C/C + + extern "C."

C/C + + extern "C."

Common styles

extern "C" {...} extern "C" Return-type func-name (type, type) {}extern "C" return-type func-name (type, type); Meaning: in C + +, the source file is compiled in C language.

Example//t_extern_yes.cpp

1. extern "C"
   
2. {
   
3. int f(void)
   
4. {
   
5. return 0;
   
6. }
   
7. }

T_extern_non . cpp

1. int f(void)
   
2. {
   
3. return 0;
   
4. }

Assembly

1. GCC T_extern_non. cpp T_extern_yes. cpp
   
2. Or
3. GCC T_extern_non. cpp t_extern_yes. cpp

Get

1. .file "T_extern_non.cpp"
2. . Text
3. . Align 2
4. . Globl _Z1FV
5. . Type _ Z1FV, @function
6. _Z1FV:
7. . LFB2:
8. pushl%ebp
9. . LCFI0:
10. movl%esp,%ebp
11. . LCFI1:
12. movl $,%eax
13. popl%ebp
14. ret
15. . LFE2:
17. . Globl __gxx_personality_v0
18. . Ident "GCC: (GNU) 4.2.1 (SUSE Linux)"
19. . Section. Note . Gnu-stack, "", @progbits

1. .file "T_extern_yes.cpp"
2. . Text
3. . Align 2
4. . globl F
5. . Type F, @ function
6. f:
7. . LFB2:
8. pushl%ebp
9. . LCFI0:
10. movl%esp,%ebp
11. . LCFI1:
12. movl $,%eax
13. popl%ebp
14. ret
15. . LFE2:
17. . Globl __gxx_personality_v0
18. . Ident "GCC: (GNU) 4.2.1 (SUSE Linux)"
19. . Section. Note. Gnu-stack, "", @progbits

When using Imdiff to see only the above red flag is different, this is the function name compiled id,c++ enriched the content. If you use extern "C", tell the C + + compiler to compile with C, so you can connect the original C file compiled with C. Now simulates a C + + call to the library file.

C + + Call Library

//T_ADD.C

1. int add(int a, int b){
   
2. Return (a+b);
   
3. }

Get the static library file for C T_ADD.O

1. Gcc-c T_ADD.C

Original C-header file

1. #ifndef t_add_c__
2. #define T_ADD_C__
4. int add(int a, int b);
   
6. #endif

Modified to be a header file that can be used by C + +//t_add.h

1. #ifndef t_add_c__
2. #define T_ADD_C__
4. extern "C" int add(int a, int b);
   
6. #endif

Can be referenced by C + + files, such as//main.cpp

2. #include <stdio. h>
   
4. #include "T_add.h"
   
8. int main(void)
   
10. {
    
12. printf("1 + 2 =%d\n", add(1, 2));
    
14. return 0;
    
16. }

Can compile the

1. G++ t_add. o main. C

output

1. 1 + 2 = 3

 

How to use

Of course, the extern "C" way various,

1. Before the function, you can
2. File start end {}hold Live,
3. can also be convenient in #inldue语句加, such as
   1. extern "C" {
      
   2. #include "T_add.h"
      
   3. }

In addition, C + + Transformers will have __cplusplus macro definitions, are generally used in conjunction with

C/C + + extern "C."