What's the point of g++ -Wreorder?

Question

The g++ -Wall option includes -Wreorder. What this option does is described below. It is not obvious to me why somebody would care (especially enough to turn this on by de

Answer 1

The warning exists because if you just read the constructor, it looks like j is getting initialized before i. This becomes a problem if one is used to initialize the other, as in

struct A {
  int i;
  int j;
  A(): j (0), i (this->j) { }
};

When you just look at the constructor, this looks safe. But in reality, j has not yet been initialized at the point where it is used to initialize i, and so the code won't work as expected. Hence the warning.