Re: [boost] smart_ptrs: Custom allocators.

From: Murray Cumming (murrayc_at_[hidden])
Date: 2001-08-17 08:51:59

Peter Dimov wrote:
> 
> From: "Murray Cumming" <murrayc_at_[hidden]>
> > Sorry, I read that as 'address of myalloc', instead of 'myalloc()'. This
> > might be enough, though it's less flexible. In particular, a custom
> > allocator would allow more use of a deallocator function that took args.
> 
> 'bind' can help with this:
> 
> shared_ptr<sybase_context> p(my_create_connection(constructor-args),
> bind(&my_destroy_connection, destroy-args));

Yes, that could help but that would all be less obvious than an
allocator. However, I'm not going to push the idea too hard because I
think that Peter Dimov's
shared_ptr<my_type> p(my_alloc(), &my_drop);
idea solves most of the problem. And, even though I have a general
dislike of function pointers and the assumptions that they make about
the functions that you'd want to use, I think that this might actually
be clearer for the majority of cases.

> > > It's not as elegant as a dedicated smart handle class, granted. If you
> > > decide to go that route you'll find that detail/shared_count.hpp does
> most
> > > of the work for you. :-)
> >
> > That's not very obvious to me.
> 
> I don't have the time at the moment to write the documentation for
> shared_count (it looks like it deserves boost:: status) but I'd probably
> have to if my proposed changes to shared_ptr are accepted.
> 
> For now, simply take a look at
> 
> http://groups.yahoo.com/group/boost/files/smart_ptr/shared_ptr.hpp
> 
> Most of it is boilerplate code that supports the shared_ptr specific
> interface. The real work is done by the shared_count member 'pn'. You can
> easily adapt shared_ptr into a sybase-specific smart handle.
> 
> Of course I don't want to imply that your allocator idea is not worth
> exploring.
> 
> --
> Peter Dimov
> Multi Media Ltd.
> 
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-- 
Murray Cumming
www.murrayc.com
murrayc_at_[hidden]