基本原則：

在展開(kāi)當(dāng)前宏函數(shù)時(shí)，如果形參有#或##則不進(jìn)行宏參數(shù)的展開(kāi)，否則先展開(kāi)宏參數(shù)，再展開(kāi)當(dāng)前宏。

#是在定義兩邊加上雙引號(hào)

#define _TOSTR(s) #sprintf(_TOSTR(test ABC))
printf(_TOSTR("test ABC"));
printf(_TOSTR(_TOSTR(test ABC)));==================
預(yù)編譯結(jié)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##yprintf(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(yù)處理后的結(jié)果：
printf(HiBoy!);
printf(HiBoy!);
printf("HI_BOY");
printf("__ORIGINAL(HI_BOY)");
printf(HI_BOYHI_BOY);
printf("HI_BOY" "HI_BOY");

連續(xù)的兩個(gè)雙引號(hào)會(huì)被忽略掉

以下寫法結(jié)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##yprintf(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(yù)編譯結(jié)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! ");

總結(jié)

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