<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/128667>128667</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libc++] P3372R3: constexpr `unordered_multimap`
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++,
            c++26
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          frederick-vs-ja
      </td>
    </tr>
</table>

<pre>
    Make `unordered_multimap` constexpr as part of P3372R3.

Note that `node-handle::key()` is intentionally left not constexpr, and the constexpr-ness largely requires a user-defined hash functor.

Feature-test macro (also covers constexpr `unordered_map`):
```C++
#define __cpp_lib_constexpr_unordered_map 202502L // also in <unordered_map>
```
</pre>
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