g++ problem when attempting to cast a function pointer in an OpenGL GLU callback

[Brian Dessent]

"Day, Michael A AMRDEC/UAH" wrote:

> test.cpp:72: error: invalid conversion from `void (*)()' to `void (*)()'

Win32 API functions generally use the stdcall calling convention, not
the standard C one.  Your tcbBegin is not defined this way and this
could be what the compiler is trying to tell you, although the error
certainly isn't very clear.

If you look at glu.h:

GLAPI void APIENTRY gluTessCallback (GLUtesselator* tess, GLenum which,
_GLUfuncptr CallBackFunc);

where _GLUfuncptr is defined as:

typedef void (APIENTRY *_GLUfuncptr)();

where APIENTRY expands to "__attribute__ ((__stdcall__))".  So you'll
need to declare your callback with that attribute or else it will not
work.

Brian

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