polymorphic smart ptr downcast

From: Alexandre Carsac (acarsac_at_[hidden])
Date: 2002-11-18 12:41:22

Hi, alls
Just wondering if there is some issue to the following problem (a and b instance are not in the same block code in true life of course) :
class A;
class B : public A ...

void main()
{
  shared_ptr<A> a;
  shared_ptr<B> b(new B);
  a = b; // what i would like, but it wont compile: no copy ctor available
}

I can try to do something like:

void main()
{
  shared_ptr<A> a;
  shared_ptr<B> b(new B);
  a.reset(b.get()); // bad design, reference counter corruped
}
I do not want to do something like the following, because each time i will need of b, i will be obliged to cast again to B type.
main()
{
  shared_ptr<A> a;
  shared_ptr<A> b(dynamic_cast(new B));
  a = b;
}

Any solutions ?

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