Hi Bonk,
bonk said:
Hello, I created a MFC extension dll (using VS 2005 Beta 2) that is
supposed to export a class that uses .NET internally (See header below)
und later shall be used by a plain MFC Project (without the /CLR).
As soon as I try to specify __declspec(dllexport) (AFX_EXT_CLASS) I get
the following compiler error:
Error 2 error C3395: 'CWPFControlProxy::OnWPFButtonClick' :
__declspec(dllexport) cannot be applied to a function with the __clrcall
calling convention g:\robert_d\visual studio
2005\projects\wpfcontrols\wpfcontrols\WPFControlProxy.h 28
Could you explain what this error means and what I can do against it? I
don't see a __clrcall definition anywhere in my project ...
---- WPFControlProxy.h ------------------
#pragma once
// CWPFControlProxy
#include <msclr\event.h>
#include <msclr\auto_gcroot.h>
using namespace System;
using namespace System::Windows;
using namespace System::Windows::Controls;
using namespace System::Windows::Media;
class AFX_EXT_CLASS CWPFControlProxy : public CStatic
{
DECLARE_DYNAMIC(CWPFControlProxy)
public:
CWPFControlProxy();
virtual ~CWPFControlProxy();
CRect m_borders;
private:
HWND m_WPFHwnd;
CString m_WPFText;
Visual^ CreateRootWPFVisual();
msclr::auto_gcroot<TextBox^> m_wpfTextBox;
void OnWPFButtonClick (Object^ sender, RoutedEventArgs^ eargs);
public:
BEGIN_DELEGATE_MAP(CWPFControlProxy)
EVENT_DELEGATE_ENTRY(OnWPFButtonClick,Object^, RoutedEventArgs^)
END_DELEGATE_MAP()
void SetText (LPCTSTR text);
protected:
DECLARE_MESSAGE_MAP()
public:
afx_msg int OnCreate(LPCREATESTRUCT lpCreateStruct);
afx_msg void OnSize(UINT nType, int cx, int cy);
afx_msg void OnMouseMove(UINT nFlags, CPoint point);
afx_msg LRESULT OnSetText( WPARAM, LPARAM );
protected:
virtual BOOL PreCreateWindow(CREATESTRUCT& cs);
};
Here is what went wrong with your code:
1) You export a native class via __declspec(dllexport)
2) This exports the functions of the native class
3) Although managed functions, functions have a native calling convention -
these functions can easily be exported
4) Some managed functions have the calling convention __clrcall (not because
you explicitly wrote that, but because functions with managed types in their
signature can only have this calling convention.
5) __clrcall calling conventions can not be exported by DLLs - trying to
export them causes the problems you see here.
__clrcall tells the compiler that it should not create unmanaged->managed
thunks, but to export managed functions, unmanaged->managed thunks are
needed.
