Will a heap allocated object get deleted when I assign it to a vector and then delete the vector?-CodePudding

I'm new to computer science and I want to know if an object is being deleted if I heap allocate it and then for e. put it in a vector of pointer and then delete the vector. Will the heap object be gone? Here is an example of what I mean.

int main()
{
   Type* someHeapObject = new Type();
   
   vector<Type*> someVector(0);

   someVector.push_back(someHeapObject);
}

So here's the main part: Can I delete the heap object with delete someVector[0], and then I DON'T have to delete it anymore like this: delete someHeapObject

CodePudding user response：

There are two things that you have to take care of:

Mistake 1

In delete [] someVector you're using the delete [] form when you should be using the delete form because you used the new form and not the new[] form for allocating memory dynamically. That is, delete [] someVector is undefined behavior.

Mistake 2

The second thing that you must take care of is that you should not use two or more consecutive delete's on the same pointer.

Now, when you wrote:

someVector.push_back(someHeapObject);

a copy of the pointer someHeapObject is added to the vector someVector. This means that now there are 2 pointers pointing to the same dynamically allocated memory. One pointer is the someHeapObject and the second is the one inside the vector.

And as i said, now you should only use delete on only one of the pointers. For example you can write:

delete someHeapOjbect; //now the memory has been freed 

//YOU CAN'T USE delete someVector[0] anymore

Or you can write:

delete someVector[0]; //now te memory has been freed

//YOU CAN'T USE delete someHeapObject[0] anymore

Note that better option would be to use smart pointers instead explicitly doing memory management using new and delete.