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C Discussion Thread
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Jan 5th, 2009

Calling C++ function from C code

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Hello,
I'm quite new here, but there's a problem that needs solution. I think the title says exactly what I want to do. I need to use C for a reason I don't think is this important to mention. I tried searching Google, and found the same solution on most of the results.
After some searching I made a test application using solutions I found... but I can't get it working, I get a linker error.
If it's important: I'm using GCC 4.2.4 on a Linux.

Now some code...

main.c

C Syntax (Toggle Plain Text)
#include <stdio.h>
#include "wrp.h"
 
int main(){
    printf("wrapper\n");
    wrp();
}
#include <stdio.h>
#include "wrp.h"

int main(){
    printf("wrapper\n");
    wrp();
}

wrp.h

C Syntax (Toggle Plain Text)
#ifdef __cplusplus
extern "C"
#endif
void wrp();
#ifdef __cplusplus
extern "C"
#endif
void wrp();

cppcode.cpp

C Syntax (Toggle Plain Text)
#include <iostream>
#include "wrp.h"
 
extern "C" void wrp(){
     std::cout << "wrapper zakonczyl dzialanie!\n";
}
#include <iostream>
#include "wrp.h"

extern "C" void wrp(){
     std::cout << "wrapper zakonczyl dzialanie!\n";
}

Linker error I get:

C Syntax (Toggle Plain Text)
/tmp/cc6Irctr.o: In function `main':
main.c:(.text+0x1e): undefined reference to `wrp'
collect2: ld returned 1 exit status
/tmp/cc6Irctr.o: In function `main':
main.c:(.text+0x1e): undefined reference to `wrp'
collect2: ld returned 1 exit status

Command I use: gcc main.c -o test

Thanks in advance for Your help.
-Marek

PS. I don't know if this thread belongs to C or C++ forum.

Last edited by venomxxl; Jan 5th, 2009 at 12:47 pm.

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venomxxl

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Jan 5th, 2009

Re: Calling C++ function from C code

(Toggle Plain Text)

g++ -c cppcode.cpp
gcc -c main.c
g++ -o test main.o cppcode.o

Oh, and that might not work either.

This is how to mix C and C++
http://www.parashift.com/c++-faq-lit...c-and-cpp.html
In particular, the main() needs to be C++ so that global ctors/dtors get called.

Salem

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Posting Sage

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Jan 5th, 2009

Re: Calling C++ function from C code

It worked! I can't believe it was so simple

Output:

C Syntax (Toggle Plain Text)

wrapper
wrapper zakonczyl dzialanie!

Thanks a lot!

venomxxl

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