寫好C語言，漂亮的宏定義很重要，使用宏定義可以防止出錯(cuò)，提高可移植性，可讀性，方便性等等。下面列舉一些成熟軟件中常用的宏定義。

1. 防止一個(gè)頭文件被重復(fù)包含

1#ifndef?COMDEF_H
2#define?COMDEF_H
3//頭文件內(nèi)容
4#endif

2. 重新定義一些類型，防止由于各種平臺和編譯器的不同，而產(chǎn)生的類型字節(jié)數(shù)差異，方便移植。

1typedef?unsigned?char?boolean;?/*?Boolean?value?type.?*/
2typedef?unsigned?long?int?uint32;?/*?Unsigned?32?bit?value?*/
3typedef?unsigned?short?uint16;?/*?Unsigned?16?bit?value?*/
4typedef?unsigned?char?uint8;?/*?Unsigned?8?bit?value?*/
5typedef?signed?long?int?int32;?/*?Signed?32?bit?value?*/
6typedef?signed?short?int16;?/*?Signed?16?bit?value?*/
7typedef?signed?char?int8;?/*?Signed?8?bit?value?*/

下面的不建議使用

1typedef?unsigned?char?byte;?/*?Unsigned?8?bit?value?type.?*/
2typedef?unsigned?short?word;?/*?Unsinged?16?bit?value?type.?*/
3typedef?unsigned?long?dword;?/*?Unsigned?32?bit?value?type.?*/
4typedef?unsigned?char?uint1;?/*?Unsigned?8?bit?value?type.?*/
5typedef?unsigned?short?uint2;?/*?Unsigned?16?bit?value?type.?*/
6typedef?unsigned?long?uint4;?/*?Unsigned?32?bit?value?type.?*/
7typedef?signed?char?int1;?/*?Signed?8?bit?value?type.?*/
8typedef?signed?short?int2;?/*?Signed?16?bit?value?type.?*/
9typedef?long?int?int4;?/*?Signed?32?bit?value?type.?*/
10typedef?signed?long?sint31;?/*?Signed?32?bit?value?*/
11typedef?signed?short?sint15;?/*?Signed?16?bit?value?*/
12typedef?signed?char?sint7;?/*?Signed?8?bit?value?*/

3. 得到指定地址上的一個(gè)字節(jié)或字

1#define?MEM_B(?x?)?(?*(?(byte?*)?(x)?)?)
2#define?MEM_W(?x?)?(?*(?(word?*)?(x)?)?)

4. 求最大值和最小值

1#define?MAX(?x,?y?)?(?((x)?>?(y))???(x)?:?(y)?)
2#define?MIN(?x,?y?)?(?((x)?

5. 得到一個(gè)field在結(jié)構(gòu)體(struct)中的偏移量

1#define?FPOS(?type,?field?)?\
2/*lint?-e545?*/?(?(dword)?