<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/125184>125184</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Suppress "unknown attribute 'no_unique_address' ignored" with MSVC ABI
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
      </td>
    </tr>

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

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

<pre>
    MSVC introduced `[[msvc::no_unique_address]]` to workaround ABI break with `[[no_unique_address]]`. For portability you have to use both.

`clang-cl` gives me the warning:

```
unknown attribute 'no_unique_address' ignored [-Wunknown-attributes]
```

I don't want to suppress warnings for all unknown attributes. But I want to suppress this one, at least if `[[msvc::no_unique_address]]` is defined as well.

I propose to add a compiler flag to suppress warnings for specific attributes.

I also propose to silently ignore `[[no_unique_address]]` if `[[msvc::no_unique_address]]` is defined as well.
</pre>
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