How to print a value of reference to a pointer

Question

How can I print a value of a reference to a pointer?

int& createInt(){
    auto uPtr = make_unique<int>(2);
    auto ptr(uPtr.get() );
    return *ptr;
}

How would I print value 2 when I call createInt() function?

int& x = createInt();  // what will be the value of "x"

The code you posted is undefined behavior, because you will print the value at a deleted address. — utnapistim, Aug 14 '15 at 07:18
@utnapistim there's no UB in the posted code, but there would be if the calling code used the return value — M.M, Aug 14 '15 at 07:26
@MattMcNabb, I assumed @gath asked about how to print the `2` used in the call to `make_unique`, from the code calling `createInt`. — utnapistim, Aug 14 '15 at 08:08
But guys, if I call int& x = createInt(); will I not "copy" the reference to a new variable? — gath, Aug 14 '15 at 08:52
@gath: You'd copy the reference -- a reference to a piece of memory that has been released. — DevSolar, Aug 14 '15 at 11:13

score 0 · Answer 1 · answered Aug 14 '15 at 07:41

0

This won't work because a unique_ptr will automatically free it's memory when it goes out of scope.

http://en.cppreference.com/w/cpp/memory/unique_ptr

what you can do is

int createInt(){
    return 2;
}

or

int* createIntPtr(){
    return new int(2);
}

though that is probably bad practice. There are other things you can do like passing a reference to a value and editing it, depending on what you want though.

answered Aug 14 '15 at 07:41

Gage Ervin

105
1
8

One can return a valid reference to a local static variable. – πάντα ῥεῖ Aug 14 '15 at 07:44
Am I misunderstanding something? If it's a unique_ptr it's memory should be unprotected when the function ends, meaning even if the data still happens to be the same when accessed later, it's unsafe. – Gage Ervin Aug 14 '15 at 08:04
No your understanding is correct. I just wanted to note this for completeness. – πάντα ῥεῖ Aug 14 '15 at 08:06
Thanks; I also found this option while I was nosing around: [link](http://stackoverflow.com/questions/4316727/returning-unique-ptr-from-functions) – Gage Ervin Aug 14 '15 at 08:12

How to print a value of reference to a pointer

1 Answers1