Klaus Iglberger

• Value semantics example with vector
• v2 = createVector()
• vs = std::move(v1);
• simple defn of rvalue, lvalue: lvalue has a name you give it
• operator=(vector&&rhs) rvalue reference
• Xvalue: expiring value
• do not use the moved from value (the xvalue)

New speicial member functions

• Move constructor
• Widget (Widget &&w) = default
• Move assignment operator
• Widget &operator=(Widget &&w) = default
• “Rule of zero” if you can avoid defining default operations, good

Move constructor

Widget(Widget &&w)
: i(w.i)
, s (w.s) // bad!
{}

Widget(Widget &&w) noexcept
: i(std::move(w.i)) // not necessary but consistent
, s(std::move(w.s))
, pi(std::move (w.pi))
{
    w.pi = nullptr;
}

, pi(std::exchange(w.pi, nullptr))


• Make move operations noexcept (Core Guidelines)

Move assignment operator

• clean up all visible resources
• Transfer the content of w into this
• Leave w in a valid but undefined state
• w = std::move(w);
• phase 1: cleanup
• phase 2: member-wise move
• phase 3:

Generated

• The default move operations are generate if no copy operation or destructor is user-define
• The default copy operations are generated if no move operation is user-defined
• Note: = default and =delete count as user-defined
• Rule of five or rule of six: if you define or =delete any default operation define or =delete them all.