Are there 2 times initialization when there is a constructor with default argument [duplicate]

Question

My question is about how the member data with initializer get initialized where there is also a default argument in the constructor.

class InputPlay {

    public:
        InputPlay(std::string s = "test" ) : _s(s) {  };

    private:
        std::string _s = "default";
};

Question:

Is there are going to be 2 times initialization for the variable _s when the construct is called? aka the _s will be initialized by the string literal default and then replace by the default argument "test" in the constructor?

Answer 1

No, _s will only be initialized once. The in class initialization is syntactic sugar for synthesizing a member initializer. If you provide your own member initializer then the compiler will use that instead of synthesizing one for you from the in class initialization.