[jkflying]

Static initializers running during cleanup

When a robot class loader is cleaned up, e.g. after building the robot database, cleanStaticReferences sets the robot's static reference fields to null. Setting a static field initializes the class, so a static initializer that hadn't run yet ran on the cleanup thread instead of on the robot's thread. Its System.out output went to the main console instead of the robot's console, and robot code ran while building the robot database, which made it slower than needed.

Cleanup now skips classes that haven't been initialized, using sun.misc.Unsafe.shouldBeInitialized(). Such classes can't hold references anyway, because their static fields were never set. If the check isn't available, nothing is cleaned.

This only matters on Java 8–11. On Java 12+, cleaning static references already fails before any field is set, because Field.modifiers can't be accessed anymore.

finalize() running on the JVM's finalizer thread

The JVM calls finalize() on its finalizer thread, which the sandbox treats as safe. RobotClassRewriter now renames finalize()V methods of robot classes, and calls to them, to robocode$finalize()V, so they no longer override Object.finalize() and the JVM never calls them. Calls to finalize() of Java classes, e.g. super.finalize() with Object as superclass, are not renamed.

Impact on the RoboRumble participants:

• 3 of 1472 robot jars declare finalize(). All of these methods only clear fields, call super.finalize(), or close Rhino generators, so robots lose nothing by them no longer being called.
• The classes of kid.Toa .0.5 and kid.team.OmegaSquad .0.2 load and verify with their finalize() methods renamed.
• inonit.robocode.javascript.MyFirstRobot 1.1 fails to load the same Rhino classes with or without this change, as the verifier already denies some of them. This is a separate issue.

Testing

• RobotClassLoaderTest.finalizeIsRenamed compiles a robot with a finalize() method, and checks that it is renamed and that super.finalize() still works. It fails without the rewriter change.
• The full test suite passes on Java 17 and Java 25.
• The static initializer fix has no automated test, because the bug only exists on Java 8–11 and the tests now run on Java 17+. It was checked manually on Java 8 with a robot whose static initializer prints: before the fix, the output appeared during cleanup; after it, nothing did.

🤖 Generated with Claude Code