Re: [boost] [smart_ptr] shared_ptr template type

Subject: Re: [boost] [smart_ptr] shared_ptr template type
From: Gottlob Frege (gottlobfrege_at_[hidden])
Date: 2009-07-09 14:27:22

On Thursday, July 9, 2009, Frank Mori Hess <frank.hess_at_[hidden]> wrote:
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> I wonder if it might be better/possible to have a shared_ptr<T> that didn't
> assume its corresponding "raw" pointer type was T* but rather T.  For
> example, what is now a shared_ptr<int> would be specified as a
> shared_ptr<int*>.  The motivation would be to allow support for other classes
> as the "raw" pointer type.  For example, I might want to have a
> shared_ptr<monitor<T*> > where the monitor<T*> has an operator->() which does
> automatic locking/unlocking of a mutex before/after forwarding the
> operator->() to the plain T pointer.

I don't think lock/unlock on each -> call is typically a good idea.
 x = p->x;
 y = p->y;
That's 2 lock unlock sequences instead of one.  Inefficient and what
if y changes after you read x?
It hides the locking too much, potentially leading to abuse and mistakes.

I think alexandrescu has an article about this somewhere. (he also has
articles about how to implement locking -> operators but I think he
later recanted on the whole idea)

Tony