//code in add.cxx 
    #include "add.h"
    int sample::method()
    {
        cout<<"method is called!\n";
    }

    //code in add.h 
    #include <iostream>
    using namespace std;
    class sample
    {
        public:
        int method();
    };

    //code in mylib.cxx
    #include "add.h"
    #ifndef _cplusplus
    #define _cplusplus
    #include "mylib.h"
    #endif
     
    int myfunc()
    {
        sample ss;
        ss.method();
        return 0;
    }

    //code in mylib.h 
    #ifdef _cplusplus
    extern "C"
    {
    #endif
     
    int myfunc();
     
    #ifdef _cplusplus
    }
    #endif

    main.c 
    #include <stdio.h> 
    #include <dlfcn.h>
    #include "mylib.h"
     
    int 
    main()
    {
        int (*dlfunc)();
        void *handle; //定义一个句柄
        handle = dlopen("./mylib.so", RTLD_LAZY);//获得库句柄
        dlfunc = dlsym(handle, "myfunc"); //获得函数入口
        (*dlfunc)();
        dlclose(handle); 
     
        return 0;
    }