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    <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 crashes on dllexport inline methods with default arguments in PCH files in MS ABI mode"
   href="https://llvm.org/bugs/show_bug.cgi?id=31121">31121</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Clang crashes on dllexport inline methods with default arguments in PCH files in MS ABI mode
          </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>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>LLVM Codegen
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>rnk@google.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>Consider:

$ cat t.h
struct __declspec(dllexport) Foo {
  enum E { E0 } e;
  Foo(E e = E0) : e(e) {}
};

$ cat t.cpp

$ clang-cl -FIt.h -Yct.h t.cpp
Assertion failed: DefaultArg && "sema forgot to instantiate default args", file
..\tools\clang\lib\CodeGen\MicrosoftCXXABI.cpp, line 3877
...

Basically, dllexport interacts with PCH in interesting ways that we should
seriously revisit.

This was reduced out of blink / WebKit, which had this issue here:
<a href="https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/ViewportDescription.h?rcl=0&l=67">https://cs.chromium.org/chromium/src/third_party/WebKit/Source/core/dom/ViewportDescription.h?rcl=0&l=67</a></pre>
        </div>
      </p>
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