test/jdk/java/lang/StackWalker/ReflectionFrames.java contribution

[M-Davies]

https://github.com/ibmruntimes/openj9-openjdk-jdk11/blob/4041598f624e2222be156557efbe508b2b682ae9/test/jdk/java/lang/StackWalker/ReflectionFrames.java#L1 is failing for openj9 (see #6724).

• Identify implementation frames to ignore JTReg Failure: java/lang/StackWalker/ReflectionFrames.java #6724 (comment)
• Fix test case to ignore the frames specific to each implementation

[pdbain]

Identify which implementation is incorrect

Neither is "incorrect"; each has additional implementation-dependent stack frames which are allowed but not specified by the API. The test case should ignore these implementation-dependent frames.

[M-Davies]

@pdbain updated ^

[M-Davies]

Some frames might be cleared up by #3627. Will build and test with this to check

EDIT: Build failed with PR

[M-Davies]

The StackWalker class has an option for StackWalker.getInstance() called SHOW_HIDDEN_FRAMES which, when used with SHOW_REFLECT_FRAMES, hides frames that are implementation specific.

This implies that the frames were supposed to be hidden by default but weren't for some reason because the failing tests were running without SHOW_HIDDEN_FRAMES or SHOW_REFLECT_FRAMES enabled.

[M-Davies]

This functionality should already be enabled considering the code in the constructor of StackInspector here: https://github.com/ibmruntimes/openj9-openjdk-jdk11/blob/4041598f624e2222be156557efbe508b2b682ae9/test/jdk/java/lang/StackWalker/ReflectionFrames.java#L726

@pdbain thoughts?

[pshipton]

OpenJ9 doesn't use the OpenJDK implemention for the StackWalker, you have to look at the OpenJ9 code https://github.com/eclipse/openj9/blob/43f86dc478ddbddf25f1b640804baa49dc765dcb/jcl/src/java.base/share/classes/java/lang/StackWalker.java

[M-Davies]

So the base for implementing a fix for this test is already here in the test and the openj9 StackWalker. filter() will strip out the implementation specific frames which is implemented by parse in the StackInspector's constructor. I'm not sure how to go about using these tools for walkerHide yet however

Filter = https://github.com/ibmruntimes/openj9-openjdk-jdk11/blob/4041598f624e2222be156557efbe508b2b682ae9/test/jdk/java/lang/StackWalker/ReflectionFrames.java#L763

[M-Davies]

Looking at the code for both HS and J9, this seems like a lot of effort to fix just one test. The test is only accounting for Hotspot frames to appear and there is no current function within the test that can filter out frames that are OpenJ9 specific (this would have to be made from scratch). OpenJ9 has a very different StackWalker class compared to Hotspot so the structure of the StackInspector class in the test would have to be changed too.

In addition to this, any change made to the test would have to be approved upstream and I find it unlikely that it will be accepted by the community since we would, essentially, be modifying the test towards one implementation.

Closing this issue for the reasons stated above...