<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/102547>102547</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libc++] undefined behaviour in std::set/std::map/std::unordered_set/std::unordered_map
        </td>
    </tr>

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

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

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

<pre>
    I was implementing P3372 (constexpr containers and adaptors) in libc++ and found UB which fails evaluation in ExprConstant.cpp.

It's in these two files:
[`libcxx/include/__tree`](https://github.com/llvm/llvm-project/blob/main/libcxx/include/__tree#L1808-L1815)
[`libcxx/include/__hash_table`](https://github.com/llvm/llvm-project/blob/main/libcxx/include/__hash_table#L1813-L1820)

These are similar issue where a node / bucket is allocated, but NOT constructed, and then a subobject is constructed.
</pre>
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