Using "C" function and variables in "C++" code

Question

I need to call "C" function which is having one argument variable "struct" (which is defined in "C" file), from "C++" file.

I used 'extern "C"', but getting linking error.

Please suggest me some way to do it ?

Thanks Priyanshu

"extern C" should be used in CPP file which declaring that function — Chubsdad
– Chubsdad, Commented Sep 6, 2010 at 8:59
@Alexander Rafferty: No, it's not. C++ is mostly a superset of C, but it is not a strict superset. (As a trivial example, a C program that uses variable names that conflict with C++-specific keywords obviously is not legal C++ code.) And that doesn't say much about linking compatibilities anyway. — jamesdlin
– jamesdlin, Commented Sep 6, 2010 at 9:49
@Alexander Rafferty: If you mean most of the language, okay. If you mean most C source files, I disagree. Well-written C code often is not valid C++. For example, in C it's usually recommended not to cast the return value of malloc, but C++ disallows implicit casts from void*. — jamesdlin
– jamesdlin, Commented Sep 6, 2010 at 17:31
Yes, I did mean most of the language. Most C can be modified to fit C++ standards, unless there is far to much source code to rake through. — Alexander Rafferty
– Alexander Rafferty, Commented Sep 6, 2010 at 23:03

Chubsdad · Accepted Answer · 2010-09-06 09:10:58Z

4

Since you have not come back, here is a possible file arrangement and header file you probably should be looking at.

// Here is Header file (myh.h)

struct S{};

#ifdef __cplusplus
extern "C" {
#endif

void fn(S s);

#ifdef __cplusplus
}
#endif

// Here is CPP file (ZCPP.cpp)

#include "myh.h"

int main(){
   S s;
   fn(s);
}

// Here is C file (ZC.c)

#include <stdio.h>
#include "myh.h"

void fn(S s){
   printf("Hi\n");
}

[prompt@test ~]$ g++ zcpp.cpp zc.c

[prompt@test ~]$ ./a.out

Hi

[prompt@test ~]$

answered Sep 6, 2010 at 9:10

Chubsdad

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Comments

Lazer · Accepted Answer · 2010-09-06 17:34:15Z

0

You should read this thread How to mix C and C++ for understanding the ins and outs of mixing C and C++ code.

When done, you can also have a look at the corresponding FQA thread.

answered Sep 6, 2010 at 17:34

Lazer

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