error: ‘unique_ptr’ is not a member of ‘std’

Question

I guess it's pretty self explanatory - I can't seem to use C++11 features, even though I think I have everything set up properly - which likely means that I don't.

Here's my code:

#include <cstdlib>
#include <iostream>

class Object {
    private:
        int value;

    public:
        Object(int val) {
            value = val;
        }

        int get_val() {
            return value;
        }

        void set_val(int val) {
            value = val;
        }
};

int main() {

    Object *obj = new Object(3);
    std::unique_ptr<Object> smart_obj(new Object(5));
    std::cout << obj->get_val() << std::endl;
    return 0;
}

Here's my version of g++:

ubuntu@ubuntu:~/Desktop$ g++ --version
g++ (Ubuntu/Linaro 4.7.3-2ubuntu1~12.04) 4.7.3
Copyright (C) 2012 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

Here's how I'm compiling the code:

ubuntu@ubuntu:~/Desktop$ g++ main.cpp -o run --std=c++11
main.cpp: In function ‘int main()’:
main.cpp:25:2: error: ‘unique_ptr’ is not a member of ‘std’
main.cpp:25:24: error: expected primary-expression before ‘>’ token
main.cpp:25:49: error: ‘smart_obj’ was not declared in this scope

Note that I've tried both -std=c++11 and -std=c++0x to no avail.

I'm running Ubuntu 12.04 LTS from a flash drive on an Intel x64 machine.

[this reference](http://en.cppreference.com/w/cpp/memory/unique_ptr) tells you whcih header you need to include. — juanchopanza, Aug 06 '13 at 10:54

score 110 · Accepted Answer · answered Aug 06 '13 at 10:52

110

You need to include header where unique_ptr and shared_ptr are defined

#include <memory>

As you already knew that you need to compile with c++11 flag

g++ main.cpp -o run -std=c++11
//                  ^

answered Aug 06 '13 at 10:52

billz

41,716
7
75
95

1

I'm sorry, I'm new to C++. Why is it used as std::unique_ptr if it's defined in ? – Ark-of-Ice Oct 11 '14 at 07:21
@AoI: "std" is the namespace. "memory" only indicates the header file where it is defined. – JohnTortugo Nov 18 '14 at 03:13
A very good source to learn https://isocpp.org/blog/2015/09/quick-q-what-is-a-smart-pointer-and-when-should-i-use-one – user2235747 Jul 06 '20 at 07:15

score 0 · Answer 2 · answered Mar 17 '20 at 15:38

So here what I learned in 2020 - memory.h is at /usr/include AND in /usr/include/c++/4.8.5 and you need the second to be found before the first. In Eclipse set the order using Project->Properties->Path and Symbols->Includes->Add... path if needed and set first

score 0 · Answer 3 · answered Mar 31 '21 at 18:57

0

You need to include #include that will solve the problem, at least on my ubunto linux machine

answered Mar 31 '21 at 18:57

Oscar Rangel

107
10

error: ‘unique_ptr’ is not a member of ‘std’

3 Answers3