org.objectweb.asm.tree.analysis.BasicValue Java Examples

public InstructionGraphNode setGraphNode(final AbstractInsnNode insn,
    final BasicValue resultValue, final List<BasicValue> predecessors)
{
    if (graphNodes == null) {
        // initialize with a list of null values
        graphNodes = Lists
            .newArrayList(new InstructionGraphNode[instructions.size()]);
    }
    final int index = instructions.indexOf(insn);
    InstructionGraphNode node = graphNodes.get(index);
    if (node == null) {
        node = new InstructionGraphNode(insn, resultValue);
        graphNodes.set(index, node);
    }
    node.addPredecessors(predecessors);
    return node;
}
 

@Override
public BasicValue newValue(final Type t) {
  if (t != null) {
    final ValueHolderIden iden = HOLDERS.get(t.getDescriptor());
    if (iden != null) {
      final ReplacingBasicValue v = ReplacingBasicValue.create(t, iden, index++, valueList);
      v.markFunctionReturn();
      return v;
    }

    // We need to track use of the "this" objectref
    if ((t.getSort() == Type.OBJECT) && className.equals(t.getInternalName())) {
      final ReplacingBasicValue rbValue = ReplacingBasicValue.create(t, null, 0, valueList);
      rbValue.setThis();
      return rbValue;
    }
  }

  return super.newValue(t);
}
 

@Override
// Override this method to get unmasked type from BasicInterpreter
public BasicValue newValue(final Type type) {
    if (type == null) {
        return BasicValue.UNINITIALIZED_VALUE;
    }
    switch (type.getSort()) {
        case Type.VOID:
            return null;
        case Type.BOOLEAN:
        case Type.CHAR:
        case Type.BYTE:
        case Type.SHORT:
        case Type.INT:
        case Type.FLOAT:
        case Type.LONG:
        case Type.DOUBLE:
        case Type.ARRAY:
        case Type.OBJECT:
            return new BasicValue(type);
        default:
            throw new AssertionError();
    }
}
 

/**
 * Constructs a new {@link CheckMethodAdapter} object. This method adapter
 * will perform basic data flow checks. For instance in a method whose
 * signature is <tt>void m ()</tt>, the invalid instruction IRETURN, or the
 * invalid sequence IADD L2I will be detected.
 * 
 * @param access
 *          the method's access flags.
 * @param name
 *          the method's name.
 * @param desc
 *          the method's descriptor (see {@link Type Type}).
 * @param cmv
 *          the method visitor to which this adapter must delegate calls.
 * @param labels
 *          a map of already visited labels (in other methods).
 */
public CheckMethodAdapter(final int access, final String name, final String desc, final MethodVisitor cmv, final Map<Label, Integer> labels) {
  this(new MethodNode(Opcodes.ASM5, access, name, desc, null, null) {
    @Override
    public void visitEnd() {
      Analyzer<BasicValue> a = new Analyzer<BasicValue>(new BasicVerifier());
      try {
        a.analyze("dummy", this);
      } catch (Exception e) {
        if (e instanceof IndexOutOfBoundsException && maxLocals == 0 && maxStack == 0) {
          throw new RuntimeException("Data flow checking option requires valid, non zero maxLocals and maxStack values.");
        }
        e.printStackTrace();
        StringWriter sw = new StringWriter();
        PrintWriter pw = new PrintWriter(sw, true);
        CheckClassAdapter.printAnalyzerResult(this, a, pw);
        pw.close();
        throw new RuntimeException(e.getMessage() + ' ' + sw.toString());
      }
      accept(cmv);
    }
  }, labels);
  this.access = access;
}
 

@Override
public BasicValue binaryOperation(final AbstractInsnNode insn,
    final BasicValue value1, final BasicValue value2) throws AnalyzerException {
  /*
   * We're looking for the assignment of a local holder objectref to a member variable.
   * If we spot that, then the local holder can't be replaced, since we don't (yet)
   * have the mechanics to replace the member variable with the holder's members or
   * to assign all of them when this happens.
   */
  if (insn.getOpcode() == Opcodes.PUTFIELD) {
    if (value2.isReference() && (value1 instanceof ReplacingBasicValue)) {
      final ReplacingBasicValue possibleThis = (ReplacingBasicValue) value1;
      if (possibleThis.isThis() && (value2 instanceof ReplacingBasicValue)) {
        // if this is a reference for a holder class, we can't replace it
        if (HOLDERS.get(value2.getType().getDescriptor()) != null) {
          final ReplacingBasicValue localRef = (ReplacingBasicValue) value2;
          localRef.setAssignedToMember();
        }
      }
    }
  }

  return super.binaryOperation(insn, value1, value2);
}
 

@Override
public BasicValue naryOperation(final AbstractInsnNode insn,
    final List<? extends BasicValue> values) throws AnalyzerException {
  if (insn instanceof MethodInsnNode) {
    boolean skipOne = insn.getOpcode() != Opcodes.INVOKESTATIC;

