Re: [Boost-users] custom allocators for shared_ptr

Zeljko Vrba wrote:

On Fri, Sep 28, 2007 at 12:55:07PM +0300, Peter Dimov wrote:

...

That's what the A argument is for. You quoted the wrong clause.

Oh, sorry. You mean this constructor:

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

A question: why is the API designed so that using a custom allocator forces the user to specify a deallocator? I.e. the two are orthogonal, so why force the (use A) => (must use D) implication?

Given an Allocator concept, it'd be possible to add template shared_ptr( Y * p, A a ); In practice, it's rare for the user to want to use a custom allocator for the control block, yet not use a custom allocator for the object, so forcing him to pass a deleter as well is not as constraining. One might even argue that it removes the ambiguity that is present in the above form, where it isn't clear whether A should be used to deallocate *p as well.