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Re: Iterator destructor problem

From:
 vivekian <vivekaseeja@gmail.com>
Newsgroups:
comp.lang.c++
Date:
Mon, 25 Jun 2007 18:27:44 -0000
Message-ID:
<1182796064.768682.30910@q69g2000hsb.googlegroups.com>
On Jun 25, 12:07 pm, John Harrison <john_androni...@hotmail.com>
wrote:

Some corrections below

vivekian wrote:
vivekian wrote:

On Jun 19, 8:22 am, Obnoxious User <O...@127.0.0.1> wrote:

On Tue, 19 Jun 2007 12:34:31 +0000, vivekian wrote:

Hi,
I have this following class

[snip]

This is a snippet of code which uses this class :
        struct childInfo c ;
   c.relativeMeshId = atoi (meshId.substr(meshId.length(),1).c_str()) ;
   c.iChild = iNode ;
   (*pNode).second.children.push_back ((c)) ;

I'd guess you just cut this few lines out of a bigger context, since
neither 'iNode' nor 'pNode' are declared.

--
                                 Obnoxious User


This is the code :

#include <map>
#include <string>
#include <vector>
#include <cstdlib>
#include <iostream.h>
#include <algorithm>

class nodeInfo ;

class childInfo
{
public:
   int relativeMeshId ;
   std::map <const std::string, nodeInfo >::iterator iChild ;
   childInfo () {};
   childInfo ( const childInfo & c ) ;
   childInfo & operator= (const childInfo&) ;
};

class nodeInfo
{
public:
   std::string meshId ;
   std::vector<childInfo> children;
   nodeInfo () {};
   nodeInfo (const nodeInfo & n ) ;
   nodeInfo & operator= (const nodeInfo&) ;
};

class NodeManager
{
private:
   std::map <const std::string , struct nodeInfo > _nodeList;
public:
   NodeManager();
   virtual ~NodeManager();

   void addRoute (const std::string parentMacAddr,const std::string
                                                            childMacAddr,const std::string meshId);
} ;

NodeManager::NodeManager()
{
}

NodeManager::~NodeManager()
{
}

childInfo::childInfo ( const childInfo & c )
{
   relativeMeshId = c.relativeMeshId ;
   iChild = c.iChild ;
}

childInfo & childInfo::operator= (const childInfo & c)
{
   if ( this != &c )
   {
           relativeMeshId = c.relativeMeshId ;
           iChild = c.iChild ;
   }
   return *this ;
}

nodeInfo::nodeInfo (const nodeInfo & n)
{
   meshId = n.meshId ;
   copy (n.children.begin(), n.children.end(), children.begin()) ;
}

nodeInfo & nodeInfo::operator= (const nodeInfo &n)
{
   if (this != &n)
   {
           meshId = n.meshId;
           copy (n.children.begin(), n.children.end(), children.begin()) ;
   }
   return *this ;
}

void NodeManager::addRoute(const std::string pMacAddr,const
std::string cMacAddr,const std::string meshId)
{
   std::map <const std::string , struct nodeInfo>::iterator iNode =
_nodeList.find (cMacAddr) ;
   if (iNode == _nodeList.end())
   {
           struct nodeInfo n;
           n.meshId = meshId ;
           _nodeList[cMacAddr] = n;
           cout << "\nAdding " << n.meshId ;
   }
   else
   {
           //delete previous lineage
           //deleteRoute ( iNode -> first , iNode -> second.meshId ) ;
           iNode -> second.meshId = meshId ;
   }

   std::map <const std::string , struct nodeInfo>::iterator pNode =
_nodeList.find (pMacAddr);
   if (pNode != _nodeList.end())
   {
           cout << "\nAdding link to Parent " << pMacAddr ;
           childInfo c ;
           c.relativeMeshId = atoi (meshId.substr(meshId.length(),1).c_str()) ;
           c.iChild = iNode ;
           (*pNode).second.children.push_back ((c)) ;
   }
}

On Jun 19, 8:22 am, Obnoxious User <O...@127.0.0.1> wrote:

On Tue, 19 Jun 2007 12:34:31 +0000, vivekian wrote:

Hi,
I have this following class

[snip]

This is a snippet of code which uses this class :
        struct childInfo c ;
   c.relativeMeshId = atoi (meshId.substr(meshId.length(),1).c_str()) ;
   c.iChild = iNode ;
   (*pNode).second.children.push_back ((c)) ;

I'd guess you just cut this few lines out of a bigger context, since
neither 'iNode' nor 'pNode' are declared.

--
                                 Obnoxious User


This is the code :

#include <map>
#include <string>
#include <vector>
#include <cstdlib>
#include <iostream.h>
#include <algorithm>

class nodeInfo ;

class childInfo
{
public:
   int relativeMeshId ;
   std::map <const std::string, nodeInfo >::iterator iChild ;
   childInfo () {};
   childInfo ( const childInfo & c ) ;
   childInfo & operator= (const childInfo&) ;
};

class nodeInfo
{
public:
   std::string meshId ;
   std::vector<childInfo> children;
   nodeInfo () {};
   nodeInfo (const nodeInfo & n ) ;
   nodeInfo & operator= (const nodeInfo&) ;
};

class NodeManager
{
private:
   std::map <const std::string , struct nodeInfo > _nodeList;
public:
   NodeManager();
   virtual ~NodeManager();

   void addRoute (const std::string parentMacAddr,const std::string
                                                            childMacAddr,const std::string meshId);
} ;

