There is no check for the failed malloc https://github.com/rui314/8cc/blob/b480958396f159d3794f0d4883172b21438a8597/cpp.c#L65 may load to null deference in line https://github.com/rui314/8cc/blob/b480958396f159d3794f0d4883172b21438a8597/cpp.c#L66