Re: [boost] Re: swappable user defined types and STLport libraries

From: Peter Dimov (pdimov_at_[hidden])
Date: 2003-08-07 06:02:13

Alisdair Meredith wrote:
> David Abrahams wrote:
>
>> Err, I don't get it.  It seems to me that you only need the hack if
>> you're going to *specialize* swap.  *Using* std::swap should work
>> just fine.
>
> OK, that's because I was confused <g>
> The following is really a minimal example, so I can be clearer this
> time:
>
>
>
> #include <boost/shared_ptr.hpp>

#include <algorithm>

It is unspecified whether shared_ptr.hpp will do it for you.

> class empty
> {
> };
>
> //#define DEMONSTRATE_BUG
> # if defined( DEMONSTRATE_BUG )
> namespace   std
> {
> template<>
> void swap( empty &lhs, empty &rhs )
> {
> }
>
> }
> # endif

I think that this specialization is ill-formed if the primary swap<> isn't
in std. Your code is broken by STLport's tricks, even though it looks
correct. :-)

Try

template<> void std::swap( empty &lhs, empty &rhs )
{
}

instead and see if it works. (I think it's broken too but the compiler may
like it better.)