name hiding and fragile base problem

Question

I\'ve seen it stated that C++ has name hiding for the purposes of reducing the fragile base class problem. However, I definitely don\'t see how this helps. If the base class

Answer 1

I'll assume that by "fragile base class", you mean a situation where changes to the base class can break code that uses derived classes (that being the definition I found on Wikipedia). I'm not sure what virtual functions have to do with this, but I can explain how hiding helps avoid this problem. Consider the following:

struct A {};

struct B : public A
{
    void f(float);
};

void do_stuff()
{
    B b;
    b.f(3);
}

The function call in do_stuff calls B::f(float).

Now suppose someone modifies the base class, and adds a function void f(int);. Without hiding, this would be a better match for the function argument in main; you've either changed the behaviour of do_stuff (if the new function is public), or caused a compile error (if it's private), without changing either do_stuff or any of its direct dependencies. With hiding, you haven't changed the behaviour, and such breakage is only possible if you explicitly disable hiding with a using declaration.