Implementation supplied copy constructor and assignment operator

Question

I have a small confusion regarding the situations where the implementation (compiler) will not supply the copy constructor and the copy assignment operator.

1. When we declare the copy ctor and/or copy assignment operator in our class.
2. Some says when we derive from a class which has a private copy ctor and/or copy assignment operator.

I am a little confused about the second situation, is the second situation is precisely.
a) The implementation will not declare them for you, so you will get a compile time error.
OR
b) The implementation will declare and define them, but when the compiler defined implementation tries to find the base class' method, we will get a compile time error.

I had an interview yesterday, I said its (b) that is happening but the interviewer disagrees, he says its (a).

I tried to compile the following code in both Microsoft C/C++ 14.00 and gcc 4.4.5

struct A
{
private:
  A& operator = ( const A& );
};

struct B : A
{
};


int main()
{
  B b1;
  B b2;
  b1 = b2;

  return 0;
}

Microsoft compiler output

ctor01.cpp(9) : error C2248: 'A::operator =' : cannot access private member declared in class 'A'
ctor01.cpp(4) : see declaration of 'A::operator ='
ctor01.cpp(2) : see declaration of 'A'
This diagnostic occurred in the compiler generated function 'B &B::operator =(const B &)'

gcc compiler output

Ctor01.cpp: In member function ‘B& B::operator=(const B&)’:
Ctor01.cpp:4: error: ‘A& A::operator=(const A&)’ is private
Ctor01.cpp:8: error: within this context
Ctor01.cpp: In function ‘int main()’:
Ctor01.cpp:15: note: synthesized method ‘B& B::operator=(const B&)’ first required here 

So I think, the implementation will declare and define it, but when the compiler defined implementation tries to find the base class method, we will get a compile time error. Correct me if I am wrong.

Answer 1

Regarding the copy constructor, this is what the standard says (12.8/7) :

A program is illformed if the class for which a copy constructor is implicitly defined has:

• a nonstatic data member of class type (or array thereof) with an inaccessible or ambiguous copy constructor, or
• a base class with an inaccessible or ambiguous copy constructor.

Regarding the copy assignment operator (12.8/12) :

A program is illformed if the class for which a copy assignment operator is implicitly defined has:

• a nonstatic data member of const type, or
• a nonstatic data member of reference type, or
• a nonstatic data member of class type (or array thereof) with an inaccessible copy assignment operator, or
• a base class with an inaccessible copy assignment operator.

How the compiler reports the error, or how it actually falls into it, is pretty much irrelevant from my point of view.

However, I do believe that answer (b) is probably more correct : the base class copy assignment is declared, and it's inaccessible. The derived class has an implicitly declared copy assignment which the compiler will try to define if used, thus making the program ill-formed.