std::vector > does not compile

Question

When I declare a vector of unique_ptr's, I get this kind of error:

d:\qt\mingw64\include\c++\4.8.0\bits\stl_construct.h:75: error:
use of deleted function 'std::unique_ptr<_Tp, _Dp>::unique_ptr(
const std::unique_ptr<_Tp, _Dp>&) [with _Tp = int; _Dp = std::default_delete<int>]'

Which looks like the classical error of creating a containers of objects which have no copy constructor.

However, it is documented in everything I could find that a standard container of unique_ptrs works thanks to the c++11 move semantics.

I am compiling with MinGW-gcc 64-bit, using -std=gnu++11.

Is it supported only in c++11 and not in gnu++11?

Thanks

`4.8.0` it's not C+11-compliant, any release starting from the `4.8.1` is — user2485710, Apr 01 '14 at 14:05
Look the following link: http://stackoverflow.com/q/10613126/2724703 — Mantosh Kumar, Apr 01 '14 at 14:06
Show us a minimal example program that demonstrates your exact error so we can try it. — John Zwinck, Apr 01 '14 at 14:08
I just figured that the std::vector > is declared as a member variable in a class. Since the class has a copy constructor, and if I understand right, this is the issue. — galinette, Apr 01 '14 at 14:11
When I declare it as a local variable in a function, it compiles. — galinette, Apr 01 '14 at 14:12
You'll have to implement that copy constructor in a way that duplicates the pointed-at objects. Next time, please show a minimal example. — mic_e, Apr 01 '14 at 14:14
Isn't trying to put an explicitly non-copyable "unique" object into a container that expects the object to be copyable somewhat futile? — Damon, Apr 01 '14 at 14:22

score 2 · Answer 1 · answered Apr 01 '14 at 14:26

2

The following will compile with C++11.

#include <iostream>
#include <vector>
#include <memory>
using namespace std;

int main()
{
    std::vector<std::unique_ptr<int> > asdf;
    return 0;
}

answered Apr 01 '14 at 14:26

Joshua

328
1
7

score 2 · Accepted Answer · answered Apr 01 '14 at 15:04

The problem was not std::vector<std::unique_ptr<int> > itself, but the member variable of this type declared in a copiable class. Since the default copy constructor of the class calls the copy constructor of std::vector, which in turns calls the default constructor of std::unique_ptr, the later being deleted, compilation fails.

std::vector<std::unique_ptr<int> > compiles fine as a local variable in a function.

std::vector > does not compile

2 Answers2