I would have thought that non-const references was better? It is clear that a non-const reference can be modified. If I just wanted to let them read a value, a

I would have thought that non-const references was better? It is clear that a non-const reference can be modified. If I just wanted to let them read a value, a const reference would be clear. Do Google enforce const pointers for arguments that define where to store results? If not, you could delete the pointer they pass you. A pointer does not always indicate who owns the data clearly. Far better would be to return the values from the function (or std::move them out if you must) instead of using a parameter as a "dump your results here" flag. Stroustrup encourages this (see 5.3.3 of C++ 4th edition where he says "I don’t consider returning results through arguments particularly elegant"). IMHO, it would be better to return a std::pair<bool, std::vector<myWonderfulType>> where bool indicates the success/failure of the function, with pair.second item being the results.