    // Note if the argument is a holder, and is used as a function argument
    for(BasicValue value : values) {
      // if non-static method, skip over the receiver
      if (skipOne) {
        skipOne = false;
        continue;
      }

      if (value instanceof ReplacingBasicValue) {
        final ReplacingBasicValue argument = (ReplacingBasicValue) value;
        argument.setFunctionArgument();
      }
    }
  }

  return super.naryOperation(insn,  values);
}
 

/**
 * Checks a given class.
 * 
 * @param cr
 *          a <code>ClassReader</code> that contains bytecode for the
 *          analysis.
 * @param loader
 *          a <code>ClassLoader</code> which will be used to load referenced
 *          classes. This is useful if you are verifiying multiple
 *          interdependent classes.
 * @param dump
 *          true if bytecode should be printed out not only when errors are
 *          found.
 * @param pw
 *          write where results going to be printed
 */
public static void verify(final ClassReader cr, final ClassLoader loader, final boolean dump, final PrintWriter pw) {
  ClassNode cn = new ClassNode();
  cr.accept(new CheckClassAdapter(cn, false), ClassReader.SKIP_DEBUG);

  Type syperType = cn.superName == null ? null : Type.getObjectType(cn.superName);
  List<MethodNode> methods = cn.methods;

  List<Type> interfaces = new ArrayList<Type>();
  for (Iterator<String> i = cn.interfaces.iterator(); i.hasNext();) {
    interfaces.add(Type.getObjectType(i.next()));
  }

  for (int i = 0; i < methods.size(); ++i) {
    MethodNode method = methods.get(i);
    SimpleVerifier verifier = new SimpleVerifier(Type.getObjectType(cn.name), syperType, interfaces, (cn.access & Opcodes.ACC_INTERFACE) != 0);
    Analyzer<BasicValue> a = new Analyzer<BasicValue>(verifier);
    if (loader != null) {
      verifier.setClassLoader(loader);
    }
    try {
      a.analyze(cn.name, method);
      if (!dump) {
        continue;
      }
    } catch (Exception e) {
      e.printStackTrace(pw);
    }
    printAnalyzerResult(method, a, pw);
  }
  pw.flush();
}
 

/**
 * Checks the given class.
 *
 * @param classReader the class to be checked.
 * @param loader a <code>ClassLoader</code> which will be used to load referenced classes. May be
 *     {@literal null}.
 * @param printResults whether to print the results of the bytecode verification.
 * @param printWriter where the results (or the stack trace in case of error) must be printed.
 */
public static void verify(
    final ClassReader classReader,
    final ClassLoader loader,
    final boolean printResults,
    final PrintWriter printWriter) {
  ClassNode classNode = new ClassNode();
  classReader.accept(
      new CheckClassAdapter(Opcodes.ASM7, classNode, false) {}, ClassReader.SKIP_DEBUG);

  Type syperType = classNode.superName == null ? null : Type.getObjectType(classNode.superName);
  List<MethodNode> methods = classNode.methods;

  List<Type> interfaces = new ArrayList<Type>();
  for (String interfaceName : classNode.interfaces) {
    interfaces.add(Type.getObjectType(interfaceName));
  }

  for (MethodNode method : methods) {
    SimpleVerifier verifier =
        new SimpleVerifier(
            Type.getObjectType(classNode.name),
            syperType,
            interfaces,
            (classNode.access & Opcodes.ACC_INTERFACE) != 0);
    Analyzer<BasicValue> analyzer = new Analyzer<BasicValue>(verifier);
    if (loader != null) {
      verifier.setClassLoader(loader);
    }
    try {
      analyzer.analyze(classNode.name, method);
    } catch (AnalyzerException e) {
      e.printStackTrace(printWriter);
    }
    if (printResults) {
      printAnalyzerResult(method, analyzer, printWriter);
    }
  }
  printWriter.flush();
}
 

