<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/62844>62844</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libcxx] Use of std::aligned_storage deprecated in C++23
        </td>
    </tr>

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

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

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

<pre>
    Building libcxx with C++23 emits a bunch of deprecation warnings due to the use of `std::aligned_storage` in a few libcxx sources.

This seems to be the only kind of warning triggered by C++23 though. (supported) Tests seem to pass as well 😊

```cpp
/home/aaron/aaronmondal/llvm-project/libcxx/src/include/sso_allocator.h:37:14: warning: 'aligned_storage<240>' is deprecated [-Wdeprecated-declarations]
    typename aligned_storage<sizeof(_Tp) * _Np>::type buf_;
             ^
/home/aaron/aaronmondal/llvm-project/build/include/c++/v1/__memory/allocator_traits.h:238:33: note: in instantiation of template class 'std::__sso_allocator<std::locale::facet *, 30>' requested here
    using value_type = typename allocator_type::value_type;
                                ^
/home/aaron/aaronmondal/llvm-project/build/include/c++/v1/vector:390:22: note: in instantiation of template class 'std::allocator_traits<std::__sso_allocator<std::locale::facet *, 30>>' requested here
    typedef typename __alloc_traits::size_type              size_type;
                     ^
/home/aaron/aaronmondal/llvm-project/libcxx/src/locale.cpp:138:49: note: in instantiation of template class 'std::vector<std::locale::facet *, std::__sso_allocator<std::locale::facet *, 30>>' requested here
    vector<facet*, __sso_allocator<facet*, N> > facets_;
                                                ^
/home/aaron/aaronmondal/llvm-project/build/include/c++/v1/__type_traits/aligned_storage.h:86:8: note: 'aligned_storage<240>' has been explicitly marked deprecated here
struct _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_TEMPLATE_VIS aligned_storage
       ^
/home/aaron/aaronmondal/llvm-project/build/include/c++/v1/__config:814:39: note: expanded from macro '_LIBCPP_DEPRECATED_IN_CXX23'
#  define _LIBCPP_DEPRECATED_IN_CXX23 _LIBCPP_DEPRECATED
                                      ^
/home/aaron/aaronmondal/llvm-project/build/include/c++/v1/__config:775:49: note: expanded from macro '_LIBCPP_DEPRECATED'
#      define _LIBCPP_DEPRECATED __attribute__((__deprecated__))
                                                ^
```

cc @mordante @ldionne @philnik777 
</pre>
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