006 - Raw Pointers

New and Delete Operators

new

new provides the address for the dynamically allocated memory.

Can also allocated a block of memory:

new data_type[n];

If there is not enough memory in the heap, a type std::bad_alloc exception would be thrown. This can be suppressed with (nothrow). If that is the case, the allocation returns a nullptr.

int *p = new (nothrow) int;
if (p != nullptr)
	cout << "Allocation Failed" << endl;

delete

delete releases the memory allocated at a pointer.

delete ptr;
delete[] ptr;     // Deleted an assigned block of memory

Issues with Dynamic Memory

Memory Leaks

Memory allocation remains after it is no longer being used, and cannot be fetched again.
[Solution:] use smart pointers as deallocation is done automatically

Dangling Pointers

Memory pointers that point to some address which has been deallocated. This causes undefined behaviours.
[Solution:] assign nullptr to pointers when they have been deallocated

Double Deletion

When delete is called on the same memory location twice, this causes the program to crash or corrupt.
[Solution:] Assign nullptr to memory pointers after they have been deallocated.

Mixing new/delete with malloc() / free()

Note: you cannot interchangeably use malloc instead of new and free instead of delete. They do not work in a similar way.