Re: Initialising private base members in copy constructor

From:

"Victor Bazarov" <v.Abazarov@comAcast.net>

Newsgroups:

comp.lang.c++

Date:

Mon, 6 Aug 2007 14:37:57 -0400

Message-ID:

<f97pq4$i6c$1@news.datemas.de>

Fraser Ross wrote:

template<typename T,
  typename CounterPolicy = SimpleReferenceCount,
  typename ObjectPolicy = StandardObjectPolicy>
class CountingPtr : private CounterPolicy, private ObjectPolicy {
private:
// shortcuts:
typedef CounterPolicy CP;
typedef ObjectPolicy OP;

T* object_pointed_to;
public:

// copy constructor:
CountingPtr (CountingPtr<T,CP,OP> const& cp)
: CP((CP const&)cp), // copy policies
   OP((OP const&)cp) {
this->attach(cp); // copy pointer and increment counter
}

I'm not sure why the casts work. Why wasn't static_cast used instead?

How are the copy constructors defined in the 'CounterPolicy' and the
'ObjectPolicy' classes used to instantiate this template? IOW, you did
not post enough code to answer your question.

Since the inheritances are private I'm surprised that casts can be
done. Some compilers don't appear to even require a cast at all.

V
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