[DiSL-user] Problems using custom Transformers

[Alessio Gambi]

Dear DiSL-ers

I am having troubles in making my custom implementation working with DiSL.

So far I got to the following point:

	- Implemented Transformer interface

	- Triggered custom transformation

	- NPE (see [1]) when the transformation is applied.



I rooted the problem in the following code (DiSL.java) ~ line 440/450 (I introduced few printouts): 

public synchronized byte[] instrument(final byte[] originalBytes) throws DiSLException {

		...

		//
		// Instrument the class. If the class is modified neither by DiSL,
		// nor by any of the transformers, bail out early and return NULL
		// to indicate that the class has not been modified in any way.
		//
		final InstrumentedClass instResult = instrumentClass(inputCN);
		if (instResult == null && transformedBytes == originalBytes) {
			return null;
		}
		
In my case, I get the following condition: "instResult == null” BUT "transformedBytes != originalBytes”,
so the if statement does not trigger and later in the same method there’s an access to instResult which raise the NullPointerException

		final ClassNode instCN = instResult.classNode;


I am digging a bit into the code to understand why instResult is null, but in the meanwhile you might suggest something as well.

Best

— Alessio

[1] Console output:

     [exec] de.unisaarland.instrumentation: Info: Transforming mainP/Main
     [exec] de.unisaarland.instrumentation: DependencyTrackingClassVisitor.visit()
     [exec] de.unisaarland.instrumentation: Adding interface DependencyInstrumented to mainP/Main null java/lang/Object
     [exec] dislserver: error instrumenting mainP/Main: java.lang.NullPointerException
     [exec] 	at ch.usi.dag.disl.DiSL.instrument(DiSL.java:450)
     [exec] 	at ch.usi.dag.dislserver.RequestProcessor.process(RequestProcessor.java:71)
     [exec] 	at ch.usi.dag.dislserver.DiSLServer$ConnectionHandler.run(DiSLServer.java:99)
     [exec] 	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
     [exec] 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
     [exec] 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
     [exec] 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
     [exec] 	at java.lang.Thread.run(Thread.java:745)
     [exec] 
     [exec] DiSL-agent error: instrumentation server error:
     [exec] error instrumenting mainP/Main: java.lang.NullPointerException
     [exec] 	at ch.usi.dag.disl.DiSL.instrument(DiSL.java:450)
     [exec] 	at ch.usi.dag.dislserver.RequestProcessor.process(RequestProcessor.java:71)
     [exec] 	at ch.usi.dag.dislserver.DiSLServer$ConnectionHandler.run(DiSLServer.java:99)
     [exec] 	at java.util.concurrent.Executors$RunnableAdapter.call(Executors.java:511)
     [exec] 	at java.util.concurrent.FutureTask.run(FutureTask.java:266)
     [exec] 	at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)
     [exec] 	at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)
     [exec] 	at java.lang.Thread.run(Thread.java:745)
     [exec] 
     [exec] dislreserver: fatal error: java.io.EOFException
     [exec] 	at java.io.DataInputStream.readByte(DataInputStream.java:267)
     [exec] 	at ch.usi.dag.dislreserver.DiSLREServer.processRequests(DiSLREServer.java:105)
     [exec] 	at ch.usi.dag.dislreserver.DiSLREServer.run(DiSLREServer.java:76)
     [exec] 	at ch.usi.dag.dislreserver.DiSLREServer.main(DiSLREServer.java:58)
     [exec] 
     [exec] de.unisaarland.instrumentation: Info: Done with mainP/Main
     [exec] disl: Original class transformed
     [exec] disl: InstrumentedClass  : null
Alessio Gambi, Ph.D.
gambi at st.cs.uni-saarland.de



-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://d3s.mff.cuni.cz/pipermail/disl-user/attachments/20170420/20a063d6/attachment.html>