Use of constructor in C++

Question

This is very trivial question regarding the use of a constructor in C++. I will present in the form of an interview dialogue (it was difficult to present it in any other forms)

interviewer - what is a constructor?
me - constructor are special functions which makes sure that all objects are initialized before their use.

interviewer - what is an initializer list?
me - that is a list where all the initialization happens. A constructor's body is entered only after all the data members are initialized, or some constructor of all the member objects are called.

interviewer - that means initialization is carried out in initializer list, not inside constructor. But you said constructor initialize the object! Didn't you? Do you want to answer my first question.
me - I think constructor does assignment, it calls assignment operator on already initialized member objects.

So my question to you can be

how initializer list works?

what lies between function's starting address & starting braces [{]?

or just answer me how to convince my interviewer.

Answer 1

Technically speaking, your interpretation is accurate. No members may be initialised from inside the ctor body; only in the ctor-initializer. Any member access in the ctor body may only be assignment.

All members are "initialised" before the ctor body is entered.

However, speaking more broadly, since the body always follows the initializer, it's said that — as a unit — the object is initialised once the constructor has ended... including the body.

Partly this is because, again speaking broadly, you might consider initialisation to include some business logic that you must perform in your ctor body, even though this is not the same as actual initialisation of a data member.

Answer 2

You're overthinking it and allowing the interviewer to confuse you.

Initializing the members of an object is not the same thing as initializing the object itself. Just because the members have sane values doesn't mean the object has been constructed. Until the constructor has completed, the object itself has not been properly initialized.