<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 --- - Undefined behavior in tuple_cat / make_tuple"
   href="https://llvm.org/bugs/show_bug.cgi?id=25169">25169</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Undefined behavior in tuple_cat / make_tuple
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libc++
          </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>All Bugs
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>eugeni.stepanov@gmail.com
          </td>
        </tr>

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

        <tr>
          <th>Classification</th>
          <td>Unclassified
          </td>
        </tr></table>
      <p>
        <div>
        <pre>I'm not really sure that the problem is in <tuple>, but I don't see anything
wrong with my code, and it works as expected with libstdc++.

$ cat 1.cc

#include <cstdio>
#include <tuple>

int main()
{
  auto t1 = std::tuple_cat(std::make_tuple(std::make_tuple(1)));
  return std::get<0>(std::get<0>(t1));
}

$ clang -stdlib=libc++ -std=c++14 -O2 1.cc -S -emit-llvm -o -

define i32 @main() #0 {
entry:
  ret i32 undef
}

The tuple is undef.</pre>
        </div>
      </p>
      <hr>
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      <ul>
          <li>You are on the CC list for the bug.</li>
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