#include <string.h>
#include <GL/gl.h>
#define __USE_GNU
#include <dlfcn.h>

static const GLubyte* (*real_glGetString)( GLenum name );

static char* bad_extensions[] =
    {
        "GL_ARB_vertex_program",
        NULL
    };

GLAPI const GLubyte* GLAPIENTRY glGetString( GLenum name )
{
    if (!real_glGetString) {
        real_glGetString = dlsym(RTLD_NEXT, "glGetString");
        if ( real_glGetString == NULL ) {
            return NULL;
        }
    }

    const GLubyte* glstr = real_glGetString(name);

    if ( name == GL_EXTENSIONS ) {
        static char* extensions = NULL;
        char *ext;

        if (extensions) {
            return extensions;
        }

        extensions = malloc(8192);
        memset(extensions, 0, 8192);

        ext = strtok((char *)glstr, " ");
        while (ext != NULL) {
            int i, is_bad;

            i = 0;
            is_bad = 0;
            while ( bad_extensions[i] ) {
                if (strcmp(bad_extensions[i], ext) == 0) {
                    is_bad = 1;
                    break;
                }
                i++;
            }

            if ( ! is_bad ) {
                strcat(extensions, ext);
                strcat(extensions, " ");
            }

            ext = strtok(NULL, " ");
        }

        glstr = extensions;
    }

    return glstr;
}