JDK-8317920: JDWP-agent sends broken exception event with onthrow option

[parttimenerd]

Fix onthrow issue by passing the event info to the initialize method.

This prevents jdb from receiving a broken exception event and throwing an internal NullPointerException, upon attaching to the JDWP-agent.

---

Progress

• Change must not contain extraneous whitespace
• Commit message must refer to an issue
• Change must be properly reviewed (2 reviews required, with at least 1 Reviewer, 1 Author)

Issue

• JDK-8317920: JDWP-agent sends broken exception event with onthrow option (Bug - P4)

Reviewers

• Christoph Langer (@RealCLanger - Reviewer) ⚠️ Review applies to 278927b9
• Chris Plummer (@plummercj - Reviewer) ⚠️ Review applies to 278927b9

Reviewing

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Checkout this PR locally:
$ git fetch https://git.openjdk.org/jdk.git pull/16145/head:pull/16145
$ git checkout pull/16145

Update a local copy of the PR:
$ git checkout pull/16145
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Checkout this PR locally:
$ git pr checkout 16145

View PR using the GUI difftool:
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[bridgekeeper]

👋 Welcome back jbechberger! 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]

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• 08: Full - Incremental (30d713a5)
• 07: Full - Incremental (278927b9)
• 06: Full - Incremental (35f317e8)
• 05: Full - Incremental (5099bcdd)
• 04: Full - Incremental (1371459d)
• 03: Full - Incremental (f1f75482)
• 02: Full - Incremental (1f72b743)
• 01: Full - Incremental (3badd197)
• 00: Full (3bcb66dc)

[RealCLanger]

LGTM

[openjdk]

@parttimenerd 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:

8317920: JDWP-agent sends broken exception event with onthrow option

Reviewed-by: clanger, cjplummer

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 154 new commits pushed to the master branch:

• 4812cab: 8316587: Use ArraysSupport.vectorizedHashCode in Utf8EntryImpl
• bd02cfd: 8318540: make test cannot run .jasm tests directly
• bd3bc2c: 8317350: Move code cache purging out of CodeCache::UnloadingScope
• 292aad2: 8316436: ContinuationWrapper uses unhandled nullptr oop
• 387504c: 8317575: AArch64: C2_MacroAssembler::fast_lock uses rscratch1 for cmpxchg result
• d9ce525: 8318150: StaticProxySelector.select should not throw NullPointerExceptions
• c46a54e: 8312777: notifyJvmtiMount before notifyJvmtiUnmount
• 8f5f440: 8317692: jcmd GC.heap_dump performance regression after JDK-8292818
• 684b91e: 8315064: j.text.ChoiceFormat provides no specification on quoting behavior
• 1740950: 8314901: AES-GCM interleaved implementation using AVX2 instructions
• ... and 144 more: https://git.openjdk.org/jdk/compare/ad7a8e86e0334390f87ae44cf749d2b47f1409a1...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.

[plummercj]

/reviewers 2

[plummercj]

Do you have a test case for this?

[openjdk]

@plummercj
The total number of required reviews for this PR (including the jcheck configuration and the last /reviewers command) is now set to 2 (with at least 1 Reviewer, 1 Author).

[parttimenerd]

No. But if neccessary I could write one analogous to the OnJcmdTest, using jdb to check that no NullPointerException occurs in the JDI exception receiving code. This should test the current problem pretty reliably without too much effort.

[plummercj]

It would be good if you could do that. Also, can you provide a backtrace for the NPE in the JBS issue.

[plummercj]

Also, does onthrow ever work, or is it completely broken? If it is completely broken I'd be curious as to when/how this happened.

[parttimenerd]

I can confirm that it doesn't work properly in JDK 8, I have to check older JDKs.

But it kind of worked, because it started a debugging session after the specified exception had been thrown. It just didn't send a proper exception event. It's definitely a useful feature.

[plummercj]

So with 8 there is no NPE? Maybe JDI or jdb used to do something different and just swallowed exception event. Seeing the NPE stack trace would help determine what has changed to cause this behavior difference.

[parttimenerd]

There is an NPE on JDK 8. The onthrow option doesn't work properly there too. The bug is in the code since it is on GitHub. The stack trace in JDB looks exactly the same in JDK 8 as in JDK 21.

[plummercj]

So when you said "But it kind of worked", you were referring to both JDK 8 and current JDK, and were just pointing out that it did start the debugging session.

I'd still like to see the NPE stack trace.

