Hi, there is somes issues in lesson22 code: 1. Makefile source file (for automake) miss something in dependancie lead to go to second compilation step without proper input file generated in 1st step (object file), 2. glext.h local include should be replace by standard GL/glext.h. in configure.in: line AC_CHECK_HEADERS(GL/gl.h GL/glu.h, , AC_MSG_ERROR([OpenGL headers not found])) become AC_CHECK_HEADERS(GL/gl.h GL/glu.h, GL/glext.h, , AC_MSG_ERROR([OpenGL headers not found])) 3. command line for 1st object file miss: GL_GLEXT_PROTOTYPES define I think it will be easy to fix with enough automake/autoconf knowledge. Regards.