<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=https://github.com/llvm/llvm-project/issues/61663>61663</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            libc++ should diagnose when std::sort & friends is used with a non strict-weak order
        </td>
    </tr>

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

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

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

<pre>
    We emit a `diagnose_if` warning in C++20 mode when users call `std::sort` (or other sort-like algorithms) on e.g. floating points with `std::less`, which technically doesn't satisfy a strict weak ordering. There are probably other cases, like `std::greater` and also many more algorithms like `std::partition` and friends.

We could introduce a new heuristic trait like `__is_definitely_not_valid_strict_weak_ordering<Comparator, T, U>`, and that would be true for `std::less`, `std::greater` & friends when used with floating point types.
</pre>
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