfab269ea25a6c036e390f3484065e...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.

[dean-long]

Thumbs up.

Thanks, Dan, for the review.

So did the callers of the function just assume there was a return value?

Yes, the test creates its own ClassLoader, so the value is needed as part of class loading.

Why didn't this result in a linkage warning or some other type of warning?

I don't think there is any way to automatically detect this. The return type of a native method is not part of the symbol name for exported C functions, as far as I know. We could probably check that the result is a valid oop for native methods that return objects. That could be something extra that -Xcheck:jni does, perhaps.

How this went undetected is because the native method either throws an exception, so the result is ignored, or it calls DefineClass(), which sets the result register to the right value. This is the last line of the function, so there is a good chance that the result register will have the right value when it returns. However I was running a debug build and the function epilogue that gcc generated modified the result register to perform a stack corruption check.

[dcubed-ojdk]

Thanks for the detailed explanation!

[dean-long]

Do you I need a 2nd review for this change?

[dholmes-ora]

Do you I need a 2nd review for this change?

Yes two reviews for hotspot changes unless designated trivial.

[dholmes-ora]

Fix looks good. Thanks.

I'm somewhat concerned that nothing in the build system detected the error! It used to be that javah produced the header file with the right signatures etc and that would be included by the implementation file.

[dean-long]

Thanks David.

[dean-long]

/integrate

[openjdk]

Going to push as commit 37107fc.
Since your change was applied there have been 24 commits pushed to the master branch:

• 4999f2c: 8156593: DataOutput.write(byte[],int,int) and its implementations do not specify index out bounds
• 8480f87: 8291974: PrivateCredentialPermission should not use local variable to enable debugging
• 590de37: 8284842: Update Unicode Data Files to Version 15.0.0
• 16744b3: 8256660: Disable DTLS 1.0
• f4d8c20: 8294729: [s390] Implement nmethod entry barriers
• 7e88209: 8295964: Move InstanceKlass::_misc_flags
• 91072ee: 5074006: Swing JOptionPane shows tag as a string after newline
• 274ea1d: 8295993: use K instead of 1024 in a couple of hotspot outputs
• 9b9be88: 8295125: os::signal should be os specific
• f8cc067: 8296087: Problem list headful tests which may fail on Linux VMs
• ... and 14 more: https://git.openjdk.org/jdk/compare/907d583376dfab269ea25a6c036e390f3484065e...master

Your commit was automatically rebased without conflicts.

[openjdk]

@dean-long Pushed as commit 37107fc.

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