Move with vector::push_back
c++, c++11
Solution
In your case, there is no effective difference, since you are using compiler-provided copy constructors. You would see a noticeable performance difference when using objects that are move-constructible, and take a lot of effort to copy. In that case, using `push_back(x)` would create a copy of the object, while `push_back(move(x))` would tell `push_back()` that it may "steal" the contents of `x`, leaving `x` in an unusable and undefined state.
Consider if you had a vector of lists (`std::vector<std::list<int> >`) and you wanted to push a list containing 100,000 elements. Without `move()`, the entire list structure and all 100,000 elements will be copied. With `move()`, some pointers and other small bits of data get shuffled around, and that's about it. This will be lots faster, and will require less overall memory consumption.
Problem
Suppose I have the following code: ``` #include <vector> struct A { int a; int x; }; int main() { using namespace std; A a1; A a2; vector<A> va; va.push_back(a1); va.push_back(move(a2)); } ``` I am aware that the elements of std::vector are stored contiguously, unlike a std::list. In the above code `a2` is moved but is there really no copying of `a2` to the vector `va`? What is the difference between `va.push_back(a2);` and `va.push_back(move(a2));`?