[jdk17] RFR: JDK-8225667: Clarify the behavior of System::gc w.r.t. reference processing

[Roger Riggs]

On Wed, 30 Jun 2021 18:24:24 GMT, Mandy Chung <mchung at openjdk.org> wrote:

> This spec clarification is a follow-up to [JDK-8224760](https://bugs.openjdk.java.net/browse/JDK-8224760?focusedCommentId=14268320&page=com.atlassian.jira.plugin.system.issuetabpanels%3Acomment-tabpanel#comment-14268320) w.r.t. reference processing.  Since there is no guarantee for any memory reclamation by the invocation of `System::gc`, the spec should also clarify that there is no guarantee in determining the change of reachability of any objects or any particular number of `Reference` objects be enqueued and cleared.
> 
> CSR:
>    https://bugs.openjdk.java.net/browse/JDK-8269690

Marked as reviewed by rriggs (Reviewer).

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PR: https://git.openjdk.java.net/jdk17/pull/183