https://github.com/danmar/cppcheck/pull/2751

test-range-based-for-loop-references.cpp

#include <chrono>
#include <iostream>
#include <limits>
#include <map>
#include <memory>

class A {
  public:
    A(int Data) : Data(Data) {}

  private:
    int Data;
};

int main(int argc, char *argv[])
{
    std::map<short, std::shared_ptr<A>> elements;

    for (short i = 0; i < std::numeric_limits<short>::max(); i++) {
        elements.emplace(i, std::make_shared<A>(i));
    }

    {
        auto start__ = std::chrono::high_resolution_clock::now();
        std::size_t count = 0;
        for (const auto el : elements) {
            count += 1;
        }
        auto end__ = std::chrono::high_resolution_clock::now();
        std::cout << __func__ << ":" << __LINE__ << ": "
                  << std::chrono::duration_cast<std::chrono::nanoseconds>(
                         end__ - start__)
                         .count()
                  << "ns" << std::endl;
    }

    {
        auto start__ = std::chrono::high_resolution_clock::now();
        std::size_t count = 0;
        for (const auto &el : elements) {
            count += 1;
        }
        auto end__ = std::chrono::high_resolution_clock::now();
        std::cout << __func__ << ":" << __LINE__ << ": "
                  << std::chrono::duration_cast<std::chrono::nanoseconds>(
                         end__ - start__)
                         .count()
                  << "ns" << std::endl;
    }

    return 0;
}