From Anders F Bjorklund: When switching to "UNIX-style paths" as needed for the new includes, including <GL/gl.h> and <GL/glu.h> doesn't work anymore on Mac OS... The two headers are really located in the OpenGL SDK 1.2 CFM like this: OpenGL:Headers:gl.h OpenGL:Headers:glu.h There are also some compat copies, that *used* to work with Mac paths: OpenGL:Headers:GL/gl.h OpenGL:Headers:GL/glu.h The easiest fix is to make SDL_opengl.h include the proper header names, by adding a special case for the MACOS platform in addition to the MACOSX

/*
    headers for MMX assembler version of SDL_MixAudio
    Copyright 2002 Stephane Marchesin (stephane.marchesin@wanadoo.fr)
    This code is licensed under the LGPL (see COPYING for details)

    Assumes buffer size in bytes is a multiple of 16
    Assumes SDL_MIX_MAXVOLUME = 128
*/
#include "SDL_config.h"

#if defined(__GNUC__) && defined(__i386__) && defined(SDL_ASSEMBLY_ROUTINES)
void SDL_MixAudio_MMX_S16(char* ,char* ,unsigned int ,int );
void SDL_MixAudio_MMX_S8(char* ,char* ,unsigned int ,int );
#endif