dll中全局变量在外部进行引用
在Windows中实际导出全局变量，您必须使用类似于export / import语法的语法，例如：
1 #ifdef COMPILING_THE_DLL 2 #define MY_DLL_EXPORT extern "C" __declspec(dllexport) 3 #else 4 #define MY_DLL_EXPORT extern "C" __declspec(dllimport) 5 #endif 6 7 MY_DLL_EXPORT int my_global;
参考网址：
https://codeday.me/bug/20170811/55724.html
https://blog.csdn.net/mangobar/article/details/53390552
https://blog.csdn.net/silvervi/article/details/5055707
