Question

In my program I am creating an object of a class in a loop and storing it in a vector. Then I print the address of the object and the member variable. After that I erase them . I see that every time I see the same address assigned to my object and the member variable which is a pointer. Can any one explain this behavior.

#include <iostream>
#include <vector>

using namespace std;

typedef struct csock {
unsigned int _refCount;
mutable pthread_mutex_t _pdata_mutex;
pthread_attr_t attr;
bool _bSocketClosed;            /// used for testing while closing the socket
int _iSockFD;                   /// Holds the native socket descriptor
void* _pfnArgs; 
void* _logger;                  /// For debug logging
bool _isServiceRunning; 
pthread_t _thread_id;           /// Thread id for the listener service
int _pipes[2];                  /// For stop signal communication
pthread_mutex_t* _countMutex;
unsigned long  _idleTimeOut;                //Idle Time Out
FILE* fp;
} __attribute__((packed)) csock_t;




class csocket
{
protected:
void* _pImpl;

public :

csocket(){
csock_t* ps = new csock_t;
this->_pImpl = reinterpret_cast<void*> (ps);
std::cout<<"\n ps is "<<ps <<" _pImpl is "<<_pImpl <<endl;
}
void* getImpl()
{
    return _pImpl;
}
};


int main ()
{

vector<csocket> v;

 for (int i=0; i< 5; ++i) {
    v.push_back(csocket());
    cout<<"\n after pushback "<<v[v.size()-1].getImpl();
    cout<<"\n after pushback object is"<<&(v[v.size()-1]);
    delete (csock_t*) v[0].getImpl();
    v.erase(v.begin()+0);
}
cout <<"\n size of vector is "<<v.size();
return 0;
}

I am adding the output in my system

ps is 0x8368008 _pImpl is 0x8368008
after pushback 0x8368008
after pushback object is0x8368078

ps is 0x8368008 _pImpl is 0x8368008
after pushback 0x8368008
after pushback object is0x8368078

ps is 0x8368008 _pImpl is 0x8368008
after pushback 0x8368008
after pushback object is0x8368078

ps is 0x8368008 _pImpl is 0x8368008
after pushback 0x8368008
after pushback object is0x8368078

ps is 0x8368008 _pImpl is 0x8368008
after pushback 0x8368008
after pushback object is0x8368078

Answer 1

I think what you are looking for is storage based on a weak pointer. Your
vector stores weak pointers to the connection objects. Your main application
gets the shared pointers. The destructor for your connection object frees the
resource. Periodically you can pack the vector by erasing all weak pointers
with a use_count of zero.

class Connect;

typedef boost::shared_ptr<Connect> ConnectPtr;
typedef boost::weak_ptr<Connect> ConnectWeakPtr;
typedef std::vector<ConnectWeakPtr> ConnectVector;

ConnectVector vector;

ConnectPtr ptr( new Connect ( ... ));

vector.push_back(ptr);

void pack() {
    ConnectVector tmp;
    BOOST_FOREACH(ConnectWeakPtr const & p, mMap){
        if (p.use_count() > 0){
            tmp.insert(p);
        }
        mMap.swap(tmp);
    }
}