[BCEL-137] "Invalid method signature: TT;" when using MethodGen for a method having a generic parameter

• Type: Bug
• Status: Closed
• Priority: Blocker
• Resolution: Fixed
• Fix Version/s: 6.0
• Component/s: Main
• External issue URL: https://issues.apache.org/bugzilla/show_bug.cgi?id=48279
• External issue ID: 48279
• Assignee: Apache Commons Developers
• Reporter: Enrico Gueli
• Created: 25/Nov/09 00:16
• Updated: 07/Dec/23 21:04
• Resolved: 10/Jan/10 12:21

Description

The following code throws a "ClassFormatException: Invalid method signature: TT;" when executed:
===========================================================

import org.apache.bcel.Repository;
import org.apache.bcel.classfile.JavaClass;
import org.apache.bcel.classfile.Method;
import org.apache.bcel.generic.ConstantPoolGen;
import org.apache.bcel.generic.MethodGen;

class MyClassLoader extends ClassLoader {
@Override
public Class<?> loadClass(String name) throws ClassNotFoundException

{ if (name.startsWith("java.lang")) return super.loadClass(name); JavaClass jcl; jcl = Repository.lookupClass(name); scanMethods(jcl); byte[] data = jcl.getBytes(); return defineClass(name, data, 0, data.length); }

private void scanMethods(JavaClass jcl) {
ConstantPoolGen cpg = new ConstantPoolGen(jcl.getConstantPool());
Method[] methods = jcl.getMethods();
for (int i = 0; i < methods.length; i++)

{ MethodGen mg = new MethodGen(methods[i], jcl.getClassName(), cpg); }

}
}

class Foo<T> {
public void bar(T x) {
}
}

public class MethSignTest {
public MethSignTest()

{ Foo<Integer> foo = new Foo<Integer>(); }

@SuppressWarnings("unchecked")
public static void main(String[] args) {
try

{ MyClassLoader mcl = new MyClassLoader(); Class<MethSignTest> c = (Class<MethSignTest>) mcl .loadClass(MethSignTest.class.getName()); c.newInstance(); }

catch (Exception e)

{ e.printStackTrace(); }

}
}
===========================================================

Here's the full stack trace:

org.apache.bcel.classfile.ClassFormatException: Invalid method signature: TT;
at org.apache.bcel.classfile.Utility.typeOfSignature(Utility.java:986)
at org.apache.bcel.generic.Type.getType(Type.java:169)
at org.apache.bcel.generic.MethodGen.<init>(MethodGen.java:255)
at methodsignature.MyClassLoader.scanMethods(MethSignTest.java:26)
at methodsignature.MyClassLoader.loadClass(MethSignTest.java:17)
at java.lang.ClassLoader.loadClassInternal(ClassLoader.java:319)
at methodsignature.MethSignTest.<init>(MethSignTest.java:38)
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
at java.lang.reflect.Constructor.newInstance(Constructor.java:501)
at java.lang.Class.newInstance0(Class.java:350)
at java.lang.Class.newInstance(Class.java:303)
at methodsignature.MethSignTest.main(MethSignTest.java:47)

This misbehaviour occurs at least since revision 617860.