Re: Smart pointer referencing its owner

From:
Peter Dimov <pdimov@gmail.com>
Newsgroups:
comp.lang.c++.moderated
Date:
Sun, 8 Mar 2009 04:45:01 CST
Message-ID:
<e2c229ea-2368-42aa-bf2b-94e6a4fd640f@q18g2000vbn.googlegroups.com>
On Mar 7, 7:03 am, Pavel Minaev <int...@gmail.com> wrote:
....

I see how that works for auto_ptr now, but I'm still not so sure about
shared_ptr. Again, consider the following (simplified, not thread-
safe, not deleter & weak_ptr aware, etc - I don't think all these are
relevant here) implementation of reset() for it:

    T* ptr;
    int* refcountptr;

    void reset(T* newptr = 0) {
       if (this->refcountptr && --*this->refcountptr == 0) {
          delete this->ptr;
          delete this->refcountptr;
       }

       if (this->ptr = newptr) {
         this->refcountptr = new int(1);
       } else {
         this->refcountptr = 0;
       }
    }


Broken.

What does the Standard say in this case?


template<class Y> void reset( Y* p );

   Effects: Equivalent to shared_ptr(p).swap(*this).

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