a.cpp

#include "a.h"

A::A() {
    std::cout << "New A" << std::endl;
}

A::~A() {
    std::cout << "Destroying A" << std::endl;
}

void A::print() {
    std::cout << "Printing A" << std::endl;
}

main.cpp

extern void doTask();

int main() {
    doTask();
}

Makefile

all:
        g++ -fPIC -shared test.cpp -o libtest.so -ldl
        g++ a.cpp -shared -fPIC -o liba.so
        g++ -Wl,--unresolved-symbols=ignore-in-shared-libs main.cpp libtest.so

test.cpp

#include "a.h"
#include <dlfcn.h>

void doTask() {

    void* handle = dlopen("./liba.so", RTLD_NOW | RTLD_GLOBAL);

    A* a = new A();
    a->print();
    delete a;
}