C语言中宏定义的用法与意义.doc

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 #endif 2，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?value?*/ 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??unsigned?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.?*/ typedef??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??????sint15;???????/*?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)??(y))???(x)?:?(y)?) 5，得到一个field在结构体(struct)中的偏移量 #define?FPOS(?type,?field?)?\ /*lint?-e545?*/?(?(dword)?((?type?*)?0)-?field?)?/*lint?+e54