Thread: Dereferencing Class Pointer List

Hello there! I am currently coding the base of a future program. However, after compiling the code(no errors), there is a forced brake point. The Error says: Debug Assertion Failure, Expression: List iterations incompatible.

Please bare with me, code is not exactly small:

_medcontainer.h

Code:

 
#ifndef _MEDCONTAINER_H
#define _MEDCONTAINER_H

#include <cstring>

enum TYPE{NAME, DESC, ID, AMOUNT, ALL};

class _medContainer
{
    public:
    //////////////////////////////////////////////////////////////////////////
    //CONSTRUCTOR(S) AND DESTRUCTOR(S)
        _medContainer();
        _medContainer(char *name, char *desc, char* id, char* amount, TYPE type = NAME);
        virtual ~_medContainer();
    //////////////////////////////////////////////////////////////////////////
    //ACCESSOR FUNCTIONS
		void SetCounter(unsigned int val)      { m_Counter = val; }
		void SetName(char* val)				   { m_name = val; }
        void Setdesc(char* val)                { m_desc = val; }
		void SetId(char* val)				   { m_id = val; }
        void SetAmount(char* val)              { m_amount = val; }
        void SetSortString(char* compareString){compare = compareString;}

        char* Getname()     { return m_name; }
        char* Getdesc()     { return m_desc; }
        char* GetCompare()  { return compare; }
        char* Getid()       { return m_id; }
        char* Getamount()   { return m_amount; }

        unsigned int GetCounter() { return m_Counter; }
    //////////////////////////////////////////////////////////////////////////
    //OPERATOR OVERLOADING
    _medContainer& operator=(const _medContainer& other);

    friend bool operator<(const _medContainer& o1,const _medContainer& o2);
    friend bool operator>(const _medContainer& o1,const _medContainer& o2);
    friend bool operator==(const _medContainer& o1,const _medContainer& o2);
    friend bool operator!=(const _medContainer& o1,const _medContainer& o2);

    protected:
    private:
        unsigned int m_Counter; //MEDCONTAINER COUNTER
		char* m_name;           //NAME OF THE OBJECT
        char* m_desc;           //DESCRIPTION OF PARTICULAR OBJECT
        char* compare;          //STRING THAT WILL BE USED TO COMPRE IN SORT()
		char* m_id;             //IDENTIFICATION OF OBJECT
        char* m_amount;         //AMOUNT OF PARTICULAR OBJECT
        char m_DlastModified[9];//DAY IN WHICH IT WAS LAST MODIFIED
        char m_TlastModified[9];//TIME IN WHICH IT WAS LAST MODIFIED
};
#endif // _MEDCONTAINER_H

medutility.h

Code:

#ifndef MEDUTILITY_H
#define MEDUTILITY_H

#include "_medContainer.h"          //INCLUDE MEDCONTAINER CLASS
#include <list>                     //LIST CONTAINERS
#include <fstream>                  //IN ORDER TO LOAD/SAVE SETTINGS AND LISTS

using namespace std;

typedef list<_medContainer> medList;              //DEFINE A STANDARD LIST KEYWORD
typedef list<_medContainer*> medSearchResultList; //LIST THAT LINKS TO SEPERATE ELEMENTS OF A LISTS
typedef _medContainer* _medConPointer;

//////////////////////////////////////////////////////////////////////////
//STRUCTURE USED TO STORE SEARCH RESULTS
struct SearchResults
{
    medSearchResultList Result;
    unsigned int ResultsFound;
};

//////////////////////////////////////////////////////////////////////////
//GENERIC UTILITY FUNCTIONS
medList SortByType(medList &UnsortedList, TYPE SortBy); //USED TO SORT A MEDLIST BY TYPE

medSearchResultList* FindString(medList &SearchedList, char *keyword, TYPE FindWhere);

char* ReturnVariableString(_medContainer &Container, TYPE type); 

//////////////////////////////////////////////////////////////////////////
//SingleList CLASS - FACILITATES LIST MANIPULATION
class SingleListClass
{
public:
    medList *List;
    //////////////////////////////////////////////////////////////////////////
    //CONSTRUCTOR(S) AND DESTRUCTOR(S)
    //IN CASE FOR TEMPORARY CREATION
    SingleListClass();
    //ALLOWS TO CREAT A LIST WHILE DECLARING THE FIRTS ELEMENT
    SingleListClass(char *name, char *desc, char *id, char *amount);
    //DISMISS A SingleList OBJECT
    ~SingleListClass();

    //////////////////////////////////////////////////////////////////////////
    //DEDICATED FUNCTIONS
    medList *GetList()
    {
        return List;
    };

    bool    Add(char *name, char *desc, char *id, char *amount);
    void    Add(_medContainer& AddElement);
    void    Add();
    medSearchResultList* Find(char *keyword, TYPE type);
    int     MaxSize(){return (int)List->max_size();}
    medList Sort(TYPE Sortby);
};

