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    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - floating point NaN generation isn't considered a constant expression"
   href="https://bugs.llvm.org/show_bug.cgi?id=40324">40324</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>floating point NaN generation isn't considered a constant expression
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>Darrell.Wright@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>The following code isn't considered constexpr in clang/apple clang but does
work in gcc.  I could not find anything in the standard(not an exhaustive look)
that indicated that this would not be allowed in a constant expression.  The
worry is that if this is correct I would have to create code to ensure it
cannot happen.  I tried trunk and latest Apple Clang with 11,14,17, and 2a
standards as arguments.

#include <limits>
constexpr bool cx() {
  return std::numeric_limits<double>::infinity() -
         std::numeric_limits<double>::infinity();
}
static_assert(cx(), "");

<a href="https://gcc.godbolt.org/z/DxFd2F">https://gcc.godbolt.org/z/DxFd2F</a></pre>
        </div>
      </p>


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