stack_dup_value
push(stack_dup_value(v, ©));
push(stack_dup_value(v, ©));
struct value *stack_dup_value(const struct value *, struct value *);
stack_push(stack, stack_dup_value(value, ©));
(void)stack_dup_value(&a->data[i], &n->data[i]);