RFR: CODETOOLS-7902936 Stray VM warnings in forked PrintPropertiesMain lead to hard to debug XML parse exception

Jason Zaugg jzaugg at openjdk.java.net
Fri May 21 02:34:39 UTC 2021

On Fri, 21 May 2021 02:27:09 GMT, Jason Zaugg <jzaugg at openjdk.org> wrote:

> - Recover from stray output before the XML prelude
>   - Report the output in the exception otherwise
>   - Silence VM warnings in PrintPropertiesMain when JEP-158 (-Xlog:) is available (JRE 9+)

This code path is only exercised when specifying an alternative `-jvm`, which doesn't appear to be done in the JMH test suite, presumably because of the hassle of requiring multiple JVMs.

I manually tested the change by:

 - Running just the diagnostic on a server that gives the VM warnings about duplicate cpusets. The error message included the VM warning.
 - JMH worked again on that machine with the commit that adds `-Xlog:all=error`
 - Locally, I added `System.out.println("VM OUTPUT")` to `PrintPropertiesMain` and tested that the recovery logic worked.


PR: https://git.openjdk.java.net/jmh/pull/41

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