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    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW --- - Possible false positive in undefined-inline with __alloctr_rebind_helper"
   href="http://llvm.org/bugs/show_bug.cgi?id=20708">20708</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Possible false positive in undefined-inline with __alloctr_rebind_helper
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

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

        <tr>
          <th>OS</th>
          <td>Linux
          </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>C++
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>Axel.Naumann@cern.ch
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>dgregor@apple.com, llvmbugs@cs.uiuc.edu
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Hi,

with the attached file.h (excerpt of bits/alloc_traits.h from libstdc++ of GCC
4.9.1) and clang r212179 I get

$ clang -Wall -fsyntax-only -x c++ -std=c++11 file.h
file.h:28:3: warning: inline function '__alloctr_rebind_helper<int,
float>::_S_chk<int, float>' is not defined [-Wundefined-inline]
                _S_chk(...);
                ^
file.h:31:32: note: used here
              using __type = decltype(_S_chk<_Alloc, _Tp>(nullptr));
                                      ^
1 warning generated.

I don't think decltype should require a definition; I don't see how a
definition could change the decltype. It compiles just fine without the
warning.

As I said this happens in the wild with libstdc++ of GCC 4.9.1 (installed side
by side to the system compiler version) - where we still need to figure out why
clang thinks they are not system headers. But that shouldn't affect this issue.

Thanks!

Axel.</pre>
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