#endif

All the function definitions are taken care of.... When I do this is main()

Code:

#include "_medContainer.h"
#include "medUtility.h"
#include <iostream>

void ShowAll(medList &ReferenceList);
SingleListClass *mynewList = new SingleListClass
("Test", "Test", "341873", "1");
medSearchResultList *Results = new medSearchResultList;

int main(int argc, char *argv[])
{
	mynewList->Add();
	cout<<"BEFORE: "<<endl;
	ShowAll(*mynewList->GetList());
	medList::iterator *it = &mynewList->GetList()->begin();

	while( *it != mynewList->GetList()->end())
	{
		Results->push_back(&(**it));
		*it++;
	}
	system("PAUSE");
	cout<<"MODIFIED THROUGH POINTER LIST CLASS"<<endl;
	ShowAll(*mynewList->GetList());

	system("PAUSE");
	return(0);
}
void ShowAll(medList &ReferenceList)
{
	medList::iterator it = ReferenceList.begin();

	while(it != ReferenceList.end())
	{
		cout<<"NAME: \n\t"<<it->Getname()<<endl;
		cout<<"DESC: \n\t"<<it->Getdesc()<<endl;
		cout<<"ID: \n\t"<<it->Getid()<<endl;
		cout<<"AMOUNT: \n\t"<<it->Getamount()<<endl;
		it++;
	}
}

It compiles all right...however when I execute it gives me the error previously mentioned at this place in the code:

Code:

while( *it != mynewList->GetList()->end())
	{
		Results->push_back(&(**it));
		*it++;
	}

I know that I could use the STL string class but I am experimenting for the moment. Other suggestions are welcomed!

Thanks in advance for the people who dare to help me!

>> *it++
Don't you mean (*it)++?

Currently I haven't practiced pointers that often, and I want to know all aspects of C++. Thanks for your reply! Unfortunately I still receive the same error.

Thanks for your replies! Daved, I cannot add the type at line 309 because it is from <list.h>, I mess with that I mess with the entire library, anyhow VC++ 2005 locks the file from being modified.

Also, I'm very tired and there's so many pointers, but should this:

Code:

Results->push_back(&(**it));

be this:

Code:

Results->push_back( **it );

It does not compile.

Thanks for the reply! Well here are my thoughts:

Code:

while( *it != mynewList->GetList()->end())
	{					//EXPLANATION(S)
		Results->push_back(&**it);      //*it = iterator which points to a Container
					        //**it = (double dereference) Access the pointer that it pointer is pointing to
						//&(**it) = the address of the object being pointed by two pointers

		/*
		//APPLICATION
		Results -> push_back( --- takes a _medContainer* )
		Therefore Results -> push_back( &(**it) ); is Plausible, isn't it?
		*/
					//EXPLANATION(S)
					//Results->push_back( of type _medContainer* )
					//(**it) = The object the iterator is pointing to, Hence &_medContainer
					//So why the need for the extra ampersand(&)? 
					//Perhaps to forward the Address of the object through the pointer?
		*it++;
	}

however this

Code:

while( *it != mynewList->GetList()->end())

appears to be the problem because once I filter out the rest of while loop(the pushback() and the *it++; ) it still crashes on me

Anyone got ideas?

Well this is the section of code located on list.h that apparently is making my code break:

Code:

304: #if _HAS_ITERATOR_DEBUGGING
305: 		void _Compat(const _Myt_iter& _Right) const
306: 			{	// test for compatible iterator pair
307: 			if (this->_Mycont == 0 || this->_Mycont != _Right._Mycont)
308: 				{
309: 				_DEBUG_ERROR("list iterators incompatible");
310: 				_SCL_SECURE_TRAITS_INVALID_ARGUMENT;
311: 				}
312: 			}
313:  #else /* _HAS_ITERATOR_DEBUGGING */
314: 	protected:
315:  #endif /* _HAS_ITERATOR_DEBUGGING */
316:		_Nodeptr _Ptr;	// pointer to node
317: 		};

it also breaks before entering the while loop for the first time

This is what I got for Call Stack:

Code:

>	NewMedicine.exe!main(int argc=1, char * * argv=0x00365ea8)  Line 19	C++
 	NewMedicine.exe!__tmainCRTStartup()  Line 586 + 0x19 bytes	C
 	NewMedicine.exe!mainCRTStartup()  Line 403	C

and the yellow debugging error is on this line of code:

Code:

--->     while( *it != mynewList->GetList()->end())

Yes, I did check the debugger and it breaks before entering the first iteration. I have fixed the *it++ but the error still prevails. I am getting a headache here....