Are default constructors called automatically for member variables?

Question

Say I have this class:

//Awesome.h
class Awesome
{
    public:
        Awesome();
    private:
        membertype member;
}

//Awesome.cpp
#include "Awesome.h"

Awesome::Awesome()
:member()
{
}

If I omit the member() in the initialization list of the constructor of Awesome, will the constructor of member be called automatically? And is it only called when I don't include member in the initialization list?

Answer 1

Yes. When a variable is not given in the initalizer list, then it is default constructed automatically.

Default contruction means, that if membertype is a class or struct, then it will be default contructed, if it's a built-in array, then each element will be default constructed and if it's a build-in type, then no initialization will be performed (unless the Awesome object has static or thread-local storage duration). The last case means that the member variable can (and often will) contain unpredictable garbage in case the Awesome object is created on the stack or allocated on the heap.