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    <head>
      <base href="https://llvm.org/bugs/" />
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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 --- - Clang-cl: Preprocessor concatenate strings failure with colons"
   href="https://llvm.org/bugs/show_bug.cgi?id=30588">30588</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Clang-cl: Preprocessor concatenate strings failure with colons
          </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>Windows NT
          </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>jvapen@gmail.com
          </td>
        </tr>

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

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Created <span class=""><a href="attachment.cgi?id=17393" name="attach_17393" title="Reproduction">attachment 17393</a> <a href="attachment.cgi?id=17393&action=edit" title="Reproduction">[details]</a></span>
Reproduction

While trying to compile our MSVC code base with clang-cl, we found a
preprocessor error in string-concatenations.

If we define our concatenate the following way: (See attachment for full
reproduction)
#define M(O,P) #O ## "::" ## #P

it cannot be called with M(A::B, C)

Instead it gives errors:
error: pasting formed '"A::B""::"', an invalid preprocessing token
[-Winvalid-token-paste]</pre>
        </div>
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