CODEWITHSUNDEEP
c++c++11visual-c++visual-studio-2013
Alejandro Freeman
Alejandro Freeman

Reputation: 327

C++11 move semantics and rvalue reference

Consider the following code: 

class StringTokenizer 
{
private:
    char m_delimiter;
    std::istringstream m_string;

public:
    explicit StringTokenizer(const std::string& str, char delimiter)
    : m_string(str)
    , m_delimiter(delimiter)
    {
    }

    template <class Container>
    operator Container ()
    {
        Container container;
        for (std::string token; std::getline(m_string, token, m_delimiter); )
        {
            container.insert(container.end(), token);
        }
        return container;
    }
};

This is the usage:

vector<string> tmp = StringTokenizer("123 456", ' '); //Please note the implicit conversion

When debugging the following happens (Using VS2013):

At the return statement of conversion operator

  1. new vector constructed from container by moving
  2. container gets destructed

After function return:

  1. tmp is constructed by copy constructor

My question is why isn't tmp constructed by move constructor ?

As I understand things function return type is rvalue and should be moved.

Upvotes: 8

Views: 287

Answers (1)

user1186479
user1186479

Reputation: 63

VS2013 doesn't automatically generate the move constructor/assignment. This is solved in later versions.

https://msdn.microsoft.com/en-us/library/hh567368.aspx#rvref

Upvotes: 2

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