Re: [boost] Enabling fast swap optimization for Boost types VC9 SP1.

From: Niels Dekker - mail address until 2008-12-31 (nd_mail_address_valid_until_2008-12-31_at_[hidden])
Date: 2008-08-23 07:07:10

>> So can't this std::_Move_operation_category be
>> specialized based on some template meta programming (e.g.,
>> has_swap_member<T>::value)?

David Abrahams wrote:
> I don't know what member functions have to do with it; the real
> criterion is whether or not there's a swap available for it via ADL.

Thanks, Dave! I knew how to write has_swap_member<T> already, but I
didn't yet know about has_swap_overload<T>. Now I see, it's also at
http://svn.boost.org/svn/boost/sandbox/move/boost/move/detail/has_swap_overload.hpp

I just added another comment to the MSDN blog, mentioned your
metafunction:
http://blogs.msdn.com/vcblog/archive/2008/08/11/tr1-fixes-in-vc9-sp1.aspx

It's a pity that has_swap_overload<T> yields false negatives, when T has
std as associated namespace.  Maybe, as a workaround, VC9 SP1 could be
tweaked to apply their "Swaptimization", when has_swap_overload<T> /or/
has_swap_member<T> (using mpl::or_).  Because I still think that if T
has a swap member function, it's /very/ likely that it has a custom swap
overload as well. Assuming that developers follow the "coding standard"
to provide a non-member swap, whenever they provide a swap member
function. What do you think?

Kind regards, 

  Niels