c能编译的函数c++却不能编译

 

大神的链接：https://www.cnblogs.com/skynet/archive/2010/07/10/1774964.html

问题来源：编译简单的服务端程序，结果出现错误

$ g++ UNIX_TEXT.c -lunp
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x26): undefined reference to `Socket(int, int, int)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x26): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Socket(int, int, int)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x98): undefined reference to `Listen(int, int)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x98): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Listen(int, int)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0xbb): undefined reference to `Accept(int, sockaddr*, int*)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0xbb): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Accept(int, sockaddr*, int*)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x110): undefined reference to `Write(int, void*, unsigned long)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x110): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Write(int, void*, unsigned long)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x11d): undefined reference to `Close(int)'
/tmp/cciCxwbF.o:UNIX_TEXT.c:(.text+0x11d): relocation truncated to fit: R_X86_64_PC32 against undefined symbol `Close(int)'
collect2: error: ld returned 1 exit status

同一个程序用g++编译就无法通过，但是用gcc却可以正常运行。

原因：c++允许函数重载，c不允许。所以两者的编译和链接规则不同。

解决方法：怎样实现混合编译，c++中使用c的函数；c中使用c++的函数

修改unp.h文件

      开头：                                                                                                            

1 #ifndef    __unp_h
2 #define    __unp_h
3 
4 #ifdef __cplusplus
5 extern "C"
6 {
7 #endif

     结尾：

1 #ifdef __cplusplus
2 }
3 #endif
4 
5 #endif    /* __unp_h */