How can I resolve a function call ambiguity when multiple base classes have a member function with the same name?

Question

I have a basic question related to multiple inheritance in C++. If I have a code as shown below:

struct base1 {
   void start() { cout << "Inside base1"; }
};

struct base2 {
   void start() { cout << "Inside base2"; }
};

struct derived : base1, base2 { };

int main() {
  derived a;
  a.start();
}

which gives the following compilation error:

1>c:\mytest.cpp(41): error C2385: ambiguous access of 'start'
1>      could be the 'start' in base 'base1'
1>      or could be the 'start' in base 'base2'

Is there no way to be able to call function start() from a specific base class using a derived class object?

I don't know the use-case right now but.. still!

Castellated

I shortened the snippet. No semantics were changed. – Pendentive

Similar to #4832259 – Kinakinabalu

Rename the functions start1 and start2. – Pyramidon

@JohnPaul not the same though; this one is about two base classes with an identical function, that one is about two base classes that have a function with the same name, but differing arguments. – Aero

Answer 1

a.base1::start();

a.base2::start();

or if you want to use one specifically

class derived:public base1,public base2
{
public:
    using base1::start;
};

Aero

Answer 2

Sure!

a.base1::start();

or

a.base2::start();

Pendentive

Trying to understand - "if the inheritance were virtual, there would be no ambiguity". How is that? – Castellated

@goldenmean: That hasn't been part of my answer for a while now. – Pendentive

Answer 3

In addition to the answers above, if we are in the case of NON-VIRTUAL inheritance:

you can:

1. use static_cast<base1*>(a).start()

or

2. override start() in derived

Btw - please note the diamond problem that can appear. In this case you might want to use virtual.

Septillion