What is the difference between new and malloc in C++?
Updated 2026-07-10 · Beginner friendly
Quick answer
new is a C++ operator that allocates memory and calls the object's constructor, returns a correctly typed pointer, and is paired with delete. malloc is a C function that only allocates raw memory, does not call constructors, returns a void pointer you must cast, and is paired with free. In C++ you should prefer new, or better still smart pointers.
Key differences
- Constructor: new calls it, malloc does not.
- Type: new returns the right type, malloc returns void* needing a cast.
- Sizing: new computes the size, malloc needs sizeof by hand.
- Release: new pairs with delete, malloc pairs with free.
int* a = new int(5); // allocates and initialises
delete a;
int* b = (int*)malloc(sizeof(int)); // raw memory, no init
free(b);In the interview
The modern answer is you rarely use either directly in good C++, because smart pointers like unique_ptr manage memory for you. Mentioning that shows you follow current best practice, not just the textbook difference.
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