<html>
    <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 - PCH header is still parsed and included leading to redefinition errors (does not happen with clang-cl/GCC style pch)"
   href="https://bugs.llvm.org/show_bug.cgi?id=46352">46352</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>PCH header is still parsed and included leading to redefinition errors (does not happen with clang-cl/GCC style pch)
          </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>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>Frontend
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>nok.raven@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org, neeilans@live.com, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>// test.cpp
#include <pch.hpp>
int main() {}

// pch.hpp
#include <pch.hpp>

<span class="quote">>clang++ -c pch.hpp -I. -Xclang -emit-pch -o pch.pch</span >

<span class="quote">>clang++ test.cpp -I. -Xclang -include-pch -Xclang pch.pch -o test</span >
In file included from test.cpp:1:
.\pch.hpp:1:7: error: redefinition of 'X'
class X {};
      ^
test.cpp:1:1: note: '.\pch.hpp' included multiple times, additional include
site here
#include <pch.hpp>
^
test.cpp:1:10: note: '.\pch.hpp' included multiple times, additional include
site here
#include <pch.hpp>
         ^
.\pch.hpp:1:7: note: unguarded header; consider using #ifdef guards or #pragma
once
class X {};
      ^
1 error generated.

Clang with GCC style PCH, Clang-cl, GCC, and MSVC are fine:

// pch.cpp
#include <pch.hpp>

<span class="quote">>clang++ -c -x c++-header pch.hpp -I. -o pch.hpp.gch
>clang++ test.cpp -I. -o test</span >

<span class="quote">>clang-cl -c pch.cpp -I. -Yc"pch.hpp" -Fo"pch.o" -Fp"pch.pch"
>clang-cl test.cpp -I. -Yu"pch.hpp" -Fp"pch.pch"</span >

<span class="quote">>cl -c pch.cpp -I. -Yc"pch.hpp" -Fo"pch.o" -Fp"pch.pch"
>cl -c test.cpp -I. -Yu"pch.hpp" -Fp"pch.pch" -Fo"test.o"</span >

<span class="quote">>g++ -c -x c++-header pch.hpp -I. -o pch.hpp.gch
>g++ test.cpp -I. -o test</span ></pre>
        </div>
      </p>


      <hr>
      <span>You are receiving this mail because:</span>

      <ul>
          <li>You are on the CC list for the bug.</li>
      </ul>
    </body>
</html>