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        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Assertion failure when redefining array length"
   href="https://bugs.webkit.org/show_bug.cgi?id=158791">158791</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Assertion failure when redefining array length
          </td>
        </tr>

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

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

        <tr>
          <th>Version</th>
          <td>WebKit Local 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>JavaScriptCore
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>andre.bargull&#64;gmail.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>SVN: rev202088
Build with: perl Tools/Scripts/build-jsc --gtk --debug


The following test case triggers this assertion error:
---
ASSERTION FAILED: isLengthWritable() || !writable
---


Test case:
---
var a = [];
Object.defineProperty(a, &quot;length&quot;, {
  writable: true,
  value: {
    valueOf() {
      Object.defineProperty(a, &quot;length&quot;, {writable: false});
      return 0;
    }
  }
});
---


Stack trace:
---
#0  0x00007ffff6de7098 in WTFCrash () at ../../Source/WTF/wtf/Assertions.cpp:317
#1  0x00007ffff6b8f827 in JSC::JSArray::setLengthWritable (this=0x7fffaf1c7ed0, exec=0x7fffffffcb20, writable=true)
    at ../../Source/JavaScriptCore/runtime/JSArray.cpp:65
#2  0x00007ffff6b8fc31 in JSC::JSArray::defineOwnProperty (object=0x7fffaf1c7ed0, exec=0x7fffffffcb20, propertyName=..., descriptor=..., throwException=true)
    at ../../Source/JavaScriptCore/runtime/JSArray.cpp:118
#3  0x00007ffff6c8d2f2 in JSC::objectConstructorDefineProperty (exec=0x7fffffffcb20) at ../../Source/JavaScriptCore/runtime/ObjectConstructor.cpp:433
#4  0x00007fffb0bff028 in ?? ()
#5  0x00007fffffffcba0 in ?? ()
#6  0x00007ffff69f26a1 in llint_entry () at ../../Source/JavaScriptCore/runtime/JSCJSValueInlines.h:1054
---</pre>
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