Question

What errors does the following code contain?


class A {
    public:
        A(int x) : _x(x) {} //1
    private:
        int _x;
};

int main() { 
    A a = 10; //2
    A b(a);   
    return 0; 
}

Cosmo · Accepted Answer

There are no mistakes in line //1, there is a regular initialization list.
In line //2 object a will be initialized either directly via existing constructor A(int) (if copy elision enabled), or from the temporary object generated by the A(int) constructor and then will be copied into a via automatically generated copy constructor. The copy constructor is automatically generated by the compiler if there are no explicitly declared copy constructor.
Object b will be initialized by the automatically generated copy constructor.

Cosmo · Accepted Answer

There are no errors

Cosmo · Answer

Line 2 contains an error since A has no copy constructor by default declared

Cosmo · Answer

Line 2 contains an error since A has no default constructor

Cosmo · Answer

Line 2 contains an error since A has no public constructor by default

Cosmo · Answer

Line 1 contains an error since you cannot declare class variables in this way

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