RFR: JDK-8293156: Dcmd VM.classloaders fails to print the full hierarchy

[Thomas Stuefe]

On Fri, 16 Sep 2022 14:55:42 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Fixes a bug in the `VM.classloaders` jcmd that causes class loaders to be omitted from the output if a parent class loader never loaded any class and therefore had no associated DCmd.
> 
> The fix changes the command to not rely on the existence of a CLD structure for the loader; instead, all information (loader class name, loader name, etc) is pulled via the loader oop, which has to be always there unless its the bootstrap loader.
> 
> Also, the tests were expanded to test the display of empty loaders and empty parent loaders.
> 
> Thanks to @dholmes-ora for finding this bug.

Hi @plummercj , thanks for your Review. I worked most of your your feedback.

.. Thomas

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PR: https://git.openjdk.org/jdk/pull/10312