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

[Jason Zaugg]

On Fri, 21 May 2021 08:08:35 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> I would prefer to cover the "hard to debug" part only: dump the proper diagnostics and then fail hard

No worries, I thought I'd throw the whole gamut in here and let you decide what to include. 

> We can probably print the helpful message how to shun the VM warnings, if user is so inclined?

What advice could we give? The use can't currently add JVM options to the `PrintPropertiesMain` forked JVM.

FWIW, I haven't yet found a way to reconfigure the Linux system to avoid my particular VM warning. Not necessarily because its hard to fix, but more because I'm clueless about this part of Linux. At some point an OS upgrade would make sense but that could introduce a discontinuity into our historical benchmark results.

The other options I haven't explored, but seem easy enough to implement are:
  - use a temporary file to transfer the XML. The parent process could create the file and pass its name as an argument to `PrintPropertiesMain`.
  - use `BinaryLinkServer` to allow the the properties to be pushed back over a socket.

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