C代码调用C++函数

#ifndef H_HELLO
#define H_HELLO
#ifdef __cplusplus
extern "C" {
#endif
int getAge();
int getCount();
#ifdef __cplusplus
}
#endif
#endif

#include <iostream>
#include "hello.h"
int getAge() {
    std::cout << "get age" << std::endl;
    return 99;
}
int getCount() {
    std::cout << "get count" << std::endl;
    return 123456;
}

include <stdio.h>
#include "hello.h"

int main() {
    int age = getAge();
    int count = getCount();
    printf("%d:%d\n", age, count);
    return 0;
}

main: main.c libhello.so
    gcc main.c -L. -lhello -o main
libhello.so: hello.cpp
    g++ -fPIC -shared -o libhello.so hello.cpp
clean:
    rm -f *.o *.so main

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

int main() {
    int age = getAge();
    std::cout << age << ":" << getCount() << std::endl;
    return 0;
}