<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/102982>102982</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            Clang-cl should map `/Wall` to `-Wall`, not `-Weverything`
        </td>
    </tr>

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

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

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

<pre>
    This is *not* the same issue as https://github.com/llvm/llvm-project/issues/102583 - that issue is saying that `-Wall` works the same way as `/-Wall`, which is likely intentional

This issue is that the documented of `clang-cl` `/Wall` is extremely surprising - *both* `-Wall` and `/Wall` should be mapped to clang's `-Wall`, not `-Weverything`

It was surprising as:
- I had a clean build with MSVC `cl.exe /Wall /WX`
- I had a clean build with `clang++.exe -Wall -Werror`
- I had a failing build with `clang-cl.exe /Wall /WX`

The set of 'everything' is particularly problematic as even if you're passing `/std:c++20`, you still get `-Wc++98-compat` - of *course* my code that targets C++20 is not compatible with C++98.

While it could be argued that `/W4` is closer to clang's `-Wall`, the above makes the current mapping basically unusable for modern code. A potential middle ground would be to map `/Wall` to `-Wall -Wextra` ?
</pre>
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