I am trying to find out what the correct behavior of the following code for the latest ANSI C++. I have a base class and a derived class. In my base class I specify a variable to be used by all derived classes. The base class is abstract and specifies a virtual access function ''AccessSomeVar'' (which in my scenario I never override). In my derived class constructor I set the base class variable in the code section of the constructor (ie not with the initializer). Now in my test code, I instantiate the derived class and then have a base class pointer assigned to it. When I call ''AccessSomeVar'' via the pointer, on one compiler I get an uninitialized value for the variable and on a second compiler I get the correct value (it is non-zero too, so no mysterious compiler initializations occur). What is the "correct" behavior defined for ANSI C++? Thanks.

Let''s see if I have your thingy right. Code would really help here. Tell me if I got it wrong at all.

class Base{public:    int i;    virtual int& AccessSomeVar() { return i; }};class Derived : public Base{public:    Derived() { i = 3; }};int main(){    Base* b = new Derived();    cout << b->AccessSomeVar();}

In that code, 3 should always be printed (though it is bad form to initialize a Base data member in the Derived constructor). Do I have your code right?

How appropriate. You fight like a cow.

Yeah, that''s the code. Although I put the access var as a reference parameter rather than a return type.

I think I may have answered my own question actually. I did not realize you could put code into the parameter passed through the initializer.

I need to learn how to make a code window like you did for the code. Is there a FAQ on that or is it simply HTML?

class Base
{
public:
Base( int x, int y, int z );
virtual void GetZValue( int &z );
....
protected:
int internalz;

private:
};

class Derived : public Base
{
public:
Derived( int x, int y );
...
};

...
int PickZ( int x, int y )
{
if( x > y )
return x;
else
return y;
}

Derived::Derived( int x, int y )
: Base( x, y, PickZ( x, y ) )
{
}

Your hint about "initializations don''t belong in constructors" put me on the correct track. Instead of assigning z inside the Derived constructor, I initialize the base constructor with a value dependent on the x, y parameters. The code works on my one compiler but I don''t have access to the 2nd one yet.

Should the PickZ function be moved to its own namespace as a matter of good programming to make it only visible by the Derived class?

Thanks.

quote:
I initialize the base constructor with a value dependent on the x, y parameters.

Kudos. That''s MUCH better.

quote:Should the PickZ function be moved to its own namespace as a matter of good programming to make it only visible by the Derived class?

A better idea would be to make it a static member function of Derived.

How appropriate. You fight like a cow.

Sneftel,

Thanks for your help. Your advice on the forums is great. I suspected there would be a way to privatize it on my class but couldn''t put my finger on it. I''ll make it static and then my code will be good and happy.

Thanks!