<html>
    <head>
      <base href="https://llvm.org/bugs/" />
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - basic_string::operator= isn't exception safe"
   href="https://llvm.org/bugs/show_bug.cgi?id=31779">31779</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>basic_string::operator= isn't exception safe
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>unspecified
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>normal
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>All Bugs
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>llvm-bugs@daryl.haresign.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Assigning one string to another, where they have non-equal
propagate-on-copy-assignment allocators, does a `clear()`, followed by an
`assign()`.  The `assign()` may throw, which leaves the string in a cleared
state.

This seems to violate the requirement specified here:
  <a href="http://eel.is/c++draft/basic.string#string.require-2">http://eel.is/c++draft/basic.string#string.require-2</a>

A contrived example to show this:
  <a href="http://coliru.stacked-crooked.com/a/c43a723d04878890">http://coliru.stacked-crooked.com/a/c43a723d04878890</a></pre>
        </div>
      </p>
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