预处理器 - 样本 [英] Preprocessor - sample

问题描述

  #include   <   stdio.h  >  
   #define SIZE 10; 
   #define FUDGE SIZE -2; 
   int  main（）
 {
  int  size;  / *  真正使用的尺寸* /  
 size = FUDGE; 
 printf（ 大小为％d \ n，大小）; 
  return （ 0 ）; 
} 

以下程序的o / p大小值是多少？

解决方案

< blockquote>你编译并运行它了吗？

结果不符合预期？

当你自己执行预处理器任务时，它是预期的：

 size = FUDGE; 
  //  替换FUDGE = SIZE -2;  
 size = SIZE  -  < span class =code-digit> 2  ;; 
  //  替换SIZE = 10;  
 size =  10 ; -   2  ;; 

你看错了吗？ #define语句不需要以分号结尾。如果有的话，它也会插入。

1. 你不应该在<$ c $结尾处放置分号c> #define 语句，它们可能会在您的代码中产生不必要的副作用。
2. 在 #define 中使用表达式时出于同样的原因，你应该把它们放在括号中。

#include <stdio.h>
#define SIZE 10;
#define FUDGE SIZE -2;
int main()
{
    int size;/* size to really use */
    size = FUDGE;
    printf("Size is %d\n", size);
    return (0);
}

what is the value of size in o/p for the following program?

解决方案

Did you compile and run it?
And the result is not as expected?
It is as expected when you perform the preprocessor tasks yourself:

size = FUDGE;
// replace FUDGE = SIZE -2;
size = SIZE -2;;
// replace SIZE = 10;
size = 10; -2;;

Did you see your mistake? #define statements need no trailing semicolon. If there is one, it is also inserted.

1. You should not put semi-colons at the end of #define statements, they may have unwanted side effects in your code.
2. When using expressions in #defines you should put them in parentheses, for the same reason.

这篇关于预处理器 - 样本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！