变体宏

Question

我遇到了涉及可变参数宏的代码,我想知道这意味着什么

#define DECLARE_LEGACY_TYPES(...)  //This all of the macro - I am not holding out on anything

现在有这个类

Header file: .h
    namespace LG_Wrapper
    {
        template <LG_Thread Thread>
        class EffectApplication : public ktApplication
        {
        public:
        static EffectApplication<Thread>& GetInstance();
        protected:
            .....
            .....
            static boost::recursive_mutex mResource;
          }
    }

    DECLARE_LEGACY_TYPES(EffectApplication);  <---- What does this do ?

我想知道宏有什么影响？

更新: 我收到了很多关于此的问题,因为这个问题给人的印象是我没有发布宏的全部内容.宏没有更多内容了.我希望有.这个问题是有关本该被关闭.这个宏字面上刚刚结束(...)

 #define DECLARE_LEGACY_TYPES(...)

但是没有.这就是我在这里的原因之一,因为我不知道如何处理这种情况.这个宏有效吗？

更多信息:

这是我在另一个文件中使用的,我在项目设置中使用以下定义

LG_WRAPPER_EXPORTS
LG_THREAD_NAME=GAME

以下是代码

namespace LG_Wrapper
{

enum LG_Thread
{
    GAME,
    OTHER
};


/*
If the library itself is including this file
*/
#ifdef LG_WRAPPER_EXPORTS

    #ifndef LG_THREAD_NAME
        #error You must define LG_THREAD_NAME!
    #endif

    //Legacy types should not be used internally
    #define DECLARE_LEGACY_TYPES(...)

#else // LG_WRAPPER_EXPORTS

    //Legacy typenames are provided for convenience to the client
    #define DECLARE_LEGACY_TYPES(ClassType) \
        typedef LG_Wrapper::##ClassType##<LG_Wrapper::GAME>             ClassType; \

#endif // LG_WRAPPER_EXPORTS

} 

Answer 1

这实际上很常见,但它取决于您查看的其他代码中未提及的其他代码:

#if USING_OLD_COMPILER //when using an older compiler, use this to declare legacy types
#define DECLARE_LEGACY_TYPES(...) STUFF(__VA_ARGS__)    
#else //new compiler doesn't have to do anything special
#define DECLARE_LEGACY_TYPES(...)
#endif


//in older compilers we had to declare legacy types for this
//newer compilers don't need this step, so this does nothing at all in them.
DECLARE_LEGACY_TYPES(EffectApplication);

我实际上并不知道这个宏,所以我不知道它的实际用途.但是,通常会看到没有类似技巧定义的宏.