<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/144332>144332</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang] Improve ABI version handling in clang
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            enhancement,
            clang
      </td>
    </tr>

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

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

<pre>
    We have a language option for ABI-compatibility. The user may choose clang release version to generate code compatible with using flag `-fclang-abi-compat=` . Currently to bring a new version of known ABI, at least 3 different places need to be modified:
1. Add new value to the langopt enum:
https://github.com/llvm/llvm-project/blob/299a55a88fae4fc423c440436b2632d2a6bd800a/clang/include/clang/Basic/LangOptions.h#L171
2. Make sure it is handled here
https://github.com/llvm/llvm-project/blob/299a55a88fae4fc423c440436b2632d2a6bd800a/clang/lib/Frontend/CompilerInvocation.cpp#L3925
3. Make sure it is parsed correctly here
https://github.com/llvm/llvm-project/blob/299a55a88fae4fc423c440436b2632d2a6bd800a/clang/lib/Frontend/CompilerInvocation.cpp#L4479

So, it is at least 3 places that need to be updated every ~6 months when new release is branched. Some of the places are super easy to forget which will cause build fails like the bug resolved by https://github.com/llvm/llvm-project/pull/144109 several months after ClangABI::Ver20 was introduced.

It would be great to improve this.
</pre>
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