包含路径的字符串连接 [英] String concatenation for include path

问题描述

有没有办法连接2个字符串文字形成包含路径？

代码存根：

  #define INCLUDE_DIR/ include
 #include INCLUDE_DIR/dummy.h
  

查看此问题，答案指向不同的方向（编译器命令行）。有人提到这里似乎不可能，但我想知道这个话题是否已经挖得足够。

（我有一个使用案例，这是相关的，请只集中你的回答/评论这个问题。）

解决方案

这似乎是不可能的。我会在这里报告相关部分，从 Eric Postpischil的回答（他没有

编译器将在 #include line（per C
2011 [N1570] 6.10.2 4），但是语义没有完全定义，
不能用于连接文件路径组件，而不需要额外的
帮助C实现。所有这些允许你
do是一些简单的替换，提供一个完整的路径，例如：

  define MyPath../../path/to/my/file.h
 #include MyPath 
  


< blockquote>



链接到文档。特别是这一部分对于便携式解决方案没有什么希望：

在
a之间使用一系列预处理令牌的方法< 和> 预处理令牌对或一对字符
组合到单个标题名称预处理令牌是
实现定义。





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为了完整起见，您可以使用 http://stackoverflow.com/a/ 27830271/2436175 。我会调查，当我有一会儿...

Is there a way to concatenate 2 strings literals to form an include path?

Code stub:

#define INCLUDE_DIR "/include"
#include INCLUDE_DIR "/dummy.h"

Looking at this question, the answers point in a different direction (compiler command line). It is mentioned here that it is seemingly not possible, but I wonder if the topic has been dug enough.

(I do have an use case in which this is relevant, please focus your answers/comments on this question only.)

解决方案

It really seems this is not possible. I will report here the relevant section from Eric Postpischil's answer (he doesn't seem to be active anymore).

The compiler will do macro replacement on an #include line (per C 2011 [N1570] 6.10.2 4), but the semantics are not fully defined and cannot be used to concatenate file path components without additional assistance from the C implementation. So about all this allows you to do is some simple substitution that provides a complete path, such as:

#define MyPath "../../path/to/my/file.h"
#include MyPath

Link to documentation. In particular this section doesn't leave much hope for portable solutions:

The method by which a sequence of preprocessing tokens between a < and a > preprocessing token pair or a pair of " characters is combined into a single header name preprocessing token is implementation-defined.

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For completeness, maybe something can be tried using http://stackoverflow.com/a/27830271/2436175. I'll investigate that when I have a moment...

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