如何防止.h文件中的函数的多个定义 [英] How to prevent multiple definitions of functions from .h file

问题描述

我有一个基本的Core.h文件和许多其他的.cpp和.h文件，让我们说 - （a.cpp，ah，b.cpp，bh，c.cpp，ch）

I have a base Core.h file and many other .cpp and .h files, lets say - (a.cpp, a.h, b.cpp, b.h, c.cpp, c.h)

现在，我将Core.h文件包含在所有.h文件（ieah，bh和ch）中。在c.cpp中，我包括a.h和b.h文件。结果Core.h文件被包含两次，我得到的错误

Now, I have included Core.h file in all .h files (i.e. a.h, b.h and c.h) . And in c.cpp, I am including a.h and b.h file. As a result Core.h file is getting included two times and I am getting error of kind

/tmp/ccq7z6jY.o: In function `fileID2fileName(int)':
/home/Core.h:20: multiple definition of `fileID2fileName(int)'
/tmp/cciNkoqe.o:/home/Core.h:20: first defined here
/tmp/ccravW4I.o: In function `fileID2fileName(int)':
/home/Core.h:20: multiple definition of `fileID2fileName(int)'
/tmp/cciNkoqe.o:/home/Core.h:20: first defined here
/tmp/ccdUjOEu.o: In function `fileID2fileName(int)':
/home/Core.h:20: multiple definition of `fileID2fileName(int)'
/tmp/cciNkoqe.o:/home/Core.h:20: first defined here
collect2: ld returned 1 exit status

推荐答案

问题不是包括警卫：他们不会帮助跨越不同的翻译单位

The problem is not include guards : they won't help across different translation units.

您需要：

• a .cpp文件并只在您的.h文件中声明


• 在标题中定义 inline b
• 在标头中定义 static

• define your functions one time each in a .cpp file and only declare them in your .h file
• define them inline in your headers
• define them static in your headers

正如StackedCrooked ，包括静态函数定义但不使用它将导致适当的编译器警告。

As StackedCrooked rightly mentions, including the static function definition but not using it will result in an appropriate compiler warning.

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