Example: handle c-style callback in c++

c_lib.c

#include "c_lib.h"

#include <stdio.h>

/**
 * @brief func_ptr_
 */
static c_lib_func_ptr func_ptr_;

/**
 * @brief c_lib_regist_func_ptr
 * @param p
 */
void c_lib_regist_func_ptr(c_lib_func_ptr p)
{
    func_ptr_ = p;
}

/**
 * @brief c_lib_do_something
 */
void c_lib_do_something(int n)
{
    printf("[%s] internal callback address: %lX, param: %04X\n",
           __FUNCTION__,
           (unsigned long)func_ptr_,
           n);
}

c_lib.h

#ifndef C_LIB_H_INCLUDED
#define C_LIB_H_INCLUDED

#ifdef __cplusplus
extern "C"{
#endif

typedef void (*c_lib_func_ptr)(int a);

extern void c_lib_regist_func_ptr(c_lib_func_ptr);
extern void c_lib_do_something(int n);

#ifdef __cplusplus
}
#endif

#endif

c_lib_wrapper.hpp

#ifndef C_LIB_WRAPPER_HPP_INCLUDED
#define C_LIB_WRAPPER_HPP_INCLUDED

#ifdef __cplusplus
extern "C" {
#endif // #ifdef __cplusplus

#include "c_lib.h"

#ifdef __cplusplus
}
#endif // #ifdef __cplusplus

#include <iostream>

/**
 * @brief The ClibWrapper class
 */
class ClibWrapper
{
public:
    /**
     * @brief ClibWrapper
     */
    ClibWrapper()
    {
        regist_callback();
    }
    ~ClibWrapper() = default;

    ClibWrapper(const ClibWrapper&) = delete;
    ClibWrapper(ClibWrapper&) = delete;

private:
    void regist_callback()
    {
        static auto f = [this](int n)
                {
                    test(n);
                };
        c_lib_regist_func_ptr([](int n)
        {
            f(n);
        });
    }

    /**
     * @brief test
     * @remarks will be passed to c lib as a callback
     * @param n
     */
    void test(int n)
    {
        std::cout << __FUNCTION__ << ": " << n << std::endl;
    }
};

#endif // C_LIB_WRAPPER_HPP_INCLUDED

main.cpp

#include "c_lib.h"
#include "c_lib_wrapper.hpp"

#include <iostream>

using namespace std;

int main()
{
    ClibWrapper wrapper;
    c_lib_do_something(1024);

    //cout << "Hello World!" << endl;
    return 0;
}