如何使用C预处理程序连接字符串并在其中加点？ [英] How to concatenate strings with C preprocessor with dots in them?

问题描述

我已经阅读了以下问题，答案似乎很明确：
如何连接两次使用C预处理程序，然后按 arg ## _ ## MACRO中的宏进行扩展？

I've read the following question and the answer seems clear enough: How to concatenate twice with the C preprocessor and expand a macro as in "arg ## _ ## MACRO"?

但是如果VARIABLE在结束？

But what if VARIABLE has a dot at the end?

我正在尝试创建一个简单的宏，该宏可在结构体中递增计数器以进行调试。即使没有上述问题的帮助，我也可以轻松地做到这一点，只需

I'm trying to do a simple macro that increments counters in a struct for debugging purposes. I can easily do this even without the help from the above question simply with

#ifdef DEBUG
#define DEBUG_INC_COUNTER(x) x++
#endif

并称呼它

DEBUG_INC_COUNT(debugObj.var1);

但添加 debugObj。对每个宏来说似乎都是多余的。但是，如果我尝试串联：

But adding "debugObj." to every macro seems awfully redundant. However if I try to concatenate:

#define VARIABLE debugObj.
#define PASTER(x,y) x ## y++
#define EVALUATOR(x,y)  PASTER(x,y)
#define DEBUG_INC_COUNTER(x) EVALUATOR(VARIABLE, x)
DEBUG_INC_COUNTER(var)

gcc -E macro.c

我得到

macro.c:6:1: error: pasting "." and "var" does not give a valid preprocessing token

所以我应该如何更改它，以便

So how should I change this so that

DEBUG_INC_COUNTER(var);

生成

debugObj.var++;

？

推荐答案

忽略 ## ;仅在要连接字符串时才需要。由于参数不是字符串，因此它们之间的空格无关紧要（ debugObj。var1 与 debugObj.var1 ）。

Omit the ##; this is only necessary if you want to join strings. Since the arguments aren't strings, the spaces between them don't matter (debugObj . var1 is the same as debugObj.var1).

这篇关于如何使用C预处理程序连接字符串并在其中加点？的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！