RFR: 8276208: vmTestbase/nsk/jdb/repeat/repeat001/repeat001.java fails with "AssertionError: Unexpected output"

[Jakob Cornell]

On Mon, 1 Nov 2021 04:39:27 GMT, Jakob Cornell <duke at openjdk.java.net> wrote:

> This will fix a few issues with the tests added in #5290:
> 
> - [ ] intermittent failures
> - [x] tests should use `failure` method to report problems rather than throwing `AssertionError`

I'm not sure whether this is expected to be a platform-specific bug, but I've been assuming it is since I've never seen the failure on my Linux system.

I started with the Windows failure and noticed that the JDB loop mechanism doesn't seem to be working:


Sending command: 2 2 up
reply[0]: End of stack.
reply[1]: main[1]


That would seem to be the cause of the "Unexpected output" error, but I can't reproduce the behavior manually on the x86-64 Windows system I have access to.  With repeat on:


main[1] 2 2 up
End of stack.
main[1] End of stack.
main[1] End of stack.
main[1] End of stack.
main[1]


I wonder if Daniel can provide any more information that might enable me to reproduce the issue for debugging.  If not, I don't think I can diagnose the issue.  Another question I have is whether anybody has attempted to find the point the bug was introduced by backporting the test to earlier versions of the JDK.  I think that would essentially mean reducing the test to `2 2 up` or similar, since the `repeat` command is brand new.

I'm assuming the Mach 5 failure has the same underlying cause; I could try virtualizing Linux on PowerPC to try to reproduce that one, but that seems likely to take a lot of time and unlikely to turn up anything useful.

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PR: https://git.openjdk.java.net/jdk/pull/6182