class A 
{ 
    public: 
    A(); 
    virtual ~A(); 
    int gt(); 
    int pt(); 
private: 
    int s; 
}; 

#include <iostream>  
#include "head.h" 

A::A(){} 
A::~A(){} 
int A::gt() 
{ 
  s=10; 
} 
int A::pt() 
{ 
    std::cout<<s<<std::endl; 
} 

g++ -shared -o libmy.so firstso.cpp

#include <iostream> 
#include "head.h" 
extern "C" 
{ 
int f(); 
int f() 
{ 
A a; 
a.gt(); 
a.pt(); 
return 0; 
} 
} 

gcc -shared -o sec.so secso.cpp -L. -lmy

#include "stdio.h" 
#include "dlfcn.h" 
#define SOFILE "sec.so" 
int (*f)(); 
int main() 
{ 
void *dp; 
dp=dlopen(SOFILE,RTLD_LAZY); 
f=dlsym(dp,"f"); 
f(); 
return 0; 
} 

gcc -rdynamic -s -o myapp test.c

10
$