Re: [boost] Re: what happened to allocators in boost?

From: Gregory Colvin (gregory.colvin_at_[hidden])
Date: 2003-08-28 18:33:19

On Thursday, Aug 28, 2003, at 16:26 America/Denver, E. Gladyshev wrote:
> --- Gregory Colvin <gregory.colvin_at_[hidden]> wrote:
>>> How will I even know it, the documentation is completely
>>> ignorant on the memory issues.
>>
>> Perhaps because you work with the authors of the documentation to
>> make it sure it says what needs saying?
>
> Are the documentation authors monitoring this mailing list?
>
>> And I have no objection myself to adding an allocator parameter
>> to the shared_ptr constructor, or to making some other change that
>> serves the purpose.  So if you need a change, why not just do it,
>> try it out, and submit a patch?
>
> How about
>
> template< typename T, typename Counter = int >
> shared_ptr
> {
>    typedef Counter counter;  //counter type should be public
>
>    template <typename DataAlloc = std::allocator<T>, typename  
> CounterAlloc=std::allocator<counter>
>>
>    shared_ptr( const DataAlloc& da = DataAlloc(), const IntAlloc ia& =  
> CountAlloc() );
> };

shared_ptr doesn't allocate the data, it only deletes it, which is the  
job of the
current deleter parameter.  And the counter type is by design not part  
of the
shared_ptr type, so it doesn't belong as parameter to the shared_ptr  
template.
See:
     
http://cvs.sourceforge.net/cgi-bin/viewcvs.cgi/boost/boost/boost/ 
shared_ptr.hpp

So you what you might want is to add something more like this to  
shared_ptr:

    template<typename Data, typename Deleter, template<class Counter>  
class Allocator>
    shared_ptr(
       Data*,
       Deleter,
       const Allocator<boost::detail::sp_counted_base_impl<Data*,  
Deleter> >& );

The idea being that you can use this constructor to get complete  
control over how
a particular shared_ptr manages memory.