Develop Reference

Java call C library using native-image from GraalVM

I have a simple project: https://github.com/MarcoLunar/native-pid-test
All what it is doing is calling getpid from C library. Project is as simple as:
public static void main(String[] args) throws Exception {
System.out.println("start");
C_lib cLib = Native.loadLibrary("c", C_lib.class);
int getpid = cLib.getpid();
System.out.println("pid = " + getpid);
System.out.println("end");
}
When launching from IDE everything works fine:
start
pid = 155080
end
When trying to build using native-image from GraalVM I got this error:
[simpletest:155323] compile: 2,597.81 ms, 2.05 GB
Fatal error:org.graalvm.compiler.graph.GraalGraphError: java.lang.NullPointerException
at node: 43|&
at method: Object com.oracle.svm.reflect.JNIGeneratedMethodSupport_getFieldOffsetFromId_5041c78d77a7b3d62103393b72fc35d80d2cc709.invoke(Object, Object[])
at org.graalvm.compiler.phases.common.CanonicalizerPhase$Instance.tryCanonicalize(CanonicalizerPhase.java:397)
at org.graalvm.compiler.phases.common.CanonicalizerPhase$Instance.processNode(CanonicalizerPhase.java:325)
at org.graalvm.compiler.phases.common.CanonicalizerPhase$Instance.processWorkSet(CanonicalizerPhase.java:302)
at org.graalvm.compiler.phases.common.CanonicalizerPhase$Instance.run(CanonicalizerPhase.java:264)
at org.graalvm.compiler.phases.common.CanonicalizerPhase.run(CanonicalizerPhase.java:177)
at org.graalvm.compiler.phases.common.CanonicalizerPhase.run(CanonicalizerPhase.java:73)
at org.graalvm.compiler.phases.BasePhase.apply(BasePhase.java:214)
at org.graalvm.compiler.phases.BasePhase.apply(BasePhase.java:147)
at com.oracle.svm.hosted.code.CompileQueue.doInlineTrivial(CompileQueue.java:587)
at com.oracle.svm.hosted.code.CompileQueue.access$000(CompileQueue.java:156)
at com.oracle.svm.hosted.code.CompileQueue$TrivialInlineTask.run(CompileQueue.java:284)
at com.oracle.graal.pointsto.util.CompletionExecutor.lambda$execute$0(CompletionExecutor.java:173)
at java.util.concurrent.ForkJoinTask$RunnableExecuteAction.exec(ForkJoinTask.java:1402)
at java.util.concurrent.ForkJoinTask.doExec(ForkJoinTask.java:289)
at java.util.concurrent.ForkJoinPool$WorkQueue.runTask(ForkJoinPool.java:1056)
at java.util.concurrent.ForkJoinPool.runWorker(ForkJoinPool.java:1692)
at java.util.concurrent.ForkJoinWorkerThread.run(ForkJoinWorkerThread.java:157)
Caused by: java.lang.NullPointerException
at org.graalvm.compiler.nodes.calc.BinaryArithmeticNode.tryConstantFold(BinaryArithmeticNode.java:120)
I have tried many times, many different solutions ... but for now I have no more to check.
I am asking for help in repairing the project. I think this is possible, because with some configurations I have the same error as in https: //github.com/oracle/graal/issues/2261 ... where someone fixed it ... but didn't write the solution: (

I think currently JNA doesn't work in native image. You can use JNI if that's possible. Or you can use another interface to native code that will work specifically in the native images. Some info can be found in the javadoc of org.graalvm.nativeimage.c and its subpackages: https://www.graalvm.org/sdk/javadoc/index.html?org/graalvm/nativeimage/c/package-summary.html
Here's an example of using it: https://www.praj.in/posts/2020/opengl-demo-using-graalvm/

Cannot get to the bottom of NoClassDefFoundError error in Groovy test

I am trying to run a very simple test in groovy and just when it starts to run the test I am getting the following exception:
java.lang.NoClassDefFoundError: org/spockframework/runtime/ErrorCollector
at com.imanage.runner.ExcelReportTests.Create simple client fetch report in excel(ExcelReportTests.groovy)
Caused by: java.lang.ClassNotFoundException:
org.spockframework.runtime.ErrorCollector
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
... 1 more
I have tried to debug the test but I cant find where it is falling over, there is just no more information, can anyone explain why the test is failing?
Running in intelliJ if that makes a difference.
class ExcelReportTests extends Specification {
def setup() {
println "This will work"
}
def "Just a test"() {
when:
println "This is not printed"
then:
assert 1 == 1
}
}
I have checked all the imports and they look fine, we use gradle for dependancy management and I cleared its cache too.

