Re: [boost] [multiindex] internal scope_guard has changed access from public to protected

Subject: Re: [boost] [multiindex] internal scope_guard has changed access from public to protected
From: Thorsten Ottosen (nesotto_at_[hidden])
Date: 2010-05-07 08:01:51

Hi Joaquin,

Sorry for the slow response.

Joaquin M Lopez Munoz skrev:
> Thorsten Ottosen <nesotto <at> cs.aau.dk> writes:
> 
>> Joaquin M Lopez Munoz skrev:
>>> Yep, why can't you just define null guard as
>>>
>>> struct null_guard:boost::multi_index::detail::scope_guard_impl_base{};
>> the ?: operator seem to require that the second argument can be 
>> converted to the type of the first argument.
> 
> I might be missing something, but I think tou can simply
> write the following to circumvent the problem:
> 
> #define BOOST_AUTO_BUFFER_CONSTRUCTOR_SCOPE_GUARD() \
>   boost::has_nothrow_copy<T>::value ? \
>   static_cast<boost::multi_index::detail::scope_guard>( \
>     boost::auto_buffer_detail::null_guard()) : \
>   static_cast<boost::multi_index::detail::scope_guard>( \
>     boost::multi_index::detail::make_obj_guard( \
>       *this, \
>       &auto_buffer::deallocate, \
>       buffer_, members_.capacity_ ))
> 
> Does this work? 

It seems to work.

>Additionally, why are you doing the
> guard selection on run time? boost::has_nothrow_copy<T>::value
> is a compile-time value so you can select the exact
> type of the guard (null or otherwise) with some Boost.MPL.

Well, I'm lazy, so I didn't want to implement the functionality twice 
with and without the guard. IMO the code is very clear with this macro. 
I think the optimizer has no problem removing the empty guard.

Thanks

-Thorsten