为什么强制转换不成功？

Question

我正在尝试：

 if constexpr (Bo == ByteOrder::Network && sizeof(T) == 8)
    return reinterpret_cast<T &> 
  (be64toh(reinterpret_cast<make_unsigned_t<T>&>(val)));
 else if constexpr (Bo == ByteOrder::Host && sizeof(T) == 8)
    return reinterpret_cast<T &>(htobe64(reinterpret_cast<make_unsigned_t<T>&>(val)));

结果为：

error: invalid cast of an rvalue expression of type ‘__uint64_t {aka long unsigned int}’ to type ‘long int&’
     return reinterpret_cast<T &>(be64toh(reinterpret_cast<make_unsigned_t<T>&>(val)));

Answer 1

这是一个疏忽：