C近拍令牌级联涉及的变量 - 这可能吗？ [英] C Macro Token Concatenation involving a variable - is it possible?

问题描述

我试图定义一个宏来生成令牌名称，包含一个变量。

I'm trying to define a macro to generate a token name, containing a variable.

基本上，我想是这样的：

Basically, what I'm trying is this:

#define GLUER(x,y,z) x##y##z
#define PxDIR(x) GLUER(P,x,DIR)

int main() {
  int port;
  port = 2;
  PxDIR(port) |= 0x01;
}

我希望能产生上述声明令牌P2DIR，但根据我的编译器的输出，它的生成令牌PportDIR，这不是我想要的东西。任何帮助这里？或者就是我试图做不可能的？

I'm hoping to generate the token P2DIR in the above statement, but according to my compiler output, it's generating the token PportDIR, which is NOT what I wanted. Any help here? Or is what I'm attempting to do impossible?

推荐答案

我不认为你想做什么是可能的。 C宏是真正的编译之前展开preprocessor宏。变量端口，不被设置到运行时。

I don't think what you're trying to do is possible. C macros are really preprocessor macros that are expanded before compilation. The variable port, doesn't get set until runtime.

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