This is a summary form C++ Primer Plus

In short, you should observe these rules when you use new and delete:

• Don’t use delete to free memory that new didn’t allocate.
• Don’t use delete to free the same block of memory twice in succession.
• Use delete [] if you used new [] to allocate an array.
• Use delete (no brackets) if you used new to allocate a single entity.
• It’s safe to apply delete to the null pointer (nothing happens).