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      <base href="https://bugs.webkit.org/" />
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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - SameSizeAs* structs wrongly assume sizeof(ptr)==sizeof(std::unique_ptr)"
   href="https://bugs.webkit.org/show_bug.cgi?id=150235">150235</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>SameSizeAs* structs wrongly assume sizeof(ptr)==sizeof(std::unique_ptr)
          </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>rupsharma&#64;ea.com
          </td>
        </tr></table>
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        <pre>Hi,

In regard to all the static assertions, to check the sizes of the data-structures using SameSizeAs* structs, it is wrongly assumed, that sizeof (std::unique_ptr) is same as sizeof (pointer) for all compilers. 
Therefore, I would suggest to list them separately while computing the sizes.

To give an example:
In WebCore\dom\ElementRareData.cpp

The structure should look like:
struct SameSizeAsElementRareData : NodeRareData {
    short indices[2];
    unsigned bitfields;
    RegionOversetState regionOversetState;
    LayoutSize sizeForResizing;
    IntSize scrollOffset;

// CHANGE BEGINS HERE . Earlier it was :void* pointers[7];
    void* pointers[4];
    std::unique_ptr&lt;DatasetDOMStringMap&gt; pointer2;
    std::unique_ptr&lt;ClassList&gt; pointer3;
    std::unique_ptr&lt;NamedNodeMap&gt; pointer4;
// CHANGE ENDS HERE
};

Making the above change,  works perfectly for us without throwing any compile-time assert at:
static_assert(sizeof(ElementRareData) == sizeof(SameSizeAsElementRareData), &quot;ElementRareData should stay small&quot;);

Thanks,
Rupali</pre>
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