C ++包括保护 [英] C++ include guard

问题描述

所以我知道如何在标准的

So I know how to place an include guard in my own header files with the standard

#ifndef ...
#define ...

现在，我的问题是关于包含不是我自己的库。将是一个很好的例子。我有一个头文件需要使用字符串，所以我做以下

Now, My question is about including libraries that are not my own. would be a good example. I have a header file which requires the use of string, so I do the following

foo.h

#ifndef FOO_H
#define FOO_H

#include <string>

... code etc ...

#endif

现在，如果我有另一个头文件叫..让我们说， bar.h ，它还要求使用 string> ，如何防止多次包含？ STL库是否已经包含保护程序？

Now, if I have another header file called.. lets say, bar.h, which ALSO requires the use of <string>, how can i prevent multiple inclusions? Does the STL already have include guards in place?

推荐答案

#ifndef _GLIBCXX_STRING
#define _GLIBCXX_STRING 1

这来自gcc的

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