Run-Time Call Library (Linux)

//calllib.cpp

#include <iostream>

#ifdef __cplusplus
extern "C" {
#endif

    void hello() {
        std::cout << "hello" << '\n';
    }

#ifdef __cplusplus
}
#endif

//compile :
//g++ -c -Wall -Werror -fPIC calllib.c
//g++ -shared -o libcalllib.so calllib.o


//mylib.cpp

#include <dlfcn.h>
#include <iostream>

using namespace std;

int main() {

    cout << "C++ dlopen demo\n\n";

    // open the library
    cout << "Opening hello.so...\n";
    void* handle = dlopen("./libcalllib.so", RTLD_LAZY);

    if (!handle) {
        cerr << "Cannot open library: " << dlerror() << '\n';
        return 1;
    }

    // load the symbol
    cout << "Loading symbol hello...\n";
    typedef void (*hello_t)();

    // reset errors
    dlerror();
    hello_t hello = (hello_t) dlsym(handle, "hello");
    const char *dlsym_error = dlerror();
    if (dlsym_error) {
        cerr << "Cannot load symbol 'hello': " << dlsym_error <<
            '\n';
        dlclose(handle);
        return 1;
    }

    // use it to do the calculation
    cout << "Calling hello...\n";
    hello();

    // close the library
    cout << "Closing library...\n";
    dlclose(handle);
}

//compile :
//g++ mylib.cpp -ldl -o mylib

//and then ./mylib to execute