private void addPutfield0(CtClass target, String classname,
                              String name, String desc) {
        add(PUTFIELD);
        // target is null if it represents THIS.
        int ci = classname == null ? constPool.addClassInfo(target)
                                   : constPool.addClassInfo(classname);
        addIndex(constPool.addFieldrefInfo(ci, name, desc));
        growStack(-1 - Descriptor.dataSize(desc));
    }