[parttimenerd]

Sorry, I forgot to put the NPE somewhere. Here the NPE of JDB:

Exception in thread "event-handler" java.lang.NullPointerException: Cannot invoke "com.sun.jdi.ObjectReference.referenceType()" because the return value of "com.sun.jdi.event.ExceptionEvent.exception()" is null
        at jdk.jdi/com.sun.tools.example.debug.tty.TTY.exceptionEvent(TTY.java:171)
        at jdk.jdi/com.sun.tools.example.debug.tty.EventHandler.exceptionEvent(EventHandler.java:295)
        at jdk.jdi/com.sun.tools.example.debug.tty.EventHandler.handleEvent(EventHandler.java:133)
        at jdk.jdi/com.sun.tools.example.debug.tty.EventHandler.run(EventHandler.java:78)
        at java.base/java.lang.Thread.run(Thread.java:1583)

[plummercj]

Ok. I think overall the changes look good. I'd still like to see a test. Also, I'd like to see the jdb output after the fix. Maybe include the list output when jdb stops for the exception. It looks like jdb will print the name of the exception object and also the location where it will be caught, and I assume list will show you where it was thrown (although I think if this info is wrong in the ExceptionEvent, a jdb user would not notice so jdb it instead getting it from the current Thread info).

[parttimenerd]

After the fix (see https://mostlynerdless.de/blog/2023/10/11/jdwp-onthrow-and-a-mysterious-error/):

➜ jdb -attach 5005
Set uncaught java.lang.Throwable
Set deferred uncaught java.lang.Throwable
Initializing jdb ...
> 
Exception occurred: Ex (to be caught at: OnThrowAndJCmd.main(), line=7 bci=18)"thread=main", OnThrowAndJCmd.main(), line=6 bci=17
6                throw new Ex("");

main[1] list
2    
3        public static void main(String[] args) throws InterruptedException {
4            System.out.println("Hello world!");
5            try {
6 =>             throw new Ex("");
7            } catch (Ex e) {
8                System.out.println("Caught");
9            }
10            try {
11                throw new Ex("");
main[1] 

The problem started appearing with JDK 1.5.

I'm currently working on a test case and hope to add it in the next few hours.

[parttimenerd]

I added a minimal test case which starts a debugging session for a basic program and attaches to it via JDI to check that the JDWP-agent throws an exception event with non-null properties. The case fails for the current master and succeeds with this PR.

[plummercj]

Overall the changes look good except one minor comment typo I noted. I'd like to first run this through our CI testing to make sure there are no issues.

[plummercj]

Changes look good. I'm approving, but I think also @RealCLanger should re-review since a lot has changed since his review, including the addition of the test.

[RealCLanger]

Changes look good. I'm approving, but I think also @RealCLanger should re-review since a lot has changed since his review, including the addition of the test.

Thanks @plummercj for checking that so thoroughly, I couldn't do that. I only have a few minor suggestions for cleanups.

[RealCLanger]

Looks good, just a few last minor flaws. 😉

[RealCLanger]

Looks good to me now.

[parttimenerd]

/integrate

[openjdk]

Going to push as commit 8f4ebd8.
Since your change was applied there have been 158 commits pushed to the master branch:

• cd25d1a: 8318296: Move Space::initialize to ContiguousSpace
• 744f206: 8318525: Atomic gtest should run as TEST_VM to access VM capabilities
• 8099261: 8318489: Remove unused alignment_unit and alignment_offset
• 138437f: 8314438: NMT: Performance benchmarks are needed to have a baseline for comparison of improvements
• 4812cab: 8316587: Use ArraysSupport.vectorizedHashCode in Utf8EntryImpl
• bd02cfd: 8318540: make test cannot run .jasm tests directly
• bd3bc2c: 8317350: Move code cache purging out of CodeCache::UnloadingScope
• 292aad2: 8316436: ContinuationWrapper uses unhandled nullptr oop
• 387504c: 8317575: AArch64: C2_MacroAssembler::fast_lock uses rscratch1 for cmpxchg result
• d9ce525: 8318150: StaticProxySelector.select should not throw NullPointerExceptions
• ... and 148 more: https://git.openjdk.org/jdk/compare/ad7a8e86e0334390f87ae44cf749d2b47f1409a1...master

Your commit was automatically rebased without conflicts.

[openjdk]

@parttimenerd Pushed as commit 8f4ebd8.

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

[parttimenerd]

/backport jdk21u

[openjdk]

@parttimenerd the backport was successfully created on the branch parttimenerd-backport-8f4ebd89 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 8f4ebd89 from the openjdk/jdk repository.

The commit being backported was authored by Johannes Bechberger on 20 Oct 2023 and was reviewed by Christoph Langer and Chris Plummer.

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 parttimenerd-backport-8f4ebd89:parttimenerd-backport-8f4ebd89
$ git checkout parttimenerd-backport-8f4ebd89
# make changes
$ git add paths/to/changed/files
$ git commit --message 'Describe additional changes made'
$ git push https://github.com/openjdk-bots/jdk21u.git parttimenerd-backport-8f4ebd89

[parttimenerd]

/backport jdk17u

[openjdk]

@parttimenerd Could not automatically backport 8f4ebd89 to openjdk/jdk17u due to conflicts in the following files:

• test/jdk/com/sun/jdi/lib/jdb/Debuggee.java

Please fetch the appropriate branch/commit and manually resolve these conflicts by using the following commands in your personal fork of openjdk/jdk17u. Note: these commands are just some suggestions and you can use other equivalent commands you know.

