- ConfigurationElement(std::string key, std::string desc) : key(key), desc(desc) {}
- ConfigurationElement(std::string key, std::string desc, xbt_cfg_cb_t cb) : key(key), desc(desc), old_callback(cb) {}
+ ConfigurationElement(const std::string& key, const std::string& desc) : key(key), desc(desc) {}
+ ConfigurationElement(const std::string& key, const std::string& desc, xbt_cfg_cb_t cb)
+ : key(key), desc(desc), old_callback(cb)
+ {
+ }