https://blog.wongcw.com/2020/01/13/gcc-%e9%a0%85%e7%9b%ae%e4%bb%a3%e7%a2%bc%e7%b5%82%e6%96%bc%e5%be%9esvn-%e5%ae%8c%e5%85%a8%e5%88%87%e6%8f%9b%e8%87%b3git/