Defined Terms

• allocator Library class that allocates unconstructed memory.

• dangling pointer A pointer that refers to memory that once had an object but no longer does. Program errors due to dangling pointers are notoriously difficult to debug.

• delete Frees memory allocated by new. delete p frees the object and delete [] p frees the array to which p points. p may be null or point to memory allocated by new.

• deleter Function passed to a smart pointer to use in place of delete when destroying the object to which the pointer is bound.

• destructor Special member function that cleans up an object when the object goes out of scope or is deleted.

• dynamically allocated Object that is allocated on the free store. Objects allocated on the free store exist until they are explicitly deleted or the program terminates.

• free store Memory pool available to a program to hold dynamically allocated objects.

• heap Synonym for free store.

• new Allocates memory from the free store. new T allocates and constructs an object of type T and returns a pointer to that object; if T is an array type, new returns a pointer to the first element in the array. Similarly, new [ allocates n objects of type T and returns a pointer to the first element in the array. By default, the allocated object is default initialized. We may also provide optional initializers.

• placement new Form of new that takes additional arguments passed in parentheses following the keyword new; for example, new (nothrow) int tells new that it should not throw an exception.

• reference count Counter that tracks how many users share a common object. Used by smart pointers to know when it is safe to delete memory to which the pointers point.

• shared_ptr Smart pointer that provides shared ownership: The object is deleted when the last shared_ptr pointing to that object is destroyed.

• smart pointer Library type that acts like a pointer but can be checked to see whether it is safe to use. The type takes care of deleting memory when appropriate.

• unique_ptr Smart pointer that provides single ownership: The object is deleted when the unique_ptr pointing to that object is destroyed. unique_ptrs cannot be directly copied or assigned.

• weak_ptr Smart pointer that points to an object managed by a shared_ptr. The shared_ptr does not count weak_ptrs when deciding whether to delete its object.