Re: using swap to make assignment operator exception safe

=?Utf-8?B?R2Vvcmdl?= <>
Tue, 8 Jan 2008 19:49:00 -0800
Thanks Igor,

Do you think it is good idea to invoke class members' individual swap
function to avoid recursion?

(in my own application's class hierarchy, I will implement all swap
functions for all classes. So, swap will be invoked until POD or STL built-in


"Igor Tandetnik" wrote:

George <> wrote:

Your suggestion is if I need to utilize such swap in my class, I'd
better implement a customize swap member function other than
utilizing std::swap?

Again - std::swap uses your own copy constructor and assignment
operator. It's nothing more than

template <typename T>
void swap(T& a, T&b) {
    T temp = a;
    a = b;
    b = temp;

You can't call generic std::swap from your operator=, since std::swap
will just turn around and call operator= right back. You need a custom
implementation of swap that knows the internals of your class (usually
packaged as a member function). See for example std::vector::swap()
(which simply swaps pointers to memory buffers maintained by
std::vector, and thus is guaranteed not to throw).
With best wishes,
    Igor Tandetnik

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