[問題] 請問一個.cpp檔與.h中define的作用
開發平台(Platform): (Ex: VC++, GCC, Linux, ...)
GCC
問題(Question)：
在業界的code裡面看到的普遍寫法
在xxx.cpp裡:
#define _XXX_CPP_
void FUNCTION(void)
{
......
}
#under _XXX_CPP_
在對應的xxx.h裡:
#ifndef _XXX_H_
#define _XXX_H_
#ifdef _XXX_CPP_
#define INTERFACE
#else
#define INTERFACE extern
#endif
INTERFACE void FUNCTION(void);
#endif
請問綠色的部份，為什麼要特地這樣寫呢？
如果其它檔案，例如ooo.cpp想要使用FUNCTION()
就不能#include "xxx.h"，compiler會有問題
(compiler會說INTERFACE被定義過了，因為ooo.cpp會走#else，而xxx.cpp會走#ifdef)
因此而必須改用extern FUNCTION
但如果要extern FUNCTION，應該不需要去特地#define INTERFACE吧？
謝謝
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※ 編輯: Zoxge 來自: 123.195.197.207 (08/12 00:33)
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