Difference between revisions of "HOWTO resolve circular references in ns-3 memory disposal"

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(HOWTO resolve smart pointer circular references in ns-3 memory disposal)
(HOWTO resolve smart pointer circular references in ns-3 memory disposal)
Line 26: Line 26:
 
     ==15749==    indirectly lost: 152 bytes in 5 blocks
 
     ==15749==    indirectly lost: 152 bytes in 5 blocks
 
     ==15749==    possibly lost: 0 bytes in 0 blocks
 
     ==15749==    possibly lost: 0 bytes in 0 blocks
    ==15749==    still reachable: 10,360 bytes in 5 blocks
 
    ==15749==    suppressed: 0 bytes in 0 blocks
 
  
The preferred way to handle reference cycles like this in ns-3 is to use Object::Dispose().  This method will call the DoDispose method on the object that it is called on as well as all other objects aggregated on to it.  In the above example Class A is aggregated to Class B so we make the following change to class A:
+
The preferred way to break reference cycles like this in ns-3 is to use Object::Dispose().  This method will call the DoDispose method on the object that it is called on as well as all other objects aggregated on to it.  In the above example Class A is aggregated to Class B so we make the following change to Class A:
  
 
     class A : public Object
 
     class A : public Object
Line 41: Line 39:
 
         }
 
         }
 
     };
 
     };
 +
 +
Now the following code:
 +
 +
    int main(int argc, char* argv[])
 +
    {
 +
        Ptr<A> a = CreateObject<A>();
 +
        Ptr<B> b = CreateObject<B>();
 +
        a->m_callback = MakeCallback (&B::CallbackMethodB, b);
 +
        b->AggregateObject(a);
 +
        b->Dispose(); //a->Dispose() will work as well
 +
    }
 +
 +
will not longer have a memory leak.
 +
 +
    ==16877== LEAK SUMMARY:
 +
    ==16877==    definitely lost: 0 bytes in 0 blocks
 +
    ==16877==    indirectly lost: 0 bytes in 0 blocks
 +
    ==16877==    possibly lost: 0 bytes in 0 blocks

Revision as of 17:54, 30 August 2013

HOWTO resolve smart pointer circular references in ns-3 memory disposal

    class A : public Object
    {
    public:
       static TypeId GetTypeId (void);
       Callback<void> m_callback;
    };
    class B : public Object
    {
    public:
       static TypeId GetTypeId (void);
       void CallbackMethodB (void);
    };
     int main(int argc, char* argv[])
     {
        Ptr<A> a = CreateObject<A>();
        Ptr<B> b = CreateObject<B>();
        a->m_callback = MakeCallback (&B::CallbackMethodB, b);
        b->AggregateObject(a);
     }
     
    ==15749== LEAK SUMMARY:
    ==15749==    definitely lost: 40 bytes in 1 blocks
    ==15749==    indirectly lost: 152 bytes in 5 blocks
    ==15749==    possibly lost: 0 bytes in 0 blocks

The preferred way to break reference cycles like this in ns-3 is to use Object::Dispose(). This method will call the DoDispose method on the object that it is called on as well as all other objects aggregated on to it. In the above example Class A is aggregated to Class B so we make the following change to Class A:

    class A : public Object
    {
    public:
       static TypeId GetTypeId (void);
       Callback<void> m_callback;
       virtual void DoDispose (void)
       {
          m_callback = MakeNullCallback<void>();
       }	
    };

Now the following code:

    int main(int argc, char* argv[])
    {
       Ptr<A> a = CreateObject<A>();
       Ptr b = CreateObject<B>();
       a->m_callback = MakeCallback (&B::CallbackMethodB, b);
       b->AggregateObject(a);
       b->Dispose(); //a->Dispose() will work as well	
    }

will not longer have a memory leak.

    ==16877== LEAK SUMMARY:
    ==16877==    definitely lost: 0 bytes in 0 blocks
    ==16877==    indirectly lost: 0 bytes in 0 blocks
    ==16877==    possibly lost: 0 bytes in 0 blocks