C++: How to prevent private names from polluting derived types?

Question

I was shocked today by the fact that this code snippet has an ambiguous name reference:

class A
{
private:
    typedef int Type;
};

class B
{
public:
    typedef int Type;
};

class D : A, B
{
    Type value;//error: reference to 'Type' is ambiguous
};

Hmm! Imagine you are the author of class A and your class has already been used everywhere by different people and different projects. One day you decide to rewrite your A class. Doesn't this mean that you cannot use any new (even private) name in your new class without breaking others' code?

What is the convention here?

Answer 1

Yes you are right. Using the current format/logic/coding style might break others' code if you decide to make changes later. Try to use PIMPL or fully qualify symbols. You're example is a good one of why it's not a good idea to not use fully qualify symbols. It's the same issue with code like:

using namespace std;

The line of code above could break a lot of stuff.