RFR: 8263968: CDS: java/lang/ModuleLayer.EMPTY_LAYER should be singleton [v2]

Tue Mar 23 08:24:39 UTC 2021

On Tue, 23 Mar 2021 08:04:09 GMT, Aleksei Voitylov <avoitylov at openjdk.org> wrote:

>> With CDS and G1, test api/java_lang/ModuleLayer/Boot.html fails in JDK 16. 
>> 
>> After JDK-8253081 with CDS enabled two instances of empty layer appear in the runtime. One comes from default initialization of java/lang/ModuleLayer.EMPTY_LAYER, another one comes from CDS archive and is returned by ModuleLayer.boot().parents().get(0). The fix makes java/lang/ModuleLayer.EMPTY_LAYER a singleton with both CDS on and off, similar to java/lang/module/Configuration.EMPTY_CONFIGURATION.
>> 
>> Testing: JCK 16, jtreg (including newly added test), pre-submit GitHub actions tests.
>
> Aleksei Voitylov has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix style

Marked as reviewed by alanb (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/3131