Problem calling C++ from C code

Hi,

I have been understanding how to call C/C++ code from C++/C. Firstly I tried calling a C function from C++ code :

Code:

// cpp code
#include<iostream>

extern "C" {
void func();
}

int main(void)
{
    func();
    return 0;
}

I compiled the above code using the following command :

g++ -c main.cpp

Now, here is the C code :

Code:

#include<stdio.h>

void func()
{
    printf("\n Inside func()\n");
}

Compiled the above code using :
gcc -c func.c

Finally, I linked the C and c++ code using :

g++ main.o func.o -o out

Now, when I execute 'out', I could see the output 'Inside func()'.


As a second step, I defined a function 'fun()' in cpp file and tried to call it from C code..

Code:

//C++ code
#include<iostream>
#include<stdio.h>

void fun();

extern "C" {
void func();
}

void fun()
{
    printf("\n inside fun()\n");
}

int main(void)
{
    func();
    return 0;
}

Code:

// C code
#include<stdio.h>

extern void fun();

void func()
{
    printf("\n Inside func()\n");
    fun();
}

Now when I run the following command :

g++ -Wall main.o func.o -o out

I get the following error :

Code:

~/practice $ g++ main.o func.o -o func
func.o: In function `func':
func.c:(.text+0x14): undefined reference to `fun'
collect2: ld returned 1 exit status

I am not able to understand the reason????

I got it working by doing some modifications :

Code:

//cpp code
#include<iostream>
#include<stdio.h>


extern "C" {
void func();
}

extern "C" void fun()
{
    printf("\n inside fun()\n");
}

int main(void)
{
    func();
    return 0;
}

It might work for now, but it isn't a long term solution.
[32] How to mix C and C++ ..Updated!.., C++ FAQ