Beta_ab&& Beta::toAB() const { return move(Beta_ab(1, 1)); } This returns a dangling reference, just like with the lvalue reference case. After the function returns, the temporary object will get destructed. You should return Beta_ab by value, like the following Beta_ab Beta::toAB() const { return Beta_ab(1, 1); } Now, it’s properly moving a temporary Beta_ab object … Read more
Generalized lambda capture in C++14 In C++14 we will have the so called generalized lambda capture. This enables move capture. The following will be legal code in C++14: using namespace std; // a unique_ptr is move-only auto u = make_unique<some_type>( some, parameters ); // move the unique_ptr into the lambda go.run( [ u = move(u) … Read more
I’d say the Rule of Three becomes the Rule of Three, Four and Five: Each class should explicitly define exactly one of the following set of special member functions: None Destructor, copy constructor, copy assignment operator In addition, each class that explicitly defines a destructor may explicitly define a move constructor and/or a move assignment … Read more
First example std::vector<int> return_vector(void) { std::vector<int> tmp {1,2,3,4,5}; return tmp; } std::vector<int> &&rval_ref = return_vector(); The first example returns a temporary which is caught by rval_ref. That temporary will have its life extended beyond the rval_ref definition and you can use it as if you had caught it by value. This is very similar to … Read more
You have to understand the forwarding problem. You can read the entire problem in detail, but I’ll summarize. Basically, given the expression E(a, b, … , c), we want the expression f(a, b, … , c) to be equivalent. In C++03, this is impossible. There are many attempts, but they all fail in some regard. … Read more
It declares an rvalue reference (standards proposal doc). Here’s an introduction to rvalue references. Here’s a fantastic in-depth look at rvalue references by one of Microsoft’s standard library developers. CAUTION: the linked article on MSDN (“Rvalue References: C++0x Features in VC10, Part 2”) is a very clear introduction to Rvalue references, but makes statements about … Read more