@Override
public Value merge(Value v, Value w) {
    if (!v.equals(w)) {
        Type t = ((BasicValue)v).getType();
        Type u = ((BasicValue)w).getType();
        int tsort = t == null ? -1 : t.getSort();
        if (tsort == Type.OBJECT || tsort == Type.ARRAY) {
            int usort = u == null ? -1 : u.getSort();
            if (usort == Type.OBJECT || usort == Type.ARRAY) {
                if ("Lnull;".equals(t.getDescriptor())) {
                    return w;
                }
                if ("Lnull;".equals(u.getDescriptor())) {
                    return v;
                }
                if (isAssignableFrom(t, u)) {
                    return v;
                }
                if (isAssignableFrom(u, t)) {
                    return w;
                }
                return new BasicValue(classHierarchy.getCommonSuperType(t, u));
            }
        }
        return BasicValue.UNINITIALIZED_VALUE;
    }
    return v;
}
 

@Override
   public BasicValue binaryOperation(final AbstractInsnNode insn,
   	final BasicValue value1, final BasicValue value2)
   		throws AnalyzerException
{
	if(insn.getOpcode() == Opcodes.AALOAD)
		return new BasicValue(value1.getType().getElementType());
	return super.binaryOperation(insn, value1, value2);
}
 

@Override
   public BasicValue newValue(final Type type)
{
       if(type == null)
           return new BasicValue(Type.getType("java/lang/Object"));
       switch(type.getSort())
       {
       	case Type.VOID:
       		return null;
       	case Type.BOOLEAN:
       	case Type.CHAR:
       	case Type.BYTE:
       	case Type.SHORT:
       	case Type.INT:
       		return BasicValue.INT_VALUE;
       	case Type.FLOAT:
       		return BasicValue.FLOAT_VALUE;
       	case Type.LONG:
       		return BasicValue.LONG_VALUE;
       	case Type.DOUBLE:
       		return BasicValue.DOUBLE_VALUE;
       	case Type.ARRAY:
       	case Type.OBJECT:
       		return new BasicValue(type);
       	default:
       		throw new Error("Internal error");
       }
}
 

static void printAnalyzerResult(MethodNode method, Analyzer<BasicValue> a, final PrintWriter pw) {
  Frame<BasicValue>[] frames = a.getFrames();
  Textifier t = new Textifier();
  TraceMethodVisitor mv = new TraceMethodVisitor(t);

  pw.println(method.name + method.desc);
  for (int j = 0; j < method.instructions.size(); ++j) {
    method.instructions.get(j).accept(mv);

    StringBuilder sb = new StringBuilder();
    Frame<BasicValue> f = frames[j];
    if (f == null) {
      sb.append('?');
    } else {
      for (int k = 0; k < f.getLocals(); ++k) {
        sb.append(getShortName(f.getLocal(k).toString())).append(' ');
      }
      sb.append(" : ");
      for (int k = 0; k < f.getStackSize(); ++k) {
        sb.append(getShortName(f.getStack(k).toString())).append(' ');
      }
    }
    while (sb.length() < method.maxStack + method.maxLocals + 1) {
      sb.append(' ');
    }
    pw.print(Integer.toString(j + 100000).substring(1));
    pw.print(" " + sb + " : " + t.text.get(t.text.size() - 1));
  }
  for (int j = 0; j < method.tryCatchBlocks.size(); ++j) {
    method.tryCatchBlocks.get(j).accept(mv);
    pw.print(" " + t.text.get(t.text.size() - 1));
  }
  pw.println();
}
 

static void printAnalyzerResult(
    final MethodNode method, final Analyzer<BasicValue> analyzer, final PrintWriter printWriter) {
  Textifier textifier = new Textifier();
  TraceMethodVisitor traceMethodVisitor = new TraceMethodVisitor(textifier);

  printWriter.println(method.name + method.desc);
  for (int i = 0; i < method.instructions.size(); ++i) {
    method.instructions.get(i).accept(traceMethodVisitor);

    StringBuilder stringBuilder = new StringBuilder();
    Frame<BasicValue> frame = analyzer.getFrames()[i];
    if (frame == null) {
      stringBuilder.append('?');
    } else {
      for (int j = 0; j < frame.getLocals(); ++j) {
        stringBuilder.append(getUnqualifiedName(frame.getLocal(j).toString())).append(' ');
      }
      stringBuilder.append(" : ");
      for (int j = 0; j < frame.getStackSize(); ++j) {
        stringBuilder.append(getUnqualifiedName(frame.getStack(j).toString())).append(' ');
      }
    }
    while (stringBuilder.length() < method.maxStack + method.maxLocals + 1) {
      stringBuilder.append(' ');
    }
    printWriter.print(Integer.toString(i + 100000).substring(1));
    printWriter.print(
        " " + stringBuilder + " : " + textifier.text.get(textifier.text.size() - 1));
  }
  for (TryCatchBlockNode tryCatchBlock : method.tryCatchBlocks) {
    tryCatchBlock.accept(traceMethodVisitor);
    printWriter.print(" " + textifier.text.get(textifier.text.size() - 1));
  }
  printWriter.println();
}
 

