C++ Using base and derived constructor

gistfile1.txt

struct Base {
    Base(int a) : i(a) {}
    int i;
};

struct Derived : Base {
    Derived(int a, std::string s) : Base(a), m(s) {}

    using Base::Base; // Inherit Base's constructors.
    // Equivalent to:
    //Derived(int a) : Base(a), m() {}

    std::string m;
};
Derived now has two constructors (not counting copy/move constructors). One that takes an int and a string and one that takes just an int.

https://softwareengineering.stackexchange.com/questions/197893/why-are-constructors-not-inherited