psuter / cafebabe Goto Github PK

Full stack trace here.

Extracting the .jar with 'jar xf' and adding the parent folder to the classpath works just fine.

Maybe I'm just doing it wrong, but it seems fishy.

On line 118 here in ClassFile[1] there's a string literal "()V" which is the signature of the default constructor of the super class. There is a constant constructorSig in defaults.scala already for this purpose.

1:

CC: @manoskouk
By adding duplicated methods/fields is possible to generate ill-formed class files without any warnings; failing at runtime with ClassFormatError.
Tracking duplicated methods/fields is a bit hard since methods can change their static-ness; the check should be done on build-time...
I have a slightly more general solution; which consists in loading the class file (without resolving any dependencies) after being generated just to verify it's correctness by ensuring it passes the JVM checks.
Any comments?

Currently there is no way to generate a static initializer( i.e static{}; ) for a class, which is sometimes important for initialization before calling either Constructor or main() method.

Hi,

As asked here is minimal code reproducting the issue :

object App extends App {

  import cafebabe.ByteCodes._
  import cafebabe.AbstractByteCodes._

  val classFile = new cafebabe.ClassFile("HW", None)

  classFile.setSourceFile("HW.java")

  classFile.addDefaultConstructor

  val codeHandler = classFile.addMainMethod.codeHandler

  codeHandler <<
    GetStatic("java/lang/System", "out", "Ljava/io/PrintStream;") <<
    Ldc("Hello world!") <<
    InvokeVirtual("java/io/PrintStream", "println", "(Ljava/lang/String;)V")  /* <<
    RETURN */

  codeHandler.freeze
  classFile.writeToFile("./classfiles/HW.class")
}

As you can see, I deliberately commented the RETURN bytecode.

And here is the stack trace :

Exception in thread "main" java.lang.ArrayIndexOutOfBoundsException: 8
    at cafebabe.CodeHandler.setHeight$1(CodeHandler.scala:147)
    at cafebabe.CodeHandler.computeMaxStack(CodeHandler.scala:222)
    at cafebabe.CodeHandler.freeze(CodeHandler.scala:129)
    at App$delayedInit$body.apply(App.scala:22)
    at scala.Function0$class.apply$mcV$sp(Function0.scala:34)
    at scala.runtime.AbstractFunction0.apply$mcV$sp(AbstractFunction0.scala:12)
    at scala.App$$anonfun$main$1.apply(App.scala:60)
    at scala.App$$anonfun$main$1.apply(App.scala:60)
    at scala.collection.LinearSeqOptimized$class.foreach(LinearSeqOptimized.scala:59)
    at scala.collection.immutable.List.foreach(List.scala:76)
    at scala.collection.generic.TraversableForwarder$class.foreach(TraversableForwarder.scala:30)
    at scala.App$class.main(App.scala:60)
    at App$.main(App.scala:3)
    at App.main(App.scala)

There of course a lot of other situation where an ArrayIndexOutOfBoundsException is thrown. As soon as some required bytecodes are missing it seems to suffer from this issue.

I'm using scala 2.9.3 with cafebabe 1.2. If you need any more information, let me know.

Hi there,

So I noticed you implemented support for interfaces, but you forgot to add a method in ClassFile.scala that adds a method with no code attribute. I locally wrote a method that handles this, called addMethodHead. Maybe you can implement it (or some variation of it) in your source code. The following picture shows the method I added:

Have a good one!