@Test
public void testPut() throws Exception {
    Frame<ConstructorThisInterpreter.ThisValue> frame = new Frame<>(LOCAL_COUNT, 4);
    frame.push(ConstructorThisInterpreter.ThisValue.createNotThis(BasicValue.REFERENCE_VALUE));
    frame.push(ConstructorThisInterpreter.ThisValue.createNotThis(BasicValue.REFERENCE_VALUE));
    frame.push(ConstructorThisInterpreter.ThisValue.createThis(BasicValue.REFERENCE_VALUE));
    frame.push(ConstructorThisInterpreter.ThisValue.createNotThis(BasicValue.REFERENCE_VALUE));
    @SuppressWarnings("unchecked")
    Frame<ConstructorThisInterpreter.ThisValue>[] frames = new Frame[] {
            frame
    };
    StackThisTracker tracker = new StackThisTracker(frames);
    Assert.assertFalse(tracker.isThisTargetOfGet(0));
    Assert.assertTrue(tracker.isThisTargetOfPut(0));
}
 

@Test
public void testGet() throws Exception {
    Frame<ConstructorThisInterpreter.ThisValue> frame = new Frame<>(LOCAL_COUNT, 4);
    frame.push(ConstructorThisInterpreter.ThisValue.createNotThis(BasicValue.REFERENCE_VALUE));
    frame.push(ConstructorThisInterpreter.ThisValue.createNotThis(BasicValue.REFERENCE_VALUE));
    frame.push(ConstructorThisInterpreter.ThisValue.createNotThis(BasicValue.REFERENCE_VALUE));
    frame.push(ConstructorThisInterpreter.ThisValue.createThis(BasicValue.REFERENCE_VALUE));
    @SuppressWarnings("unchecked")
    Frame<ConstructorThisInterpreter.ThisValue>[] frames = new Frame[] {
            frame
    };
    StackThisTracker tracker = new StackThisTracker(frames);
    Assert.assertTrue(tracker.isThisTargetOfGet(0));
    Assert.assertFalse(tracker.isThisTargetOfPut(0));
}
 

@Override
public ThisValue newValue(Type type) {
    ThisValue result = null;
    BasicValue original = this.underlying.newValue(type);
    if (null != original) {
        if (this.isNextThis) {
            // WARNING:  This is where we assume that we are being asked to describe the "this".
            result = ThisValue.createThis(original);
            this.isNextThis = false;
        } else {
            result = ThisValue.createNotThis(original);
        }
    }
    return result;
}
 

/**
 * Checks the given class.
 *
 * @param classReader the class to be checked.
 * @param loader a <code>ClassLoader</code> which will be used to load referenced classes. May be
 *     {@literal null}.
 * @param printResults whether to print the results of the bytecode verification.
 * @param printWriter where the results (or the stack trace in case of error) must be printed.
 */
public static void verify(
    final ClassReader classReader,
    final ClassLoader loader,
    final boolean printResults,
    final PrintWriter printWriter) {
  ClassNode classNode = new ClassNode();
  classReader.accept(
      new CheckClassAdapter(Opcodes.ASM7, classNode, false) {}, ClassReader.SKIP_DEBUG);

  Type syperType = classNode.superName == null ? null : Type.getObjectType(classNode.superName);
  List<MethodNode> methods = classNode.methods;

  List<Type> interfaces = new ArrayList<>();
  for (String interfaceName : classNode.interfaces) {
    interfaces.add(Type.getObjectType(interfaceName));
  }

  for (MethodNode method : methods) {
    SimpleVerifier verifier =
        new SimpleVerifier(
            Type.getObjectType(classNode.name),
            syperType,
            interfaces,
            (classNode.access & Opcodes.ACC_INTERFACE) != 0);
    Analyzer<BasicValue> analyzer = new Analyzer<>(verifier);
    if (loader != null) {
      verifier.setClassLoader(loader);
    }
    try {
      analyzer.analyze(classNode.name, method);
    } catch (AnalyzerException e) {
      e.printStackTrace(printWriter);
    }
    if (printResults) {
      printAnalyzerResult(method, analyzer, printWriter);
    }
  }
  printWriter.flush();
}
 

