<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 - empty range-for loop over map is not optimized away"
   href="https://bugs.llvm.org/show_bug.cgi?id=46564">46564</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>empty range-for loop over map is not optimized away
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>libraries
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>All
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

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

        <tr>
          <th>Component</th>
          <td>Loop Optimizer
          </td>
        </tr>

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

        <tr>
          <th>Reporter</th>
          <td>trass3r@gmail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>llvm-bugs@lists.llvm.org
          </td>
        </tr></table>
      <p>
        <div>
        <pre>#include <algorithm>
#include <map>
#include <string>
#include <vector>

using Map = std::map<int, std::vector<std::string>>;

void f1(const Map& m)
{
    for (const auto& p : m)
    { (void)p; }
}
void f2(const Map& m)
{
    std::for_each(m.begin(), m.end(), [](const std::pair<const int,
std::vector<std::string>>& p){
    (void)p; });
}

Does work for f2. gcc eliminates both:
<a href="https://godbolt.org/z/E-LCJV">https://godbolt.org/z/E-LCJV</a></pre>
        </div>
      </p>


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