RFR: 8353835: Implement JEP 500: Prepare to Make Final Mean Final [v3]

Alan Bateman alanb at openjdk.org
Sat Sep 27 13:10:04 UTC 2025


> Implementation changes for [JEP 500: Prepare to Make Final Mean Final](https://openjdk.org/jeps/500).
> 
> Field.set (and Lookup.unreflectSetter) are changed to allow/warn/debug/deny when mutating a final instance field. JFR event recorded if final field mutated. Spec updates to Field.set, Field.setAccessible and Module.addOpens to align with the proposal in the JEP.
> 
> HotSpot is updated to add support for the new command line options. To aid diagnosability, -Xcheck:jni reports a fatal error when a mutating a final field with JNI, and -Xlog:jni=debug can help identity when JNI code mutates finals. For now, JNI code is allowed to set the "write-protected" fields System.in/out/err, we can re-visit once we change the System.setIn/setOut/setErr methods to not use JNI (I prefer to keep this separate to this PR because there is a small startup regression to address when changing System.setXXX).
> 
> There are many new tests. A small number of existing tests are changed to run /othervm as reflectively opening a package isn't sufficient. Changing the tests to /othervm means that jtreg will launch the agent with the command line options to open the package.
> 
> Testing: tier1-6

Alan Bateman has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains 23 commits:

 - Merge branch 'master' into JDK-8353835
 - Merge branch 'master' into JDK-8353835
 - Improve setters and test cleanup
 - Merge branch 'master' into JDK-8353835
 - Merge branch 'master' into JDK-8353835
 - Review feedback
 - Change ciField::initialize_from to use is_mutable_static_final, suggested by Vladimir Ivanov
 - Merge branch 'master' into JDK-8353835
 - Test cleanup
 - More improvements
 - ... and 13 more: https://git.openjdk.org/jdk/compare/af8fb20a...545557d9

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

Changes: https://git.openjdk.org/jdk/pull/25115/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25115&range=02
  Stats: 4557 lines in 62 files changed: 4380 ins; 54 del; 123 mod
  Patch: https://git.openjdk.org/jdk/pull/25115.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25115/head:pull/25115

PR: https://git.openjdk.org/jdk/pull/25115


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