Do I need to use delete for each new in C++?

Question

If I have a function like:

void MyFunctoin(int size){
// ...
int *arr=new int[size];
// ...
}

• Is there a memory leak?
• If yes, is there a way to solve it without using delete?

Answer 1

The answer to your title question is simple: yes, every new must be matched by a delete. In your case, since you used new[], there must be a delete[] somewhere.

But you don't need to write it yourself. It is usually much better to use a class that manages its own resources. In your case, you'd be better off using an STL container such as array<> or vector<>. This is, either:

std::array<int, size> arr; // fixed size (known at compile time)

or

std::vector<int> arr; // variable size

In vector, all the necessary calls to new and delete are done inside the container and you needn't care about them.

You could write your function this way:

#include <vector>

void MyFunctoin(int size){
  // ...
  std::vector<int> arr(size);
  // ...
}

and there would not be any memory leak with no need to call delete anywhere. You don't need to specify size when constructing arr if you don't want to.

Answer 2

Yes, it is. Use smart pointers/STL containers (for example std::vector/boost::shared_array/std::unique_ptr<T[]> in your case).