extern in shared libraries(.so)

Hello everyone.
 
I've got some problem using extern function in shared library.I want to use some extern functions in shared library, which will be declared in main program code.
I've got library file's with some code, let them be:
klib.h
klib.cpp
kklib.cpp
In both .cpp files i declared extern function

//Some headers
extern void hello_printer(int _T);
....
class KL
{
   public:
   int printer()
   {
      hello_printer(10);
      //someaction;
   }
};

After compiling I've got klib.so, put it in path folder.
Also I've got some main.cpp file with:
 

#include<stdio.h>
void hello_printer(int _T)
{
     for(;_T>0;_T--)printf("%i",_T);
}
int main()
{
     //some code with calling class KL
}

I't also compiled with (linking with klib.so) no error's, but when I run it I've got:

path_to_library/klib.so:undefined symbol: hello_printer()__FiPc

 
Is it possible? Please,can someone help me to manage with this problem?