Should constructor initialize all the data members of the class?

Question

I have a situation like this:

class A {
public:
  A() : n(0) {}
private:
  int n;
  int m;
}

There is simply no meaning in the application logi

Answer 1

Fully disagree with all the answers and comments. There is absolutely no need to default initialze a member when it is not needed. This is why C/C++ never initializes built-in types as members or automatic variables - because doing so would impede performance. Of course, it is not a problem when you create your object/variable once (that's why statics are default-initialized), but for something happening in a tight loop default initialization might eat valuable nanoseconds.

The one exception to this rule would, in my view, be pointers (if you happen to have raw pointers in your code). Raw pointers should be NULL-initialized, since having invalid pointer is a direct way to undefined behaviour.