Re: [boost] [shared_ptr] Best Practices - new_shared_ptr

From: Larry Evans (cppljevans_at_[hidden])
Date: 2006-03-26 16:11:22

On 03/26/2006 01:19 PM, Vaclav Vesely wrote:
[snip]
> IMHO const reference forwarding and explicit wrapping of non-const 
> reference parameters with boost::ref is comfortable enough and feasible 
> with current compilers. See the attachment.
> 
> If there will be there a will to add my implementation into Boost, I 
> will write an appendix to the Best Practices.
> 
> Regards,
> Vaclav
[snip]
> namespace boost
> {
> 
> #if !defined(BOOST_MAX_NEW_ARITY)
>     #define BOOST_MAX_NEW_ARITY 10
> #endif
> 
> #define BOOST_NEW_TEMPLATE(z, n, d)                                         \
> template<typename T BOOST_PP_ENUM_TRAILING_PARAMS(n, typename A)>           \
> T new_(BOOST_PP_ENUM_BINARY_PARAMS(n, A, const& a))                         \
> {                                                                           \
>     return T(new T::element_type(BOOST_PP_ENUM_PARAMS(n, a)));              \
> }                                                                           \
> /**/
> 
> BOOST_PP_REPEAT(BOOST_PP_INC(BOOST_MAX_NEW_ARITY), BOOST_NEW_TEMPLATE,
>     BOOST_PP_EMPTY())
> 
> #undef BOOST_NEW_TEMPLATE
> 
> } // namespace boost
> 

This would not be useful for a smart pointer:

   template<class Referent>
   struct only_heap_ptrs
   ;

which didn't have a CTOR taking a Referent* argument.
IOW, there would be no:

   template<class Referent>
   only_heap_ptrs<Referent>::only_heap_ptrs(Referent* a_heap_ptr);

Such a smart pointer would avoid a mistake like:

   int i;
   only_heap_ptrs<int> pi(&i);

OTOH, this was one of the purposes of the auto_overhead template
class of http://tinyurl.com/f2r7h.  OTOH, it's very easy to reuse
auto_overhead to write new_ AFAICT.