std::copy_n and destination vector size unchanged

If I reserve some space for a vector, and then I copy some values in it with std::copy_n(), I get the values copied correctly and accessible, but the size of the vector is still zero. Is this the expected behaviour? Should I resize the vector instead, even if it is not as efficient?

#include <algorithm>
#include <iostream>
#include <vector>

int main()
{
    std::vector<double> src, dest;

    for(double x = 0.0; x < 100.0; ++x)
        src.push_back(x);

    dest.reserve(src.size());

    std::copy_n(src.cbegin(), src.size(), dest.begin());

    std::cout << "src.size() = " << src.size() << std::endl;
    std::cout << "dest.size() = " << dest.size() << std::endl;

    for(size_t i = 0; i < src.size(); ++i)
        std::cout << dest[i] << "  ";

}

Compilers tested: clang, gcc, Visual C++