The size of unique_ptr has a lot to do with the deleter. For specific differences, see the analysis of the following code. Do not let unique_ptr occupy too much space, otherwise it will not achieve the same effect as a raw pointer.
#include <iostream>
#include <memory>
using namespace std;
class Widget {
int m_x;
int m_y;
int m_z;
public:
Widget(int x, int y, int z) :
m_x(x), m_y(y), m_z(z)
{
}
void print() {
cout << m_x << "," << m_y << "," << m_z << endl;
}
~Widget()
{
cout << "Widget dtor" << endl;
}
};
struct DeleteWithLog {
void operator()(Widget* w) {
data++;
delete w;
cout << "------ DeleteWithLog delete w" << endl;
}
int data;
};
void deleteFunction(Widget* w) {
delete w;
cout << "------ deleteFunction delete w" << endl;
}
int main()
{
{
unique_ptr<Widget> w1(new Widget(1, 2, 3));
w1->print();
cout <<"sizeof(w1) = " <<sizeof(w1) << endl;
cout << "------ default delete" << endl;
}
{
DeleteWithLog dw;
unique_ptr<Widget, DeleteWithLog> w2(new Widget(10, 20, 30));
w2->print();
cout << "sizeof(w2) = " << sizeof(w2) << endl;
}
int data1, data2, data3;
{
auto lambda = [=](Widget * w) {
cout << data1 << data2 << data3 << endl;
delete w;
cout << "------ lambda delete w" << endl;
};
unique_ptr<Widget, decltype(lambda)> w3(new Widget(100, 200, 300), lambda);
w3->print();
cout << "sizeof(w3) = " << sizeof(w3) << endl;
}
{
unique_ptr<Widget, void(*)(Widget*)>
w4(new Widget(1000, 2000, 3000), deleteFunction);
w4->print();
cout << "sizeof(w4) = " << sizeof(w4) << endl;
}
system("pause");
}
result:
