https://stackoverflow.com/questions/10041453/eclipse-c-type-could-not-be-resolved-error-even-though-build-is-successful
https://blog.csdn.net/fjx1173865548/article/details/78477231
即使添加了所有项目需要的依赖的头文件，include path也完整时，依然会存在该问题，重启eclipse项目也不行，
终于在Stack Overflow里找到解决办法：
Project -> C/C++ index -> Freshen all files，即可解决~
