std::make_pair will make a replica. It’s going to by no means return a pair with reference sorts.
Your return std::make_pair(true, myMap.at(...)); will return a std::pair<bool, MyData> (copying the results of myMap.at(...)), which converts to a std::pair<bool, const MyData&>, the place the returned worth’s .second is certain to the short-term that’s instantly destroyed. This implies your operate returns a dangling reference.
Use std::pair‘s constructor:
// One among:
return { true, myMap.at(...) };
return std::pair<bool, const MyData&>(true, myMap.at(...));
(Additionally think about using simply const MyData*, returning nullptr if it’s not discovered. Barring that, std::non-obligatory<std::reference_wrapper<const MyData>> can also be a good selection to switch pair with bool)
