C中的宏的使用(宏嵌套/宏展開/可變參數宏)

基本原則：

在展開當前宏函數時，如果形參有#或##則不進行宏參數的展開，否則先展開宏參數，再展開當前宏。

#是在定義兩邊加上雙引號

1.  
   #define _TOSTR(s) #s
2.  
    
3.  
   printf(_TOSTR(test ABC))
4.  
   printf(_TOSTR("test ABC"));
5.  
   printf(_TOSTR(_TOSTR(test ABC)));
6.  
    
7.  
   ==================
8.  
   預編譯結果：
9.  
   printf("test ABC")
10.  
    printf("\"test ABC\"");
11.  
    printf("_TOSTR(test ABC)");

##是原樣代入

 

1.  
   #define HI_BOY HiBoy!
2.  
   #define __ORIGINAL(s) s
3.  
   #define _TOSTR(s) #s
4.  
   #define STR_CONCAT(x, y) x##y
5.  
    
6.  
   printf(HI_BOY);
7.  
   printf(__ORIGINAL(HI_BOY));
8.  
   printf(_TOSTR(HI_BOY));
9.  
   printf(_TOSTR(__ORIGINAL(HI_BOY)));
10.  
    printf(STR_CONCAT(HI_BOY, HI_BOY ));
11.  
    printf(STR_CONCAT(_TOSTR(HI_BOY), _TOSTR(HI_BOY) ));
12.  
    ===========================================================
13.  
    預處理後的結果：
14.  
    printf(HiBoy!);
15.  
    printf(HiBoy!);
16.  
    printf("HI_BOY");
17.  
    printf("__ORIGINAL(HI_BOY)");
18.  
    printf(HI_BOYHI_BOY);
19.  
    printf("HI_BOY" "HI_BOY");

連續的兩個雙引號會被忽略掉

以下寫法結果一樣：

1.  
   printf("this is a test sentence. are you ok?\n");
2.  
   printf("this is a test ""sentence."" are you ok?\n");
3.  
   printf("this is a test sentence." " are you ok?\n");
4.  
   printf("this is a" " test ""sentence. are"" you ok?\n");
5.  
    
6.  
   ==============
7.  
   this is a test sentence. are you ok?
8.  
   this is a test sentence. are you ok?
9.  
   this is a test sentence. are you ok?
10.  
    this is a test sentence. are you ok?

嵌套

1.  
   #define QUOTATION "
2.  
   #define HI_BOY HiBoy!
3.  
   #define __ORIGINAL(s) s
4.  
   #define _TOSTR(s) #s
5.  
   #define STR_CONCAT(x, y) x##y
6.  
    
7.  
   printf(HI_BOY);
8.  
   printf(__ORIGINAL(HI_BOY));
9.  
   printf(_TOSTR(HI_BOY));
10.  
    printf(_TOSTR(__ORIGINAL(HI_BOY)));
11.  
    printf(STR_CONCAT(HI_BOY, HI_BOY ));
12.  
    printf(STR_CONCAT( _TOSTR(HI_BOY), _TOSTR(HI_BOY) ));
13.  
    printf( STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ));
14.  
    printf( _TOSTR(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) )));
15.  
    printf(_TOSTR(__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))));
16.  
    printf( ""(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))"");
17.  
    printf(_TOSTR(__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))));
18.  
    printf( QUOTATION(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))QUOTATION);
19.  
    printf( QUOTATION STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) )QUOTATION);
20.  
     
21.  
     
22.  
    ==================================================
23.  
    預編譯結果：
24.  
    printf(HiBoy!);
25.  
    printf(HiBoy!);
26.  
    printf("HI_BOY");
27.  
    printf("__ORIGINAL(HI_BOY)");
28.  
    printf(HI_BOYHI_BOY);
29.  
    printf("HI_BOY" "HI_BOY");
30.  
    printf( HiBoy!HiBoy!);
31.  
    printf( "STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) )");
32.  
    printf("__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))");
33.  
    printf( ""(HiBoy!HiBoy!)"");
34.  
    printf("__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))");
35.  
    printf( "(HiBoy!HiBoy!)");
36.  
    printf( " HiBoy!HiBoy! ");

參考

 https://blog.csdn.net/Pillary/article/details/53705158

 

轉載於:https://my.oschina.net/SamXIAO/blog/2877664