Member declaration order for structs and classes are important. You want to order the smallest to the largest (or vice versa) in order to avoid what’s known as ‘padding’. Padding is basically what the compiler will use to keep the memory allocation of the struct/class aligned in memory. This padding tends to be wasted space unless some compiler specific enhancement is occurring.
What I learned today was that Microsoft’s C++ compiler actually has extra padding involved, by design. And the solution to avoid the extra previous memory being stolen from you? Quite elementary, how could you not know? Inheriting from an empty abstract class makes your objects smaller.