template<class T>
inline Foam::autoPtr<T>::operator const T&() const
{
    return operator()();
}

operator()()函数定义如下：

template<class T>
inline T& Foam::autoPtr<T>::operator()()
{
    if (!ptr_)
    {
        FatalErrorInFunction
            << "object of type " << typeid(T).name()
            << " is not allocated"
            << abort(FatalError);
    }

    return *ptr_;
}