difference in initialization constructor

user_17973183 0
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I have a simple class with two objects in main(). Are there any differences in the initialization of the constructor ?

//#include <systemd/sd-bus.h>

#include <iostream>
#include <memory>

class Simple
{
    private:
        int a;
    public:
        Simple(int b) : a(b) { }
        void show() { std::cout << a; }
};


int main()
{
    Simple firstObj = Simple(5);
    firstObj.show();

    Simple secondObj(5);
    secondObj.show();

    return 0;
}
c++
2 Answers

  • Pre-C++17,

    first one uses also copy(Pre-c++11)/move constructor (which might be elided) whereas second uses only Simple(int).

  • Since C++17,

    both are equivalent.

user_26845390

Simple firstObj = Simple(5); performs copy initialization, Simple secondObj(5); performs direct initialization, since C++17 they have the exact same effect: the object is initialized by the constructor Simple::Simple(int) directly.

user_33097900
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