<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/69890>69890</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Value initialization with implied zero-initialization does not occur for derived class
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          Fedr
      </td>
    </tr>
</table>

<pre>
    This program
```
struct A {
 constexpr A() {}
    int x;
};

struct B : A {
    int y;
};

static_assert( B().x == 0 );
```
shall be accepted because
1. `()` performs value-initialization on `B`: http://eel.is/c++draft/dcl.dcl#dcl.init.general-16.4

2. Since `B`'s ctor is not user-provided, that resolves to zero-initialization followed by default-initialization: http://eel.is/c++draft/dcl.dcl#dcl.init.general-9.1.2

3. Zero-initialization of `B` propagates to `A`, then propagates to `x` and zeroes it, regardless of `A` having a user-provided constructor or not: http://eel.is/c++draft/dcl.dcl#dcl.init.general-6.2

4. Lastly default-initialization of `B` calls `B`'s constructor and in turn calls `A`'s constructor.

Unfortunatly, only MSVC implemented zero-initialization in this scenario by now. Online demo: https://godbolt.org/z/YMv94rabv

GCC has a similar defect, see https://gcc.gnu.org/bugzilla/show_bug.cgi?id=108993

Related discussion: https://stackoverflow.com/a/77273671/7325599
</pre>
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