<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/96726>96726</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang][libc++] std::addressof silences -Waddress-of-packed-member diagnostics. 
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang,
            libc++
      </td>
    </tr>

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

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

<pre>
    We recently had a bug where we were inadvertently taking an address of a packed member inside some template code. `std::addressof` appears to prevent `-Waddress-of-packed-member` diagnostics.  It would be good if clang somehow treated `std::addressof(x)` as equivalent to `&a` for the purposes of providing diagnostics for  `-Waddress-of-packed-member`.

[Godbolt minimal example](https://godbolt.org/z/P613roxn5)

In general, it looks like clang doesn't diagnose when an lvalue reference is taken to an unaligned member. For our use-case, it would be nice if -Waddress-of-packed-member would diagnose all lvalue references to unaligned members. Although I could understand if just adding a heuristic for `std::addressof` is more palatable.


</pre>
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