difference between constructor and new/malloc , difference between destructor and delete/free

[Devcook]

What is the difference between the following-
a] constructor and new/malloc?
b] destructor and delete/free?

And what are the general rules to take care of so that memory does not leak?

[Disch]

What is the difference between the following-

- A constructor is automatically called whenever an object is created.
- new is the C++ operator to dynamically create objects (new will call constructors)
- malloc is the C function to dynamically allocate memory (malloc will not call constructors)
- A destructor is automatically called whenever an object is destroyed.
- delete is the C++ operator to destroy objects created with new (delete will call destructors)
- free is the C function to release dynamic memory allocated with malloc (free will not call destructors)

And what are the general rules to take care of so that memory does not leak?

Some general rules:

- Don't use malloc/free at all. They don't have any place in C++. They're for C.

- Don't use new/delete unless you absolutely have to (read: 99% of the time you do not have to).

- Use container classes like vector, map, set, deque, etc to handle dynamically sized arrays/containers. Let those classes worry about allocation/destruction.

- Use smart pointers like unique_ptr, shared_ptr, etc for individual allocations.

- RAII is your friend. If you are manually deleting objects or doing cleanup... you are probably doing something wrong.