C-style cast suceeds whereas static_cast reports error

I am using Visual Studio 2005:

The following code fails:

Code:

---

using namespace NepwareGames::MainApplication;

CApplicationCallback *pWin = static_cast<CApplicationCallback *>(new CWindow);

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The error reported is

Code:

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1>j:\nepwaregames\nepwaregames\nepwaregames.cpp(28) : error C2243: 'static_cast' : conversion from 'NepwareGames::MainApplication::CWindow *' to 'NepwareGames::MainApplication::CApplicationCallback *' exists, but is inaccessible

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However the C-style cast works fine and the program executes as expected.

The following are the declaration of the classes:

Code:

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namespace NepwareGames
{
        namespace MainApplication
        {
                class CApplicationCallback
                {
                public:
                        // pure virtual functions
                        virtual ~CApplicationCallback(void)= 0 {}
                        virtual bool CreateEx(DWORD dwExStyle, LPCTSTR lpszClass, LPCTSTR lpszName, DWORD dwStyle,
                                                                        int x, int y, int nWidth, int nHeight, HWND hParent,
                                                                        HMENU hMenu, HINSTANCE hInst) = 0;
                        virtual WPARAM MessageLoop(void) = 0;
                        virtual BOOL ShowWindow(int nCmdShow) const = 0;
                        virtual BOOL UpdateWindow(void) const = 0;
                };

                class CApplication
                {
                public:
                        static CApplication * Create (CApplicationCallback *par);
                };
        }
}

---

Code:

---

namespace NepwareGames
{
        namespace MainApplication
        {
                class CWindow : CApplicationCallback
                {
                private:
                        CApplication *m_CApplication;
                private:
                        virtual void OnDraw(HDC hDC){}
                        virtual void OnKeyDown(WPARAM wParam, LPARAM lParam);
                        virtual LRESULT WndProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
                        static LRESULT CALLBACK WindowProc(HWND hWnd, UINT uMsg, WPARAM wParam, LPARAM lParam);
                        virtual void GetWndClassEx(WNDCLASSEX & wc);
                public:
                        HWND  m_hWnd;

                        CWindow(void) : m_hWnd(NULL) {}
                        ~CWindow(void) {}
                        virtual bool CreateEx(DWORD dwExStyle, LPCTSTR lpszClass, LPCTSTR lpszName, DWORD dwStyle,
                                                                        int x, int y, int nWidth, int nHeight, HWND hParent,
                                                                        HMENU hMenu, HINSTANCE hInst);
                        bool RegisterClass(LPCTSTR lpszClass, HINSTANCE hInst);
                        virtual WPARAM MessageLoop(void);
                        virtual BOOL ShowWindow(int nCmdShow) const
                        {
                                return ::ShowWindow(m_hWnd, nCmdShow);
                        }
                        virtual BOOL UpdateWindow(void) const
                        {
                                return ::UpdateWindow(m_hWnd);
                        }
                };
        }
}

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Please help

I may be missing something, but why do you even need a cast? CWindow is a derived class of CApplicationCallback so you don't need a cast to assign a derived pointer to a base pointer.

Hi Yves,

Earlier I didn't use any casts. While not using any cast it gives the following error:

Code:

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1>j:\nepwaregames\nepwaregames\nepwaregames.cpp(28) : error C2243: 'type cast' : conversion from 'NepwareGames::MainApplication::CWindow *' to 'NepwareGames::MainApplication::CApplicationCallback *' exists, but is inaccessible

---

The "inaccessible" thing is very puzzling. Default constructors are available for the both. Any ideas?

Apparently, class inheritance in C++ is private by default... can you spot the error in your code? :D I found this out by searching - *

Quote:

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Originally Posted by Yves M

I may be missing something, but why do you even need a cast? CWindow is a derived class of CApplicationCallback so you don't need a cast to assign a derived pointer to a base pointer.

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Yes you missed something. His inheritance is private.

Try making the inheritance public thus:

Code:

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class CWindow : public CApplicationCallback
{
// etc.
};

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Ah, yes ;)

Thanks Mybowlcut.

Gosh!!! I spent half an hour with this. :thumb:

Haha no probs.. thanks for helping me out all those times! Feels great to help someone smarter than me, even if NMTop40 was only seconds away haha. :p