  static void setAppend(SetType& set, const VariantType& v) {
    if (!v.isInteger() && !v.isString()) {
      throw HPHP::serialize::UnserializeError(
        "Keysets can only contain integers or strings"
      );
    }
    set.append(v);
  }
The product does not properly control the amount of recursion which takes place,  consuming excessive resources, such as allocated memory or the program stack.