Windows下的DLL、Linux下的库或是C++中调用C的库，均可能用到import/export。本文讨论一种通用的import/export宏定义的使用实践。
        如下所示，"common.h"定义了可以跨平台的import/export宏定义，"something.h"定义了某个类头文件的import/export定义，"something.cpp"实现类并export类，使用该类的文件仅需#include "something.h"，由于没有定义宏SOME_EXPORTS，所以缺省是import啦。

       "common.h"中包括：
       #ifdef  WIN32
         #ifdef __cplusplus 
           #define DLL_EXPORT_C_DECL extern "C" __declspec(dllexport)
           #define DLL_IMPORT_C_DECL extern "C" __declspec(dllimport)
           #define DLL_EXPORT_DECL extern __declspec(dllexport)
           #define DLL_IMPORT_DECL extern __declspec(dllimport)
           #define DLL_EXPORT_CLASS_DECL __declspec(dllexport)
           #define DLL_IMPORT_CLASS_DECL __declspec(dllimport)
         #else
           #define DLL_EXPORT_DECL __declspec(dllexport)
           #define DLL_IMPORT_DECL __declspec(dllimport)
         #endif
    #else
         #ifdef __cplusplus
           #define DLL_EXPORT_C_DECL extern "C"
           #define DLL_IMPORT_C_DECL extern "C"
           #define DLL_EXPORT_DECL extern
           #define DLL_IMPORT_DECL extern
           #define DLL_EXPORT_CLASS_DECL
           #define DLL_IMPORT_CLASS_DECL
      #else
           #define DLL_EXPORT_DECL extern
           #define DLL_IMPORT_DECL extern
      #endif
    #endif
 

   "something.h"中包括：
    #include "common.h"
    #ifdef SOME_EXPORTS
       #define SOME_CLASS DLL_EXPORT_CLASS_DECL
       #define SOME_API   DLL_EXPORT_DECL
    #else
       #define SOME_CLASS DLL_IMPORT_CLASS_DECL
       #define SOME_API   DLL_IMPORT_DECL
    #endif

    class SOME_CLASS MyClass {}
    SOME_API void MyFunc() {}

    "something.cpp"实现MyClass，头文件包括：
    #define  SOME_EXPORTS
    #include "something.h"

      小鸡射手一直采用这种方法export DLL中的类，如Plugin的实现一文中谈到的C++实现Plugin。当然这也是借鉴OpenSource的做法的。