<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/146005>146005</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            [clang-cl] missing `__threadid` `_threadid` and `__threadhandle` in `stddef.h`
        </td>
    </tr>

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

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

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

<pre>
    MSVC provides two functions and one macro inside `ucrt`'s `stddef.h`
```cpp
_ACRTIMP extern unsigned long  __cdecl __threadid(void);
#define _threadid (__threadid())
_ACRTIMP extern uintptr_t __cdecl __threadhandle(void);
```
However when I choose `clang-cl` toolset, they are no longer available.
</pre>
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