介绍 - 1.53.0
https://www.boost.org/doc/libs/1_53_0/libs/coroutine/doc/html/coroutine/intro.html
并发问题 - sybase.powerbuilder.pfc
https://codeverge.com/sybase.powerbuilder.pfc/concurrency-issue/815769
如何避免并发访问问题 - sybase.powerbuilder.database
https://codeverge.com/sybase.powerbuilder.database/how-to-avoid-concurrent-acces-is/814817
3-1，overflow & underflow - 知乎
https://zhuanlan.zhihu.com/p/57554498
underflow 、overflow 下溢和上溢 - the_tops - 博客园
https://www.cnblogs.com/the-tops/p/5886201.html
什么是下溢？
https://www.computerhope.com/jargon/u/underflo.htm