Illegal reflective access operation (java 11)

[ccleve]

This is the same as #33 and #34. Adding a bit more information.

I'm using OpenJDK version 11.0.1 on a Mac. Using version 2.3.1 of the compiler library.

The error is:
WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by net.openhft.compiler.CompilerUtils (file:/Users/ccleve/.m2/repository/net/openhft/compiler/2.3.1/compiler-2.3.1.jar) to method java.lang.ClassLoader.defineClass(java.lang.String,byte[],int,int)
WARNING: Please consider reporting this to the maintainers of net.openhft.compiler.CompilerUtils
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations
WARNING: All illegal access operations will be denied in a future release

This warning is getting dumped to the console. I'm guessing that it's going to System.err.

The code I'm using is almost identical to the sample code in the Readme.

My best guess is that the problem is in CompilerUtils, these lines:

DEFINE_CLASS_METHOD = ClassLoader.class.getDeclaredMethod("defineClass", String.class, byte[].class, int.class, int.class);
DEFINE_CLASS_METHOD.setAccessible(true);

Here's a discussion of the issue: https://stackoverflow.com/questions/50251798/what-is-an-illegal-reflective-access

Can you subclass the classloader and get a reference to that defineClass() method, without having to do reflection?

[adamlalikos]

@dpisklov / @ccleve / OpenHFT team: Since this is still just a warning in Java 11, I don't think anyone is currently effected.

However, the warning does state All illegal access operations will be denied in a future release. So I'd imagine anyone using the Java-Runtime-Compiler will be effected with Java's next release (12, which is not LTS). I can try to fork the project to see if I can fix, and submit a pull request in the near future to fix this issue now rather than wait.

[MartyIX]

1. I don't believe the next release will break the code (no mention here: https://jdk.java.net/12/release-notes or here: https://openjdk.java.net/projects/jdk/12/). The warning does not state that it will be denied in the very next release. It will be some time in the future, I expect it will take a long time given how many issues (mostly warnings) there are, in the wild, with transitions from JDK 8 to JDK 9+.

2. There is standard API for defining classes in JDK 9+, namely: https://docs.oracle.com/javase/9/docs/api/java/lang/invoke/MethodHandles.Lookup.html#defineClass-byte:A- but it "Defines a class to the same class loader ... as this lookup's lookup class." so it's not that powerful as the non-standard API where you can specify ClassLoader.

3. You can get rid of the warning by using java --add-exports <module>/<package>=<target-module> [...] when you run your application or to your build script. (something like java --add-exports java.base/java.lang=ALL-UNNAMED [...])

[dpisklov]

This has been fixed in #34, but there was no release to pick this up yet. I will release it now.

[dpisklov]

2.3.4 is released.