Compiling and linking C code invoking C++ function - c++

Question

I have a problem when invoking a C++ method from my C code. The method I need to invoke in the C++ code is not within a class. I am trying to setup a simple example and I have the following files:
//header.h
#ifdef __cplusplus
#include <iostream>
extern "C" {
#endif
int print(int i, double d);
#ifdef __cplusplus
}
#endif
//ccode.c
#include "header.h"
main() {
printf("hello");
print(2,2.3);
}
//cppcode.cc
#include "header.h"
using namespace std;
int print(int i, double d)
{
cout << "i = " << i << ", d = " << d;
}
Probably my error is in the way I am trying to compile and link this. I am doing the following:
g++ -c cppcode.cc -o cppcode.o
That goes fine.
gcc ccode.c cppcode.o -o ccode
Here I get the following errors:
cppcode.o: In function `print':
cppcode.cc:(.text+0x16): undefined reference to `std::cout'
cppcode.cc:(.text+0x1b): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
cppcode.cc:(.text+0x28): undefined reference to `std::basic_ostream<char, std::char_traits<char> >::operator<<(int)'
cppcode.cc:(.text+0x35): undefined reference to `std::basic_ostream<char, std::char_traits<char> >& std::operator<< <std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*)'
cppcode.cc:(.text+0x42): undefined reference to `std::basic_ostream<char, std::char_traits<char> >::operator<<(double)'
cppcode.o: In function `__static_initialization_and_destruction_0(int, int)':
cppcode.cc:(.text+0x6b): undefined reference to `std::ios_base::Init::Init()'
cppcode.cc:(.text+0x70): undefined reference to `std::ios_base::Init::~Init()'
collect2: ld returned 1 exit status
I assume that this happens because I am using the C compiler. What is the correct way to compile and link this small example?
The idea is that I have the C code running and just invoke the C++ functions, without having to rewrite them in C. Thanks in advance for help!
I am using Ubuntu 12.04, gcc version 4.6.3

Answer 1

You need to link C++ runtime library.
gcc ccode.c cppcode.o -o ccode -lstdc++

Answer 2

You should compile and link separately. Use g++ to link in order to get the proper standard library.
g++ -c cppcode.cc -o cppcode.o
gcc -c ccode.c -o ccode.o
g++ ccode.o cppcode.o -o ccode

Answer 3

The g++ compiler automatically links your program with the standard cpp library.
When you compile with gcc, the linker can find reference to that.
You have two options.
One is to compile the c file with g++. Second is to force the linkage of the standard cpp library.
Here's whats written in gcc guide:
-static-libstdc++
When the g++ program is used to link a C++ program, it normally automatically links against libstdc++. If libstdc++ is available as a shared library, and the -static option is not used, then this links against the shared version of libstdc++. That is normally fine. However, it is sometimes useful to freeze the version of libstdc++ used by the program without going all the way to a fully static link. The -static-libstdc++ option directs the g++ driver to link libstdc++ statically, without necessarily linking other libraries statically.
Run the following command:
gcc ccode.c cppcode.o -o ccode -lstdc++