static std::vector<std::string> read_stat_file(const std::string &fn) {
    /*
     * Returns list of strings by space delimiter.
     */
    std::vector<std::string> s_buffer;
    {
        std::ifstream stat(fn);

        for (std::string token; std::getline(stat, token, ' ');) {
            s_buffer.push_back(token);
        }
        stat.close();
    }
    return s_buffer;
}

auto s_buffer = read_stat_file("/proc/self/stat");
...
//Failed to check s_buffer length
...
auto new_user_time = std::stoull(s_buffer[13]); //Crash