这个宏包装展示了什么概念? [英] What concept is being exhibited in this macro wrapping?

问题描述

一堆代码刚刚交给我，我对标头中的宏感到困惑.我不明白它们的用途:

A bunch of code just got handed over to me and I got baffled by macros in the header. I could not understand what they are for:

#define WRAPPER_MACRO(symbol) symbol
#define ANOTHER_SYMBOL WRAPPER_MACRO(ANOTHER_SYMBOL)
#define PREFIXED_ANOTHER_SYMBOL WRAPPER_MACRO(PFX_ANOTHER_SYMBOL)

为什么这样做?有什么好处?

Why do this? What is the benefit?

这不是我代码库中的实际逐字代码，但它具有相同的模板.我只是替换了宏名.

This is not the actual verbatim code from my codebase but it has the same template. I just replaced macro names.

推荐答案

正如@Michael所说，我们需要确定真正的宏才能知道.但是，如果没有它们，我愿意做出一些可能会帮助您的猜测.

As @Michael said, we'll need to see the real macros to know for sure. But without them, I'm willing to take a few guesses that might help you out.

宏嵌套可能是字符串化.这部分代码来自我维护的代码库:

The macro nesting is probably a stringification thing. This bit of code is from a codebase I maintain:

// As per http://gcc.gnu.org/onlinedocs/cpp/Stringification.html:
// "If you want to stringify the result of expansion of a macro argument, you
// have to use two levels of macros."
#ifndef STRINGIFY
#define STRINGIFY(s) TOSTRING(s)
#define TOSTRING(s) #s
#endif

我还猜测您的PREFIXED_ANOTHER_SYMBOL宏正在执行与此类似的操作，使用#或##预处理程序指令将某个符号添加到您喂入宏的任何内容之前.

I'm also guessing your PREFIXED_ANOTHER_SYMBOL macro is doing something similar to this, using the # or ## preprocessor directives to prepend a certain symbol to whatever you feed the macro.

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