<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 --- - Clang-cl does not support /DMYDEF#value"
   href="https://llvm.org/bugs/show_bug.cgi?id=25984">25984</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Clang-cl does not support /DMYDEF#value
          </td>
        </tr>

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

        <tr>
          <th>Version</th>
          <td>unspecified
          </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>Driver
          </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>llvm-bugs@lists.llvm.org
          </td>
        </tr>

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Ref <a href="https://msdn.microsoft.com/en-us/library/hhzbb5c8.aspx">https://msdn.microsoft.com/en-us/library/hhzbb5c8.aspx</a>
The syntax of defining constants via the command line of MSVC supports both
/DMYDEF=0 as /DMYDEF#0

Clang-cl only supports the first one.
If you use the second one, I get the following warning.

Error given by clang-cl of version 3.5:
<command line>(10,14): warning : ISO C99 requires whitespace after the macro
name [-Wc99-extensions]
  #define MYDEF#0 1

Note: I have also noticed this already in the latest builds of 3.8, though for
this reproduction, I have not yet upgraded my compiler.</pre>
        </div>
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