On Saturday, May 26, 2012 04:54 PM, Ingo Loehken wrote:
Hello,
i just recognized, that std::swap is not overload for boost::shared_ptr, meaning that using swap with std namespace ends up with unexpected results in respect to performance.
Is this by intent ?
If you look at the synopsis: http://www.boost.org/doc/libs/1_49_0/libs/smart_ptr/shared_ptr.htm#Synopsis You'll see a member swap and a free function swap in the boost namespace, this free function is intended to be found with ADL. There is a note on that page: "[swap is defined in the same namespace as shared_ptr as this is currently the only legal way to supply a swap function that has a chance to be used by the standard library.]" If you look at the implementation of boost::swap you'll see something like: namespace boost { void swap(T& a, T& b) { using std::swap; swap(a, b); } } Which allows you to swap with ADL or std::swap fallback. I don't think you want to explicitly call ::std::swap from user code. Details: http://www.boost.org/doc/libs/1_49_0/libs/utility/swap.html Ben