从接触 C 语言时, 我就不大喜欢宏; 但为了看懂别人的代码也不得不去了解.
宏可定义在源程序的任意位置, 但一般放在 .data 前面.
有些简单的宏可以用 equ、textequ 或 = 来代替, 但宏有更复杂的功能.
"宏" 的本质是 "替换", 但又像极了 "子过程";
所以即有宏过程(macro procedure)、也有宏函数(macro function).
它既以有参数(可以是: 常数、变量、寄存器、指令、表达式), 有时也需要像子过程一样声明.
宏可以指定哪些参数是必须的, 还可以给参数默认值.
宏可以包含数据(.data)和代码(.code)、还可以嵌套.
宏中的注释使用 ;; 如果只用 ; 将会被一起替换到代码中.
宏的功能很强大, 现在常用的 PrintDec、PrintHex、PrintString、PrintText 等等都是宏.
再强大它也只是 "文本替换".
"宏" 和 "子程序" 相比:
1、宏展开后顺序执行, 不像调用子程序跳来跳去, 这样程序会更 "快";
2、宏展开后会让代码量增大, 导致程序变 "大".
一个简单的宏:
; Test34_1.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib ;定义一个 mExit 宏 mExit macro PrintLine ret endm .code sum proc v1, v2, v3 mov eax, v1 add eax, v2 add eax, v3 ret sum endp ; main proc invoke sum, 11, 22, 33 PrintDec eax ;66 ;PrintLine ;ret mExit ;mExit 将被替换为上面两行代码 main endp end main
一个代替求和函数的宏:
; Test34_2.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib mSum macro v1, v2, v3 mov eax, v1 add eax, v2 add eax, v3 endm .code main proc mSum 11, 22, 33 PrintDec eax ;66 PrintLine mSum 11, 22, 33, 44, 55 ;多余的参数会被忽略 PrintDec eax ;66 PrintLine ret main endp end main
宏参数的默认值:
; Test34_3.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib ;参数 v1、v2 通过 REQ 标识说明是必备参数 ;参数 v3、v4 给出了默认值 mSum macro v1:req, v2:req, v3:=<33>, v4:=<44> mov eax, v1 add eax, v2 add eax, v3 add eax, v4 endm .code main proc mSum 11, 22 PrintDec eax ;110 PrintLine ret main endp end main
EXITM: 退出宏
; Test34_4.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib mPrint macro PrintText '第一行' PrintText '第二行' exitm PrintText '第三行' endm .code main proc mPrint ;只会输出前两行 ret main endp end main
PURGE: 取消宏
; Test34_5.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib mPrint macro PrintText '第一行' PrintText '第二行' PrintText '第三行' PrintLine endm .code main proc mPrint mPrint purge mPrint ;可用逗号隔开取消多个宏 mPrint ;这个宏不会展开了 ret main endp end main
宏中 local 的使用:
; Test34_6.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib ;从三个数中求最大数的宏 mMax macro v1, v2, v3 LOCAL L1, L2 ;;如没有这句, 宏在多次展开时会让 L1、L2 重名, 这样宏会把标号名称协调好 mov eax, v1 cmp eax, v2 jge L1 mov eax, v2 L1: cmp eax, v3 jge L2 mov eax, v3 L2: endm .code main proc mMax 11, 22, 33 PrintDec eax ;33 ret main endp end main
灵活的参数, 用到 & 操作符:
; Test34_7.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib ;求最数中的最大值: mMax macro v1, v2 LOCAL L1 mov eax, v1 cmp eax, v2 jge L1 mov eax, v2 L1: endm ;求最数中的最小值: mMin macro v1, v2 LOCAL L1 mov eax, v1 cmp eax, v2 jle L1 mov eax, v2 L1: endm ;能把 JGE 或 JLE 做参数: mCom1 macro XX, v1, v2 LOCAL L1 mov eax, v1 cmp eax, v2 XX L1 mov eax, v2 L1: endm ;能通过参数让 J*E 变为 JGE 或 JLE: mCom2 macro X, v1, v2 LOCAL L1 mov eax, v1 cmp eax, v2 J&X&E L1 ;;这里用到特殊操作符 & mov eax, v2 L1: endm .code main proc mMax 11, 22 PrintDec eax ;22 mMin 11, 22 PrintDec eax ;11 mCom1 JGE, 11, 22 PrintDec eax ;22 mCom1 JLE, 11, 22 PrintDec eax ;11 mCom2 G, 11, 22 PrintDec eax ;22 mCom2 L, 11, 22 PrintDec eax ;11 ret main endp end main
特殊操作符: &、<>、%、!
& ;替换操作符 <> ;字符串传递操作符 % ;表达式操作符, 也用于得到一个变量或常量的值 ! ;转义操作符
; Test34_8.asm .386 .model flat, stdcall include windows.inc include kernel32.inc include masm32.inc include debug.inc includelib kernel32.lib includelib masm32.lib includelib debug.lib ;自定义的宏 mPrint macro Text PrintText '* &Text& *' endm .code main proc ;该宏会把参数直接替换过去 mPrint 1234 ;* 1234 * ;要保证参数的完整应该使用 <> mPrint 12,34 ;* 12 * mPrint <12,34> ;* 12,34 * ;需要计算结果应该使用 %() mPrint 34+12 ;* 34+12 * mPrint %(34+12) ;* 46 * ;用到 &、<、>、%、! 应该使用 ! 转义 mPrint 10 !% 2 = %(10/2)!! ;* 10 % 2 = 5! * ret main endp end main