create vector of objects on the stack ? (c++)

Question

I am creating a temporary vector of pointers to myObject objects. But I am wondering about what happens to the objects I created...

{
    std::vector<myObject *> myVector;
    myVector.reserve(5);

    for (int i = 0 ; i < 5 ; ++i){
        myVector[i] = new myObject();
    }
}

I assume that at the end of the scope myVector is destroyed and all the pointers with it, but as I created the objects with the keyword new , does it means that those objects still exist somewhere on the heap ? Should I destroy them manually before the end of the scope ?

Answer 1

You should use the following

std::vector<std::unique_ptr<myObject>> myVector(5);
for (auto& obj : myVector)
{
    obj = std::make_unique<myObject>();
}

This will create your vector with size 5 , instead of you having to resize it afterwards. On that note, you would have had to do so with resize instead of reserve .

If your vector is of std::unique_ptr , then you don't have to worry about memory management, the pointers will clean themselves up when the vector falls out of scope.

Answer 2

Yes, those objects still exist and you must delete them.

Alternatively you could use std::vector<std::unique_ptr<myObject>> instead, so that your objects are delete d automatically.

Or you could just not use dynamic allocation as it is more expensive and error-prone.

Also note that you are misusing reserve . You either want to use resize , or reserve paired with push_back .

Answer 3

Remember: You Need to destroy every object you created with new !

This means, your objects are not destroyed, only the pointers. You Need to do something like this:

for (int i = 0 ; i < 5 ; ++i){
    delete myVector[i];
}

Answer 4

remember: each new should be 'paired' with delete .

So yes - those objects remain in the heap - you have a memory leak.

Either create a loop calling delete, or change type of vector to store std::unique_ptr<myObject> - this will delete pointers automatically.