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    <head>
      <base href="https://bugs.llvm.org/">
    </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 - boost::regex match but not std::regex"
   href="https://bugs.llvm.org/show_bug.cgi?id=40052">40052</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>boost::regex match but not std::regex
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>6.0
          </td>
        </tr>

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

        <tr>
          <th>OS</th>
          <td>FreeBSD
          </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>georg-bsd@schorsch-tech.de
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org, mclow.lists@gmail.com
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=21237" name="attach_21237" title="Testcase">attachment 21237</a> <a href="attachment.cgi?id=21237&action=edit" title="Testcase">[details]</a></span>
Testcase

I got the attached program. It has a global locale set (de_DE.UTF-8).

I think it might be a bug in libc++ because 
on Windows(MSVC 2013 & MSVC 2017) and on Linux (gcc 8.2 + libstdc++) this regex
(from std) matches with the global locale from boost. Also the regex from boost
matches (replace std::regex by boost::regex). 

This bug triggers only (also on my box and only on freebsd with clang and
libc++) when i use boost::locale. With std::locale() it matches.

I already submitted this bug to FreeBSD and to boost.org.

For reference, here are the links
<a href="https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233994">https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=233994</a>

Boost.locale says:
[quote]
Boost.Regex and Boost.Locale aren't related, the locale generated by
Boost.Locale is "C" locale with addons unrelated to Boost.Regex
[/quote]
<a href="https://github.com/boostorg/locale/issues/35">https://github.com/boostorg/locale/issues/35</a>

FreeBSD says, it is a bug in boost.locale.

As both of my direct upstream bugtrackers seem to "dislike" this bug, i report
it to clang/libc++ directly.</pre>
        </div>
      </p>


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