<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/77843>77843</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libc++abi] lack of the detection of libunwind library files.
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++,
            libc++abi
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          ye-luo
      </td>
    </tr>
</table>

<pre>
    Triggered by https://github.com/llvm/llvm-project/pull/77687
`libc++abi` doesn't seem have strong enough dependency check/handling of libunwind.

My local build stops at
```
/usr/bin/ld: cannot find -lunwind_shared: No such file or directory
clang++: error: linker command failed with exit code 1 (use -v to see invocation)
make[5]: *** [libcxxabi/src/CMakeFiles/cxxabi_shared.dir/build.make:117: /gpfs/jlse-fs0/users/yeluo/opt/llvm-clang/build_mirror_offload_nightly/lib/x86_64-unknown-linux-gnu/libc++abi.so.1.0] Error 1
```
this kind of issue should be detected in the cmake stage of libcxxabi not at compile time.
</pre>
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