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      <base href="https://bugs.webkit.org/" />

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          <th>Bug ID</th>

          <td><a class="bz_bug_link 

          bz_status_NEW "

   title="NEW - LazyNeverDestroyed is not thread safe in debug builds, causing assertions"

   href="https://bugs.webkit.org/show_bug.cgi?id=144378">144378</a>

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        </tr>

        <tr>

          <th>Summary</th>

          <td>LazyNeverDestroyed is not thread safe in debug builds, causing assertions

          </td>

        </tr>

        <tr>

          <th>Classification</th>

          <td>Unclassified

          </td>

        </tr>

        <tr>

          <th>Product</th>

          <td>WebKit

          </td>

        </tr>

        <tr>

          <th>Version</th>

          <td>528+ (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>Web Template Framework

          </td>

        </tr>

        <tr>

          <th>Assignee</th>

          <td>webkit-unassigned&#64;lists.webkit.org

          </td>

        </tr>

        <tr>

          <th>Reporter</th>

          <td>ap&#64;webkit.org

          </td>

        </tr>

        <tr>

          <th>CC</th>

          <td>akling&#64;apple.com, andersca&#64;apple.com, cdumez&#64;apple.com, zan&#64;falconsigh.net

          </td>

        </tr></table>

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        <div>

        <pre>Thread 28 Crashed:: WebCore: Worker

0   com.apple.JavaScriptCore          0x00000001128509da WTFCrash + 42 (Assertions.cpp:321)

ASSERT(m_isConstructed);

1   com.apple.JavaScriptCore          0x0000000112862ed2 WTF::LazyNeverDestroyed&lt;std::__1::mutex&gt;::asPtr() + 66 (NeverDestroyed.h:102)

2   com.apple.JavaScriptCore          0x0000000112862e85 WTF::LazyNeverDestroyed&lt;std::__1::mutex&gt;::operator std::__1::mutex&amp;() + 21 (NeverDestroyed.h:94)

3   com.apple.JavaScriptCore          0x0000000112862161 WTF::cachedCollatorMutex() + 577 (CollatorICU.cpp:62)

4   com.apple.JavaScriptCore          0x0000000112861c8b WTF::Collator::Collator(char const*, bool) + 43 (CollatorICU.cpp:120)

5   com.apple.JavaScriptCore          0x0000000112861c4c WTF::Collator::Collator(char const*, bool) + 44 (CollatorICU.cpp:146)

6   com.apple.JavaScriptCore          0x0000000112788a4b JSC::stringProtoFuncLocaleCompare(JSC::ExecState*) + 155 (StringPrototype.cpp:1429)

LazyNeverDestroyed has a non-trivial constructor in debug builds, which is obviously wrong to have for the pattern we normally use it with.

static std::mutex&amp; cachedCollatorMutex()

{

    static std::once_flag onceFlag;

    static LazyNeverDestroyed&lt;std::mutex&gt; mutex;

    std::call_once(onceFlag, []{

        mutex.construct();

    });

    return mutex;

}</pre>

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