指向#define的指针 [英] Pointer to #define
问题描述
我只是想知道是否有可能引用#define常量的指针。如果是，该怎么办？
I was just curious to know if it is possible to have a pointer referring to #define constant. If yes, how to do it?
推荐答案
#define 指令是预处理器的指令，这意味着预处理器会在编译任何内容之前调用它。
The #define directive is a directive to the preprocessor, meaning that it is invoked by the preprocessor before anything is even compiled.
因此，如果您输入：
#define NUMBER 100
然后稍后键入：
int x = NUMBER;
您的编译器实际看到的内容就是：
What your compiler actually sees is simply:
int x = 100;
基本上就像您在字处理器中打开源代码一样并进行查找/替换，将每次出现的 NUMBER替换为 100。因此，您的编译器不知道 NUMBER 的存在。只有预编译预处理器知道 NUMBER 的含义。
It's basically as if you had opened up your source code in a word processor and did a find/replace to replace each occurrence of "NUMBER" with "100". So your compiler has no idea about the existence of NUMBER. Only the pre-compilation preprocessor knows what NUMBER means.
因此，如果您尝试使用 NUMBER 的地址，则编译器会认为您尝试使用整数文字常量的地址，该地址无效。
So, if you try to take the address of NUMBER, the compiler will think you are trying to take the address of an integer literal constant, which is not valid.
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