c++ - 是否允许类型相同但大小不同的双关数组？

Question

相同类型但大小不同的类型双关数组是否仍然违反严格别名？

int arr[4];
int(&ref)[2] = reinterpret_cast<int(&)[2]>(arr);

arr[0] = 0; //write to original
ref[0]; //read from pun

Answer 1

我们可以争论如下； [expr.reinterpret.cast]/11 :

A glvalue expression of type T1 can be cast to the type “reference to T2” if an expression of type “pointer to T1” can be explicitly converted to the type “pointer to T2” using a reinterpret_cast. The result refers to the same object as the source glvalue, but with the specified type.

[conv.array] :

An lvalue or rvalue of type “array of N T” […] can be converted to a prvalue of type “pointer to T”. The result is a pointer to the first element of the array.

即可以说，我们有一个指针指向第一个元素(不仅仅是代表地址)。它属于该元素的类型。因此访问 ref[0] 应该被定义。

按照这个逻辑，这样写也是可以的

auto& ref = reinterpret_cast<unsigned(&)[200]>(arr);
std::cout << ref[0];