Creating the objects in storage other than “array of N unsigned char” and access to it throught pointer to containing object.

I see code:

```cpp
struct S2 {
int i;
};

struct S {
uint64_t data[sizeof(S2)];
};

S s{};
new(reinterpret_cast(&s)) S2{};
auto i = reinterpret_cast(&s)->i;
```

This creates objects in the memory other than _“array of N unsigned char”_ (or _“array of N std​::​byte”_) and accessing them through a pointer of a non-_pointer-interconvertible_ type.
However, does this not violate the established acceptable storage variants and the _pointer-interconvertible_ rules ([[intro.object#3]](https://eel.is/c++draft/intro.object#3), [[basic.life#9]](https://eel.is/c++draft/basic.life#9) and [[basic.compound#5]](https://eel.is/c++draft/basic.compound#5))?

Shouldn't there be `unsigned char data[];` here?

https://github.com/llvm/llvm-project/blob/db5cd626b97a887cd237f9be9372cd3750fc7a02/libunwind/include/libunwind.h#L178
https://github.com/llvm/llvm-project/blob/52a880d30ba6cba38579ad7f51289d9ebe0c3719/libunwind/src/libunwind.cpp#L86

Shouldn't there be `cursor->data` here (or, alternatively, invoke std::launder)?

https://en.cppreference.com/w/cpp/utility/launder.html#Example

[[expr.add#6]](https://eel.is/c++draft/expr.add#6)

> For addition or subtraction, if the expressions P or Q have type “pointer to cv T”, where T and the array element type are not [similar](https://eel.is/c++draft/conv.qual#def:similar_types), the behavior is undefined[.](https://eel.is/c++draft/expr.add#6.sentence-1)

https://github.com/llvm/llvm-project/blob/e56161ef9841d61ea06e6b0a79e195e9a84addb1/libunwind/src/UnwindCursor.hpp#L2119