<table border="1" cellspacing="0" cellpadding="8">
    <tr>
        <th>Issue</th>
        <td>
            <a href=http://email.email.llvm.org/c/eJylVEtvnDAQ_jXmMioCs8vjwCHJdnNNpd4jAwO4MjbyI-n--w4szXbTjaKqyDw8883rmzGN6U41y5NtJQeW3DGeSd2q0CGw7KEVzqH1LPt6S2uF7sx0Ua5PqT1MQmrGS8YrYMX9WQ50-dOMHfbgfMeyO1rKDNrYSajnTjpvZRO8NJpck1M4sOyG7eFsOQsrpudFCE83cW8xJp9WVVbA4xXsEYar_QG6t_1F2hrtPDzBnFK9BInXsOfSrszfgPwT4EYoL88uF_DM34M6ExqFYLeohB4Yf6AszkBg_EgLvo_SgZIaYQoUXRti3nSyPxEy_oeQrDhsH9ezoGTTMn5PC3ohlQM_IvRSCwWE2dwSmFJrsBXB4SL_q0EkA4etRa9OC1GepsOBgNfRqNXi1giQjWl-YOtXDpfCgaZtyUAvJu84-SACydfGPNMc-xVkQHpohaZbKfIm_McJMF64RWtmtMIbu3UzT-Koq7OuyioRieBHY-tvIfycVXBGYxSsqkfvZ7fwsDZqkH4MTdzSWeFHpV5-v77M1pxLPErnAjr62PMqyaOxbopdnzd70ZTlbl8WO6zSsq9EzvM9zztMIyUaVK5me-oPv3SKNmx_iP4_BVnzhKcp5yXnuzLL4iRPeZb0mJQpF6LYsV2CdNBVvPiJjR0iW68umzA4Uipi012UNC5y0Ihbxn8wtqXspVdYf_JrWHtnXtC-WulxO3YTTsaeorWAes3-F4OrcXw>52906</a>
        </td>
    </tr>

    <tr>
        <th>Summary</th>
        <td>
            std::lognormal_distribution can overwrite const memory
        </td>
    </tr>

    <tr>
      <th>Labels</th>
      <td>
            libc++
      </td>
    </tr>

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

    <tr>
      <th>Reporter</th>
      <td>
          Quuxplusone
      </td>
    </tr>
</table>

<pre>
    ```
#include <cassert>
#include <random>

int main() {
    typedef std::lognormal_distribution<> D;
    typedef D::param_type P;
    typedef std::mt19937 G;
    G g;
    D d;

    const P p1 = d.param();
    const P p2 = d.param();
    assert(p1 == p2);
    double r1 = d(g, p1); // This line must not modify p1.
    assert(p1 == p2);
}
```
libc++ fails the final `assert`, because `D::param_type` secretly contains a whole `normal_distribution` object(!) and then `d(g, p1)` secretly contains a `const_cast` so it can call that `normal_distribution`'s `operator()`.
</pre>
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