<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/131700>131700</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Overly pedantic [[noreturn]] restriction
        </td>
    </tr>

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

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

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

<pre>
    C++11 says that the first declaration of a function must specify the `[[noreturn]]` attribute if any declaration specifies it.

All of gcc, clang, and MSVC provide compiler-specific mechanisms to indicate a function is "noreturn".  gcc and clang have `attribute((noreturn))`, while MSVC has `__declspec(noreturn)`.  gcc and MSVC treat their compiler-specific attributes as satisfying the first declaration attribute requirement, but clang does not.  That is, this compiles cleanly with gcc, but clang issues a warning
```
attribute((noreturn)) void testfn(int);
[[noreturn]] void testfn(int);
```
and this compiles cleanly with MSVC, but clang issues a warning
```
__declspec(noreturn) void testfn(int);
[[noreturn]] void testfn(int);
```
</pre>
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