how do I know if these two versions of scala are exactly the same?

Question

I have two different copies of scala version 2.9.2 from the Scala-Lang website.

No. 1 is binary code: scala-2.9.2.tgz

No. 2 is source code: scala-sources-2.9.2.tgz

I built scala from the source code. I have tried using both in an application and the binary works but the compiled source code does not.

My use case: I am compiling a tiny scala file that I wrote (see below for an example), then creating a jar, and then running "main" from within that jar on the command line. To make that jar, I must include "scala-library.jar" (from this SO answer) on the classpath. I need to be able to use the scala-sources that I build so that I can modify the source code later on.

When I use the compiled source code, I get an error regarding serialVersionUID, whereas the binary code does not cause this issue.

Exact error message (when using the scala that I build from source):

java.io.InvalidClassException: scala.collection.mutable.WrappedArray$ofRef; local class incompatible: stream classdesc serialVersionUID = 8184381945838716286, local class serialVersionUID = 6238838760334617323

Example code that I am running for deserializing a file:

object test {
    def main(args: Array[String]) {
        var infile = args(0)
        val thing1 : MyClass = withObjectInput(infile) { 
          f => f.readObject().asInstanceOf[MyClass] 
        }
    }    
}

Answer 1

If MyClass doesn't explicitly supply a serialVersionUID, the the compiler generates one. This will be different for different versions of javac used when compiling it.

So this error will be caused by a mismatch between the version of javac that you used for compiling scala-library and the version that was used for the downloaded binary.