Problem with C++ dll...

[st1]

Hi all...i'm a newbie in the forum...and actually quite new in C++...so here it goes:
So, i'm not an experienced C++ developer and I'm messing around with some dlls:
so here's a problem I have encountered:
in a project I have a base class BC (say private members are x,y) and a derived class DC (say private members are x,y,z) which inherits from the previous class. I also have a function foo in another cpp file which I want to export it to Excel through a dll. In the body of the function foo, I construct and initialize an object DC(x,y,z). Everything works fine if I run this function in C++...inheritance works as expected. But when I try to run it from Excel using the constructed dll, it seems as if the private members x,y were never initialized, while z is correctly initialized!!! (in fact I figured that out by making the function FOO output x,y,z in Excel; z comes out correctly, but x,y come out as 1376260, which of course has no relation to the value they were initialized) So, do you have any ideas about how to resolve the problem?

Best,

steven

[weaknessforcats]

What does your dll code look like???

I preseume you have your C++ code in a .cpp file AND your dll functions in a .c file (because a dll only works with un-mangled names and that you have a .def file that exports the names of your dll functions.

You will need to call your C++ functions in the .cpp file using a C function in your .c file. Be sure you understand how to use extern "C".

[st1]

so here's the code I've written (simplified):
I decided to export the classes hoping that I would correct the bug but I don't mind if they're not exported. The only function I need in fact to export is the function "test": I tried to write a definition file, but it allowed me to add under EXPORT only the function test and not the classes themselves (I think this is because the classes are not declarations).

////////////////////////////////////////////////
class __declspec(dllexport) BC{
protected:
int x;
double y;
public:
BC();
BC(x,y);

int get_x(){
return x;
};

void set_x(int n){
x=n;
};

void set_y(double y){
y=y_;

};
};
/////////////////////////////////////////////////////////////////
#include "BC.h"
BC::BC(){};

BC::BC(int x_, double y_){
x=x_;
y=y_;
};


////////////////////////////////////////////////////////////////////

#include "BC.h"

using namespace std;

class __declspec(dllexport) DC: public BC{

private:
double K;

public:

DC();
DC(int x_, double y_, double K_);

double get_K(){
return K;
};

};



//////////////////////////////////////////////////////////////////////////
#include "DC.h"

using namespace std;


DC::DC():BC(){};

DC::
DC(int x_, double y_, double K_)
:BC(x,y){
K=K_;
};

////////////////////////////////////////////////////////////////////////////////
#include "DC.h"
#define RC_double _declspec(dllexport) double _stdcall

RC_double test(int n1, double n2, double n3){
DC L(n1,n2,n3);

return L.get_y(); //this appears in Excel as if it has never been initialized
//return L.get_K() //this appears fine in the excel i.e =n3
};
////////////////////////////////////////////////////////////////////////////////