What is the order of evaluation in a member initializer list?

Question

I have a constructor that takes some arguments. I had assumed that they were initialized in the order listed, but in one case, it appears they were being initialized in reverse, resulting in an abort. When I reversed the arguments, the program stopped aborting.

Below is an example of the syntax I'm using. a_ needs to be initialized before b_ in this case. Can you ensure this order of initialization?

class A
{
  public:
    OtherClass a_;
    AnotherClass b_;

    A(OtherClass o, string x, int y)
      : a_(o)
      , b_(a_, x, y) {}
};

Answer 1

It depends on the order of data member declarations in the class. So a_ will be the first one, then b_ will be the second one in your example.