Fix illegal reflective access operations (Java 9)

[jeremydlawrence]

WARNING: An illegal reflective access operation has occurred
WARNING: Illegal reflective access by jnr.posix.JavaLibCHelper to method sun.nio.ch.SelChImpl.getFD()
WARNING: Please consider reporting this to the maintainers of jnr.posix.JavaLibCHelper
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

[huntc]

Just wondering how this is going to be fixable without either lobbying for the JDK to provide a supported SelChImpl or moving away from sun.nio.ch entirely... any thoughts out there?

[Zhuinden]

Hey, this project is an example for Java 8->9 migration and that this code here will break after Java 9 by default: https://docs.oracle.com/javase/9/migrate/toc.htm#JSMIG-GUID-7BB28E4D-99B3-4078-BDC4-FC24180CE82B

[PaulSandoz]

Could you bring this use-case to OpenJDK either by mailing nio-dev@openjdk.java.net and/or logging an issue here https://bugreport.java.com/bugreport/ (which will eventually end up at https://bugs.openjdk.java.net/secure/Dashboard.jspa).

Note that JNR will continue to still work on Java 11. Illegal access operations will be denied in a future release to be determined.

[ohumbel]

@PaulSandoz Are you aware of a discussion on nio-dev or of a bug report we could follow?
I searched the nio-dev archives from June on, and I believe I haven't found a matching topic (but I might be wrong).

[charleskorn]

This doesn't fix the root cause of the problem, but if you want to suppress the warnings, adding --add-opens java.base/sun.nio.ch=ALL-UNNAMED --add-opens java.base/java.io=ALL-UNNAMED to your java command line will hide them.

[schaumb]

I running into the same problem with the following code:

    int i = JavaLibCHelper.getfdFromDescriptor(new FileDescriptor());

One possible solution can be hacking with JNI, because there isn't any check when native code wants to access private field.

Test.java

import java.io.FileDescriptor;

public class Test {
    public static native int getFD(FileDescriptor oth);

    public static void main(String[] args) {
        System.load(new File("Test").getAbsolutePath()); // load compiled shared lib 
        int fd = getFD(new FileDescriptor());
    }
}

~Test.h

/*
 * Class:     Test
 * Method:    getFD
 * Signature: (Ljava/io/FileDescriptor;)I
 */
JNIEXPORT jint JNICALL Java_Test_getFD
  (JNIEnv *, jclass, jobject);

~Test.cpp

jint Java_Test_getFD(JNIEnv * env, jclass, jobject o) {
    jclass clazz = env->GetObjectClass(o);
    jfieldID fd = env->GetFieldID(clazz,"fd","I");
    jint res = (jint)env->GetIntField(o, fd);

    env->DeleteLocalRef(clazz);

    return res;
}

It can be write the same logic for SelChImpl class too.

[schaumb]

For FILE_DESCRIPTOR_FD it can be used
sun.nio.ch.IOUtil.fdVal and sun.nio.ch.IOUtil.newFD.