1. “What is it?” While std::move() is technically a function – I would say it isn’t really a function. It’s sort of a converter between ways the compiler considers an expression’s value. 2. “What does it do?” The first thing to note is that std::move() doesn’t actually move anything. It changes an expression from being … 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 need to inform C++ (specifically std::vector) that your move constructor and destructor does not throw, using noexcept. Then the move constructor will be called when the vector grows. This is how to declare and implement a move constuctor that is respected by std::vector: A(A && rhs) noexcept { std::cout << “i am the move … Read more
In addition to what visitor said : The function void emplace_back(Type&& _Val) provided by MSCV10 is non conforming and redundant, because as you noted it is strictly equivalent to push_back(Type&& _Val). But the real C++0x form of emplace_back is really useful: void emplace_back(Args&&…); Instead of taking a value_type it takes a variadic list of arguments, … Read more
First, “ref-qualifiers for *this” is a just a “marketing statement”. The type of *this never changes, see the bottom of this post. It’s way easier to understand it with this wording though. Next, the following code chooses the function to be called based on the ref-qualifier of the “implicit object parameter” of the function†: // … Read more
I find it easiest to understand move semantics with example code. Let’s start with a very simple string class which only holds a pointer to a heap-allocated block of memory: #include <cstring> #include <algorithm> class string { char* data; public: string(const char* p) { size_t size = std::strlen(p) + 1; data = new char[size]; std::memcpy(data, … Read more