1 C++中 #ifdef 和#endif的作用
https://blog.csdn.net/fly_yr/article/details/39964035
2 C++成员运算符(.)和(->)
https://blog.csdn.net/liitdar/article/details/80491259
https://blog.csdn.net/fly_yr/article/details/39964035
https://blog.csdn.net/liitdar/article/details/80491259