c++ - std::bit_cast 生成多个值的值表示的示例是什么？

Question

以下是引用自[bit.cast]下的标准(草案n4861)(强调的是我的)

Returns: An object of type To. Implicitly creates objects nested within the result (6.7.2). Each bit of the value representation of the result is equal to the corresponding bit in the object representation of from. Padding bits of the result are unspecified. For the result and each object created within it, if there is no value of the object’s type corresponding to the value representation produced, the behavior is undefined. If there are multiple such values, which value is produced is unspecified.

所以我的问题是， std::bit_cast 生成对应于多个不同值的值表示的场景示例是什么？

Answer 1

总和类型浮现在脑海中。 union 可以有相同类型的成员:

union u {
    int a;
    int b;
};

现在，如果我们将一些东西位转换成 u ，我们会得到什么样的 u ？是 a 处于事件状态还是 b 之一？这些是 u 形式上不同的值，但它们似乎具有相同的值表示。