<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/64509>64509</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Should -Wmissing-variable-declarations not trigger on `register` variables?
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            clang:diagnostics
      </td>
    </tr>

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

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

<pre>
    Via: https://lore.kernel.org/all/CAKwvOd=8kxkD9p+WW-F047ShN=r32SLYYfpgZhyDw3BXTDd-KA@mail.gmail.com/

I'm looking to enable -Wmissing-variable-declarations in the Linux kernel (gcc-14 just gained support for that warning, too).

In one case I noticed that:

```c
register unsigned long current_stack_pointer asm("rsp");
```
declared in a header would trigger this:
```
> arch/x86/include/asm/asm.h:208:10: note: declare 'static' if the variable is not intended to be used outside of this translation unit
```
but note that variables with register storage CANNOT also be static.

So we could add:
```c
extern unsigned long current_stack_pointer;
```
before the
```c
register unsigned long current_stack_pointer asm("rsp");
```
but that seems excessive. Perhaps we can simply not diagnose in that case?  (I will file a bug against GCC as well).
</pre>
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