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Austrian Coder

Maybe simple function pointer problem

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Hi! I am working on a extensionmanager for opengl. I want this feature: gExtensionManager->RegisterSetupFunction("GL_ARB_MegaCoolEffect", SetupARB_MegaCoolEffect); And then gExtensionManager->IsExtensionSupported("GL_ARB_MegaCoolEffect"); The last call checks if the extension is supported, when yes it looks if there is a function to call when extension is found - the Setupfunction for the extension. An example for a setupfunction:
	// ==================================

	// example setup function

	void CExtensionManager::SetupMultitexturing()
	{
		// multitexture extension

		glMultiTexCoord1dARB	= (PFNGLMULTITEXCOORD1DARBPROC)		GetProcAdress("glMultiTexCoord1dARB");
		glMultiTexCoord1dvARB	= (PFNGLMULTITEXCOORD1DVARBPROC)	GetProcAdress("glMultiTexCoord1dvARB");	
		glMultiTexCoord1fARB	= (PFNGLMULTITEXCOORD1FARBPROC)		GetProcAdress("glMultiTexCoord1fARB");
		glMultiTexCoord1fvARB	= (PFNGLMULTITEXCOORD1FVARBPROC)	GetProcAdress("glMultiTexCoord1fvARB");
		glMultiTexCoord1iARB	= (PFNGLMULTITEXCOORD1IARBPROC)		GetProcAdress("glMultiTexCoord1iARB");
		glMultiTexCoord1ivARB	= (PFNGLMULTITEXCOORD1IVARBPROC)	GetProcAdress("glMultiTexCoord1ivARB");
		glMultiTexCoord1sARB	= (PFNGLMULTITEXCOORD1SARBPROC)		GetProcAdress("glMultiTexCoord1sARB");
		glMultiTexCoord1svARB	= (PFNGLMULTITEXCOORD1SVARBPROC)	GetProcAdress("glMultiTexCoord1svARB");
		glMultiTexCoord2dARB	= (PFNGLMULTITEXCOORD2DARBPROC)		GetProcAdress("glMultiTexCoord2dARB");
		glMultiTexCoord2dvARB	= (PFNGLMULTITEXCOORD2DVARBPROC)	GetProcAdress("glMultiTexCoord2dvARB");	
		glMultiTexCoord2fARB	= (PFNGLMULTITEXCOORD2FARBPROC)		GetProcAdress("glMultiTexCoord2fARB");
		glMultiTexCoord2fvARB	= (PFNGLMULTITEXCOORD2FVARBPROC)	GetProcAdress("glMultiTexCoord2fvARB");
		glMultiTexCoord2iARB	= (PFNGLMULTITEXCOORD2IARBPROC)		GetProcAdress("glMultiTexCoord2iARB");
		glMultiTexCoord2ivARB	= (PFNGLMULTITEXCOORD2IVARBPROC)	GetProcAdress("glMultiTexCoord2ivARB");
		glMultiTexCoord2sARB	= (PFNGLMULTITEXCOORD2SARBPROC)		GetProcAdress("glMultiTexCoord2sARB");
		glMultiTexCoord2svARB	= (PFNGLMULTITEXCOORD2SVARBPROC)	GetProcAdress("glMultiTexCoord2svARB");
		glMultiTexCoord3dARB	= (PFNGLMULTITEXCOORD3DARBPROC)		GetProcAdress("glMultiTexCoord3dARB");
		glMultiTexCoord3dvARB	= (PFNGLMULTITEXCOORD3DVARBPROC)	GetProcAdress("glMultiTexCoord3dvARB");
		glMultiTexCoord3fARB	= (PFNGLMULTITEXCOORD3FARBPROC)		GetProcAdress("glMultiTexCoord3fARB");
		glMultiTexCoord3fvARB	= (PFNGLMULTITEXCOORD3FVARBPROC)	GetProcAdress("glMultiTexCoord3fvARB");
		glMultiTexCoord3iARB	= (PFNGLMULTITEXCOORD3IARBPROC)		GetProcAdress("glMultiTexCoord3iARB");
		glMultiTexCoord3ivARB	= (PFNGLMULTITEXCOORD3IVARBPROC)	GetProcAdress("glMultiTexCoord3ivARB");
		glMultiTexCoord3sARB	= (PFNGLMULTITEXCOORD3SARBPROC)		GetProcAdress("glMultiTexCoord3sARB");
		glMultiTexCoord3svARB	= (PFNGLMULTITEXCOORD3SVARBPROC)	GetProcAdress("glMultiTexCoord3svARB");
		glMultiTexCoord4dARB	= (PFNGLMULTITEXCOORD4DARBPROC)		GetProcAdress("glMultiTexCoord4dARB");
		glMultiTexCoord4dvARB	= (PFNGLMULTITEXCOORD4DVARBPROC)	GetProcAdress("glMultiTexCoord4dvARB");	
		glMultiTexCoord4fARB	= (PFNGLMULTITEXCOORD4FARBPROC)		GetProcAdress("glMultiTexCoord4fARB");
		glMultiTexCoord4fvARB	= (PFNGLMULTITEXCOORD4FVARBPROC)	GetProcAdress("glMultiTexCoord4fvARB");
		glMultiTexCoord4iARB	= (PFNGLMULTITEXCOORD4IARBPROC)		GetProcAdress("glMultiTexCoord4iARB");
		glMultiTexCoord4ivARB	= (PFNGLMULTITEXCOORD4IVARBPROC)	GetProcAdress("glMultiTexCoord4ivARB");
		glMultiTexCoord4saARB	= (PFNGLMULTITEXCOORD4SARBPROC)		GetProcAdress("glMultiTexCoord4saARB");
		glMultiTexCoord4svARB	= (PFNGLMULTITEXCOORD4SVARBPROC)	GetProcAdress("glMultiTexCoord4svARB");
		glActiveTextureARB		= (PFNGLACTIVETEXTUREARBPROC)		GetProcAdress("glActiveTextureARB");
		glClientActiveTextureARB= (PFNGLCLIENTACTIVETEXTUREARBPROC)	GetProcAdress("glClientActiveTextureARB");
	}
The only problem: // resgister test setup function RegisterSetupFunction("GL_ARB_multitexture", SetupMultitexturing); --> error C2664: ''RegisterSetupFunction'' :cannot convert parameter 2 from void (void)'' to ''void (__cdecl *)(void)'' Here are other code snipps
typedef void(*VoidFuncPointer)();
typedef std::multimap<const char*, VoidFuncPointer> SetupMap;
...
...
void RegisterSetupFunction(String Extension, VoidFuncPointer Func);
So can anybody help me? Thanks, Christian

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It''s because it''s a member function. you need a global function, or you need to define a function pointer to a class member function. take a look at this thread:

http://gamedev.net/community/forums/topic.asp?topic_id=164594

void (__cdecl *)(void) means that you want a function of type __cdecl. member functions in classes are always of the type thiscall

My Site

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Pointers to member functions and pointers to non-member functions are incompatible. There a no possibility of conversion whatsoever.

Workaround : store and use function objects instead of function pointers. See boost::function (link in signature) for an example.


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