1、C语言宏定义技巧C语言宏定义技巧(常用宏定义)写好C语言,漂亮的宏定义很重要,使用宏定义可以防止出错,提高可移植性,可读性,方便性 等等。下面列举一些成熟软件中常用得宏定义。1,防止一个头文件被重复包含#ifndef COMDEF_H#define COMDEF_H/头文件内容#endif2,重新定义一些类型,防止由于各种平台和编译器的不同,而产生的类型字节数差异,方便移植。typedef unsigned char boolean; /* Boolean value type. */typedef unsigned long int uint32; /* Unsigned 32 bit va
2、lue */typedef unsigned short uint16; /* Unsigned 16 bit value */typedef unsigned char uint8; /* Unsigned 8 bit value */typedef signed long int int32; /* Signed 32 bit value */typedef signed short int16; /* Signed 16 bit value */typedef signed char int8; /* Signed 8 bit value */下面的不建议使用typedef unsign
3、ed char byte; /* Unsigned 8 bit value type. */typedef unsigned short word; /* Unsinged 16 bit value type. */typedef unsigned long dword; /* Unsigned 32 bit value type. */typedef unsigned char uint1; /* Unsigned 8 bit value type. */typedef unsigned short uint2; /* Unsigned 16 bit value type. */typede
4、f unsigned long uint4; /* Unsigned 32 bit value type. */typedef signed char int1; /* Signed 8 bit value type. */typedef signed short int2; /* Signed 16 bit value type. */typedef long int int4; /* Signed 32 bit value type. */typedef signed long sint31; /* Signed 32 bit value */typedef signed short si
5、nt15; /* Signed 16 bit value */typedef signed char sint7; /* Signed 8 bit value */3,得到指定地址上的一个字节或字#define MEM_B( x ) ( *( (byte *) (x) ) )#define MEM_W( x ) ( *( (word *) (x) ) )4,求最大值和最小值#define MAX( x, y ) ( (x) (y) ? (x) : (y) )#define MIN( x, y ) ( (x) field ) /*lint +e545 */6,得到一个结构体中field所占用的字
6、节数#define FSIZ( type, field ) sizeof( (type *) 0)-field )7,按照LSB格式把两个字节转化为一个Word#define FLIPW( ray ) ( (word) (ray)0) * 256) + (ray)1 )8,按照LSB格式把一个Word转化为两个字节#define FLOPW( ray, val ) (ray)0 = (val) / 256); (ray)1 = (val) & 0xFF)9,得到一个变量的地址(word宽度)#define B_PTR( var ) ( (byte *) (void *) &(var) )#de
7、fine W_PTR( var ) ( (word *) (void *) &(var) )10,得到一个字的高位和低位字节#define WORD_LO(xxx) (byte) (word)(xxx) & 255)#define WORD_HI(xxx) (byte) (word)(xxx) 8)11,返回一个比X大的最接近的8的倍数#define RND8( x ) (x) + 7) / 8 ) * 8 )12,将一个字母转换为大写#define UPCASE( c ) ( (c) = a & (c) = 0 & (c) = 0 & (c) = A & (c) = a & (c) (val
8、) ? (val)+1 : (val)16,返回数组元素的个数#define ARR_SIZE( a ) ( sizeof( (a) ) / sizeof( (a0) ) )17,返回一个无符号数n尾的值MOD_BY_POWER_OF_TWO(X,n)=X%(2n)#define MOD_BY_POWER_OF_TWO( val, mod_by ) ( (dword)(val) & (dword)(mod_by)-1) )18,对于IO空间映射在存储空间的结构,输入输出处理#define inp(port) (*(volatile byte *) (port)#define inpw(port
9、) (*(volatile word *) (port)#define inpdw(port) (*(volatile dword *)(port)#define outp(port, val) (*(volatile byte *) (port) = (byte) (val)#define outpw(port, val) (*(volatile word *) (port) = (word) (val)#define outpdw(port, val) (*(volatile dword *) (port) = (dword) (val)2005-9-9添加19,使用一些宏跟踪调试A N
10、S I标准说明了五个预定义的宏名。它们是:_ L I N E _ F I L E _ D A T E _ T I M E _ S T D C _如果编译不是标准的,则可能仅支持以上宏名中的几个,或根本不支持。记住编译程序也许还提供其它预定义的宏名。_ L I N E _及_ F I L E _宏指令在有关# l i n e的部分中已讨论,这里讨论其余的宏名。_ D AT E _宏指令含有形式为月/日/年的串,表示源文件被翻译到代码时的日期。源代码翻译到目标代码的时间作为串包含在_ T I M E _中。串形式为时:分:秒。如果实现是标准的,则宏_ S T D C _含有十进制常量1。如果它含有
11、任何其它数,则实现是非标准的。可以定义宏,例如:当定义了_DEBUG,输出数据信息和所在文件所在行#ifdef _DEBUG#define DEBUGMSG(msg,date) printf(msg);printf(“%d%d%d”,date,_LINE_,_FILE_)#else#define DEBUGMSG(msg,date)#endif20,宏定义防止使用是错误用小括号包含。例如:#define ADD(a,b) (a+b)用dowhile(0)语句包含多语句防止错误例如:#difne DO(a,b) a+b;a+;应用时:if(.)DO(a,b); /产生错误else解决方法: #difne DO(a,b) doa+b;a+;while(0)
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