How to create a memory leak in C++?

I was just wondering how you could create a system memory leak using C++. I have done some googling on this but not much came up, I am aware that it is not really feasible to do it in C# as it is managed code but wondered if there was a simple way to do this with C++? I just thought it would be interesting to see how much the system suffers because of code not being written properly. Thanks.