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From: Michael Anderson (michael.anderson_at_[hidden])
Date: 2007-03-01 21:09:21

Peter Dimov wrote:
>> So the solution I've come up with means that the Foo object only gets
>> destroyed when both the barptr and the fooptr are destroyed.
>> Unfortunately this requires additions to the shared_ptr class (the
>> patch is below). The changes are _very_ similar to what is used for
>> handling the pointer conversions and casts.
> There has been a formal proposal to add an "aliasing constructor" (as in
> your patch, but public and without the tag) to std::tr1::shared_ptr and I'm
> considering adding one for 1.35.

That's nice to hear, as a few other people inside my company have
mentioned that such a feature would be useful to them. (and we'd rather
not patch our copies of the boost libraries)

> In the meantime,
... snip ...
> you can use:
> template<class T, class M> shared_ptr<M> member_pointer(
> shared_ptr<T> const & t, M* m)
> {
> return shared_ptr<M>( m, bind( &shared_ptr<T>::reset, t ) );
> }

This seems to work perfectly.
One thing to note is that this solution uses extra memory for storing an
internal copy of the boost shared pointer and the custom deleter.

> A similar trick is described in:

This is nifty as it lets you get back to the parent pointer if you want,
but is essentially the same as the method outlined above (not a
criticism, just a note for those who dont want to follow the link)

So in summary: these are both great solutions, but I feel that an
aliasing constructor would be a great addition to the boost shared
pointers library.


Michael Anderson

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