Hi Stefan,
Ah! This bug is so wicked. The following code works until the last line:
package test;
object test {
class A(as: Array[S])
case class S(s: String)
def main(args : Array[String]) : Unit = {
Console.println("hello world");
val xxx = S("hello");
Console.println(xxx.s);
val clazz = Class.forName("test.test$S");
Console.println("clazz: " + clazz);
val unbox = java.lang.reflect.Array.newInstance(clazz, 10);
Console.println("array: " + unbox);
// crash: next line
Console.println(new A(Array()))
}
}
And the reason why: the JDT launcher loads library classes from a
different more privledged class loader than the application. This means
that the code in the library will load only from the library's class
loader and not the application's, which means our use of reflection to
get at application classes in the Scala run-time will not work with the
JDT launcher. Actually this is a pretty common setup for security
reasons as far as I understand it (prevents trojan string attacks: its
probably true in web browsers - should test). When invoked from the
command line, the Scala library is treated like part of the application
rather than a privledged system library, so it is loaded from the
application's class loader and hence forName between the library and the
application will behave the same. In Eclipse, this isn't true, and as a
result we get a crash.
As for the fix, I think we shouldn't depend on the Scala library and
application class loaders being the same. But we are going to have to
Thanks for finding this!
Sean
Stefan Matthias Aust wrote:
> I wounder, why I get an exception. I'm using the Eclipse plugin 2.1.3.
>
> Example code:
>
> package test;
>
> object test {
> class A(as: Array[S])
> case class S(s: String)
>
> def main(args: Array[String]): Unit = {
> Console.println(new A(Array()))
> }
> }
>
> Error message:
>
> Exception in thread "main" java.lang.ClassNotFoundException: test/test$S
> at java.lang.Class.forName0(Native Method)
> at java.lang.Class.forName(Class.java:169)
> at scala.runtime.BoxedAnyArray.unbox(BoxedAnyArray.scala:150)
> at scala.runtime.ScalaRunTime$.arrayValue(ScalaRunTime.scala:107)
> at test.test$.main(test.scala:8)
> at test.test.main(test.scala)
>
> I decompiled the generated code and it looks like
>
> Object obj = ScalaRunTime$.MODULE$.arrayValue(
> Predef$.MODULE$.Array(
> new BoxedObjectArray((Object[])new test.S[0])), "test.test$S");
> test.A a = new test.A((test.S[])(
> (obj instanceof BoxedArray)
> ? ScalaRunTime$.MODULE$.arrayValue((BoxedArray)obj, "test.test$S")
> : obj));
> Console$.MODULE$.println(a);
>
> Line 150 of BoxedAnyArray.scala is
>
> unboxed = java.lang.reflect.Array.newInstance(
> Class.forName(elemTag), length);
>
> which also looks good.
>
> I tried the Eclipse-compiled code with scala 2.1.3 from sbaz and that
> worked just fine.
>
Locked
