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    <p>You don't <em>have</em> to worry about it, in the sense that when you user-declare a destructor (or anything else listed in 12.8/9), that blocks the default move constructor from being generated. So there's not the same risk as there is with copies, that the default is wrong.</p> <p>So, as the first pass leave them alone. There may be places in your existing code where C++11 move semantics allow a move, whereas C++03 dictates a copy. Your class will continue to be copied, and if that caused no performance problems in C++03 then I can't immediately think of any reason why it would in C++11. If it did cause performance problems in C++03, then you have an opportunity to fix a bug in your code that you never got around to before, but that's an opportunity, not an obligation ;-)</p> <p>If you later implement move construction and assignment, they will be moved, and in particular you'll want to do this if you think that C++11 clients of your class are less likely to use "swaptimization" to avoid copies, more likely to pass your type by value, etc, than C++03 clients were.</p> <p>When writing new classes in C++11, you need to consider and implement move under the same criteria that you considered and implemented <code>swap</code> in C++03. A class that can be copied implements the C++11 concept of "movable", (much as a class that can be copied in C++03 can be swapped via the default implementation in <code>std</code>), because "movable" doesn't say what state the source is left in - in particular it's permitted to be unchanged. So a copy <em>is</em> valid as a move, it's just not necessarily an efficient one, and for many classes you'll find that unlike a "good" move or swap, a copy can throw.</p> <p>You might find that you have to implement move for your classes in cases where you have a destructor (hence no default move constructor), and you also have a data member which is movable but not copyable (hence no default copy constructor either). That's when move becomes important semantically as well as for performance.</p>
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