0 Replies Latest reply on Dec 28, 2011 11:07 AM by Wanja Gayk

    Javassist 3.15.0-GA, StackOverflowError with $sig in call to static method, can anyone confirm?

    Wanja Gayk Newbie

      Cheers,

       

      here's an Example of a possible bug I've found.

      Could anyone confirm this or prove me an idiot, so I can either file a bug report or go kill myself in shame?

       

      Using $sig or $class as method parameter only seems to work on nonstatic methods, on static methods I get a StackOverflow Error.

      Have I missed something in the dicumentation or is that a serious bug?

       

      I could reproduce this with the latest JRE6 and the current JRE7:

       

      Using $sig:

       

      instrumenting class: de/plush/brix/instrumentation/Main (995 bytes)

      instrumenting class: javassist/runtime/Desc (3280 bytes)

      Exception in thread "main" java.lang.StackOverflowError

      at javassist.runtime.Desc.getParams(Desc.java)

      at javassist.runtime.Desc.getParams(Desc.java)

      at javassist.runtime.Desc.getParams(Desc.java)

      [..]

       

      Using $class:

       

      instrumenting class: de/plush/brix/instrumentation/Main (995 bytes)

      instrumenting class: javassist/runtime/Desc (3280 bytes)

      Exception in thread "main" java.lang.StackOverflowError

      at javassist.runtime.Desc.getClazz(Desc.java)

      at javassist.runtime.Desc.getClazz(Desc.java)

      [...]

       

      Compile the following code, create JAR-File, have a manifest like:

       

      Manifest-Version: 1.0

      Ant-Version: Apache Ant 1.8.2

      Created-By: 1.7.0_02-b13 (Oracle Corporation)

      Premain-Class: de.plush.brix.instrumentation.Agent

      Class-Path: javassist.jar

       

      Start some Main.class with the jvm-arg:

      -javaagent:${project_loc}\Agent.jar

       

      And watch it happen.

       

      package de.plush.brix.instrumentation;

       

      public class Main {

      void foo() {

        System.out.println("Hello world");

        }

      public static void main(final String[] args) {

        new Main().foo();

      }

      }

       

      package de.plush.brix.instrumentation;

       

      import java.io.IOException;

      import java.lang.instrument.ClassFileTransformer;

      import java.lang.instrument.IllegalClassFormatException;

      import java.lang.instrument.Instrumentation;

      import java.lang.reflect.Modifier;

      import java.security.ProtectionDomain;

      import java.util.Arrays;

       

      import javassist.ByteArrayClassPath;

      import javassist.CannotCompileException;

      import javassist.ClassPool;

      import javassist.CtClass;

      import javassist.CtMethod;

      import javassist.NotFoundException;

       

      public class Agent implements ClassFileTransformer {

       

      public Agent(final String agentArgs, final Instrumentation instrumentation) {

        instrumentation.addTransformer(this);

      }

       

      public static void premain(final String agentArgs, final Instrumentation inst) {

        new Agent(agentArgs, inst);

      }

       

      public static void before(Class[] paramTypes) { //works

      System.out.println("test passed");

      }

       

      public static void before(Class paramTypes) { //works

      System.out.println("test passed");

      }

       

      public static void beforeStatic(Class[] paramTypes) { //stackOverflow

        System.out.println("test passed");

      }

       

      public static void beforeStatic2(Class paramTypes) { //stackOverflow

      System.out.println("test passed");

      }

       

      @Override

      public byte[] transform(final ClassLoader loader, final String className, final Class<?> classBeingRedefined, final ProtectionDomain protectionDomain,

      final byte[] classfileBuffer) throws IllegalClassFormatException {

       

        System.out.println("instrumenting class: " + className + " (" + classfileBuffer.length + " bytes)");

       

        try {

        final String javaClassName = className.replace('/', '.');

        // turn bytecodes into a Javassist CtClass

        final CtClass clazz = createClass(classfileBuffer, javaClassName);

        // add output at the beginning and end of each method

        for (final CtMethod method : clazz.getMethods()) {

         if (!isInherited(javaClassName, method)) {

           if (Modifier.isStatic(method.getModifiers())) {

            method.insertBefore("{"+Agent.class.getName() + ".beforeStatic($sig);}"); // -- $sig kills it!

            // method.insertBefore("{"+Agent.class.getName() + ".beforeStatic2($class);}"); // -- $class kills it too!

           } else {

            method.insertBefore("{"+Agent.class.getName() + ".before($sig);}"); // -- works

            // method.insertBefore("{"+Agent.class.getName() + ".before2($class);}"); // --works too

          }

         }

        }

        return clazz.toBytecode();

      } catch (final NotFoundException e) {

         throw new RuntimeException(e);

      } catch (final CannotCompileException e) {

         if (!e.getMessage().contains("no method body")) {

          throw new RuntimeException(e);

         }

        // don't care

      } catch (final IOException e) {

        throw new RuntimeException(e);

      }

      return classfileBuffer;

      }

       

      private boolean isInherited(final String javaClassName, final CtMethod method) {

        return !method.getLongName().startsWith(javaClassName);

      }

       

      private CtClass createClass(final byte[] classfileBuffer, final String javassistClassName) throws NotFoundException {

      final ClassPool cp = ClassPool.getDefault();

      cp.insertClassPath(new ByteArrayClassPath(javassistClassName, classfileBuffer));

      final CtClass cc = cp.get(javassistClassName);

      return cc;

      }

      }