mark_stack       1154 gc.c               mark_stack_ptr = mark_stack;
mark_stack       1157 gc.c           #define MARK_STACK_EMPTY (mark_stack_ptr == mark_stack)
mark_stack       1187 gc.c               p = (mark_stack_ptr - mark_stack) + tmp_arry;
mark_stack       1188 gc.c               MEMCPY(tmp_arry, mark_stack, VALUE, p - tmp_arry);
mark_stack       1358 gc.c           	    if (mark_stack_ptr - mark_stack < MARK_STACK_MAX) {