[boost] Re: live_ptr

From: Alan Griffiths (alan_at_[hidden])
Date: 1999-08-01 16:12:05

In message <000801bedc3e$fb008170$37781990_at_[hidden]>, Greg Colvin
<gcolvin_at_[hidden]> writes
>Although it seems impossible to create a non-intrusive weak
>pointer class that can track the liveness of an arbitrary class of
>object, it is possible to create one that tracks the liveness of
>objects controlled by shared_ptr.
>
>The changes to out current shared_ptr would be:
>
>   Switch to the "indirect" implementation of shared_ptr.  That
>   is, the shared_ptr contains just a pointer to a handle struct
>   containing a pointer to the object shared and the count.
>
>   Add a second count field for the number of weak pointers using
>   the object.  When the number of shared pointers goes to zero
>   the shared object is deleted and the pointer to object field is
>   zeroed out, but the handle struct is not deleted until both
>   counters go to zero.

There is an existing, tested implementation along these lines on my
website (I called the pointers "counted_ptr" and "uncounted_ptr").  If
anyone wants to bring these into boost format and submit them then I
hearby grant permission. (I was hoping to do this myself, but I won't
have time for the foreseeable future.)

There is also a smart pointer that replicates the referenced object on
assignment.

There is an overview at:

    http://www.octopull.demon.co.uk/arglib/
-- 
Alan Griffiths  (alan_at_[hidden])  http://www.octopull.demon.co.uk/
ACCU Chairman   (chair_at_[hidden])             http://www.accu.org/