When should I use the new keyword in C++?

Question

I\'ve been using C++ for a short while, and I\'ve been wondering about the new keyword. Simply, should I be using it, or not?

1) With the new keywo

Answer 1

Method 1 (using new)

• Allocates memory for the object on the free store (This is frequently the same thing as the heap)
• Requires you to explicitly delete your object later. (If you don't delete it, you could create a memory leak)
• Memory stays allocated until you delete it. (i.e. you could return an object that you created using new)
• The example in the question will leak memory unless the pointer is deleted; and it should always be deleted, regardless of which control path is taken, or if exceptions are thrown.

Method 2 (not using new)

• Allocates memory for the object on the stack (where all local variables go) There is generally less memory available for the stack; if you allocate too many objects, you risk stack overflow.
• You won't need to delete it later.
• Memory is no longer allocated when it goes out of scope. (i.e. you shouldn't return a pointer to an object on the stack)

As far as which one to use; you choose the method that works best for you, given the above constraints.

Some easy cases:

• If you don't want to worry about calling delete, (and the potential to cause memory leaks) you shouldn't use new.
• If you'd like to return a pointer to your object from a function, you must use new