<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJylkM1u3SAQhZ8Gb1AswGBfFiySRln1HSrAg02CwQJ8f96-xFWVbKtKaOYMIx19c0yaH2qtdS9oeEbsrb3F1_UwvU1bG0K4_m1Pe07vYGsbTUimNekMh0nOZNR6lMSOlFoCbiTU0oE7MU2Xi5BEfxp4Y-_3Jkq2rW6wpfzo7b4jNvy8yB6RV0Se_9QfOuKSNkgR8OKvgDfA7QvuettDkyYdFdcV8BFncD7CjG_6gYa3blbDLAepO33UNWV187FCfgopdUcO_36nL-WA0oRgcuLdqozmxsIonJScE81HQS5MOhBSghuo7YI2EIpC4gUxFuGGT4umkXjt_p_AK0YYI5RwMlEpRC8l5dYOfHLSzJQ7xAls2of-06dPeemyOi3NsZS2DL7U8rXUpfglApzAjbD6GkC1lHWBFvgetI_4Bvrj114znqHUfNjqU_yWvYFVX33K3cmqTtDfx7LCDQ>52974</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            please explain weak_ptr destruction undefined behavior
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            new issue
      </td>
    </tr>

    <tr>
      <th>Assignees</th>
      <td>
      </td>
    </tr>

    <tr>
      <th>Reporter</th>
      <td>
          winter-loo
      </td>
    </tr>
</table>

<pre>
    https://github.com/llvm/llvm-project/blob/9fb4e79d06aa690c611c0ef601c134f57788590a/libcxx/src/memory.cpp#L89.

Can someone give me an example about the undefined way?
</pre>
<img width="1px" height="1px" alt="" src="http://email.email.llvm.org/o/eJyVUEmO3SAQPQ3eoLYA44EFi05aveo7tBgKmwSDBfgPtw_tKEq2kUpVr6ZXT6WTfcqt1qOg4RWx92arr9upe5P2loRw-xNejpx-gKkt1SHpFoTTHGZhyaTUJIiZKDUE3ESooQN34zwvyyiI-iLw2jweDZRsmt9hT_nZm-NAbPhYRI_IGyKvv_13FXFJO6QIePU3wDvgVoKH2o_QoE5nxXUDfEYLzkew-K6eaHjvrBysGITqqq8BZJtWBdriEZSP-A7q5-dRM7ZQaj5N9Sn-w6FhUzefcnfm8P8v8aWcUBoYmZh5t0lnFmthak9xs9NqAcaNWRrgZLB0mbugNIQi0fgNMRbhji-KhtH41nnJCGOEEk5mKsaxF4K2_YHPTmhLuUOcwK586L909CmvXZaXJH2upTWDL7X8bapS_BoBrnONX511S1nefayQX0JK3XVdXup_AajJrUs">