c++ 복사생성자,복사초기화,RVO

복사생성자 복사초기화 RVO

자신과 똑같은 타입의 데이터가 들어오면 복사하는 것을 말한다. 

컴파일러의 판단
복사할려는 value가 r_value면 복사하지않고 바로 생성한다.
함수로 return받으면 debug 일때면 복사생성자를 사용하고(다른주소를 가진다) release에선 바로 생성(주소값이 같다)한다.

 

복사생성자 막기

copy constructor를 private로 보내면 복사생성자를 사용할 수 없다. 

#include <iostream>
#include <cassert>

using namespace std;
class Fraction {
private:
	int m_num;
	int m_den;

public:
	Fraction(int num, int den) 
		:m_num(num), m_den(den) 
	{
		assert(den != 0);
	}

	Fraction(const Fraction &frc)
		:m_num(frc.m_num), m_den(frc.m_den) {
		cout << "copy constructor called" << endl;
	}

	friend std::ostream & operator << (std::ostream & out, const Fraction & f) {
		out << f.m_num << " / " << f.m_den << endl;
		return out;
	}
};

Fraction doSomething()
{
	Fraction temp(1, 2);
	return temp;
}

int main()
{
	Fraction frac(3, 5);

	Fraction cpFrac(frac);

	cout << cpFrac << endl;
	return 0;
}