Question

please help to figure this out.
I have some leaking code, and I don’t know how to handle it

vector <ItemClass> items( 10 );
items[1] = ItemClass( "DVD Player", 560 );
items[5] = * new ItemClass( "Blu Ray Player", 900 );

How should I free memory for items[5] ?
I’m getting error on my attempts of freeing memory

delete &items[5];

delete [] &items[5];

I even tried something like

ItemClass * delItem = &items[5];
items[5] = item4;
delete delItem;

I’m getting “corruption of the heap” in VS2010 Ultimate

Answer 1

There is a strange use and mix up of storing new-allocated objects in vectors in your code. Usually you should handle lists all in the same way. Thus my examples below will be more explicit, and independent from each other which should help you understand the differences.

Use delete for objects only. See code below.

Use delete [] for “native” arrays only, not for vector or similar container classes or objects inside them.

I will not give an example for arrays though, since arrays might be more confusing.

Default example stack:

vector <ItemClass> items( 10 );

// does not need to be deleted because item is on the stack
ItemClass item("device1", "10"); 
items.push_back(item);

Default example with heap allocation:

vector <ItemClass*> items( 10 );

ItemClass* pItem = new ItemClass("device2", "20");
items.push_back(pItem);

// delete all items inside vector
for (int i = 0; i < items.size(); i++)
{
    ItemClass* pToDelete = items[i];
    delete pToDelete;
    items.erase(i);
}

The following examples should be avoided and are for clarifying things up only! Use at own risk.

Storing addresses of stack variables:

vector <ItemClass*> items( 10 );

// does not need to be deleted because item is on the stack
ItemClass item("device3", "30"); 
items.push_back( &item ); // storing a reference to item

// No need to delete this item that points to something on the stack.
// However you might not be able to tell items apart which have been 
// created on the heap or the stack, so just dont do it.

If you mix up with the example before and store references and pointers you must handle it yourself. My recommendation: Do not do this.

Storing dereferenced items:

vector <ItemClass> items( 10 );

ItemClass* pItem = new ItemClass("device4", "40"); 
items.push_back(*pItem);

// must be deleted because allocated on the heap
// Again you can not tell which item is allocated on stack or heap. Avoid this.