<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/56655>56655</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            std::codecvt<char8_t, wchar_t, std::mbstate_t> is not implemented in libc++
        </td>
    </tr>

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

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

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

<pre>
    Repro:

```cpp
#include <codecvt>
int x = sizeof(std::codecvt<char8_t, wchar_t, std::mbstate_t>);
```

causes

```
<source>:4:9: error: implicit instantiation of undefined template 'std::codecvt<char8_t, wchar_t, __mbstate_t>'
int x = sizeof(std::codecvt<char8_t, wchar_t, std::mbstate_t>);
        ^
/opt/compiler-explorer/clang-trunk-20220721/bin/../include/c++/v1/__locale:952:85: note: template is declared here
template <class _InternT, class _ExternT, class _StateT> class _LIBCPP_TEMPLATE_VIS codecvt;
                                                                                    ^
1 error generated.
Compiler returned: 1
```

godbolt repro: https://gcc.godbolt.org/z/E6cEPcMzv
</pre>
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