RFR: CODETOOLS-7902930: JOL: Bring back GraphWalker visitors [v2]

[Aleksey Shipilev]

On Fri, 21 May 2021 09:33:07 GMT, Martin Junghanns <github.com+318788+s1ck at openjdk.org> wrote:

>> Hey @shipilev First of all: Thanks for this useful library. I wanted to switch from jol 0.10 to 0.15 in one of my projects because of some issues on openJDK 15. I discovered that the ability to register visitors had been removed at some point. The interface `org.openjdk.jol.info.GraphVisitor` is actually still around. I find that feature quite useful as it allows users to compute some custom statistics of the object graph. I tried to use the `GraphLayout` to access the GPRs, but it's all package-private.
>> 
>> It would be nice if we could bring the feature back. Also, if you think the approach is not ideal, we can maybe figure out something else.
>> 
>> Thanks for your time.
>
> Martin Junghanns has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Avoid virtual calls in GraphWalker#walk

Delivered in JOL 0.16.

-------------

PR: https://git.openjdk.java.net/jol/pull/15