NULL pointer is the same as deallocating it?

Question

I was working on a piece of code and I was attacked by a doubt: What happens to the memory allocated to a pointer if I assign NULL to that pointer?

For instance:

Answer 1

This is a classic leak. As you say, the memory remains allocated but nothing is referencing it, so it can never be reclaimed - until the process exits.

The memory should be deallocated with delete - but using a smart pointer (e.g. std::auto_ptr or boost::shared_ptr (or tr1::shared_ptr) to wrap the pointer is a much safer way of working with pointers.

Here's how you might rewrite your example using std::auto_ptr:

std::auto_ptr a( new MyClass() );

/*...do something in the meantime...*/

a.reset();

(Instead of the call to reset() you could just let the auto_ptr instance go out of scope)