Is there a performance difference between i++ and ++i in C++?

Question

We have the question is there a performance difference between i++ and ++i in C?

What\'s the answer for C++?

Answer 1

Time to provide folks with gems of wisdom ;) - there is simple trick to make C++ postfix increment behave pretty much the same as prefix increment (Invented this for myself, but the saw it as well in other people code, so I'm not alone).

Basically, trick is to use helper class to postpone increment after the return, and RAII comes to rescue

#include 

class Data {
    private: class DataIncrementer {
        private: Data& _dref;

        public: DataIncrementer(Data& d) : _dref(d) {}

        public: ~DataIncrementer() {
            ++_dref;
        }
    };

    private: int _data;

    public: Data() : _data{0} {}

    public: Data(int d) : _data{d} {}

    public: Data(const Data& d) : _data{ d._data } {}

    public: Data& operator=(const Data& d) {
        _data = d._data;
        return *this;
    }

    public: ~Data() {}

    public: Data& operator++() { // prefix
        ++_data;
        return *this;
    }

    public: Data operator++(int) { // postfix
        DataIncrementer t(*this);
        return *this;
    }

    public: operator int() {
        return _data;
    }
};

int
main() {
    Data d(1);

    std::cout <<   d << '\n';
    std::cout << ++d << '\n';
    std::cout <<   d++ << '\n';
    std::cout << d << '\n';

    return 0;
}

Invented is for some heavy custom iterators code, and it cuts down run-time. Cost of prefix vs postfix is one reference now, and if this is custom operator doing heavy moving around, prefix and postfix yielded the same run-time for me.