Problem with EXTERN "C"

Hello,

I'm a a pretty new programmer just beginning to play around with C and C++. I use Linux and am compiling with gcc/g++ 4.3.2 however I'm coming across a strange problem that I just can't resolve.

I'm trying to write a simple program to just see the possibilities of calling C++ code from C. The main() function is in C :

#include <stdio.h>
#include <stdlib.h>
#include "cpp_main.h"

/*
 * 
 */
int main(int argc, char** argv) {
    int return_value;
    return_value = cpp_main(argc,argv);
    return (return_value);
}

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The function cpp_main() is written in C++, and is in file cpp_main.cpp :

#include "cpp_main.h"
//#include "testclass.h"

//int cpp_main(int argc, char** argv);
/*extern "C" {
    int cpp_main(int argc, char** argv);
}*/

int cpp_main(int argc, char** argv){
    char *testtext = "Some Test Text to display.\n";
    //TestClass::WriteMessage(testtext);
    
    return(0);
}

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And cpp_main.h is :

//#ifndef _CPP_MAIN_H
//#define _CPP_MAIN_H

// Declare cpp_main() function
//int cpp_main(int argc, char** argv);
extern "C" {
   void cpp_main(int argc, char** argv);
};

//#endif	/* _CPP_MAIN_H */

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However when I try to build the executable I receive this error :

cpp_main.h:6: error: expected identifier or ‘(’ before string constant


gcc is telling me there is something wrong with extern "C"... ?!?!!?

If I take the line from the header file and paste it directly into cpp_main.cpp everything compiles and links ok... but why won't it work with the header file ?

Any help is much appreciated

Steve

 

extern "C" cant be understood by pure C compiler wich is called when you compile main.c

 

Yes.. I see the error of my ways now. So the obvious thing (which I did) was to remove the #include "cpp_main.h" from the C file, but I expected this then to cause an 'un-declared' function error or error that the function cpp_main() could not be found but no.. gcc compiled and linked with no complaints at all... so what's the point of a header file if it's not needed to link or declare functions.. or have I misunderstood the purpose of headers ?

 

Usualy if you need declare function written in C you have to use something like this

#ifdef __cplusplus
#define EXTCFUNC extern "C"
#elseif
#define EXTCFUNC extern
#endif
EXTCFUNC cpp_main(int argc, char** argv);

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