Question

unique_ptr<int> p1 (new int (15));

unique_ptr<int> p2 (p1);

unique_ptr<int> p3;

p3=p1;

1. Which line(s) will trigger a compile error?

2. Which lines will trigger a segmentation fault?

P3 = make_unique<int> (25);

cout<< *p1 << endl;

cout<< *p3 << endl;

Answer 1

A.Which line(s) will trigger a compile error?

unique_ptr<int> p1 (new int (15));

unique_ptr<int> ppq2 (p1);

unique_ptr<int> p3;

p3=p1;

Explanation:

The above underlined, bold lines will give compiler error. Because, those lines make conflict with semantics of unique_ptr.

Based on its name, it can't be shared between multiple owners. At any point of time, only one entity can have the ownership.

unique_ptr<int> p2 (p1); This line is trying to copy p1 using copy constructor, but copying unique pointer is not allowed.

p3=p1; This line is trying is trying to copy p1 using assignment operator, but copying unique pointer is not allowed.

B. Which lines will trigger a segmentation fault?

p3 = make_unique<int> (25);

cout<< *p1 << endl;

cout<< *p3 << endl;

p3 = make_unique<int>(25);

returns unique_pointer which manages integer pointer and initializes integer value to 25

cout<< *p1 << endl;

printing resided value in memory hold by p1

cout<< *p3 << endl;

printing resided value in memory hold by p3

So, no line will trigger a segmentation fault. All 3 statements are valid and generate proper output.