RFR: 8353835: Implement JEP 500: Prepare to Make Final Mean Final [v4]
Alan Bateman
alanb at openjdk.org
Sun Sep 28 16:44:56 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 incrementally with one additional commit since the last revision:
RemoveFields(duration) and filter internal frames
-------------
Changes:
- all: https://git.openjdk.org/jdk/pull/25115/files
- new: https://git.openjdk.org/jdk/pull/25115/files/545557d9..0041ef4a
Webrevs:
- full: https://webrevs.openjdk.org/?repo=jdk&pr=25115&range=03
- incr: https://webrevs.openjdk.org/?repo=jdk&pr=25115&range=02-03
Stats: 57 lines in 5 files changed: 46 ins; 4 del; 7 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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