What happens when there is no default constructor?

If no user-defined constructor exists for a class A and one is needed, the compiler implicitly declares a default parameterless constructor A::A() . This constructor is an inline public member of its class.

A derived class can only be constructed once all base class’ are fully constructed. So it doesn’t matter if you call the base class’ constructor or not . If you don’t call, as long as there is a default constructor available for compiler to determine, it will be called. Otherwise compiler will throw error.

Not having a default constructor is no problem, as long as you don’t use one . Always specifying an argument at construction is ok, when there is no obvious default argument.11 Kas 2011