C++ multiple inheritance function call ambiguity

Sure!

a.base1::start();

or

a.base2::start();

a.base1::start();

a.base2::start();

or if you want to use one specifically

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

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.