On Tue, 15 Jul 2025 03:00:12 GMT, Serguei Spitsyn <sspit...@openjdk.org> wrote:
>> My concern was that Set/GetLocal could produce JVMTI_ERROR_OPAQUE_FRAME for >> a native frame, and JDI was not handling this, but is appears that JDI is >> prevening Set/GetLocal on a native frame. Read on for more details. >> >> It looks like historically Set/GetLocal has returned >> JVMTI_ERROR_OPAQUE_FRAME for native methods. However, JDI does not check for >> this, so I had some concern about that because JVMTI_ERROR_OPAQUE_FRAME >> would result in a JDIInternalError. However, I think now that JDI would >> never result in a JVMTI Set/GetLocal call when the frame is native because >> of checks JDI does ahead of time. The JDI Set/GetValue APIs take a >> LocalVariable, the source of which would preclude ever getting one for a >> frame that is for a native method. I think what is most common is to call >> StackFrame.visibleVariables() to get all the LocalVariables, and if this is >> done on a native method, you simply get no LocalVariables, thus you have >> nothing to pass to Set/GetLocal. >> >> So I think the only time JDI will see JVMTI_ERROR_OPAQUE_FRAME is for the >> virtual thread case, which for SetLocal requires that the frame be the >> topmost frame and the virtual thread be mounted. The JDI spec is already >> covering this, so probably no changes are needed. > > Okay, thanks. This sounds right. 👍 ...but JDWP might need some work. StackFrame.SetValues and GetValues only mentions OPAQUE_FRAME for SetValues of a virtual thread. However, I don't think there is anything to prevent them being called on a native frame. You might expect INVALID_SLOT in that case because it would not be possible to specify a valid slot for a local when there are none, but from the code you gave above it looks like slot checks are made after the native method check. So if a combination of a native method and invalid slot results in OPAQUE_FRAME, then we need to update the JDWP spec to reflect this. The other choice is to make JVMTI return INVALID_SLOT when the method is native. And speaking of INVALID_SLOT, it missing in the JDWP spec for SetValues, but is there for GetValues. It seems that should be fixed. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/26111#discussion_r2206190118
