Re: [openvrml-develop] Link failure in building OpenVRML-0.16.1 on Mac OS X ppc

[Braden M. <br...@en...>]

I've managed to locate a PPC Mac where I can test this a bit. For those
of you playing along with the home game, try this...

Go to line 290
of /System/Library/Frameworks/OpenGL.framework/Headers/glu.h. You should
find the declaration of gluTessCallback there; note that it's inside an
extern "C" block. Copy the declaration of gluTessCallback.

Now go to src/libopenvrml-gl/openvrml/gl/viewer.cpp. Create an extern
"C" block after <OpenGL/glu.h> is included and paste the definition of
gluTessCallback there. You should wind up with something that looks like
this:

        # if HAVE_APPLE_OPENGL_FRAMEWORK                                                                                                                                               
        #   include <OpenGL/gl.h>                                                                                                                                                      
        #   include <OpenGL/glu.h>                                                                                                                                                     
        # else                                                                                                                                                                         
        #   include <GL/gl.h>                                                                                                                                                          
        #   include <GL/glu.h>                                                                                                                                                         
        # endif                                                                                                                                                                        
                                                                                                                                                                                       
        extern "C" {                                                                                                                                                                   
        extern void gluTessCallback (GLUtesselator* tess, GLenum which, GLvoid (*CallBackFunc)());                                                                                     
        }                                                                                                                                                                              

Now compile. Here's what you get:

        ../../../src/libopenvrml-gl/openvrml/gl/viewer.cpp:42: error: declaration of C function 'void gluTessCallback(GLUtesselator*, GLenum, GLvoid (*)())' conflicts with
        /System/Library/Frameworks/OpenGL.framework/Headers/glu.h:290: error: previous declaration 'void gluTessCallback(GLUtesselator*, GLenum, GLvoid (*)(...))' here

WTF??? That is some first class brain damage there.

I know nothing about how frameworks work on Mac OS X; but I can only
guess from this behavior that the compiler is checking something *other*
than the source code (i.e., glu.h) for the type associated with the
external symbol--presumably some sort of manifest associated with the
framework.

Clues welcome.

In the absence of further input with a better suggestion, I'm going to
make the declaration of TessCB dependent on HAVE_APPLE_OPENGL_FRAMEWORK:

        # if HAVE_APPLE_OPENGL_FRAMEWORK
            typedef GLvoid (*OPENVRML_GL_CALLBACK_ TessCB)(...);
        # else
            typedef GLvoid (*OPENVRML_GL_CALLBACK_ TessCB)(GLvoid);
        # endif

-- 
Braden McDaniel                           e-mail: <br...@en...>
<http://endoframe.com>                    Jabber: <br...@ja...>