# Fetch the up-to-date version of the target branch
$ git fetch --no-tags https://git.openjdk.org/jdk17u.git master:master

# Check out the target branch and create your own branch to backport
$ git checkout master
$ git checkout -b parttimenerd-backport-8f4ebd89

# Fetch the commit you want to backport
$ git fetch --no-tags https://git.openjdk.org/jdk.git 8f4ebd892148f2c23fd11672a10aaf787a0be2eb

# Backport the commit
$ git cherry-pick --no-commit 8f4ebd892148f2c23fd11672a10aaf787a0be2eb
# Resolve conflicts now

# Commit the files you have modified
$ git add files/with/resolved/conflicts
$ git commit -m 'Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb'

Once you have resolved the conflicts as explained above continue with creating a pull request towards the openjdk/jdk17u with the title Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb.

[RealCLanger]

/backport jdk17u

This is the wrong repo. For jdk17 you have to got to jdk17u-dev.

[parttimenerd]

Oh, thank you.

[parttimenerd]

/backport jdk17u-dev

[openjdk]

@parttimenerd Could not automatically backport 8f4ebd89 to openjdk/jdk17u-dev due to conflicts in the following files:

• test/jdk/com/sun/jdi/lib/jdb/Debuggee.java

Please fetch the appropriate branch/commit and manually resolve these conflicts by using the following commands in your personal fork of openjdk/jdk17u-dev. Note: these commands are just some suggestions and you can use other equivalent commands you know.

# Fetch the up-to-date version of the target branch
$ git fetch --no-tags https://git.openjdk.org/jdk17u-dev.git master:master

# Check out the target branch and create your own branch to backport
$ git checkout master
$ git checkout -b parttimenerd-backport-8f4ebd89

# Fetch the commit you want to backport
$ git fetch --no-tags https://git.openjdk.org/jdk.git 8f4ebd892148f2c23fd11672a10aaf787a0be2eb

# Backport the commit
$ git cherry-pick --no-commit 8f4ebd892148f2c23fd11672a10aaf787a0be2eb
# Resolve conflicts now

# Commit the files you have modified
$ git add files/with/resolved/conflicts
$ git commit -m 'Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb'

Once you have resolved the conflicts as explained above continue with creating a pull request towards the openjdk/jdk17u-dev with the title Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb.

[openjdk]

@parttimenerd Could not automatically backport 8f4ebd89 to openjdk/jdk11u due to conflicts in the following files:

• test/jdk/com/sun/jdi/lib/jdb/Debuggee.java

Please fetch the appropriate branch/commit and manually resolve these conflicts by using the following commands in your personal fork of openjdk/jdk11u. Note: these commands are just some suggestions and you can use other equivalent commands you know.

# Fetch the up-to-date version of the target branch
$ git fetch --no-tags https://git.openjdk.org/jdk11u.git master:master

# Check out the target branch and create your own branch to backport
$ git checkout master
$ git checkout -b parttimenerd-backport-8f4ebd89

# Fetch the commit you want to backport
$ git fetch --no-tags https://git.openjdk.org/jdk.git 8f4ebd892148f2c23fd11672a10aaf787a0be2eb

# Backport the commit
$ git cherry-pick --no-commit 8f4ebd892148f2c23fd11672a10aaf787a0be2eb
# Resolve conflicts now

# Commit the files you have modified
$ git add files/with/resolved/conflicts
$ git commit -m 'Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb'

Once you have resolved the conflicts as explained above continue with creating a pull request towards the openjdk/jdk11u with the title Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb.

[parttimenerd]

/backport jdk11u-dev

[openjdk]

@parttimenerd Could not automatically backport 8f4ebd89 to openjdk/jdk11u-dev due to conflicts in the following files:

• test/jdk/com/sun/jdi/lib/jdb/Debuggee.java

Please fetch the appropriate branch/commit and manually resolve these conflicts by using the following commands in your personal fork of openjdk/jdk11u-dev. Note: these commands are just some suggestions and you can use other equivalent commands you know.

# Fetch the up-to-date version of the target branch
$ git fetch --no-tags https://git.openjdk.org/jdk11u-dev.git master:master

# Check out the target branch and create your own branch to backport
$ git checkout master
$ git checkout -b parttimenerd-backport-8f4ebd89

# Fetch the commit you want to backport
$ git fetch --no-tags https://git.openjdk.org/jdk.git 8f4ebd892148f2c23fd11672a10aaf787a0be2eb

# Backport the commit
$ git cherry-pick --no-commit 8f4ebd892148f2c23fd11672a10aaf787a0be2eb
# Resolve conflicts now

# Commit the files you have modified
$ git add files/with/resolved/conflicts
$ git commit -m 'Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb'

Once you have resolved the conflicts as explained above continue with creating a pull request towards the openjdk/jdk11u-dev with the title Backport 8f4ebd892148f2c23fd11672a10aaf787a0be2eb.