Re: boost:shared_ptr<> exception in checked_delete(..)

From: rogeeff (rogeeff_at_[hidden])
Date: 2002-09-08 17:45:45

--- In Boost-Users_at_y..., "Julia Donawald" <yg-boost-users_at_m...> 
wrote:
> Hi,
> the folllowing works not too:
> 
> #include <vector>
> #include <shared_ptr.hpp>
> 
> class Foo
> {
> public:
>  Foo()
>  {
>  };
>  virtual ~Foo()
>  {
>  };
> };
> 
> class Double_Foo
> {
>  public:
>      Double_Foo()
>      {
>      };
>      Double_Foo(Foo* pFoo1, Foo* pFoo2) : m_Foo1(pFoo1), m_Foo2
(pFoo2)
>      {
>      };
>      virtual ~Double_Foo()
>      {
>      };
> 
> protected:
>      typedef boost::shared_ptr<Foo> FooDataPtr;
> 
>      FooDataPtr m_Foo1;
>      FooDataPtr m_Foo2;
> };
> 
> int main()
> {
>      Foo* pFoo = new Foo();
> 
>      Double_Foo DoubFoo(pFoo, pFoo);
> 
>      return 0;
> }
> 
> 
> I got the same error as in my former post. I read a bit about 
shared_ptr.
> Maybe it has something to do with a cyclic, but I thought in 
anohter case of
> cyclic data, namely if I have an object A which points to B and B 
holds a
> member which points back to A.... that's in my case not?
> If it has something to do with cyclic data then how can I solve it 
with
> weak_ptr?
> 
> Thanks in advance
> Julia

In both your examples you are getting in the same trouble related to 
the fact that you managed to make the same memory mnaged by 2 
independent shared_ptr. So it's obvous that when you try to free 
memory second time yuo are getting some kind of alarm, depend on 
compiler. May be in a form of exception. You should always make sure 
that memory is managed by the only smart_ptr. In this case this 
would mean hat your code should look like this:

int main()
{
     boost::shared_ptr<Foo> pFoo = new Foo();

     Double_Foo DoubFoo(pFoo, pFoo);

     return 0;
}

And DoubFoo should be changed to accept shared_ptrs ( or const 
references ) instead of raw pointers.

Regards,

Gennadiy.