java.lang.VerifyError: (class: Main, method: main signature: ([Ljava/lang/String;)V) Stack size too large

I've been looking into the ASM library. First I wrote a program to build a hello world class and then I thought I'd try something a little more involved, build a class that creates a PythonInterpreter(part of the the Jython library) and executes a python file. The result is the following, unfortunately I get the exception I named this question after when I try to execute the resulting class.

public class Main {
public static void main(String[] args) {
    String mainFile = "main.py";

    ClassWriter mainClass = new ClassWriter(ClassWriter.COMPUTE_MAXS);
    mainClass.visit(Opcodes.V1_5, Opcodes.ACC_PUBLIC, "Main", null, "java/lang/Object", null);
    MethodVisitor mainMethod = mainClass.visitMethod(Opcodes.ACC_PUBLIC + Opcodes.ACC_STATIC, "main", "([Ljava/lang/String;)V", null, null);

    mainMethod.visitTypeInsn(Opcodes.NEW, "org/python/util/PythonInterpreter");
    mainMethod.visitMethodInsn(Opcodes.INVOKESPECIAL, "org/python/util/PythonInterpreter", "<init>", "()V");

    mainMethod.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "out", "Ljava/io/PrintStream;");
    mainMethod.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "org/python/util/PythonInterpreter", "setOut", "(Ljava/io/PrintStream;)V");
    mainMethod.visitFieldInsn(Opcodes.GETSTATIC, "java/lang/System", "err", "Ljava/io/PrintStream;");
    mainMethod.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "org/python/util/PythonInterpreter", "setErr", "(Ljava/io/PrintStream;)V");

    mainMethod.visitLdcInsn(mainFile);
    mainMethod.visitMethodInsn(Opcodes.INVOKEVIRTUAL, "org/python/util/PythonInterpreter", "execFile", "(Ljava/lang/String;)V");
    mainMethod.visitInsn(Opcodes.RETURN);

    mainMethod.visitEnd();
    mainClass.visitEnd();

    try{
        byte[] b = mainClass.toByteArray();
        FileOutputStream writer = new FileOutputStream("Main.class");
        writer.write开发者_JS百科(b);
        writer.close();
    }catch(IOException e){
        e.printStackTrace();
    }
}

}

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When you come to the setOut and setErr methods, you have only an argument, and no object to invoke the method on. (The call to <init> "consumed" the object it initialized!)

Same applies for the call to execFile. You have an argument (mainFile) but no object to invoke execFile on.

Try to add three DUP instructinos right after NEW. (To save enough references for the three method calls you want to do on that object.)