@Override
public BasicValue unaryOperation(final AbstractInsnNode insn,
    final BasicValue value)
    throws AnalyzerException
{
    return createNode(insn, super.unaryOperation(insn, null), value);
}
 

/**
 * Checks the given class.
 *
 * @param classReader the class to be checked.
 * @param loader a <code>ClassLoader</code> which will be used to load referenced classes. May be
 *     {@literal null}.
 * @param printResults whether to print the results of the bytecode verification.
 * @param printWriter where the results (or the stack trace in case of error) must be printed.
 */
public static void verify(
    final ClassReader classReader,
    final ClassLoader loader,
    final boolean printResults,
    final PrintWriter printWriter) {
  ClassNode classNode = new ClassNode();
  classReader.accept(
      new CheckClassAdapter(Opcodes.ASM7, classNode, false) {}, ClassReader.SKIP_DEBUG);

  Type syperType = classNode.superName == null ? null : Type.getObjectType(classNode.superName);
  List<MethodNode> methods = classNode.methods;

  List<Type> interfaces = new ArrayList<Type>();
  for (String interfaceName : classNode.interfaces) {
    interfaces.add(Type.getObjectType(interfaceName));
  }

  for (MethodNode method : methods) {
    SimpleVerifier verifier =
        new SimpleVerifier(
            Type.getObjectType(classNode.name),
            syperType,
            interfaces,
            (classNode.access & Opcodes.ACC_INTERFACE) != 0);
    Analyzer<BasicValue> analyzer = new Analyzer<BasicValue>(verifier);
    if (loader != null) {
      verifier.setClassLoader(loader);
    }
    try {
      analyzer.analyze(classNode.name, method);
    } catch (AnalyzerException e) {
      e.printStackTrace(printWriter);
    }
    if (printResults) {
      printAnalyzerResult(method, analyzer, printWriter);
    }
  }
  printWriter.flush();
}
 

private static ReplacingBasicValue filterReplacement(final BasicValue basicValue) {
  if (basicValue instanceof ReplacingBasicValue) {
    final ReplacingBasicValue replacingValue = (ReplacingBasicValue) basicValue;
    if (replacingValue.isReplaceable()) {
      return replacingValue;
    }
  }

  return null;
}
 

@Override
protected boolean isAssignableFrom(Type t, Type u) {
    if (t.equals(u)) {
        return true;
    }
    // Null is assignable to any reference type
    if ("Lnull;".equals(u.getDescriptor()) && t.getSort() >= Type.ARRAY) {
        return true;
    }
    Type et, eu;
    if (t.getSort() == Type.ARRAY) {
        if (u.getSort() != Type.ARRAY ) {
            return false;
        }
        et = t.getElementType();
        eu = u.getElementType();
        int dt = t.getDimensions();
        int du = u.getDimensions();
        boolean isObject = et.equals(((BasicValue)BasicValue.REFERENCE_VALUE).getType());
        // u must be an array of equals dimension or bigger dimension if t is Object
        if (dt == du || dt < du && isObject) {
            // Ok
        } else {
            return false;
        }
    } else {
        et = t; 
        eu = u;
    }
    /*
    Type commonType = classHierarchy.getCommonSuperType(et, eu);
    */
    // isAssignableFrom(Number, Integer) => getCommonSuperType(Integer, Number) == Number        
    // Use ClassHierarchy.isSubclass biased behavior (for performance)
    Type commonType = classHierarchy.getCommonSuperType(eu, et);
    return commonType.equals(et);

}
 

SuspendContinuationPoint(
        Integer lineNumber,
        MethodInsnNode invokeInstruction,
        Frame<BasicValue> frame) {
    // lineNumber is null if it doesn't exist
    Validate.notNull(invokeInstruction);
    // stateModifierMethod is null if it doesn't exist
    Validate.notNull(frame);

    this.lineNumber = lineNumber;
    this.invokeInstruction = invokeInstruction;
    this.continueExecutionLabel = new LabelNode();
    this.frame = frame;
}
 

private static boolean isNull(BasicValue value) {
    if (null == value)
        return true;
    if (!value.isReference())
        return false;
    Type type = value.getType();
    return "Lnull;".equals(type.getDescriptor()); 
}
 

