c++ default - Constructor initialization-list evaluation order




2 Answers

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

initializer vs

I have a constructor that takes some arguments. I had assumed that they were constructed in the order listed, but in one case it appears they were being constructed in reverse resulting in an abort. When I reversed the arguments the program stopped aborting. This is an example of the syntax I'm using. The thing is, a_ needs to be initialized before b_ in this case. Can you guarantee the order of construction?

e.g.

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

    OtherClass a_;
    AnotherClass b_;
};



The standard reference for this now appears to be 12.6.2 section 13.3:

(13.3) — Then, non-static data members are initialized in the order they were declared in the class definition (again regardless of the order of the mem-initializers).




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c++ gcc c++-faq