shared_ptr problems

Newsgroup: comp.lang.c++

Subject: shared_ptr problems

From: cpisztest@...

Date: Thu, 24 Apr 2014 14:34:39 -0700 (PDT)



I wasn't around at design time, but I get to fix the problem...story of my life!



I know about boost::weak_ptr and would use that if the problem was limited to

classes A and B, but C has a public accessor that gives away shared_ptrs to As and I don't know what to do there.



I was thinking of trying to guarentee that Bs and Cs are only created by As and seeing if the compiler complained or not (unknown code base). If I can guarentee that Bs and Cs are only created by and used by As, then I can safely use weak_ptrs...I think. I could do that by hiding constructors of Bs and Cs making them private and friending them to A....I think.



Any thoughts/ideas?



The mess where nothing gets destroyed:



-----

#ifndef A_H

#define A_H



#include <boost/shared_ptr.hpp>

#include <boost/enable_shared_from_this.hpp>



#include <list>



class B;

class C;



class A : public boost::enable_shared_from_this<A>

{

public:



typedef boost::shared_ptr<A> SharedPtr;



A();

~A();



void Foo();



private:



std::list<B *> m_collectionOfBs;



void CleanupBs();

};



#endif

-----

#ifndef B_H

#define B_H



#include "A.h"

#include "C.h"



//--------

class B

{

public:



B(A::SharedPtr a);

~B();



private:



C m_c;

};



#endif

-----

#ifndef C_H

#define C_H



#include "A.h"



class C

{

public:



C(A::SharedPtr a);

~C();



A::SharedPtr GetA();



private:



A::SharedPtr m_a;

};



#endif

-----



#include "A.h"

#include "B.h"



A::A()

{

}



A::~A()

{

CleanupBs();

}



void A::Foo()

{

B * newbie = new B(shared_from_this());

m_collectionOfBs.push_back(newbie);

}



void A::CleanupBs()

{

std::list<B *>::iterator it = m_collectionOfBs.begin();



while (!m_collectionOfBs.empty() &&

it != m_collectionOfBs.end())

{

delete (*it);

it = m_collectionOfBs.erase(it);

}

}

-----

#include "B.h"



B::B(A::SharedPtr a)

:

m_c(a)

{

}



B::~B()

{

}

-----

#include "C.h"



C::C(A::SharedPtr a)

:

m_a(a)

{

}



C::~C()

{

}



A::SharedPtr C::GetA()

{

return m_a;

}

-----

#include "A.h"



int main()

{

A::SharedPtr a(new A());

a->Foo();



return 0;

}

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