C中的宏的使用(宏嵌套/宏展開/可變參數宏) 原

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

#define _TOSTR(s) #s

printf(_TOSTR(test ABC))
printf(_TOSTR("test ABC"));
printf(_TOSTR(_TOSTR(test ABC)));

==================
預編譯結果：
printf("test ABC")
printf("\"test ABC\"");
printf("_TOSTR(test ABC)");

##是原樣代入

 

#define HI_BOY HiBoy!
#define __ORIGINAL(s) s
#define _TOSTR(s) #s
#define STR_CONCAT(x, y) x##y

printf(HI_BOY);
printf(__ORIGINAL(HI_BOY));
printf(_TOSTR(HI_BOY));
printf(_TOSTR(__ORIGINAL(HI_BOY)));
printf(STR_CONCAT(HI_BOY, HI_BOY ));
printf(STR_CONCAT(_TOSTR(HI_BOY), _TOSTR(HI_BOY) ));
===========================================================
預處理後的結果：
printf(HiBoy!);
printf(HiBoy!);
printf("HI_BOY");
printf("__ORIGINAL(HI_BOY)");
printf(HI_BOYHI_BOY);
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：

printf("this is a test sentence. are you ok?\n");
printf("this is a test ""sentence."" are you ok?\n");
printf("this is a test sentence."   " are you ok?\n");
printf("this is a"           " test ""sentence. are"" you ok?\n");

==============
this is a test sentence. are you ok?
this is a test sentence. are you ok?
this is a test sentence. are you ok?
this is a test sentence. are you ok?

嵌套

#define  QUOTATION "
#define HI_BOY HiBoy!
#define __ORIGINAL(s) s
#define _TOSTR(s) #s
#define STR_CONCAT(x, y) x##y

printf(HI_BOY);
printf(__ORIGINAL(HI_BOY));
printf(_TOSTR(HI_BOY));
printf(_TOSTR(__ORIGINAL(HI_BOY)));
printf(STR_CONCAT(HI_BOY, HI_BOY ));
printf(STR_CONCAT( _TOSTR(HI_BOY), _TOSTR(HI_BOY) ));
printf(                  STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ));
printf(           _TOSTR(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) )));
printf(_TOSTR(__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))));
printf(           ""(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))"");
printf(_TOSTR(__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))));
printf(           QUOTATION(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))QUOTATION);
printf(           QUOTATION STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) )QUOTATION);


==================================================
預編譯結果：
printf(HiBoy!);
printf(HiBoy!);
printf("HI_BOY");
printf("__ORIGINAL(HI_BOY)");
printf(HI_BOYHI_BOY);
printf("HI_BOY" "HI_BOY");
printf(                  HiBoy!HiBoy!);
printf(           "STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) )");
printf("__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))");
printf(           ""(HiBoy!HiBoy!)"");
printf("__ORIGINAL(STR_CONCAT( __ORIGINAL(HI_BOY), __ORIGINAL(HI_BOY) ))");
printf(           "(HiBoy!HiBoy!)");
printf(           " HiBoy!HiBoy! ");

參考

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