error在c语言的用法,C语言进阶：23、#error和#line的用法

#error用于生成一个编译错误消息

用法：#error message

message不需要用双引号包围#error编译指示字用于自定义程序员特有的编译错误消息，类似的，#warning用于生成编译警告。

#error是一种预编译指示字，可用于提示编译条件是否满足#ifndef __cpluscplus //C++内置的宏 通过检测这个宏的存在，来进行错误提醒。

#error This file should be processed with C++ compiler

#endif

编译过程中任意错误信息意味着无法生成最终的可执行程序。#include

void f()

{

#if ( PRODUCT == 1 )

printf("This is a low level product!\n");

#elif ( PRODUCT == 2 )

printf("This is a middle level product!\n");

#elif ( PRODUCT == 3 )

printf("This is a high level product!\n");

#else

#warning The macro Product is NOT defined! //#error The macro Product is NOT defined!

#endif

}

int main()

{

f();

printf("1. Query Information.\n");

printf("2. Record Information.\n");

printf("3. Delete Information.\n");

#if ( PRODUCT == 1 )

printf("4. Exit.\n");

#elif ( PRODUCT == 2 )

printf("4. High Level Query.\n");

printf("5. Exit.\n");

#elif ( PRODUCT == 3 )

printf("4. High Level Query.\n");

printf("5. Mannul Service.\n");

printf("6. Exit.\n");

#endif

return 0;

}

运行输出：~/will$ gcc 23-2.c

23-2.c: In function ‘f’:

23-2.c:12: error: #error The macro Product is NOT defined!

将#error修改为warnning：~/will$ gcc 23-2.c

23-2.c: In function ‘f’:

23-2.c:12: warning: #warning The macro Product is NOT defined!

~/will$

~/will$ ./a.out

1. Query Information.

2. Record Information.

3. Delete Information.

条件编译：~/will$ gcc -DPRODUCT=3 23-2.c

~/will$ ./a.out

This is a high level product!

1. Query Information.

2. Record Information.

3. Delete Information.

4. High Level Query.

5. Mannul Service.

6. Exit.#line预处理器指示字

#line用于强制指定新的行号和编译文件名，并对源程序的代码重新编号。

用法：#line number filename

filename 可省略

#line编译指示字的本质是重定义 __FILE__ 和 __LINE__

行号从重新定义的文件名起始计算。(从最靠近主函数的地方开始计算)#include

// The code section is written by A.

// Begin

#line 1 "a.c"

// End

// The code section is written by B.

// Begin

#line 1 "b.c"

// End

// The code section is written by Delphi.

// Begin

#line 1 "willwilling's.c"

int main()

{

printf("%s : %d\n", __FILE__, __LINE__);

printf("%s : %d\n", __FILE__, __LINE__);

return 0;

}

// End

编译运行：~/will$ gcc 23-3.c

~/will$ ./a.out

willwilling's.c : 5

willwilling's.c : 7

小结：

#error用于自定义一条编译错误

#warning用于自定义一条编译警告信息

#error和#warning常用于条件编译的情形

#line用于强制指定新的行号和编译文件名。