Re: [Boost-users] custom allocators for shared_ptr

From: Ion Gaztañaga (igaztanaga_at_[hidden])
Date: 2007-09-28 04:59:32

Cory Nelson wrote:
> It would be useful if shared_ptr and family provided a way to give a
> custom allocator.  For instance, to replace the quick allocator with a
> lock-free one.

boost::shared_ptr is already ready to accept allocators:

http://www.boost.org/libs/smart_ptr/shared_ptr.htm

template<class Y, class D> shared_ptr(Y * p, D d);
template<class Y, class D, class A> shared_ptr(Y * p, D d, A a);

     Requirements: p must be convertible to T *. D must be 
CopyConstructible. The copy constructor and destructor of D must not 
throw. The expression d(p) must be well-formed, must not invoke 
undefined behavior, and must not throw exceptions. A must be an 
Allocator, as described in section 20.1.5 (Allocator requirements) of 
the C++ Standard.

     Effects: Constructs a shared_ptr that owns the pointer p and the 
deleter d. The second constructor allocates memory using a copy of a.

     Postconditions: use_count() == 1 && get() == p.

     Throws: std::bad_alloc, or an implementation-defined exception when 
a resource other than memory could not be obtained.

     Exception safety: If an exception is thrown, d(p) is called.

     Notes: When the the time comes to delete the object pointed to by 
p, the stored copy of d is invoked with the stored copy of p as an argument.

Regards,

Ion