Just a short snippet illustrating the basics of object construction in C++11.

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
#include <iostream>
using namespace std;

class A {
    private:
        int x;
    public:
        static void f(A a) {}

        static A create() {
            return A(3);
        }

        A() {
            // cout << "empty ctor" << endl;
        }

        explicit A(int x_) : x{x_} {
            // cout << "init ctor" << endl;
        }

        A(const A& other) {
            cout << "copy ctor" << endl;
            x = other.x;
        }

        A& operator=(const A& other) {
            cout << "assignment copy" << endl;
            x = other.x;
            return *this;
        }

        A(A&& other) : x{move(other.x)} {
            cout << "move ctor" << endl;
        }

        A& operator=(A&& other) {
            cout << "assignment move" << endl;
            if (this != &other) {
                x = move(other.x);
            }
            return *this;
        }
};

int main()
{
    A a{3};

    // as if A is an primitive type, pass by value
    // copy ctor; the two ways are identical
    auto b = a;
    // auto b{a};

    // call empty ctor
    A c;
    // assignment copy
    c = b;

    // implicit conversion from int to A; explicit prevents such conversion
    // additionally, copy-constructor can be disabled via this specifier as well
    // A::f(3);

    // copy elision; equivalent to direct initialization
    auto d = A::create();
    // auto d = A(3);

    // forcing to call move ctor; identical
    auto e = static_cast<A&&>(A::create());
    // auto e = move(A::create());

    A f;
    // assignment move
    f = A::create();

    return 0;
}
1
2
3
4
5
$ clang++ -std=c++11 -stdlib=libc++ test.cc && ./a.out
copy ctor
assignment copy
move ctor
assignment move

ยงReference