Beautiful C++: 30 Core Guidelines for Writing Clean, Safe, and Fast Code

Chapter 2.4

C.47: Define and initialize member variables in the order of member declaration

There is only one order of initialization of member data, which is the order of decla-ration. You cannot change this. There are very good reasons for this being an immu-table rule, which we will describe in this chapter.

But first, an example. Bryn, a new engineer at a large firm, is asked to write a pop-ulation service for finding out how many people are in the building. A server locked away in the bowels of the building handles admissions and exits. It is old and slow. Etched on the front in red lettering is the name of a forgotten hardware company long ago sold to a rapacious and overfunded startup. Queries are rather cumber-some and time consuming. ...