Re: Is this a good reference-counting smart pointer class?
On Mar 29, 11:48 pm, douglas <Protoman2...@gmail.com> wrote:
On Mar 29, 12:46 am, Juha Nieminen <nos...@thanks.invalid> wrote:
douglas wrote:
So, how do I fix it?
Share the reference counter with all the copies, rather than
replicating it.
Or could I modify the classes to have a mutable ref count
variable, and have the SmrtPtr class add and subtract from
that, and free the ptr when that var hits 0. Would that be
intrusive ref counting?
That's what is meant by intrusive reference counting, yes.
The version having the separate counter object (from Barton and
Nackman, for example) has the advantage that it works with all
types of objects, even ones in the standard or some third party
library. On the other hand, it is extremely fragile---it's far
too easy to end up with two counter objects. For this reason, I
would avoid it at all cost in critical code. The invasive
version (from Scott Meyers, for example) typically requires that
the pointed to object ultimately derive from a base class
containing the counter. This means that you can't use it on
existing classes directly (but it's trivial to wrap an existing
class so that you can use it); it also has implications when
multiple inheritance is involved. On the other hand, it's
fairly robust. (As robust as reference counting can be.)
--
James Kanze (GABI Software) email:james.kanze@gmail.com
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