Weka DiscriminantAnalysis NoClassDefFoundError

I'm trying to use MultiClassFLDA in discriminant analysis package but I always get an error on running the code and defining a new instance of the MultiClassFLDA class
Exception in thread "main" java.lang.NoClassDefFoundError: no/uib/cipr/matrix/Vector
at assignment2.face.tryLDA(face.java:141)
at assignment2.Assignment2.main(Assignment2.java:106)
Caused by: java.lang.ClassNotFoundException: no.uib.cipr.matrix.Vector
at java.net.URLClassLoader.findClass(URLClassLoader.java:381)
at java.lang.ClassLoader.loadClass(ClassLoader.java:424)
at sun.misc.Launcher$AppClassLoader.loadClass(Launcher.java:331)
at java.lang.ClassLoader.loadClass(ClassLoader.java:357)

It seems to be linked to some dynamic class loading in newer versions of Weka, presumably within the Weka Package Manager: that class is defined in the mtj.jar, which is bundled inside weka.jar. In that other question, an answer suggested to extract the mtj.jar and add it to your classpath.
As I didn't have this problem with other Filters, my guess is that MultiClassFLDA is not implemented correctly: I found out is that if you use another Filter before, that specific class will get loaded:
// Run a dummy Filter for correct initialization
Filter f = new Standardize();
f.setInputFormat(data);
Filter.useFilter(new Instances("", params, 0), f); // Dummy run on empty dataset
// Now run the MultiClassFLDA
f = new MultiClassFLDA();
f.setInputFormat(data);
data = Filter.useFilter(data, f);
N.B. that is a really ugly hack! I used it to be able to work. I'll edit my answer when I find the appropriate way to do it (other than extracting the jar from Weka itslef).

Why does java.lang.VerifyError mean?

While I've tried to use the following code snippet with the Groovy in-operator explanation the VerifyError has occured. Have you guys any idea about?
The code and console output is below.
class Hello extends ArrayList {
boolean isCase(Object val) {
return val == 66
}
static void main(args) {
def myList = new Hello()
myList << 55
assert 66 in myList
assert !myList.contains(66)
}
}
The error log:
Exception in thread "main" java.lang.VerifyError: (class: Hello, method: super$1$stream signature: ()Ljava/util/stream/Stream;) Illegal use of nonvirtual function call
at java.lang.Class.forName0(Native Method)
at java.lang.Class.forName(Class.java:259)
at com.intellij.rt.execution.application.AppMain.main(AppMain.java:116)
The code origin from the topic How does the Groovy in operator work?.
Update:
Groovy Version: 1.8.6 JVM: 1.6.0_45 Vendor: Sun Microsystems Inc. OS: Linux

Check this out.
It's for Java, but generally problem is, that you are using wrong library versions. The class is there, but different version than expected.
http://craftingjava.blogspot.co.uk/2012/08/3-reasons-for-javalangverfiyerror.html
Probably you have messed up Groovy or Java SDK installations.

IncompatibleClassChangeError in Java

After learning Lambda Expressions in Java, I tried to practice some simple examples. But in my first example only I am getting the following error.
Exception in thread "main" java.lang.IncompatibleClassChangeError
at java.lang.invoke.MethodHandleNatives.linkMethodHandleConstant(MethodHandleNatives.java:384)
at com.example.lambda.HelloLambda.main(HelloLambda.java:15)
Caused by: java.lang.NoSuchMethodException: no such method: java.lang.invoke.LambdaMetafactory.metaFactory(Lookup,String,MethodType,MethodHandle,MethodHandle,MethodType)CallSite/invokeStatic
at java.lang.invoke.MemberName.makeAccessException(MemberName.java:763)
at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:880)
at java.lang.invoke.MethodHandles$Lookup.resolveOrFail(MethodHandles.java:1019)
at java.lang.invoke.MethodHandles$Lookup.linkMethodHandleConstant(MethodHandles.java:1284)
at java.lang.invoke.MethodHandleNatives.linkMethodHandleConstant(MethodHandleNatives.java:382)
... 1 more
Caused by: java.lang.NoSuchMethodError: java.lang.invoke.LambdaMetafactory.metaFactory(Ljava/lang/invoke/MethodHandles$Lookup;Ljava/lang/String;Ljava/lang/invoke/MethodType;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodHandle;Ljava/lang/invoke/MethodType;)Ljava/lang/invoke/CallSite;
at java.lang.invoke.MethodHandleNatives.resolve(Native Method)
at java.lang.invoke.MemberName$Factory.resolve(MemberName.java:852)
at java.lang.invoke.MemberName$Factory.resolveOrFail(MemberName.java:877)
... 4 more
The error seems an error because of backward compatibility issue. But don't know how to fix this. Many answers in StackOverFlow suggested Recompilation could fix this issue. But still I am getting this error.
My code
package com.example.lambda;
public class HelloLambda {
static String firstname = "ChanSek";
static String lastname = "Nayak";
interface HelloService {
String hello();
}
public static void main(String[] args) {
HelloService helloService =
() -> {String hello="Hello " + firstname + " " + lastname;
return hello;};
System.out.println(helloService.hello());
}
}
The code compiles fine. But running gives the above mentioned error.
I am using JDK1.8.0 snapshot.

Is it possibly because of this?
http://bugs.sun.com/bugdatabase/view_bug.do?bug_id=8019635
The way lambdas have been done in Java 8 has changed, very recently (07/2013), in a not backwards compatible way.
If you've somehow managed to compile with a compiler which talks PRE beta 103 lambdas, but are running with a JRE of POST 103 lambdas, you'll have problems.
(The hint for me here is that the metafactory name used to be mixed case, but in java 1.8.0 beta 103 appears to be lower case - you're searching for mixed case, but not finding it.)