Re: About member variable initilization and default constructor issues

In Inside C++ object Model, Lippman said there are four cases in which
compile will sythesize a default constructor to initialize the member
variables if the constructor is absent:

1. there is a virtual function;

2. virtual inheritance;

3.base class with explicit default constructor;

4.member object with explicit default constructor.

e.g.

class A {

public:

      int i;

      A* p;
}
int main()
{
     A a;
    if(a.i ==0 || a.p == 0) //do something
}

The behavior is undefined for the above case. If we modify class A to
have any one of the four characeristics, then the member variables
will be initialized in the default constructor sythesysized by the
compiler, as though
A():i(0),p(0){} is defined in the class.

But I try this in different compilers, and yield different results. My
question is : Is Lippman teaching ISO standard, or compiler-
dependent? Thanks