<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/126603>126603</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [libc][POSIX][unistd] implement getsid
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc
      </td>
    </tr>

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

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

<pre>
    Building llvm against llvm-libc fails with:
```
/llvm-project-main/llvm/lib/Support/LockFileManager.cpp:120:33: error: use of undeclared identifier 'getsid'
```
Looks like this is provided by unistd.h on POSIX systems.
</pre>
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