Recent changes to 37: Robot imported based on a jar file cannot run due to error: loader constraint violation

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

Flemming N. Larsen — Tue, 24 Oct 2023 20:01:55 -0000

I have created a new release 1.9.5.2 just now. You can download it from here:
https://sourceforge.net/projects/robocode/files/robocode/1.9.5.2/robocode-1.9.5.2-setup.jar

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

darren — Tue, 24 Oct 2023 01:12:38 -0000

@fnl Thank you for you quick response, I will try it.

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

Flemming N. Larsen — Mon, 23 Oct 2023 22:00:45 -0000

I have made a fix in the RobotClassLoader that works on my system, and I should like you to try it out with an alpha version of the next version 1.9.5.2:
https://robocode.sourceforge.io/files/robocode-1.9.5.2-alfa-setup.jar

If it works, I will make a release soon.

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

Flemming N. Larsen — Mon, 23 Oct 2023 10:04:09 -0000

For now, a temporary fix is to set the -DNOSECURITY=true option on the command line. That is, put this line in the java command in the robocode.bat or robocode.sh file.
This disables the security manager and changes the way the classes are loaded.

I still work on a real fix. But it is not an easy one, and could take some time.

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

darren — Mon, 23 Oct 2023 01:37:00 -0000

@fnl Thanks you, looking forward your answer.

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

Flemming N. Larsen — Sun, 22 Oct 2023 19:32:03 -0000

I can reproduce the problem, and trying to find a prober fix for it.

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

Flemming N. Larsen — Sun, 22 Oct 2023 12:34:12 -0000

OK. I will have a look and see if I can reproduce it. And if so, I will figure out how it can be solved. 👍

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

darren — Thu, 19 Oct 2023 09:32:04 -0000

Hi @fnl, help!
The problem still there, could you help take a look.
voidious.Diamond 1.0: Throwable: java.lang.LinkageError: loader constraint violation: when resolving method "voidious.utils.MovementPredictor.nextLocation(Lvoidious/Diamond;)Ljava/awt/geom/Point2D$Double;" the class loader (instance of net/sf/robocode/host/security/RobotClassLoader) of the current class, voidious/radar/DiamondEyes, and the class loader (instance of sun/misc/Launcher$AppClassLoader) for the method's defining class, voidious/utils/MovementPredictor, have different Class objects for the type voidious/Diamond used in the signature

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

darren — Thu, 19 Oct 2023 08:34:02 -0000

Hi Flemming,
Yes I packed the jar file using "Robot/Package robot or team" menu.
OK, let me try with java 8, thanks!

#37 Robot imported based on a jar file cannot run due to error: loader constraint violation

Flemming N. Larsen — Thu, 19 Oct 2023 08:30:10 -0000

Why there are two class loader for same class?

Robocode is using its own class loader due to security reasons as it needs to put security restrictions on robots running within the same JVM.

Regarding the import error. Did you use the Robot/team packager of Robocode? f not, make sure to use it:

Call the packager from the menu:
Robot -> Package robot or team

If you did use the packager, I expect this to be a problem with never versions of Java making use of modules and putting more restrictions on Java Reflection. So you could try to run Robocode on an older version of Java e.g. version 8 or 11?