[crac] RFR: Fix NPE on ZipFile$Source access

Fri Apr 8 10:16:03 UTC 2022

On Thu, 3 Mar 2022 13:52:31 GMT, Anton Kozlov <akozlov at openjdk.org> wrote:

> A race between ZipFile$CleanableResource.run() and ZipFile$Resource.beforeCheckpoint() can lead to NullPointerException when zsrc == null. This is observed on some runs of JavaCompilerCRaC.java from #16. The change aligns beforeCheckpoint() with the run(), providing the zsrc check and the proper locking.

Ping? It's not critical, but fixes a annoying exception during checkpoint.

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PR: https://git.openjdk.java.net/crac/pull/17