<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/154331>154331</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Building LLVM and MLIR with LLVM_REQUIRED_CXX_STANDARD c++23
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            mlir
      </td>
    </tr>

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

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

<pre>
    Building llvm with c++23 seems to not yet be supported.
I'm keen on building it anyways to use 'import std;' in [NebulaStream](https://github.com/nebulastream/nebulastream) which uses LLVM with MLIR as a dependency.

I'm making patches to get the build working based on the llvmorg-20.1.8 release, and many of them seem to still be relevant when building against the release candidates for 21 and 22.

When switching the LLVM_REQUIRED_CXX_STANDARD variable to 23 on the 20.1.8 release many errors are encountered.
Most of the issues relate to the constexpr changes of unique_ptr in c++23.

I'd like to make a PR to share the changes I am making to get this working and see if any of them could be useful for the next 20.x.x release or other major releases. 
</pre>
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