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          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Undefined behavior in StdLibExtras.h, bitCount"
   href="https://bugs.webkit.org/show_bug.cgi?id=160565">160565</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Undefined behavior in StdLibExtras.h, bitCount
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>WebKit
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>WebKit Nightly Build
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>Unspecified
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Unspecified
          </td>
        </tr>

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

        <tr>
          <th>Severity</th>
          <td>Normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P2
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>WebCore Misc.
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>webkit-unassigned&#64;lists.webkit.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>jbedard&#64;apple.com
          </td>
        </tr></table>
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        <pre>In StdLibExtras.h bitCount, there is undefined behavior on return.  The line:
    return (((bits + (bits &gt;&gt; 4)) &amp; 0xF0F0F0F) * 0x1010101) &gt;&gt; 24
almost always has undefined behavior.  In this case, the overflow is expected.  However, compiler optimization (given that this function is an inline) with constants may preform unexpected operations</pre>
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