Re: [boost] Re: how do I release shared_ptr ?

From: Peter Dimov (pdimov_at_[hidden])
Date: 2004-01-08 08:39:33

Joe Gottman wrote:
>
>     One major use for unique() is copy-on-write.  The code would look
> something like:
>
>     void write_to(shared_ptr<Foo> p, const Foo &newValue)

You mean "shared_ptr<Foo> & p", right?

>     { // For simplicity, assume p.get() != 0
>         if (p.unique()) {
>             *p = newValue;
>         } else {
>             p.reset(new Foo(newValue));
>         }
>     }
>
> Under the current definition of unique(), this code is impossible to
> make thread-safe if weak_ptrs might exist.

True... On the other hand, copy on write classes typically do not expose the
shared_ptr<Foo> to the world, so the current unique() is enough.