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

[Alex Menkov]

On Tue, 15 Jul 2025 22:07:40 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.

It looks good.
I added cleanup suggestion in the implementation

src/jdk.jdi/share/classes/com/sun/tools/jdi/StackFrameImpl.java line 401:

> 399:                 // previous frame is native, in which case we throw NativeMethodException
> 400:                 for (int i = 0; i < 2; i++) {
> 401:                     StackFrameImpl sf;

There is nothing implementation-specific here.
I'd suggest to:
- `StackFrameImpl` -> `StackFrame`;
- `MethodImpl` -> `Method`;
- remove `validateStackFrame` at line 408 ('MethodImpl.location()' calls it)

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PR Comment: https://git.openjdk.org/jdk/pull/26335#issuecomment-3076343535
PR Review Comment: https://git.openjdk.org/jdk/pull/26335#discussion_r2208948088