file.c:2444
static VALUE
rb_stat_R(obj)
    VALUE obj;
{
    struct stat *st = get_stat(obj);

#ifdef S_IRUSR
    if (rb_stat_rowned(obj))
	return st->st_mode & S_IRUSR ? Qtrue : Qfalse;
#endif
#ifdef S_IRGRP
    if (group_member(get_stat(obj)->st_gid))
	return st->st_mode & S_IRGRP ? Qtrue : Qfalse;
#endif
#ifdef S_IROTH
    if (!(st->st_mode & S_IROTH)) return Qfalse;
#endif
    return Qtrue;
}
