I understand I can provide a custom allocator for most of the stl containers. If I record memory allocations in this custom allocator, then I can keep track of memory allocations. For example, with the help of MyAllocator in std::vector<T, MyAllocator<T>>, we can alway tell how much memory is consumed by this vector.

However, such allocators only applies to stl containers. If we want to keep track of a custom class, we have to come up with some other ideas.

One idea is that we can override operator new and operator new []. However, there are some drawbacks:

1. operator new and operator new [] apply only to allocations by the new operators, which usually allocates on heap. Ok, maybe this is not too much a problem since we cares heap memory the most.
2. operator new and operator new [] do not apply to dynamic memory allocations inside the class. For example, given type T, if I allocated some memory by a = new R [10000] in T::T(), then such memory allocation will not be tracked by operator new and operator new [].
3. Talk more about the upper case. There is problem even if I have also implemented R‘s operator new. Because it only allows me to summery how much memory T allocates, and how much memory R allocates respectively. However what I want to know is how much memory T allocates including all its fields at some timepoint. That means if I called a = new R [10000], then I can somehow find the instance of T has allocated sizeof(T) + sizeof(R) * 1000, rather than that the instance of T has allocated sizeof(T) and another 1000 instances of R has allocated sizeof(R).

So I wonder how to do that.