RFR: 8309400: JDI spec needs to clarify when OpaqueFrameException and NativeMethodException are thrown [v2]

[Serguei Spitsyn]

On Wed, 16 Jul 2025 03:32:34 GMT, Chris Plummer <cjplummer at openjdk.org> wrote:

>> Fix how ThreadReference.popFrame() and ThreadReference.forceEarlyReturn deal with JDWP OPAQUE_FRAME error.
>> 
>> Before virtual threads, OpaqueFrameException did not exist and these API always threw NativeMethodException when JDWP OPAQUE_FRAME error was returned. For virtual threads OpaqueFrameException was added to handle the case where a virtual thread was not suspended at an event, so the JDI implementation was updated to throw OpaqueFrameException if it detected that a native method was not the cause. It turns out however that JVMTI (and therefore JDWP) can return OPAQUE_FRAME error for reasons other than a native method or the special virtual thread case, and for platform threads we were incorrectly throwing NativeMethodException in these cases. This PR fixes that. For platform threads we now only throw NativeMethodException if a native method is detected, and otherwise throw OpaqueFrameException.
>> 
>> The spec language is also being cleaned up to better align with JVMTI. Rather than calling out all the reasons for OpaqueFrameException, a more generic explanation is given.
>> 
>> This is somewhat of a preliminary PR so I can get some feedback. I still need to do a CR and complete testing.
>
> Chris Plummer has updated the pull request incrementally with one additional commit since the last revision:
> 
>   update based on feedback

I've posted one concern on the spec updates. Otherwise, it looks okay to me.
I guess, a CSR will be filed for this update. I'm not sure what do you mean by CR in the description. Do I understand this right that a potential JDWP spec update we touched out of this PR will be considered separately?

src/jdk.jdi/share/classes/com/sun/jdi/ThreadReference.java line 406:

> 404:      *
> 405:      * @throws OpaqueFrameException if target VM is unable to pop this frame
> 406:      * (e.g. a virtual thread is not suspended at an event).

Nit: I'm not sure the comment at line 406 is fully correct. The `IncompatibleThreadStateException` will be thrown if a virtual thread is not suspended. So, the `OpaqueFrameException` will be thrown only when a virtual thread is suspended but not at an event. The same concern should apply for the line  488.

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Marked as reviewed by sspitsyn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/26335#pullrequestreview-3028456818
PR Review Comment: https://git.openjdk.org/jdk/pull/26335#discussion_r2212652535