NodeManager::NodeManager()
{
}

NodeManager::~NodeManager()
{
}

childInfo::childInfo ( const childInfo & c )
{
   relativeMeshId = c.relativeMeshId ;
   iChild = c.iChild ;
}

childInfo & childInfo::operator= (const childInfo & c)
{
   if ( this != &c )
   {
           relativeMeshId = c.relativeMeshId ;
           iChild = c.iChild ;
   }
   return *this ;
}

nodeInfo::nodeInfo (const nodeInfo & n)
{
   meshId = n.meshId ;
   copy (n.children.begin(), n.children.end(), children.begin()) ;
}

nodeInfo & nodeInfo::operator= (const nodeInfo &n)
{
   if (this != &n)
   {
           meshId = n.meshId;
           copy (n.children.begin(), n.children.end(), children.begin()) ;
   }
   return *this ;
}

void NodeManager::addRoute(const std::string pMacAddr,const
std::string cMacAddr,const std::string meshId)
{
   std::map <const std::string , struct nodeInfo>::iterator iNode =
_nodeList.find (cMacAddr) ;
   if (iNode == _nodeList.end())
   {
           struct nodeInfo n;
           n.meshId = meshId ;
           _nodeList[cMacAddr] = n;
           cout << "\nAdding " << n.meshId ;
   }
   else
   {
           //delete previous lineage
           //deleteRoute ( iNode -> first , iNode -> second.meshId ) ;
           iNode -> second.meshId = meshId ;
   }

   std::map <const std::string , struct nodeInfo>::iterator pNode =
_nodeList.find (pMacAddr);
   if (pNode != _nodeList.end())
   {
           cout << "\nAdding link to Parent " << pMacAddr ;
           childInfo c ;
           c.relativeMeshId = atoi (meshId.substr(meshId.length(),1).c_str()) ;
           c.iChild = iNode ;
           (*pNode).second.children.push_back ((c)) ;
   }
}


Your code has bugs.

First error is you write assignment operators and copy constructors when
they are not needed. This is a mistake.

More seriously this copy ctor is bugged

nodeInfo::nodeInfo (const nodeInfo & n)
{
        meshId = n.meshId ;
        copy (n.children.begin(), n.children.end(), children.begin()) ;

}

because you fail to allocate any space for the children vector.
Ironaically if you hadn't bothered to write this copy constructor, then
there would not have been a bug. Which is my first point, don't write
copy constructors or assignment operators when they are not needed, it's
asking for trouble. Assignment operator has simialar bug. As before, get
rid, problem goes away.

Third point, this line is bugged

c.relativeMeshId = atoi (meshId.substr(meshId.length(),1).c_str()) ;

perhaps you meant

c.relativeMeshId = atoi (meshId.substr(meshId.length()-1,1).c_str()) ;

john


Yes, thats what i thought initially, there should be no need of copy
constructor or assignment operators since there is no dynamic
allocation of memory. Below is the code which is present when the copy
constructors and assignment operators are removed. The main.cpp and
the output follow it :

// NodeManager.h
//------------------
#ifndef NODEMANAGER_H_
#define NODEMANAGER_H_

#include <map>
#include <string>
#include <vector>
#include <cstdlib>
#include <iostream.h>
#include <algorithm>

class nodeInfo ;

class childInfo
{
public:
    int relativeMeshId ;
    std::map <std::string, nodeInfo >::iterator iChild ;
    childInfo () {} ;
    ~childInfo () {} ;
};

class nodeInfo
{
public:
    std::string meshId ;
    std::vector<childInfo> children;
    nodeInfo () {};
    ~nodeInfo () {} ;
};

class NodeManager
{
private:
    std::map <std::string , struct nodeInfo > _nodeList;
public:
    NodeManager();
    virtual ~NodeManager();

    void addRoute (const std::string parentMacAddr,const std::string
                                 childMacAddr,const std::string meshId);
    void deleteRoute (const std::string childMacAddr,const std::string
meshId);
    void getRoute (const std::string macAddr,const std::string
&meshId);
};

#endif /*NODEMANAGER_H_*/

//NodeManager.cpp
//---------------

#include "NodeManager.h"

NodeManager::NodeManager()
{
}

NodeManager::~NodeManager()
{
}

void NodeManager::addRoute(const std::string pMacAddr,const
std::string cMacAddr,const std::string meshId)
{
    std::vector<childInfo> trial ;
    std::map <std::string , struct nodeInfo>::iterator iNode =
_nodeList.find (cMacAddr) ;
    if (iNode == _nodeList.end())
    {
        struct nodeInfo n;
        n.meshId = meshId ;
        _nodeList[cMacAddr] = n;
        cout << "\nAdding " << n.meshId ;
    }
    else
    {
        //delete previous lineage
        iNode -> second.meshId = meshId ;
    }

    std::map <std::string , struct nodeInfo>::iterator pNode =
_nodeList.find (pMacAddr);
    if (pNode != _nodeList.end())
    {
        childInfo c ;
        c.relativeMeshId = atoi
(meshId.substr(meshId.length()-1,1).c_str()) ;
        c.iChild = iNode ;
        (*pNode).second.children.push_back ((c)) ;
    }
}

// main.cpp

#include "LibMgr/NodeManager.h"

int main ( int argc , char *argv[] )
{
    NodeManager n ;
    n.addRoute("" , "a" ,"11") ;
    n.addRoute("" , "b" ,"12") ;
    n.addRoute("" , "c" ,"13") ;
    n.addRoute("a", "d" ,"111") ;
    n.addRoute("a", "e" ,"112") ;
    n.addRoute("b", "f" ,"121") ;
    n.addRoute("c", "g" ,"131") ;
    n.addRoute("c", "h" ,"132") ;
    n.addRoute("c", "i" ,"133") ;
}

// Output
// ------
Adding 11
Adding 12
Adding 13
Segmentation fault

Thanks,
Vivekian

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