<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 - Frontend segmentation fault involving C++20 lambda template"
   href="https://bugs.llvm.org/show_bug.cgi?id=49470">49470</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Frontend segmentation fault involving C++20 lambda template
          </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>normal
          </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>pkeir@outlook.com
          </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>Created <span class=""><a href="attachment.cgi?id=24600" name="attach_24600" title="The C++ file producing the seg fault">attachment 24600</a> <a href="attachment.cgi?id=24600&action=edit" title="The C++ file producing the seg fault">[details]</a></span>
The C++ file producing the seg fault

Attempting to compile the program below (and attached) produces a clang
frontend  command failure and segmentation fault on 64-bit Ubuntu 20.10 with
the command `clang++ -std=c++2a zip_with.cpp`.

#include <array>

template <typename F, typename T, std::size_t N, typename... As>
constexpr auto zip_with(const F f, const std::array<T, N>& a, const As&... as)
{
  auto vred = [&]<std::size_t I>() { return f(a[I],as[I]...); };

  auto iseq = [&]<typename I, I... Is>(std::integer_sequence<I,Is...>) {
    return std::array{vred.template operator()<Is>()...};
  };

  return iseq(std::make_index_sequence<N>{});
}

int main(int argc, char *argv[])
{
  std::array x{1,2,3}, y{4,5,6};
  zip_with([](int a, int b) { return a+b; }, x, y);
  return 0;
}</pre>
        </div>
      </p>


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