CList in vc++ with Class pointers

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Hi,
I have a CList(BaseList) that takes a base class pointer as a argument as shown in below code.My doubt is whether BaseList will delete the d1 pointer when it goesd out of the scope or i have to delete it manually(delete d1).can you please provide any article on this.

C#

class CBase
{
public:
    CBase()
    {
        cout<<"in CBase Constructor::"<<this<<endl;
    }
    virtual ~CBase()
    {
        cout<<"in CBase Destructor::"<<this<<endl;
    }
    virtual void fun1() = 0;
    virtual void fun2() = 0;
};
class CDerived1:public CBase
{
public:
    CDerived1()
    {
        cout<<"in CDerived Constructor::"<<this<<endl;
    }
    virtual ~CDerived1()
    {
        cout<<"in CDerived Destructor::"<<this<<endl;
    }
    void fun1(){};
    void fun2(){};
};
typedef CList<CBase*> BaseList;
int _tmain(int argc, TCHAR* argv[], TCHAR* envp[])
{
    int nRetCode = 0;
    BaseList ouBaseList;
    CBase* d1 = new CDerived1();
    //CDerived1 d1;
    ouBaseList.AddHead(d1);
    //delete d1;
    return nRetCode;
}

Posted 8-Feb-11 20:19pm

వేంకటనారాయణ(venkatmakam)

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Andrew Brock · Answer 1 · 2011-02-08T21:08:00

I believe it doesn't it doesn't.

You can find out yourself however.
Place the following at the top of the function _tmain

#if defined(DEBUG) | defined(_DEBUG)
	_CrtSetDbgFlag(_CRTDBG_ALLOC_MEM_DF | _CRTDBG_LEAK_CHECK_DF);
#endif

In short, this will print memory leaks if there are any to the Output Window (where you see the compiling progress and loaded modules). If nothing is printed, there are no leaks.

I would recommend putting this as early as possible in every program that you write.
It will help you find memory leaks. If you put it in when you start the project it will narrow down the possibilities of where it could be.

If any leaks are found, a number and small portion of the data is printed.
if you use the function _CrtSetBreakAlloc(the_number); it will break the program when that memory block is getting allocated.

Albert Holguin · Answer 2 · 2011-02-12T07:52:00

Solution 4

Generally speaking, if you new an object you must delete it. "New" creates objects on the heap that must be manually deleted, sometimes the framework deletes some things automatically but generally you do it manually. Whenever writing unmanaged C++, match every new with a delete.

Posted 12-Feb-11 7:52am

Albert Holguin

Comments

Espen Harlinn 17-Mar-11 10:45am

Good advice - my 5

Niklas L · Answer 3 · 2011-02-08T22:22:00

Most generic collections does not delete pointers. Consider:

CList<int> intList;
intList.AddHead(1); // cannot delete

CList<char*> charPtrList;
charPtrList.AddHead("hello"); // Cannot free
charPtrList.AddHead(new char); // Could free with delete
charPtrList.AddHead(new char[10]); // Could free, but with delete[]
charPtrList.AddHead(strdup("hello")); // Could free, but with free()

It would be a mess to auto-delete data in a generic way.

Venki_2u · Answer 4 · 2011-02-08T23:00:00

Solution 3

Hi,

No the memory allocated to d1 will not be freed even when the baselist goes out of scope. you have to call the delete for d1 explicitly. If the STL container scope is exited all objects within that container are reclaimed automatically. But only non-pointer types are reclaimed, the data of stored pointers is untouched.

Posted 8-Feb-11 23:00pm

Venki_2u

Updated 8-Feb-11 23:01pm

v2

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వేంకటనారాయణ(venkatmakam) 9-Feb-11 5:59am

Yes you are right.I written a sample code and i came to know that non pointer types are automatically reclaimed.thanks for the answer.

CList in vc++ with Class pointers

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