[Clang] Layout of struct with [[msvc::no_unique_address]] is different from MSVC

[philnik777]

struct S {};

struct T {
  [[msvc::no_unique_address]] S s;
};

struct V {};

struct W : T, V {};

static_assert(sizeof(W) == 1);

MSVC is happy with this code while Clang thinks sizeof(W) should be 2.

[llvmbot]

@llvm/issue-subscribers-clang-frontend

Author: Nikolas Klauser (philnik777)

``` struct S {};

struct T {
[[msvc::no_unique_address]] S s;
};

struct V {};

struct W : T, V {};

static_assert(sizeof(W) == 1);

MSVC is happy with this code while Clang thinks `sizeof(W)` should be 2.

</details>

[shafik]

This looks like: #143245 please confirm

[philnik777]

Yeah, looks like it's the same thing.