Pure virtual function call

morando (163)
I need help to overcome this problem:

Window base class
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class Window
{
protected:
    ...
    static LRESULT CALLBACK StaticWindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
	virtual LRESULT WindowProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam) = 0;
public:
    ...
};

LRESULT CALLBACK Window::StaticWindowProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
	Window* pWindow;
  
	if(WM_NCCREATE == msg)
	{
		pWindow = reinterpret_cast<Window*>( ((LPCREATESTRUCT)lParam)->lpCreateParams );
		SetWindowLongPtr(hWnd, GWL_USERDATA, reinterpret_cast<LONG_PTR>( pWindow ));
	}
	else
	{
		pWindow = reinterpret_cast<Window*>( GetWindowLongPtr(hWnd,GWL_USERDATA) );
		if(nullptr == pWindow) 
		{
			return DefWindowProc(hWnd, msg, wParam, lParam);
		}
	}

	pWindow->hwnd = hWnd;
	return pWindow->WindowProc(hWnd, msg, wParam, lParam);
}


Window "child" class
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class MainWindow : public Window
{
private:
public:
    ...
    LRESULT WindowProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam);
};

// implementation of base pure virtual method
LRESULT MainWindow::WindowProc(HWND hWnd, UINT msg, WPARAM wParam, LPARAM lParam)
{
    ...
}


And got error: "R6025 - pure virtual function call"

Any ideas how to do this?

Thanks for your time.
andywestken (4094)
How are you passing the pointer to CreateWindow(Ex) in the first place?

Are you using reinterpret_cast to cast a MainWindow* to PVOID?

Andy
Last edited on
morando (163)
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Window::Window(...)
{
...
hwnd = CreateWindow(
			className.c_str(), winTitle.c_str(), wndStyle,              
			center ? windowLeft : rect.x, center ? windowTop : rect.y, realWidth, realHeight,
			nullptr, nullptr, hinstance, this);
...
}
Last edited on
andywestken (4094)
Ah ha!

You shouldn't call virtual functions from inside a constructor. The vtable isn't fully fixed up until the construction of the instance is complete.

Try reworking things so you use 2-phase construction.

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Window::Window(...) : hwnd(nullptr), ...
{
}

bool Window::Init() // or whatever makes sense to you
{
    ...

    hwnd = CreateWindow(
			className.c_str(), winTitle.c_str(), wndStyle,              
			center ? windowLeft : rect.x,
			center ? windowTop : rect.y,
			realWidth, realHeight,
			nullptr, nullptr, hinstance, this);
    ...
}


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Window* wnd = new Window;
wnd->Init();

...


Andy
Last edited on
morando (163)
Thats it. Thanks.
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