<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 - Crash on invalid recursive variadic template struct definition"
   href="https://bugs.llvm.org/show_bug.cgi?id=45207">45207</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Crash on invalid recursive variadic template struct definition
          </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>release blocker
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++2a
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>ryan_greenblatt@brown.edu
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>I have filed the same bug on github here:
<a href="https://github.com/llvm/llvm-project/issues/181">https://github.com/llvm/llvm-project/issues/181</a>, but I am posting here for
completeness.

This happens with 10 rc2/rc3 and latest dev built from source.

This is a pretty minimal reproduction:
```
template <char First, char... Rest> struct Recursive {
  using next = typename Recursive<Rest...>::type;
  using type = notdefined<next::anything>;
};
```

Build with `clang++ -std=c++2a test.cpp`
It doesn't crash with `-std=c++17`

I made a docker container which reproduces the issue:
<a href="https://hub.docker.com/r/greenblattryan/clang-crash-recursive-template">https://hub.docker.com/r/greenblattryan/clang-crash-recursive-template</a>.

Backtrace: <a href="https://github.com/llvm/llvm-project/files/4333084/backtrace.txt">https://github.com/llvm/llvm-project/files/4333084/backtrace.txt</a>

Here is a zip with the backtrace, preprocessed source and associated run
script.
<a href="https://github.com/llvm/llvm-project/files/4333081/bug-report.zip">https://github.com/llvm/llvm-project/files/4333081/bug-report.zip</a></pre>
        </div>
      </p>


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