The constructor for MethodGen:

public MethodGen(Method, String, ConstantPoolGen)

does not properly initialize the max_stack and max_local variables from the
Method object. Thus the following sequence of actions will produce a
non-verifying class, even though it clearly shouldn't:

ClassGen cg = new ClassGen(javaClass);
Method m = cg.getMethodAt(0);
MethodGen mg = new MethodGen(m, cg.getClassName(), cg.getConstantPool());
cg.setMethodAt(mg.getMethod(), 0);
cg.getJavaClass().dump(...);

Bug can be fixed by adding the following the constructor:

Code c = m.getCode();
max_stack = c.getMaxStack();
max_locals = c.getMaxLocals();