C++ virtual function table memory cost

Question

Consider:

class A
{
    public:
        virtual void update() = 0;
}

class B : public A
{
    public:
        void update() { /* stuff goes in here... */ }
         


        

Answer 1

Not an answer to the question directly, but also consider that the declaration order of your data members can increase or decrease your real memory consumption per class object. This is because most compilers can't (read: don't) optimize the order in which class members are laid out in memory to decrease internal fragmentation due to alignment woes.