Program: 3104
Project: 3104
Buggy source:
protected Class loadClass(InstrumentCommand instr) throws IOException {
  String[] args=instr.getArguments();
  this.btraceCode=instr.getCode();
  try {
    verify(btraceCode);
  }
 catch (  Throwable th) {
    if (debug)     Main.debugPrint(th);
    errorExit(th);
    return null;
  }
  this.filter=new ClassFilter(onMethods);
  if (debug)   Main.debugPrint("String_Node_Str");
  ClassWriter writer=InstrumentUtils.newClassWriter(btraceCode);
  ClassReader reader=new ClassReader(btraceCode);
  ClassVisitor visitor=new Preprocessor(writer);
  if (BTraceRuntime.classNameExists(className)) {
    className+="String_Node_Str" + getCount();
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    onCommand(new RenameCommand(className));
    visitor=new ClassRenamer(className,visitor);
  }
  try {
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    InstrumentUtils.accept(reader,visitor);
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    btraceCode=writer.toByteArray();
  }
 catch (  Throwable th) {
    if (debug)     Main.debugPrint(th);
    errorExit(th);
    return null;
  }
  Main.dumpClass(className,className,btraceCode);
  if (debug)   Main.debugPrint("String_Node_Str" + className);
  this.runtime=new BTraceRuntime(className,args,this,inst);
  if (debug)   Main.debugPrint("String_Node_Str" + className);
  if (debug)   Main.debugPrint("String_Node_Str");
  byte[] codeBuf=removeMethods(btraceCode);
  if (debug)   Main.debugPrint("String_Node_Str");
  if (debug)   Main.debugPrint("String_Node_Str");
  onCommand(new OkayCommand());
  boolean enteredHere=BTraceRuntime.enter();
  try {
    BTraceRuntime.leave();
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    if (shouldAddTransformer()) {
      this.btraceClazz=runtime.defineClass(codeBuf);
    }
 else {
      this.btraceClazz=runtime.defineClass(codeBuf,false);
    }
    if (debug)     Main.debugPrint("String_Node_Str" + className);
  }
 catch (  Throwable th) {
    if (debug)     Main.debugPrint(th);
    errorExit(th);
    return null;
  }
 finally {
    if (!enteredHere)     BTraceRuntime.enter();
  }
  return this.btraceClazz;
}

Fixed version (ground truth):
protected Class loadClass(InstrumentCommand instr) throws IOException {
  String[] args=instr.getArguments();
  this.btraceCode=instr.getCode();
  try {
    verify(btraceCode);
  }
 catch (  Throwable th) {
    if (debug)     Main.debugPrint(th);
    errorExit(th);
    return null;
  }
  this.filter=new ClassFilter(onMethods);
  if (debug)   Main.debugPrint("String_Node_Str");
  ClassWriter writer=InstrumentUtils.newClassWriter(btraceCode);
  ClassReader reader=new ClassReader(btraceCode);
  ClassVisitor visitor=new Preprocessor(writer);
  if (BTraceRuntime.classNameExists(className)) {
    className+="String_Node_Str" + getCount();
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    onCommand(new RenameCommand(className));
    visitor=new ClassRenamer(className,visitor);
  }
  try {
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    InstrumentUtils.accept(reader,visitor);
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    btraceCode=writer.toByteArray();
  }
 catch (  Throwable th) {
    if (debug)     Main.debugPrint(th);
    errorExit(th);
    return null;
  }
  Main.dumpClass(className,className,btraceCode);
  if (debug)   Main.debugPrint("String_Node_Str" + className);
  this.runtime=new BTraceRuntime(className,args,this,inst);
  if (debug)   Main.debugPrint("String_Node_Str" + className);
  if (debug)   Main.debugPrint("String_Node_Str");
  byte[] codeBuf=removeMethods(btraceCode);
  if (debug)   Main.debugPrint("String_Node_Str");
  if (debug)   Main.debugPrint("String_Node_Str");
  runtime.send(new OkayCommand());
  boolean enteredHere=BTraceRuntime.enter();
  try {
    BTraceRuntime.leave();
    if (debug)     Main.debugPrint("String_Node_Str" + className);
    if (shouldAddTransformer()) {
      this.btraceClazz=runtime.defineClass(codeBuf);
    }
 else {
      this.btraceClazz=runtime.defineClass(codeBuf,false);
    }
    if (debug)     Main.debugPrint("String_Node_Str" + className);
  }
 catch (  Throwable th) {
    if (debug)     Main.debugPrint(th);
    errorExit(th);
    return null;
  }
 finally {
    if (!enteredHere)     BTraceRuntime.enter();
  }
  return this.btraceClazz;
}