Re: Subclass copy constructor not calling parent copy constructor

On 24 Jun., 03:35, Timie Milie <tim.milst...@googlemail.com> wrote:


There maybe several reasons and some of them we can't answer,
because your code above has been truncated to a form that is
not well-formed anymore.
Independent from this, the above class definitions aren't written
in a way that would make something like "it goes into the B copy
constructor but not the A copy constructor" observable, so we
have no reason to discuss about something that isn't observable.

Debugging behavior doesn't belong to the categories of
observable behavior.

Even if you make your code well-formed and ensure that each
copy constructor call of A and B would become observable, there
is no guarantee that the copy constructor of A will be called under
special conditions, which are described in 12.8 [class.copy]/15
(N2857), because C++ gives special freedom for the compiler
to eliminate copies. So make sure that your actual code doesn't
match one of the cases mentioned there.

The following example does not belong to these optimization
situations and if you compile and start this one:

---------------------------
#include <iostream>

class A {
public:
   A(){}
   A(const A& a) {
     std::cout << "Visiting A(const A&)" << std::endl;
   }
};

class B : public A {
public:
   B() : A() {}
   B(const B& b) : A(b) {
     std::cout << "Visiting B(const B&)" << std::endl;
   }
};

B b1;
B b2(b1);

int main() { }
---------------------------

and if you don't see output like this

Visiting A(const A&)
Visiting B(const B&)

there is something wrong with your compiler.

[I'm sure that the VS2005 compiler will pass this test]

HTH & Greetings from Bremen,

Daniel Kr?gler

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