TryCatchInvokeContinuationPoint(
        Integer lineNumber,
        MethodInsnNode invokeInstruction,
        Frame<BasicValue> frame) {
    // lineNumber is null if it doesn't exist
    Validate.notNull(invokeInstruction);
    Validate.notNull(frame);

    this.lineNumber = lineNumber;
    this.invokeInstruction = invokeInstruction;
    this.continueExecutionLabel = new LabelNode();
    this.exceptionExecutionLabel = new LabelNode();
    this.tryCatchBlock = new TryCatchBlockNode(null, null, null, null);
    this.frame = frame;
}
 

@Override
public BasicValue naryOperation(final AbstractInsnNode insn,
    final List<? extends BasicValue> values)
    throws AnalyzerException
{
    return createNode(insn, super.naryOperation(insn, null),
        (BasicValue[]) values.toArray(new BasicValue[values.size()]));
}
 

@Override
protected boolean isAssignableFrom(Type t, Type u) {
    if (t.equals(u)) {
        return true;
    }
    // Null is assignable to any reference type
    if ("Lnull;".equals(u.getDescriptor()) && t.getSort() >= Type.ARRAY) {
        return true;
    }
    Type et, eu;
    if (t.getSort() == Type.ARRAY) {
        if (u.getSort() != Type.ARRAY ) {
            return false;
        }
        et = t.getElementType();
        eu = u.getElementType();
        int dt = t.getDimensions();
        int du = u.getDimensions();
        boolean isObject = et.equals(BasicValue.REFERENCE_VALUE.getType());
        // u must be an array of equals dimension or bigger dimension if t is Object
        if (dt == du || dt < du && isObject) {
            // Ok
        } else {
            return false;
        }
    } else {
        et = t; 
        eu = u;
    }
    /*
    Type commonType = classHierarchy.getCommonSuperType(et, eu);
    */
    // isAssignableFrom(Number, Integer) => getCommonSuperType(Integer, Number) == Number        
    // Use ClassHierarchy.isSubclass biased behavior (for performance)
    Type commonType = classHierarchy.getCommonSuperType(eu, et);
    return commonType.equals(et);

}
 

SynchronizationPoint(
        InsnNode monitorInstruction,
        Frame<BasicValue> frame) {
    Validate.notNull(monitorInstruction);
    Validate.notNull(frame);
    Validate.isTrue(monitorInstruction.getOpcode() == Opcodes.MONITORENTER || monitorInstruction.getOpcode() == Opcodes.MONITOREXIT);

    this.monitorInstruction = monitorInstruction;
    this.frame = frame;
}
 

private static boolean isNull(BasicValue value) {
    if (null == value)
        return true;
    if (!value.isReference())
        return false;
    Type type = value.getType();
    return "Lnull;".equals(type.getDescriptor()); 
}
 

NormalInvokeContinuationPoint(
        Integer lineNumber,
        MethodInsnNode invokeInstruction,
        Frame<BasicValue> frame) {
    // lineNumber is null if it doesn't exist
    Validate.notNull(invokeInstruction);
    // stateModifierMethod is null if it doesn't exist
    Validate.notNull(frame);

    this.lineNumber = lineNumber;
    this.invokeInstruction = invokeInstruction;
    this.continueExecutionLabel = new LabelNode();
    this.frame = frame;
}
 

@Override
protected boolean isAssignableFrom(Type t, Type u) {
    if (t.equals(u)) {
        return true;
    }
    // Null is assignable to any reference type
    if ("Lnull;".equals(u.getDescriptor()) && t.getSort() >= Type.ARRAY) {
        return true;
    }
    Type et, eu;
    if (t.getSort() == Type.ARRAY) {
        if (u.getSort() != Type.ARRAY ) {
            return false;
        }
        et = t.getElementType();
        eu = u.getElementType();
        int dt = t.getDimensions();
        int du = u.getDimensions();
        boolean isObject = et.equals(BasicValue.REFERENCE_VALUE.getType());
        // u must be an array of equals dimension or bigger dimension if t is Object
        if (dt == du || dt < du && isObject) {
            // Ok
        } else {
            return false;
        }
    } else {
        et = t; 
        eu = u;
    }
    /*
    Type commonType = classHierarchy.getCommonSuperType(et, eu);
    */
    // isAssignableFrom(Number, Integer) => getCommonSuperType(Integer, Number) == Number        
    // Use ClassHierarchy.isSubclass biased behavior (for performance)
    Type commonType = classHierarchy.getCommonSuperType(eu, et);
    return commonType.equals(et);

}